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1.
Stephane Sarrazin William C. Lamanna Jeffrey D. Esko 《Cold Spring Harbor perspectives in biology》2011,3(7)
Heparan sulfate proteoglycans are found at the cell surface and in the extracellular matrix, where they interact with a plethora of ligands. Over the last decade, new insights have emerged regarding the mechanism and biological significance of these interactions. Here, we discuss changing views on the specificity of protein–heparan sulfate binding and the activity of HSPGs as receptors and coreceptors. Although few in number, heparan sulfate proteoglycans have profound effects at the cellular, tissue, and organismal level.Heparan sulfate proteoglycans (HSPGs) are glycoproteins, with the common characteristic of containing one or more covalently attached heparan sulfate (HS) chains, a type of glycosaminoglycan (GAG) (Esko et al. 2009). Cells elaborate a relatively small set of HSPGs (∼17) that fall into three groups according to their location: membrane HSPGs, such as syndecans and glycosylphosphatidylinositol-anchored proteoglycans (glypicans), the secreted extracellular matrix HSPGs (agrin, perlecan, type XVIII collagen), and the secretory vesicle proteoglycan, serglycin (Esko et al. 1985), which allowed functional studies in the context of a cell culture model (Zhang et al. 2006). A decade later, the first HSPG mutants in a model organism (Drosophila melanogaster) were identified (Rogalski et al. 1993; Nakato et al. 1995; Häcker et al. 1997; Bellaiche et al. 1998; Lin et al. 1999), which was followed by identification of mutants in nematodes, tree frogs, zebrafish, and mice (and3).3). HS is evolutionarily ancient and its composition has remained relatively constant from Hydra to humans (Yamada et al. 2007; Lawrence et al. 2008).
Open in a separate windowHS, heparan sulfate; CS, chondroitin sulfate; PG, proteoglycan.aThe variation in core mass is because of species differences.bThe number of chains is based on the number of putative attachment sites for chain initiation as well as data from the literature; the actual number of chains varies by method, tissue, and species.
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Open in a separate windowFigure 1 shows in pictorial form many of the systems in which HSPGs participate.
Table 1.
Heparan sulfate proteoglycans| Class | Proteoglycan | Core mass (kDa)a | Chain type (number)b | Tissue | Human disease |
|---|---|---|---|---|---|
| Membrane-bound | Syndecan-1–syndecan-4 | 31–45 | HS (2–3) in Sdc2 and Sdc4; HS/CS (3–4 HS/1-2 CS) in Sdc1 and Sdc3 | Epithelial cells, fibroblasts | |
| Glypican-1–glypican-6 | 57–69 | HS (1–3) | Epithelial cells, fibroblasts | Simpson–Golabi–Behmel syndrome (overgrowth) (GPC3) (Pilia et al. 1996); omodysplasia (skeletal dysplasia) (GPC6) (Campos-Xavier et al. 2009) | |
| Betaglycan (part-time PG) | 110 | HS/CS (1–2) | Fibroblasts | ||
| Neuropilin-1 (part-time PG) | 130 | HS or CS (1) | Endothelial cells | ||
| CD44v3 | 37 | HS (1) | Lymphocytes | ||
| Secretory vesicles | Serglycin | 10–19 | Heparin/CS (10–15) | Mast cells, hematopoietic cells | |
| Extracellular matrix | Perlecan | 400 | HS (1–4) | Basement membranes | Schwartz–Jampel syndrome (skeletal dysplasia) (Nicole 2000; Arikawa-Hirasawa et al. 2001) |
| Agrin | 212 | HS (2–3) | Basement membranes | ||
| Collagen XVIII | 150 | HS (1–3) | Epithelial cells, basement membranes | Knobloch syndrome type I (Sertie et al. 2000) |
Table 2.
Mutants altered in HSPG core proteins| Gene | Proteoglycan | Phenotype (references) |
|---|---|---|
| Sdc1 | Syndecan-1 | Null allele: viable; increase in inflammation-mediated corneal angiogenesis (Gotte et al. 2002, 2005); corneal epithelial cells migrate more slowly, show reduced localization of α9 integrin during wound closure and fail to increase in proliferation after wounding (Stepp et al. 2002); enhanced leukocyte-endothelial interaction in the retina (Gotte et al. 2002, 2005); increase in medial and intimal smooth muscle cell replication and neointimal lesion after injury (Fukai et al. 2009); reduced cardiac fibrosis and dysfunction during angiotensin II–induced hypertension (Schellings et al. 2010); not required for follicle initiation and development (Richardson et al. 2009); accumulates plasma triglycerides, and shows prolonged circulation of injected human VLDL and intestinally derived chylomicrons (Stanford et al. 2009); juvenile mice resistant to carcinogen-induced tumorigenesis (McDermott et al. 2007); increased basal protein leakage and more susceptible to protein loss induced by combinations of IFN-γ, TNF-α, and increased venous pressure (Bode et al. 2008); exacerbates anti-GBM nephritis shifting Th1/Th2 balance toward a Th2 response (Rops et al. 2007); no role in hepatocyte infection by Plasmodium yoelii sporozoites (Bhanot 2002); normal larval development of Trichinella spiralis, but modestly reduced Th2 responses during infection (Beiting et al. 2006); less susceptible to Pseudomonas aeruginosa infection (Haynes et al. 2005); reduced P. aeruginosa infection rate and virulence (Park et al. 2001); protected from Staphylococcus aureus beta-toxin-induced lung injury (Hayashida et al. 2009a); exaggerated airway hyperresponsiveness, eosinophilia, and lung IL-4 responses to allergens (Xu et al. 2005); exaggerated CXC chemokines, neutrophilic inflammation, organ damage, and lethality in LPS endotoxemia (Hayashida et al. 2009b); prolonged recruitment of inflammatory cells in dextran sodium sulfate (DSS)-induced colitis and delayed type hypersensitivity (Masouleh et al. 2009; Floer et al. 2010). |
| Sdc2 | Syndecan-2 | No mutants reported. Sdc2 antisense impairs angiogenesis in human microvascular endothelial cells (Noguer et al. 2009); morpholinos inhibit cell migration and fibrillogenesis during embryogenesis in zebrafish (Arrington and Yost 2009). |
| Sdc3 | Syndecan-3 | Null allele: viable; altered feeding behavior (Strader et al. 2004); no phenotype in synovial endothelial cells (Patterson et al. 2005); enhanced long-term potentiation (LTP) in area CA1 (brain) and impaired performance in tasks assessing hippocampal function (Kaksonen et al. 2002); more sensitive to inhibition of food intake by the melanocortin agonist MTII (Reizes et al. 2003); perturbs laminar structure of the cerebral cortex as a result of impaired radial migration, and neural migration in the rostral migratory stream is impaired (Hienola et al. 2006); novel form of muscular dystrophy characterized by impaired locomotion, fibrosis, and hyperplasia of myonuclei and satellite cells (Cornelison et al. 2004). |
