Association of the SNP rs2623047 in the HSPG modification enzyme SULF1 with an Australian Caucasian Breast Cancer Cohort

Breast cancer is the second most common cancer worldwide and the most common cancer reported in women. This malignant tumour is characterised by a number of specific features including uncontrolled cell proliferation. It ranks fifth in the world as a cause of cancer death overall in developed countries and is the second most frequent cause of cancer death in women. Early diagnosis increases 5-year survival rates up to 95%. Heparan sulfate proteoglycans (HSPGs) are complex proteins composed of a core protein to which a number of highly sulfated side chains attach, ubiquitous to the cell surface and within the extracellular matrix. HSPG side chains are synthesised by a highly co-ordinated process resulting in distinct sulfation patterns, which determine specific interactions with cell-signalling partners including growth factors, their receptors, ligands and morphogens. The enzymes responsible for chain initiation, elongation and sulfation are critical for creating HS chain variability conferring biological functionality. This study investigated a single nucleotide polymorphism in SULF1, the enzyme responsible for the 6-O desulfation of heparan sulfate side chains. We investigated this SNP in an Australian Caucasian case–control breast cancer population and found a significant association between SULF1 and breast cancer at both the allelic and genotypic levels (allele, p = 0.016; genotype, p = 0.032). Our results suggest that the rs2623047 SNP in SULF1 may impact breast cancer susceptibility. Specifically, the T allele of rs2623047 in SULF1 is associated with an increased risk of developing breast cancer in our cohort. The identification of markers including SULF1 may improve detection of this disease at its earliest stages improving patient treatment and prognosis.     

The SULFs,Extracellular Sulfatases for Heparan Sulfate,Promote the Migration of Corneal Epithelial Cells during Wound Repair

Corneal epithelial wound repair involves the migration of epithelial cells to cover the defect followed by the proliferation of the cells to restore thickness. Heparan sulfate proteoglycans (HSPGs) are ubiquitous extracellular molecules that bind to a plethora of growth factors, cytokines, and morphogens and thereby regulate their signaling functions. Ligand binding by HS chains depends on the pattern of four sulfation modifications, one of which is 6-O-sulfation of glucosamine (6OS). SULF1 and SULF2 are highly homologous, extracellular endosulfatases, which post-synthetically edit the sulfation status of HS by removing 6OS from intact chains. The SULFs thereby modulate multiple signaling pathways including the augmentation of Wnt/ß-catenin signaling. We found that wounding of mouse corneal epithelium stimulated SULF1 expression in superficial epithelial cells proximal to the wound edge. Sulf1^−/−, but not Sulf2^−/−, mice, exhibited a marked delay in healing. Furthermore, corneal epithelial cells derived from Sulf1^−/− mice exhibited a reduced rate of migration in repair of a scratched monolayer compared to wild-type cells. In contrast, human primary corneal epithelial cells expressed SULF2, as did a human corneal epithelial cell line (THCE). Knockdown of SULF2 in THCE cells also slowed migration, which was restored by overexpression of either mouse SULF2 or human SULF1. The interchangeability of the two SULFs establishes their capacity for functional redundancy. Knockdown of SULF2 decreased Wnt/ß-catenin signaling in THCE cells. Extracellular antagonists of Wnt signaling reduced migration of THCE cells. However in SULF2- knockdown cells, these antagonists exerted no further effects on migration, consistent with the SULF functioning as an upstream regulator of Wnt signaling. Further understanding of the mechanistic action of the SULFs in promoting corneal repair may lead to new therapeutic approaches for the treatment of corneal injuries.     

Heparin increases the infectivity of Human Papillomavirus Type 16 independent of cell surface proteoglycans and induces L1 epitope exposure

Human Papillomaviruses (HPVs) are the etiological agents of cervical cancer, and HPV‐16 is the most prevalent type. Several HPVs require heparan sulfate proteoglycans (HSPGs) for cell binding. Here, we analyse the phenomenon that preincubation of HPV‐16 with increasing concentrations of heparin results in partial restoration rather than more efficient inhibition of infection. While corroborating that the HSPGs are cell‐binding receptors for HPV‐16, heparin‐preincubated virus bound to the extracellular matrix (ECM) via laminin‐332. Furthermore, the interaction of virions with heparin, a representative of the highly sulfated S‐domains of heparan sulfate (HS) chains of HSPGs, allowed HPV‐16 infection in the absence of cell surface HSPGs. Therefore, we concluded that specific glycan moieties but not specific HSPG protein backbones are required for infection. The increased binding of an epitope‐specific antibody to the viral capsid after heparin binding suggested that initial conformational changes in the HPV‐16 virion occur during infection by interaction with‘heparin‐like’ domains of cellular HSPGs. We propose that HS sequences with specific sulfation patterns are required to facilitate HPV‐16 infection.     