| Sdc4 | Syndecan-4 | Null allele: viable; enhanced fibrin deposition in degenerating fetal vessels in the placental labyrinth (Ishiguro et al. 2000); delayed angiogenesis in wound granulation tissue (Echtermeyer et al. 2001); defective subcellular localization of mTOR Complex2 and Akt activation in endothelial cells, affecting endothelial cell size, NOS, and arterial blood pressure (Partovian et al. 2008); decreased macrophage uptake of phospholipase A2-modified LDL (Boyanovsky et al. 2009); mesangial expansion, enhanced matrix collagens I and IV, fibronectin and focal segmental glomerulosclerosis in males, and induction of Sdc2 in glomeruli (Cevikbas et al. 2008); more susceptible to hepatic injury, and thrombin-cleaved form of osteopontin is significantly elevated after concanavalin-A injection (Kon et al. 2008); less damage in osteoarthritic cartilage in a surgically induced model of osteoarthritis (Echtermeyer et al. 2009); explanted satellite cells fail to reconstitute damaged muscle and are deficient in activation, proliferation, MyoD expression, myotube fusion, and differentiation (Cornelison et al. 2004); vibrissae are shorter and have a smaller diameter because of suboptimal response to fibroblast growth factors (Iwabuchi and Goetinck 2006); lower phosphorylation levels of focal adhesion kinase (Wilcox-Adelman et al. 2002); random migration of fibroblasts as a result of high delocalized Rac1 activity (Bass et al. 2007); defective RGD-independent cell attachment to transglutaminase-fibronectin matrices (Telci et al. 2008); impaired suppression of production of IL-1β by TGF-α (Ishiguro et al. 2002); decreased neutrophil recruitment and increased myofibroblast recruitment and interstitial fibrosis after bleomycin-treatment, no inhibition of fibrosis with recombinant CXCL10 protein (Jiang et al. 2010); hypersensitivity to LPS because of decreased TGF-β suppression of IL-1 production in monocytes and neutrophils (Ishiguro et al. 2001). |
| Gpc1 | Glypican-1 | Null allele: viable; reduced brain size (Jen et al. 2009). Athymic mutant mice show decreased tumor angiogenesis and metastasis (Aikawa et al. 2008). |
| Gpc2 | Glypican-2 | No mutants reported. |
| Gpc3 | Glypican-3 | Null allele: viable; resembles Simpson–Golabi–Behmel overgrowth syndrome, including somatic overgrowth, renal dysplasia, accessory spleens, polydactyly, and placentomegaly (Cano-Gauci et al. 1999; Chiao et al. 2002); defects in cardiac and coronary vascular development (Ng et al. 2009); alterations in Wnt signaling, in vivo inhibition of the noncanonical Wnt/JNK signaling, activation of canonical Wnt/β-catenin signaling (Song et al. 2005); increased Hedgehog signaling (Capurro et al. 2008); abnormal rates of proliferation and apoptosis in cortical and medullary collecting duct cells (Grisaru et al. 2001); delay in endochondral ossification, impairment in the development of the myelomonocytic lineage (Viviano et al. 2005). |
| Gpc4 | Glypican-4 | Zebrafish knypek controls cell polarity during convergent extension (Topczewski et al. 2001); craniofacial skeletal defects in adult fish (LeClair et al. 2009). |
| Gpc5 | Glypican-5 | No mutants reported. |
| Gpc6 | Glypican-6 | Impaired endochondral ossification and omodysplasia (Campos-Xavier et al. 2009). |
| Tgfbr3 | Betaglycan | Null allele: embryonic lethal; heart and liver defects (Stenvers et al. 2003); defect in seminiferous cord formation in E12.5–13.5 embryos (Sarraj et al. 2010). |
| Hspg2 | Perlecan | Null allele: embryonic lethal (E10–12); developmental angiogenesis altered in zebrafish (Zoeller et al. 2009); high incidence of malformations of the cardiac outflow tract, lack of well-defined spiral endocardial ridges (Costell et al. 2002); lower amounts of collagen IV and laminins in embryonic hearts, reduced function in infarcted hearts from heterozygous mice (Sasse et al. 2008); absence of acetylcholinesterase at the neuromuscular junctions (Arikawa-Hirasawa et al. 2002); cephalic and skeletal abnormalities (Arikawa-Hirasawa et al. 1999); cerebral ectopias, exencephaly (Girós et al. 2007); increased cross-sectional area of myosin heavy chain type IIb fibers in the tibialis anterior muscle (Xu et al. 2010b); diminished osteocyte canalicular pericellular area (Thompson et al. 2011). |
| Exon 3 deletion (Hspg23/3) viable: proteinuria after protein loading (Morita et al. 2005); monocyte/macrophage influx impaired in Hspg23/3Col18a1−/– mice in a model of renal ischemia/reperfusion (Celie et al. 2007). | ||
| Secreted as CSPG in some tissues (Danielson et al. 1992; Govindraj et al. 2002; Vogl-Willis and Edwards 2004; West et al. 2006), but relationship of CSPG isoform to phenotypes not established. | ||
| Prg1 | Serglycin | Null allele: viable; secretory granule defects in mast cells (Abrink et al. 2004); dense core formation is defective in mast cell granules (Henningsson et al. 2006); defective secretory granule maturation and granzyme B storage in cytotoxic T cells (Grujic et al. 2005); no effect on macrophages (Zernichow et al. 2006); platelets and megakaryocytes contain unusual scroll-like membranous inclusions (Woulfe et al. 2008); enlargement of multiple lymphoid organs, decrease in the proportion of CD4+ cells, more pronounced airway inflammatory response in older mice (Wernersson et al. 2009); increased virulence of Klebsiella pneumoniae (Niemann et al. 2007); defective regulation of antiviral CD8+ T-cell responses (Grujic et al. 2008). |
| Agrn | Agrin | Null allele: embryonic lethal; reduced number, size, and density of postsynaptic acetylcholine receptor aggregates in muscles; abnormal intramuscular nerve branching and presynaptic differentiation (Gautam et al. 1996,1999); smaller brains (Serpinskaya et al. 1999); abnormal development of interneuronal synapses (Gingras et al. 2007); increased resistance to excitotoxic injury (Hilgenberg et al. 2002); reduced number of cortical presynaptic and postsynaptic specializations (Ksiazek et al. 2007). |
| Floxed allele: Inactivation in podocytes does not affect glomerular charge selectivity or glomerular architecture (Harvey et al. 2007). | ||
| Col18a1 | Collagen XVIII | Null allele: viable; increased microvascular growth (Li and Olsen 2004); increased angiogenesis associated with atherosclerotic plaques (Moulton et al. 2004); delayed regression of blood vessels in the vitreous along the surface of the retina after birth and lack of or abnormal outgrowth of retinal vessels (Fukai et al. 2002); larger choroidal neovascularization lesions and increased vascular leakage (Marneros et al. 2007); accelerated healing and vascularization rate of excisional dorsal skin wounds (Seppinen et al. 2008); anomalous anastomoses of vasculature; disruption of the posterior iris pigment epithelial cell layer with release of melanin granules, severe thickening of the stromal iris basement membrane zone (Marneros and Olsen 2003); increase in the amount of retinal astrocytes (Hurskainen et al. 2005); more severe glomerular and tubulointerstitial injury in induced anti-GBM glomerulonephritis (Hamano et al. 2010); monocyte/macrophage influx impaired in Hspg23/3Col18a1−/– mice in a model of renal ischemia/reperfusion (Celie et al. 2007); mild chylomicronemia (Bishop et al. 2010). |
Table 3.
Mouse mutants altered in HS biosynthesis| Gene | Enzyme | Phenotype |
|---|---|---|
| Xt1 | Xylosyltransferase-1 | No mutants reported. |
| Xt2 | Xylosyltransferase-2 | Null allele: viable; polycystic kidney and livers (Condac et al. 2007). |
| GalTI (β4GalT7) | Galactosyltransferase I | Human mutants: defective chondroitin substitution of decorin and biglycan in an Ehlers–Danlos patient (Gotte and Kresse 2005; Seidler et al. 2006). |
| GalTII (β3GalT6) | Galactosyltransferase II | No mutants reported. |
| Glcat1 | Glucuronyltransferase I | Null allele: embryonic lethal (4–8-cell stage) (Izumikawa et al. 2010). |
| Extl3 | N-acetylglucosaminyl transferase I | Floxed allele: Inactivation in islets decreases growth and insulin secretion (Takahashi et al. 2009). |
| Ext1/Ext2 | HS Copolymerase (N-acetylglucosaminyl-glucuronyltransferase) | Null allele: embryonic lethal (E6-7.5); lack of mesoderm differentiation (Lin et al. 2000; Stickens et al. 2005); heterozygotes develop rib growth plate exostoses (Stickens et al. 2005; Zak et al. 2011); unaltered vascular permeability in heterozygous mice (Xu et al. 2010a). |
| Floxed allele of Ext1: defective brain morphogenesis and midline axon guidance after nestin-Cre inactivation (Inatani et al. 2003); no effect on adaptive immune response in CD15Cre mice (Garner et al. 2008); altered T-cell and dendritic cell homing to lymph nodes in Tie2Cre mice (Bao et al. 2010); rib growth plate exostosis formation in Col2Cre mice (Jones et al. 2010; Matsumoto et al. 2010; Zak et al. 2011). | ||
| Ndst1 | N-acetylglucosaminyl N-deacetylase/N-sulfotransferase-1 | Null allele: Perinatal lethal; lung hypoplasia, defective forebrain, lens, and skull development (Fan et al. 2000; Ringvall et al. 2000; Grobe et al. 2005; Pan et al. 2006). |
| Floxed allele: decreased chemokine transcytosis and presentation and neutrophil infiltration in Tie2Cre mice (Wang et al. 2005); decreased allergen-induced airway hyperresponsiveness and inflammation because of reduction in recruitment of eosinophils, macrophages, neutrophils, and lymphocytes in Tie2Cre mice (Zuberi et al. 2009); decreased pathological angiogenesis in Tie2Cre mice (Fuster et al. 2007); decreased vascular VEGF-induced hyperpermeability (Xu et al. 2010a); decreased vascular smooth muscle cell proliferation, vessel size, and vascular remodeling after arterial injury in SM22αCre mice (Adhikari et al. 2010a); mild effect on T-cell response in Tie2Cre;Ndst2−/−mice (Garner et al. 2008); defective lacrimal gland development and Fgf10-Fgfr2b complex formation and signaling in LeCre mice (Pan et al. 2008); defective lobuloalveolar development in mammary gland (Crawford et al. 2010). | ||
| Ndst2 | N-acetylglucosaminyl N-deacetylase/N-sulfotransferase-2 | Null allele: viable; mast cell deficiency and defective storage of proteases (Forsberg et al. 1999; Humphries et al. 1999); compounding mutation with Ndst1 reduces l-selectin interactions (Wang et al. 2005). |
| Ndst3 | N-acetylglucosaminyl N-deacetylase/N-sulfotransferase-3 | Null allele: viable; floxed allele available (Pallerla et al. 2008). |
| Ndst4 | N-acetylglucosaminyl N-deacetylase/N-sulfotransferase-4 | No mutants reported. |
| Glce | Uronyl C5 epimerase | Null allele: perinatal lethal; renal agenesis (Li et al. 2003). |
| H2st | Uronyl 2-O-sulfotransferase | Null allele: perinatal lethal; renal agenesis; skeletal and ocular defects (Bullock et al. 1998; Merry et al. 2001); defective cerebral cortical development (McLaughlin et al. 2003); altered lacrimal gland development (Qu et al. 2011). |
| Floxed allele: altered lipoprotein clearance in AlbCre mice (Stanford et al. 2010); altered branching morphogenesis in the mammary gland (Garner et al. 2011). | ||
| H3st1 | Glucosaminyl 3-O-sulfotransferase 1 | Null allele: partially penetrant lethality; no alteration in coagulation (HajMohammadi et al. 2003); fertility defects because of impaired ovarian function and placenta development (Shworak et al. 2002; HajMohammadi et al. 2003). |
| H3st2 | Glucosaminyl 3-O-sulfotransferase 2 | Null allele; viable; no neuronal phenotype (Hasegawa and Wang 2008). |
| H3st3 | Glucosaminyl 3-O-sulfotransferase 3 | No mutants reported. |
| H3st4 | Glucosaminyl 3-O-sulfotransferase 4 | No mutants reported. |
| H3st5 | Glucosaminyl 3-O-sulfotransferase 5 | No mutants reported. |
| H3st6 | Glucosaminyl 3-O-sulfotransferase 6 | No mutants reported. |
| H6st1 | Glucosaminyl 6-O-sulfotransferase 1 | Null allele: embryonic lethal (Habuchi et al. 2007; Sugaya et al. 2008). |
| Gene trap allele: embryonic lethal; retinal axon guidance defects (Pratt et al. 2006). | ||