Further evidence that papillomavirus capsids exist in two distinct conformations

Cell surface heparan sulfate proteoglycans (HSPGs) serve as primary attachment receptors for human papillomaviruses (HPVs). To demonstrate that a biologically functional HPV-receptor interaction is restricted to a specific subset of HSPGs, we first explored the role of HSPG glucosaminoglycan side chain modifications. We demonstrate that HSPG O sulfation is essential for HPV binding and infection, whereas de-N-sulfated heparin interfered with VLP binding but not with HPV pseudoinfection. This points to differences in VLP-HSPG and pseudovirion-HSPG interactions. Interestingly, internalization kinetics of VLPs and pseudovirions, as measured by fluorescence-activated cell sorting analysis, also differ significantly with approximate half times of 3.5 and 7.5 h, respectively. These data suggest that differences in HSPG binding significantly influence postbinding events. We also present evidence that pseudovirions undergo a conformational change after cell attachment. A monoclonal antibody (H33.J3), which displays negligible effectiveness in preattachment neutralization assays, efficiently neutralizes cell-bound virions. However, no difference in H33.J3 binding to pseudovirions and VLPs was observed in enzyme-linked immunosorbent assay and virus capture assays. In contrast to antibody H33.B6, which displays equal efficiencies in pre- and postattachment neutralization assays, H33.J3 does not block VLP binding to heparin, demonstrating that it interferes with steps subsequent to virus binding. Our data strongly suggest that H33.J3 recognizes a conformation-dependent epitope in capsid protein L1, which undergoes a structural change after cell attachment.     

SULF1 and SULF2 regulate heparan sulfate-mediated GDNF signaling for esophageal innervation

Heparan sulfate (HS) plays an essential role in extracellular signaling during development. Biochemical studies have established that HS binding to ligands and receptors is regulated by the fine 6-O-sulfated structure of HS; however, mechanisms that control sulfated HS structure and associated signaling functions in vivo are not known. Extracellular HS 6-O-endosulfatases, SULF1 and SULF2, are candidate enzymatic regulators of HS 6-O-sulfated structure and modulate HS-dependent signaling. To investigate Sulf regulation of developmental signaling, we have disrupted Sulf genes in mouse and identified redundant functions of Sulfs in GDNF-dependent neural innervation and enteric glial formation in the esophagus, resulting in esophageal contractile malfunction in Sulf1(-/-);Sulf2(-/-) mice. SULF1 is expressed in GDNF-expressing esophageal muscle and SULF2 in innervating neurons, establishing their direct functions in esophageal innervation. Biochemical and cell signaling studies show that Sulfs are the major regulators of HS 6-O-desulfation, acting to reduce GDNF binding to HS and to enhance GDNF signaling and neurite sprouting in the embryonic esophagus. The functional specificity of Sulfs in GDNF signaling during esophageal innervation was established by showing that the neurite sprouting is selectively dependent on GDNF, but not on neurotrophins or other signaling ligands. These findings provide the first in vivo evidence that Sulfs are essential developmental regulators of cellular HS 6-O-sulfation for matrix transmission and reception of GDNF signal from muscle to innervating neurons.     

Genetic Variation in SULF2 Is Associated with Postprandial Clearance of Triglyceride-Rich Remnant Particles and Triglyceride Levels in Healthy Subjects

Context

Nonfasting (postprandial) triglyceride concentrations have emerged as a clinically significant cardiovascular disease risk factor that results from accumulation of remnant triglyceride-rich lipoproteins (TRLs) in the circulation. The remnant TRLs are cleared from the circulation by hepatic uptake, but the specific mechanisms involved are unclear. The syndecan-1 heparan sulfate proteoglycan (HSPG) pathway is important for the hepatic clearance of remnant TRLs in mice, but its relevance in humans is unclear.

Objective

We sought to determine whether polymorphisms of the genes responsible for HSPG assembly and disassembly contribute to atherogenic dyslipoproteinemias in humans.

Patients And Design

We performed an oral fat load in 68 healthy subjects. Lipoproteins (chylomicrons and very low density lipoproteins 1 and 2) were isolated from blood, and the area under curve and incremental area under curve for postprandial variables were calculated. Single nucleotide polymorphisms in genes encoding syndecan-1 and enzymes involved in the synthesis or degradation of HSPG were genotyped in the study subjects.

Results

Our results indicate that the genetic variation rs2281279 in SULF2 associates with postprandial clearance of remnant TRLs and triglyceride levels in healthy subjects. Furthermore, the SNP rs2281279 in SULF2 associates with hepatic SULF2 mRNA levels.

Conclusions

In humans, mild but clinically relevant postprandial hyperlipidemia due to reduced hepatic clearance of remnant TRLs may result from genetic polymorphisms that affect hepatic HSPG.     

A novel SULF1 splice variant inhibits Wnt signalling but enhances angiogenesis by opposing SULF1 activity

The importance of SULF1 in modulating the activities of multiple signalling molecules is now well established. Several studies, however, reported little or no effect of Sulf1 null mutations, questioning the relevance of this gene to in vivo development. The failure of SULF1 deletion to influence development may be predicted if one considers the involvement of a naturally occurring SULF1 antagonist, generated by alternative splicing of the same gene. We demonstrate that while the previously described SULF1 (SULF1A) enhances Wnt signalling, the novel shorter isoform (SULF1B) inhibits Wnt signalling. Our studies show developmental stage specific changes in the proportions of SULF1A and SULF1B isoforms at both the mRNA and protein levels in many developing tissues, with particularly pronounced changes in developing and adult blood vessels. Unlike SULF1A, SULF1B promotes angiogenesis and is highly expressed in endothelial cells during early blood vessel development while SULF1A predominates in mature endothelial cells. We propose that the balance of two naturally occurring SULF1 variants, with opposing functional activities, may regulate the overall net activities of multiple secreted factors and the associated signalling cascades essential for normal development and maintenance of most tissues.     

Heparan Sulfate Proteoglycans Play a Dual Role in Regulating Fibroblast Growth Factor-2 Mitogenic Activity in Human Breast Cancer Cells

The human breast cancer cell lines MCF-7 and MDA-MB-231 differ in their responsiveness to fibroblast growth factor-2 (FGF-2). This growth factor stimulates proliferation in well-differentiated MCF-7 cells, whereas the less well-differentiated MDA-MB-231 cells are insensitive to this molecule. To investigate the potential regulation of FGF-2 mitogenic activity by heparan sulfate proteoglycans (HSPG), we have treated human breast cancer cells by glycosaminoglycan degrading enzymes or a metabolic inhibitor of proteoglycan sulfation: sodium chlorate. The interaction between FGF-2 and proteoglycans was assayed by examining the binding of¹²⁵I-FGF-2 to breast cancer cell cultures as well as to cationic membranes loaded with HSPG. Using MCF-7 cells, we showed that heparinase treatment inhibited FGF-2 binding to HSPG and completely abolished FGF-2 induced growth; chlorate treatment of MCF-7 cells decreased FGF-2 binding to HSPG and cell responsiveness in a dose-dependent manner. This demonstrates a requirement of adequately sulfated HSPG for FGF-2 growth-promoting activity on MCF-7 cells. In highly invasive MDA-MB-231 cells which produce twice as much HSPG as MCF-7 cells and which are not normally responsive to exogenously added FGF-2, chlorate treatment decreased FGF-2 binding to HSPG and induced FGF-2 mitogenic effect. This chlorate effect was dose dependent and observed at concentrations of 10–30 mM;higher chlorate concentrations completely abolished the FGF-2 effect. This shows that the HSPG level of sulfation can also negatively regulate the biological activity of FGF-2. Taken together, these results demonstrate a crucial role for HSPG in both positive and negative control of FGF-2 mitogenic activity in breast cancer cell proliferation.     