| Floxed allele: systemic inactivation embryonic lethal (Izvolsky et al. 2008); no change in plasma triglycerides in AlbCre mice (Stanford et al. 2010). | ||
| H6st2 | Glucosaminyl 6-O-sulfotransferase 2 | Null allele: viable (Sugaya et al. 2008); HS6ST-2, but not HS6ST-1, morphants in zebrafish show abnormalities in the branching morphogenesis of the caudal vein (Chen et al. 2005). |
| H6st3 | Glucosaminyl 6-O-sulfotransferase 3 | No mutants reported. |
| Hpa | Heparanase, transgene | Accelerated wound angiogenesis, enhanced delayed type hypersensitivity response (Zcharia et al. 2005; Edovitsky et al. 2006; Ilan et al. 2006); accumulation of intracellular crystals of protein Ym1 in macrophages (Waern et al. 2010); resistance to amyloid protein A amyloidosis (Li et al. 2005); age-related enlargement of lymphoid tissue and altered leukocyte composition (Wernersson et al. 2009). |
| Hpa | Heparanase | Null allele: viable; altered MMP-2 and MMP-14 expression (Zcharia et al. 2009). |
| Sulf1 | Endo-6-sulfatase 1 | Null allele: viable; esophageal defect (Ai et al. 2007; Ratzka et al. 2008); enhanced osteoarthritis, MMP-13, ADAMTS-5, and noggin elevated, col2a1 and aggrecan reduced in cartilage and chondrocytes (Otsuki et al. 2010). |
| Sulf2 | Endo-6-sulfatase 2 | Null allele: viable; behavioral defects (Lamanna et al. 2006); enhanced osteoarthritis, MMP-13, ADAMTS-5, and noggin elevated, col2a1 and aggrecan reduced in cartilage and chondrocytes (Otsuki et al. 2010). |
| Gene trap allele: Sulf2GT(pGT1TMpfs)155Ska, no phenotype (Lum et al. 2007). |
- HSPGs are present in basement membranes (perlecan, agrin, and collagen XVIII), where they collaborate with other matrix components to define basement membrane structure and to provide a matrix for cell migration.
- HSPGs are found in secretory vesicles, most notably serglycin, which plays a role in packaging granular contents, maintaining proteases in an active state, and regulating various biological activities after secretion such as coagulation, host defense, and wound repair.
- HSPGs can bind cytokines, chemokines, growth factors, and morphogens, protecting them against proteolysis. These interactions provide a depot of regulatory factors that can be liberated by selective degradation of the HS chains. They also facilitate the formation of morphogen gradients essential for cell specification during development and chemokine gradients involved in leukocyte recruitment and homing.
- HSPGs can act as receptors for proteases and protease inhibitors regulating their spatial distribution and activity.
- Membrane proteoglycans cooperate with integrins and other cell adhesion receptors to facilitate cell-ECM attachment, cell–cell interactions, and cell motility.
- Membrane HSPGs act as coreceptors for various tyrosine kinase-type growth factor receptors, lowering their activation threshold or changing the duration of signaling reactions.
- Membrane HSPGs act as endocytic receptors for clearance of bound ligands, which is especially relevant in lipoprotein metabolism in the liver and perhaps in the formation of morphogen gradients during development.
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The heparan sulfate proteoglycans present in a deoxycholate extract of rat brain were purified by ion exchange chromatography, affinity chromatography on lipoprotein lipase agarose, and gel filtration. Heparitinase treatment of the heparan sulfate proteoglycan fraction (containing 86% heparan sulfate and 10% chondroitin sulfate) that was eluted from the lipoprotein lipase affinity column with 1 M NaCl led to the appearance of a major protein core with a molecular size of 55,000 daltons, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Comparison of the effects of heparinase and heparitinase treatment revealed that the heparan sulfate proteoglycans of brain contain a significant proportion of relatively short N-sulfoglucosaminyl 6-O-sulfate [or N-sulfoglucosaminyl](alpha 1-4)iduronosyl 2-O-sulfate(alpha 1-4) repeating units and that the portions of the heparan sulfate chains in the vicinity of the carbohydrate-protein linkage region are characterized by the presence of D-glucuronic acid rather than L-iduronic acid. After chondroitinase treatment of a proteoglycan fraction that contained 62% chondroitin sulfate and 21% heparan sulfate (eluted from lipoprotein lipase with 0.4 M NaCl), the charge and density of a portion of the heparan sulfate-containing proteoglycans decreased significantly. These results indicate that a population of "hybrid" brain proteoglycans exists that contain both chondroitin sulfate and heparan sulfate chains covalently linked to a common protein core. 相似文献
4.