SULF1/SULF2 splice variants differentially regulate pancreatic tumour growth progression

This study highlights the highly dynamic nature of SULF1/SULF2 splice variants in different human pancreatic cancers that regulate the activities of multiple cell signalling pathways in development and disease. Most pancreatic tumours expressed variable levels of both SULF1 and SULF2 variants including some expression during inflammation and pancreatitis. Many ductal and centro-acinar cell-derived pancreatic tumours are known to evolve into lethal pancreatic ductal adenocarcinomas but the present study also detected different stages of such tumour progression in the same tissue biopsies of not only acinar cell origin but also islet cell-derived cancers. The examination of caerulein-induced pancreatic injury and tumorigenesis in a Kras-driven mouse model confirmed the activation and gradual increase of SULF1/SULF2 variants during pancreatitis and tumorigenesis but with reduced levels in Stat3 conditional knockout mice with reduced inflammation. The significance of differential spatial and temporal patterns of specific SULF1/SULF2 splice variant expression during cancer growth became further apparent from their differential stimulatory or inhibitory effects on growth factor activities, tumour growth and angiogenesis not only during in vitro but also in vivo growth thus providing possible novel therapeutic targets.     

The heparan sulfate proteoglycan (HSPG) glypican‐3 mediates commitment of MC3T3‐E1 cells toward osteogenesis

Heparan sulfate (HS) sugar chains attached to core proteoglycans (PGs) termed HSPGs mediate an extensive range of cell–extracellular matrix (ECM) and growth factor interactions based upon their sulfation patterns. When compared with non‐osteogenic (maintenance media) culture conditions, under established osteogenic culture conditions, MC3T3‐E1 cells characteristically increase their osteogenic gene expression profile and switch their dominant fibroblast growth factor receptor (FGFR) from FGFR1 (0.5‐fold decrease) to FGFR3 (1.5‐fold increase). The change in FGFR expression profile of the osteogenic‐committed cultures was reflected by their inability to sustain an FGF‐2 stimulus, but respond to BMP‐2 at day 14 of culture. The osteogenic cultures decreased their chondroitin and dermatan sulfate PGs (biglycan, decorin, and versican), but increased levels of the HS core protein gene expression, in particular glypican‐3. Commitment and progress through osteogenesis is accompanied by changes in FGFR expression, decreased GAG initiation but increased N‐ and O‐sulfation and reduced remodeling of the ECM (decreased heparanase expression) resulting in the production of homogenous (21 kDa) HS chain. With the HSPG glypican‐3 expression strongly upregulated in these processes, siRNA was used to knockdown this gene to examine the effect on osteogenic commitment. Reduced glypican‐3 abrogated the expression of Runx2, and thus differentiation. The reintroduction of this HSPG into Runx2‐null cells allowed osteogenesis to proceed. These results demonstrate the dependence of osteogenesis on specific HS chains, in particular those associated with glypican‐3. J. Cell. Physiol. 220: 780–791, 2009. © 2009 Wiley‐Liss, Inc.     

Role of Heparan Sulfate in Attachment to and Infection of the Murine Female Genital Tract by Human Papillomavirus