A27L Protein Mediates Vaccinia Virus Interaction with Cell Surface Heparan Sulfate 总被引：4，自引：7，他引：4 
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下载免费PDF全文 Vaccinia virus has a wide host range and infects mammalian cells of many different species. This suggests that the cell surface receptors for vaccinia virus are ubiquitously expressed and highly conserved. Alternatively, different receptors are used for vaccinia virus infection of different cell types. Here we report that vaccinia virus binds to heparan sulfate, a glycosaminoglycan (GAG) side chain of cell surface proteoglycans, during virus infection. Soluble heparin specifically inhibits vaccinia virus binding to cells, whereas other GAGs such as condroitin sulfate or dermantan sulfate have no effect. Heparin also blocks infections by cowpox virus, rabbitpox virus, myxoma virus, and Shope fibroma virus, suggesting that cell surface heparan sulfate could be a general mediator of the entry of poxviruses. The biochemical nature of the heparin-blocking effect was investigated. Heparin analogs that have acetyl groups instead of sulfate groups also abolish the inhibitory effect, suggesting that the negative charges on GAGs are important for virus infection. Furthermore, BSC40 cells treated with sodium chlorate to produce undersulfated GAGs are more refractory to vaccinia virus infection. Taken together, the data support the notion that cell surface heparan sulfate is important for vaccinia virus infection. Using heparin-Sepharose beads, we showed that vaccinia virus virions bind to heparin in vitro. In addition, we demonstrated that the recombinant A27L gene product binds to the heparin beads in vitro. This recombinant protein was further shown to bind to cells, and such interaction could be specifically inhibited by soluble heparin. All the data together indicated that A27L protein could be an attachment protein that mediates vaccinia virus binding to cell surface heparan sulfate during viral infection. 相似文献
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Tarja K. Kinnunen 《PloS one》2014,9(7)
Heparan sulfate proteoglycans (HSPGs) play critical roles in the development and adult physiology of all metazoan organisms. Most of the known molecular interactions of HSPGs are attributed to the structurally highly complex heparan sulfate (HS) glycans. However, whether a specific HSPG (such as syndecan) contains HS modifications that differ from another HSPG (such as glypican) has remained largely unresolved. Here, a neural model in C. elegans is used to demonstrate for the first time the relationship between specific HSPGs and HS modifications in a defined biological process in vivo. HSPGs are critical for the migration of hermaphrodite specific neurons (HSNs) as genetic elimination of multiple HSPGs leads to 80% defect of HSN migration. The effects of genetic elimination of HSPGs are additive, suggesting that multiple HSPGs, present in the migrating neuron and in the matrix, act in parallel to support neuron migration. Genetic analyses suggest that syndecan/sdn-1 and HS 6-O-sulfotransferase, hst-6, function in a linear signaling pathway and glypican/lon-2 and HS 2-O-sulfotransferase, hst-2, function together in a pathway that is parallel to sdn-1 and hst-6. These results suggest core protein specific HS modifications that are critical for HSN migration. In C. elegans, the core protein specificity of distinct HS modifications may be in part regulated at the level of tissue specific expression of genes encoding for HSPGs and HS modifying enzymes. Genetic analysis reveals that there is a delicate balance of HS modifications and eliminating one HS modifying enzyme in a compromised genetic background leads to significant changes in the overall phenotype. These findings are of importance with the view of HS as a critical regulator of cell signaling in normal development and disease. 相似文献
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Lukasz Wujak Miroslava Didiasova Dariusz Zakrzewicz Helena Frey Liliana Schaefer Malgorzata Wygrecka 《The Journal of biological chemistry》2015,290(11):7027-7039
Hageman factor (FXIIa) initiates the intrinsic coagulation pathway and triggers the kallikrein-kinin and the complement systems. In addition, it functions as a growth factor by expressing promitogenic activities toward several cell types. FXIIa binds to the cell surface via a number of structurally unrelated surface receptors; however, the underlying mechanisms are not yet fully understood. Here, we demonstrate that FXIIa utilizes cell membrane-bound glycosaminoglycans to interact with the cell surface of human lung fibroblasts (HLF). The combination of enzymatic, inhibitory, and overexpression approaches identified a heparan sulfate (HS) component of proteoglycans as an important determinant of the FXIIa binding capacity of HLF. Moreover, cell-free assays and competition experiments revealed preferential binding of FXIIa to HS and heparin over dextran sulfate, dermatan sulfate, and chondroitin sulfate A and C. Finally, we demonstrate that fibroblasts isolated from the lungs of the patients suffering from idiopathic pulmonary fibrosis (IPF) exhibit enhanced FXIIa binding capacity. Increased sulfation of HS resulting from elevated HS 6-O-sulfotransferase-1 expression in IPF HLF accounted, in part, for this phenomenon. Application of RNA interference technology and inhibitors of intracellular sulfation revealed the cooperative action of cell surface-associated HS and urokinase-type plasminogen activator receptor in the accumulation of FXIIa on the cell surface of IPF HLF. Moreover, FXIIa stimulated IPF HLF migration, which was abrogated by pretreatment of cells with heparinase I. Collectively, our study uncovers a novel role of HS-type glycosaminoglycans in a local accumulation of FXIIa on the cell membrane. The enhanced association of FXIIa with IPF HLF suggests its contribution to fibrogenesis. 相似文献
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Wuyang Zhu Lihua Wang Yiliang Yang Juan Jia Shihong Fu Yun Feng Ying He Jin-Ping Li Guodong Liang 《PloS one》2010,5(3)
Cell culture-adapted strains of Sindbis virus (SINV) initially attach to cells by the ability to interact with heparan sulfate (HS) through selective mutation for positively charged amino acid (aa) scattered in E2 glycoprotein (W. B. Klimstra, K. D. Ryman, and R. E. Johnston, J. Virol. 72: 7357–7366, 1998). Here we have further confirmed that interaction of E2 protein with HS is crucial for cellular infection of SINV based on the reverse genetic system of XJ-160 virus, a Sindbis-like virus (SINLV). Both SINV YN87448 and SINLV XJ-160 displayed similar infectivity on BHK-21, Vero, or C6/36 cells, but XJ-160 failed to infect mouse embryonic fibroblast (MEF) cells. The molecular mechanisms underlying the selective infectivity of XJ-160 were approached by substituting the E1, E2, or both genes of XJ-160 with that of YN87448, and the chimeric virus was denominated as XJ-160/E1, XJ-160/E2, or XJ-160/E1E2, respectively. In contrast to the parental XJ-160, all chimeric viruses became infectious to wild-type MEF cells (MEF-wt). While MEF-Ext
−/− cells, producing shortened HS chains, were resistant not only to XJ-160, but also to YN87448 as well as the chimeric viruses, indicating that the inability of XJ-160 to infect MEF-wt cells likely due to its incompetent discrimination of cellular HS. Treatment with heparin or HS-degrading enzyme resulted in a substantial decrease in plaque formation by YN87448, XJ-160/E2, and XJ-160/E1E2, but had marginal effect on XJ-160 and XJ-160/E1, suggesting that E2 glycoprotein from YN87448 plays a more important role than does E1 in mediating cellular HS-related cell infection. In addition, the peptide containing 145–150 aa from E2 gene of YN87448 specifically bound to heparin, while the corresponding peptide from the E2 gene of XJ-160 essentially showed no binding to heparin. As a new dataset, these results clearly confirm an essential role of E2 glycoprotein, especially the domain of 145–150 aa, in SINV cellular infection through the interaction with HS. 相似文献
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Our previous studies demonstrated that the cell culture-grown hepatitis C virus of genotype 2a (HCVcc) uses apolipoprotein E (apoE) to mediate its attachment to the surface of human hepatoma Huh-7.5 cells. ApoE mediates HCV attachment by binding to the cell surface heparan sulfate (HS) which is covalently attached to the core proteins of proteoglycans (HSPGs). In the present study, we further determined the physiological importance of apoE and HSPGs in the HCV attachment using a clinical HCV of genotype 1b (HCV1b) obtained from hepatitis C patients and human embryonic stem cell-differentiated hepatocyte-like cells (DHHs). DHHs were found to resemble primary human hepatocytes. Similar to HCVcc, HCV1b was found to attach to the surface of DHHs by the apoE-mediated binding to the cell surface HSPGs. The apoE-specific monoclonal antibody, purified HSPGs, and heparin were all able to efficiently block HCV1b attachment to DHHs. Similarly, the removal of heparan sulfate from cell surface by treatment with heparinase suppressed HCV1b attachment to DHHs. More significantly, HCV1b attachment was potently inhibited by a synthetic peptide derived from the apoE receptor-binding region as well as by an HSPG-binding peptide. Likewise, the HSPG-binding peptide prevented apoE from binding to heparin in a dose-dependent manner, as determined by an in vitro heparin pull-down assay. Collectively, these findings demonstrate that HSPGs serve as major HCV attachment receptors on the surface of human hepatocytes to which the apoE protein ligand on the HCV envelope binds. 相似文献
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13.
Kyousuke Kobayashi Kentaro Kato Tatsuki Sugi Hitoshi Takemae Kishor Pandey Haiyan Gong Yukinobu Tohya Hiroomi Akashi 《The Journal of biological chemistry》2010,285(3):1716-1725
Erythrocyte invasion is critical to the pathogenesis and survival of the malarial parasite, Plasmodium falciparum. This process is partly mediated by proteins that belong to the Duffy binding-like family, which are expressed on the merozoite surface. One of these proteins, BAEBL (also known as EBA-140), is thought to bind to glycophorin C in a sialic acid-dependent manner. In this report, by the binding assay between recombinant BAEBL protein and enzyme-treated erythrocytes, we show that the binding of BAEBL to erythrocytes is mediated primarily by sialic acid and partially through heparan sulfate (HS). Because BAEBL binds to several kinds of HS proteoglycans or purified HS, the BAEBL-HS binding was found to be independent of the HS proteoglycan peptide backbone and the presence of sialic acid moieties. Furthermore, both the sialic acid- and HS-dependent binding were disrupted by the addition of soluble heparin. This inhibition may be the result of binding between BAEBL and heparin. Invasion assays demonstrated that HS-dependent binding was related to the efficiency of merozoite invasion. These results suggest that HS functions as a factor that promotes the binding of BAEBL and merozoite invasion. Moreover, these findings may explain the invasion inhibition mechanisms observed following the addition of heparin and other sulfated glycoconjugates. 相似文献
14.
Alphaviruses are arthropod-borne viruses with wide species ranges and diverse tissue tropisms. The cell surface receptors which allow infection of so many different species and cell types are still incompletely characterized. We show here that the widely expressed glycosaminoglycan heparan sulfate can participate in the binding of Sindbis virus to cells. Enzymatic removal of heparan sulfate or the use of heparan sulfate-deficient cells led to a large reduction in virus binding. Sindbis virus bound to immobilized heparin, and this interaction was blocked by neutralizing antibodies against the viral E2 glycoprotein. Further experiments showed that a high degree of sulfation was critical for the ability of heparin to bind Sindbis virus. However, Sindbis virus was still able to infect and replicate on cells which were completely deficient in heparan sulfate, indicating that additional receptors must be involved. Cell surface binding of another alphavirus, Ross River virus, was found to be independent of heparan sulfate. 相似文献
15.
Monocyte Adhesion to Activated Aortic Endothelium: Role of L-Selectin and Heparan Sulfate Proteoglycans 总被引：13，自引：1，他引：12 下载免费PDF全文
下载免费PDF全文 Laura Giuffr Anne-Sophie Cordey Natacha Monai Yanik Tardy Marc Schapira Olivier Spertini 《The Journal of cell biology》1997,136(4):945-956
This study examines the role of L-selectin in monocyte adhesion to arterial endothelium, a key pathogenic event of atherosclerosis. Using a nonstatic (rotation) adhesion assay, we observed that monocyte binding to bovine aortic endothelium at 4°C increased four to nine times upon endothelium activation with tumor necrosis factor (TNF)-α. mAb-blocking experiments demonstrated that L-selectin mediates a major part (64 ± 18%) of monocyte attachment. Videomicroscopy experiments performed under flow indicated that monocytes abruptly halted on 8-h TNF-α–activated aortic endothelium, ~80% of monocyte attachment being mediated by L-selectin. Flow cytometric studies with a L-selectin/IgM heavy chain chimeric protein showed calcium-dependent L-selectin binding to cytokine-activated and, unexpectedly, unactivated aortic cells. Soluble L-selectin binding was completely inhibited by anti–L-selectin mAb or by aortic cell exposure to trypsin. Experiments with cycloheximide, chlorate, or neuraminidase showed that protein synthesis and sulfate groups, but not sialic acid residues, were essential for L-selectin counterreceptor function. Moreover, heparin lyases partially inhibited soluble L-selectin binding to cytokine-activated aortic cells, whereas a stronger inhibition was seen with unstimulated endothelial cells, suggesting that cytokine activation could induce the expression of additional ligand(s) for L-selectin, distinct from heparan sulfate proteoglycans. Under flow, endothelial cell treatment with heparinase inhibited by ~80% monocyte attachment to TNF-α–activated aortic endothelium, indicating a major role for heparan sulfate proteoglycans in monocyte–endothelial interactions. Thus, L-selectin mediates monocyte attachment to activated aortic endothelium, and heparan sulfate proteoglycans serve as arterial ligands for monocyte L-selectin. 相似文献
16.