The host factors required for in vivo infection have not been investigated for any papillomavirus. Using a recently developed murine cervicovaginal challenge model, we evaluated the importance of heparan sulfate proteoglycans (HSPGs) in human papillomavirus (HPV) infection of the murine female genital tract. We examined HPV type 16 (HPV16) as well as HPV31 and HPV5, for which some evidence suggests that they may differ from HPV16 in their utilization of HSPGs as their primary attachment factor in vitro. Luciferase-expressing pseudovirus of all three types infected the mouse genital tract, although HPV5, which normally infects nongenital epidermis, was less efficient. Heparinase III treatment of the genital tract significantly inhibited infection of all three types by greater than 90% and clearly inhibited virion attachment to the basement membrane and cell surfaces, establishing that HSPGs are the primary attachment factors for these three viruses in vivo. However, the pseudoviruses differed in their responses to treatment with various forms of heparin, a soluble analog of heparan sulfate. HPV16 and HPV31 infections were effectively inhibited by a highly sulfated form of heparin, but HPV5 was not, although it bound the compound. In contrast, a N-desulfated and N-acylated variant preferentially inhibited HPV5. Inhibition of infection paralleled the relative ability of the variants to inhibit basement membrane and cell surface binding. We speculate that cutaneous HPVs, such as HPV5, and genital mucosal HPVs, such as HPV16 and -31, may have evolved to recognize different forms of HSPGs to enable them to preferentially infect keratinocytes at different anatomical sites.Papillomaviruses (PVs) are icosahedral DNA viruses that have evolved into numerous genotypes that productively infect diverse vertebrates in a species-specific manner. These viruses also display strict tissue specificity, productively infecting only epithelial cells in the skin and mucosa. These features have inhibited viral propagation in vitro and retarded the development of in vivo models for infection. The human PVs (HPVs) belonging to the alpha genus preferentially infect the genital mucosa, and a subset of this genus include the types (e.g., HPV16, -18, -31, -33, and -45) that are the causative agents of cervical carcinoma. HPV types belonging to the beta genus generally cause asymptomatic skin infections, but certain beta types (e.g., HPV5 and -8) are associated with cutaneous squamous cell carcinomas in individuals with the rare genetic disorder epidermodysplasia verruciformis.As with other viruses, virion attachment to the host cell is required for successful PV infection. In vitro studies have implicated cell surface heparan sulfate (HS) proteoglycans (HSPGs) as the primary attachment factors for most HPV types (13, 15). HSPGs are composed of a core protein with covalently attached repeating disaccharide units known as glycosaminoglycans. Posttranslational modification of the glycosaminoglycans by acetylation and sulfation leads to substantial heterogeneity that varies across cell type and growth conditions (20, 23). HSPGs are nearly ubiquitously expressed on mammalian cell surfaces, where they are involved in diverse biological processes, including organogenesis, growth factor and cytokine binding, and wound healing. They are also integral components of the basement membrane (BM), the specialized extracellular matrix (ECM) that surrounds most tissues. In this locale, their putative functions include regulation of BM permeability, binding of growth factors, and a role in cellular adhesion (reviewed in reference 10).HSPGs can also help mediate infection by acting as receptors/coreceptors for some bacterial and viral pathogens (reviewed in reference 12). It is well established that HPV16 utilizes attachment to HSPGs for efficient infection in vitro. However, in vitro studies investigating other HPV types, such as HPV31 and HPV5, have described possible differences. Infection with HPV31 has been reported to be HSPG independent in keratinocyte lines such as HaCaT, although not in other, more transformed lines (17). Also, heparin, which shares the same disaccharide units with HS but is more homogeneous and has a higher level of sulfation, did not inhibit HPV5 infection at doses that efficiently blocked HPV16 infection in vitro (3).In addition to binding cell surfaces, PVs also bind strongly to the ECM deposited by epithelial cells in vitro and onto the BM in vivo (5, 9, 18). Laminin 5 appears to be the primary molecule mediating in vitro ECM binding (6). However, interaction with an HS moiety on the ECM may be critical for transfer of infectious virions to the cell surface (21). PV cell surface binding in vitro may arise independently of ECM binding; however, the kinetics of in vivo infection suggest that virion binding to the BM may be essential. It is therefore possible that this aspect of in vivo infection could differ from what has been seen in vitro.It is unclear if HSPGs play any role in PV infection in vivo, as the cellular factors and processes involved in PV infection of epithelial tissues in vivo have not been examined previously. There is a clear precedent of in vitro HSPG dependence for infection of cell lines that does not reflect an in vivo function. For instance, HSPGs facilitate human immunodeficiency virus infection of certain permissive lymphoid cell lines in vitro, yet they play no role in the infection of primary blood lymphocytes (14).In this study, we utilized our recently developed murine cervicovaginal challenge model (18), which is useful to examine establishment of HPV infection in vivo, to investigate the HSPG dependency of HPV infection, examining both binding and infection of HPV16 pseudovirions in the presence of agents that either compete for HS binding or remove HS from cell surfaces. Because of the published data suggesting possible differences from HPV16 in HSPG dependency for in vitro infection, we also evaluated HPV5 and HPV31 pseudovirions.     