Marie E. Oskarsson Kailash Singh Jian Wang Israel Vlodavsky Jin-ping Li Gunilla T. Westermark 《The Journal of biological chemistry》2015,290(24):15121-15132
Deposition of β cell toxic islet amyloid is a cardinal finding in type 2 diabetes. In addition to the main amyloid component islet amyloid polypeptide (IAPP), heparan sulfate proteoglycan is constantly present in the amyloid deposit. Heparan sulfate (HS) side chains bind to IAPP, inducing conformational changes of the IAPP structure and an acceleration of fibril formation. We generated a double-transgenic mouse strain (hpa-hIAPP) that overexpresses human heparanase and human IAPP but is deficient of endogenous mouse IAPP. Culture of hpa-hIAPP islets in 20 mm glucose resulted in less amyloid formation compared with the amyloid load developed in cultured islets isolated from littermates expressing human IAPP only. A similar reduction of amyloid was achieved when human islets were cultured in the presence of heparin fragments. Furthermore, we used CHO cells and the mutant CHO pgsD-677 cell line (deficient in HS synthesis) to explore the effect of cellular HS on IAPP-induced cytotoxicity. Seeding of IAPP aggregation on CHO cells resulted in caspase-3 activation and apoptosis that could be prevented by inhibition of caspase-8. No IAPP-induced apoptosis was seen in HS-deficient CHO pgsD-677 cells. These results suggest that β cell death caused by extracellular IAPP requires membrane-bound HS. The interaction between HS and IAPP or the subsequent effects represent a possible therapeutic target whose blockage can lead to a prolonged survival of β cells. 相似文献
17.
Characterization of Hepatitis C Virus E2 Glycoprotein Interaction with a Putative Cellular Receptor, CD81 总被引：35，自引：0，他引：35 下载免费PDF全文
下载免费PDF全文 Mike Flint Catherine Maidens Larry D. Loomis-Price Christine Shotton Jean Dubuisson Peter Monk Adrian Higginbottom Shoshana Levy Jane A. McKeating 《Journal of virology》1999,73(8):6235-6244
A truncated soluble form of the hepatitis C virus E2 glycoprotein, E2661, binds specifically to the surface of cells expressing human CD81 (hCD81) but not other members of the tetraspanin family (CD9, CD63, and CD151). No differences were noted between the level of E2661 binding to hCD81 expressed on the surface of rat RBL or KM3 cells compared to Daudi and Molt-4 cells, suggesting that additional human-cell-specific factors are not required for the primary interaction of E2 with the cell surface. E2 did not interact with African green monkey (AGM) CD81 on the surface of COS cells, which differs from the hCD81 sequence at four residues within the second extracellular region (EC2) (amino acids [aa] 163, 186, 188, and 196), suggesting that one or more of these residues defines the site of interaction with E2. Various recombinant forms of CD81 EC2 show differences in the ability to bind E2, suggesting that CD81 conformation is important for E2 recognition. Regions of E2 involved in the CD81 interaction were analyzed, and our data suggest that the binding site is of a conformational nature involving aa 480 to 493 and 544 to 551 within the E2 glycoprotein. Finally, we demonstrate that ligation of CD81 by E2661 induced aggregation of lymphoid cells and inhibited B-cell proliferation, demonstrating that E2 interaction with CD81 can modulate cell function. 相似文献
18.
Nicole Hagen Karen Bayer Kathrin R?sch Michael Schindler 《Molecular & cellular proteomics : MCP》2014,13(7):1676-1689
Hepatitis C virus (HCV) is a global health problem and one of the main reasons for chronic liver diseases such as cirrhosis and hepatocellular carcinoma. The HCV genome is translated into a polyprotein which is proteolytically processed into 10 viral proteins. The interactome of the HCV proteins with the host cell has been worked out; however, it remains unclear how viral proteins interact with each other. We aimed to generate the interaction network of these 10 HCV proteins using a flow-cytometry-based FRET assay established in our laboratory (Banning, C., Votteler, J., Hoffmann, D., Koppensteiner, H., Warmer, M., Reimer, R., Kirchhoff, F., Schubert, U., Hauber, J., and Schindler, M. (2010) A flow cytometry-based FRET assay to identify and analyse protein-protein interactions in living cells. PLoS One 5, e9344).HCV proteins were constructed as fusions with the chromophores CFP and YFP. All HCV fusions were expressed and localized to specific subcellular compartments, indicating that they were functional. FACS-FRET measurements identified a total of 20 interactions; 13 of these were previously described and have now been confirmed in living cells via our method. Among the seven novel protein binding pairs, HCV p7 plays a pivotal role. It binds to the HCV capsid protein Core and the two glycoproteins E1 and E2. These interplays were further demonstrated in the relevant context of Huh7.5 liver cells expressing infectious HCV.Our work demonstrates the feasibility of rapidly generating small interaction networks via FACS-FRET and defines the network of intra-HCV protein interactions. Furthermore, our data support an important role of p7 in HCV assembly.Hepatitis C virus (HCV)1 belongs to the family of Flaviviridae and is the only member of the genus Hepacivirus. The ∼9.5-kB positive-strand RNA genome is directly translated via an internal ribosomal entry site into a polyprotein. This is proteolytically processed by cellular and viral proteases into structural (Core, E1, E2) and nonstructural (p7, NS2, NS3, NS4A/B, and NS5A/B) proteins (1). In recent decades, light was shed on the importance and biological relevance of most HCV proteins, which ultimately led to the development of the first specific antiviral therapy involving inhibition of the NS3 serine protease (2). However, because HCV is highly variable and because of the rapid emergence of drug resistance, additional therapeutic approaches are urgently needed (2). An impressive body of data was derived from protein interaction or siRNA screens investigating the interplay of HCV proteins with cellular factors (3–5). Although these screens are essential in order for researchers to understand how HCV manipulates the host cell, their potential benefit for novel therapeutic approaches could be limited. HCV is a chronic viral infection, and targeting host factors might result in drugs with severe adverse effects. Thus, a promising strategy would be to specifically inhibit interactions among viral proteins. Surprisingly, until now, a comprehensive analysis of the putative interactions and the interplay of HCV proteins with each other in living human cells has been lacking.In the present work, we did an extensive and thorough analysis of intra-HCV protein interactions. We used our novel flow-cytometry-based FRET assay that allows rapid assessment of the interplay between proteins in thousands of living cells (6). Therefore, this experimental approach enables quantification and statistical evaluation of all results. From the total of 20 interactions established by FACS-FRET, we chose to further investigate three that were not yet described in the literature. The putative HCV viroporin p7 binds to the structural proteins, and this was verified via biochemical methods in cells expressing fully infectious HCV.The established network of intra-HCV protein interactions in living mammalian cells provides new insights into the biology of this important human pathogen. Furthermore, we identified several HCV protein interactions that could be targeted for antiviral therapy. 相似文献
19.