Safe haven under constant attack—The Chlamydia‐containing vacuole

Chlamydia belong to the group of obligate intracellular bacteria that reside in a membrane bound vacuole during the entire intracellular phase of their life cycle. This vacuole called inclusion shields the bacteria from adverse influences in the cytosol of the host cell like the destructive machinery of the cell‐autonomous defence system. The inclusion thereby prevents the digestion and eradication in specialised compartments of the intact and viable cell called phagolysosomes or autophagolysosomes. It is becoming more and more evident that keeping the inclusion intact also prevents the onset of cell intrinsic cell death programmes that are activated upon damage of the inclusion and direct the cell to destruct itself and the pathogen inside. Chlamydia secrete numerous proteins into the inclusion membrane to protect and stabilise their unique niche inside the host cell. We will focus in this review on the diverse attack strategies of the host aiming at the destruction of the Chlamydia‐containing inclusion and will summarise the current knowledge on the protection mechanisms elaborated by the bacteria to maintain the integrity of their replication niche.     

Heparan sulfate-independent cell binding and infection with furin-precleaved papillomavirus capsids

Papillomavirus infection normally involves virion binding to cell surface heparan sulfate proteoglycans (HSPGs). However, we found that human papillomavirus type 16 pseudovirions efficiently bound and infected cells lacking HSPGs if their L2 capsid protein was precleaved by furin, a cellular protease required for infection. The inability of pseudovirions to efficiently bind and infect cultured primary keratinocytes was also overcome by furin precleavage, suggesting that the defect involves altered HSPG modification. We conclude that the primary function of HSPG binding is to enable cell surface furin cleavage of L2 and that binding to a distinct cell surface receptor(s) is a subsequent step of papillomavirus infection.     

LTBP-2 has multiple heparin/heparan sulfate binding sites

Latent transforming growth factor-beta-1 binding protein-2 (LTBP-2) is a protein of poorly understood function associated with fibrillin-1-containing microfibrils during elastinogenesis. In this study we investigated the molecular interactions of LTBP-2 with heparin and heparan sulfate proteoglycans (HSPGs) since unidentified cell surface HSPGs are critical for normal fiber assembly. In solid phase assays, heparin conjugated to albumin (HAC) bound strongly to recombinant full-length human LTBP-2. This interaction was completely blocked by addition of excess heparin, but not chondroitin sulfate, confirming specificity. Analysis of binding to LTBP-2 fragments showed that HAC bound strongly to N-terminal fragment LTBP-2 NT(H) and more weakly to central fragment LTBP-2 C(H). No binding was detected to C-terminal fragment LTBP-2 CT(H). Kds for heparin binding were calculated for full-length LTBP-2, LTBP-2 NT(H) and LTBP-2 C(H) as 0.9 nM, 0.7 nM and 80 nM respectively. HAC interaction with fragment LTBP-2 NT(H) was not sensitive to EDTA or EGTA indicating that binding had no requirement for Ca²⁺ ions whereas HAC binding to fragment LTBP-2 C(H) was markedly reduced by these chelating agents indicating a degree of Ca²⁺ dependence. Inhibition studies with synthetic peptides identified three major heparin binding sequences in fragment LTBP-2 NT(H), including sequence LTEKIKKIKIV in the first large cysteine-free domain of LTBP-2, adjacent to the previously identified fibulin-5 binding site. LTBP-2 was found to interact strongly in a heparin-inhibitable manner with cell surface HSPG syndecan-4, but showed no interaction with recombinant syndecan-2. LTBP-2 also showed strong interaction with the heparan sulfate chains of basement membrane HSPG, perlecan. The potential importance of HSPG–LTBP-2 interactions in elastic fiber assembly and microfibril attachment to basement membranes is discussed.     