以[35S」-Na2SO4为示踪物,观察人正常主动脉中的硫酸乙酸肝素蛋白聚糖（HSPG）对培养的第一代人脐静脉内皮细胞（hUVEC）合成蛋白聚糖（PG）的影响．用解聚提取法及离子交换柱层析分离人主动脉HSPG．35S-PGs的混合物用离子交换及凝胶过滤柱层析法分离35S-HSPG,35S-硫酸软骨素-硫酸皮肤素PG（35S-CSDSPG）及35S-硫酸皮肤素PG（35S-DSPG）．结果发现实验组（加HSPG）与对照组（未加HSPG）相比,hU-VEC的35S-PGs总量（培养液+细胞层）无差别,但实验组培养液中35S-PGs总量升高、35S-DSPG、35S-CSDSPG及其相对百分含量均升高,而35S-HSPG及其百分含量降低．细胞层的35S-PGs,35S-HSPG及其相对百分含量降低,35S-DSPG及其相对百分含量升高,而CSDSPG未见差别． 相似文献
20.
Heparan Sulfate Proteoglycans Are Receptors for the Cell-surface Trafficking and Biological Activity of Transglutaminase-2 总被引：1，自引：0，他引：1
Alessandra Scarpellini Ren��e Germack Hugues Lortat-Jacob Takashi Muramatsu Ellen Billett Timothy Johnson Elisabetta A. M. Verderio 《The Journal of biological chemistry》2009,284(27):18411-18423
Transglutaminase type 2 (TG2) is both a protein cross-linking enzyme and a cell adhesion molecule with an elusive unconventional secretion pathway. In normal conditions, TG2-mediated modification of the extracellular matrix modulates cell motility, proliferation and tissue repair, but under continuous cell insult, higher expression and elevated extracellular trafficking of TG2 contribute to the pathogenesis of tissue scarring. In search of TG2 ligands that could contribute to its regulation, we characterized the affinity of TG2 for heparan sulfate (HS) and heparin, an analogue of the chains of HS proteoglycans (HSPGs). By using heparin/HS solid-binding assays and surface plasmon resonance we showed that purified TG2 has high affinity for heparin/HS, comparable to that for fibronectin, and that cell-surface TG2 interacts with heparin/HS. We demonstrated that cell-surface TG2 directly associates with the HS chains of syndecan-4 without the mediation of fibronectin, which has affinity for both syndecan-4 and TG2. Functional inhibition of the cell-surface HS chains of wild-type and syndecan-4-null fibroblasts revealed that the extracellular cross-linking activity of TG2 depends on the HS of HSPG and that syndecan-4 plays a major but not exclusive role. We found that heparin binding did not alter TG2 activity per se. Conversely, fibroblasts deprived of syndecan-4 were unable to effectively externalize TG2, resulting in its cytosolic accumulation. We propose that the membrane trafficking of TG2, and hence its extracellular activity, is linked to TG2 binding to cell-surface HSPG.Transglutaminase type 2 (TG2,2 EC 2.3.2.13) is the most widespread member of a large family of enzymes that catalyze the Ca2+-dependent post-translational modification of proteins leading to intra- or intermolecular Nϵ(γ-glutamyl)lysine bonds (1, 2). Unlike other family members, TG2 is uniquely exported through a yet to be elucidated non-conventional pathway. Once secreted, TG2 finds in the extracellular compartment the ideal conditions of high Ca2+ and low GTP concentration for the activation of its intrinsic transamidation activity (cross-linking) (2, 3). Intracellularly, GTP binding suppresses the Ca2+-dependent cross-linking activity and determines the additional GTPase activity of TG2 (4, 5), which is responsible for signal transduction (6). Once externalized, TG2 remains tightly bound to the cell surface and to the extracellular matrix (ECM) (7, 8), and it is rarely found free in the conditioned medium, unless overexpressed by cell transfection (9).Extracellular TG2 activity is involved in the cross-linking of the ECM, conferring resistance to matrix metalloproteinase and promoting cell-matrix interactions via cross-linking of fibronectin (FN) and collagen (1, 7, 11, 12). TG2 has an additional non-enzymatic role in the matrix as an integrin-β1 co-receptor (8) by supporting RGD-independent cell adhesion to FN (8, 13, 14).Extracellular cross-linking and TG2-mediated adhesion facilitate the repair process in many tissue compartments (1, 2, 15, 16). On the other hand, uncontrolled cross-linking as a consequence of chronic cell insult and secretion of TG2 has been implicated in a number of pathological conditions, including kidney, liver, and pulmonary fibrosis (17–20).Understanding how TG2 is exported and targeted to the cell surface is critical for limiting its cellular secretion and extracellular action. Although a key trigger for TG2 export is cell stress (2, 21, 22), TG2 is not unspecifically released, because extracellular trafficking occurs in the absence of leakage of intracellular components and cells remain viable (23). We know that TG2 requires the tertiary structure of its active site region to be secreted (9); moreover, TG2 is acetylated on the N terminus (24), a process reported to affect membrane targeting of non-conventional secreted proteins (25). Two main binding partners for TG2, FN and integrin-β1, have both been attributed a possible role in the transport of TG2 to the cell surface (8, 26). FN was shown to co-localize with TG2 once released (26), and integrin-β1 to co-associate with TG2 in cells induced to differentiate (8).TG2 has also long been known to have some affinity for heparin (27, 28), a highly sulfated analogue of heparan sulfate (HS) glycosaminoglycan chains, which are abundant constituents of the cell surface/ECM. HS chains are linear polysaccharides consisting of alternating N-acetylated or N-sulfated glucosamine units (GlcNAc or GlcNS), and uronic acids (glucuronic acid GlcA or iduronic acid IdoA residues) (29), which only exist covalently bound to the core protein of cell-surface proteoglycans (syndecans and glypicans) and secreted proteoglycans (29). Heparin binding is a property common to many ECM proteins (29), but the level of affinity has never been established for TG2, which makes it difficult to estimate the real biological significance of this interaction. Heparan sulfate proteoglycans (HSPG) bind ECM ligands through the HS chains, influencing their biological activity, trafficking, and secretion. Among the HSPG subfamilies, the syndecans act as co-receptors for both ECM components and soluble ligands (30), and syndecan-4 has overlapping roles with extracellular TG2 in wound healing and fibrosis (31, 32). In this study, we show that TG2 has a surprisingly high affinity for heparin and HS, raising the hypothesis that HSPG are involved in its biological activity. We demonstrate that HSPGs are essential for the transamidating activity of TG2 at the cell surface and that syndecan-4 acts as a receptor for TG2, which is involved in the trafficking and cell-surface localization, and thus activity of TG2. 相似文献