Roles of heparan sulfate sulfation in dentinogenesis

Cell surface heparan sulfate (HS) is an essential regulator of cell signaling and development. HS traps signaling molecules, like Wnt in the glycosaminoglycan side chains of HS proteoglycans (HSPGs), and regulates their functions. Endosulfatases Sulf1 and Sulf2 are secreted at the cell surface to selectively remove 6-O-sulfate groups from HSPGs, thereby modifying the affinity of cell surface HSPGs for its ligands. This study provides molecular evidence for the functional roles of HSPG sulfation and desulfation in dentinogenesis. We show that odontogenic cells are highly sulfated on the cell surface and become desulfated during their differentiation to odontoblasts, which produce tooth dentin. Sulf1/Sulf2 double null mutant mice exhibit a thin dentin matrix and short roots combined with reduced expression of dentin sialophosphoprotein (Dspp) mRNA, encoding a dentin-specific extracellular matrix precursor protein, whereas single Sulf mutants do not show such defective phenotypes. In odontoblast cell lines, Dspp mRNA expression is potentiated by the activation of the Wnt canonical signaling pathway. In addition, pharmacological interference with HS sulfation promotes Dspp mRNA expression through activation of Wnt signaling. On the contrary, the silencing of Sulf suppresses the Wnt signaling pathway and subsequently Dspp mRNA expression. We also show that Wnt10a protein binds to cell surface HSPGs in odontoblasts, and interference with HS sulfation decreases the binding affinity of Wnt10a for HSPGs, which facilitates the binding of Wnt10a to its receptor and potentiates the Wnt signaling pathway, thereby up-regulating Dspp mRNA expression. These results demonstrate that Sulf-mediated desulfation of cellular HSPGs is an important modification that is critical for the activation of the Wnt signaling in odontoblasts and for production of the dentin matrix.     

Combinatorial Roles of Heparan Sulfate Proteoglycans and Heparan Sulfates in Caenorhabditis elegans Neural Development

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.     

SULF2 Expression Is a Potential Diagnostic and Prognostic Marker in Lung Cancer

Aims

Lung cancer is one of the most deadly cancers; median survival from diagnosis is less than one year in those with advanced disease. Novel lung cancer biomarkers are desperately needed. In this study, we evaluated SULF2 expression by immunohistochemistry and its association with overall survival in a cohort of patients with non-small cell lung cancer (NSCLC). We also looked for the presence of SULF2 protein in plasma to evaluate its potential as an early detection biomarker for NSCLC.

Methods

We identified patients who underwent surgical resection for pulmonary adenocarcinoma or squamous cell carcinoma at our institution. A section from each paraffin-embedded specimen was stained with a SULF2 antibody. A pathologist determined the percentage and intensity of tumor cell staining. Survival analysis was performed using a multivariate Cox proportional hazards model. Using a novel SULF2 ELISA assay, we analyzed plasma levels of SULF2 in a small cohort of healthy donors and patients with early stage NSCLC.

Results

SULF2 staining was present in 82% of the lung cancer samples. Squamous cell carcinomas had a higher mean percentage of staining than adenocarcinomas (100% vs. 60%; p<0.0005). After adjusting for age, sex, race, histologic type, stage, and neoadjuvant therapy, there was a non-significant (31%; p = 0.65) increase in the risk of death for patients with adenocarcinoma with SULF2 staining in tumor cells. In contrast, there was a significant decrease in the risk of death (89%; p = 0.02) for patients with squamous cell carcinoma with SULF2 staining in tumor cells. SULF2 protein was present in plasma of patients with early stage NSCLC, and soluble SULF2 levels increased with age. Finally, plasma SULF2 levels were significantly elevated in early stage NSCLC patients, compared to healthy controls.

Conclusions

Tumor expression of SULF2 may affect prognosis in NSCLC, while blood SULF2 levels may have a significant role in the diagnosis of this fatal disease.     

Requirements for receptor engagement during infection by adenovirus complexed with blood coagulation factor X

Human adenoviruses from multiple species bind to coagulation factor X (FX), yet the importance of this interaction in adenovirus dissemination is unknown. Upon contact with blood, vectors based on adenovirus serotype 5 (Ad5) binds to FX via the hexon protein with nanomolar affinity, leading to selective uptake of the complex into the liver and spleen. The Ad5:FX complex putatively targets heparan sulfate proteoglycans (HSPGs). The aim of this study was to elucidate the specific requirements for Ad5:FX-mediated cellular uptake in this high-affinity pathway, specifically the HSPG receptor requirements as well as the role of penton base-mediated integrin engagement in subsequent internalisation. Removal of HS sidechains by enzymatic digestion or competition with highly-sulfated heparins/heparan sulfates significantly decreased FX-mediated Ad5 cell binding in vitro and ex vivo. Removal of N-linked and, in particular, O-linked sulfate groups significantly attenuated the inhibitory capabilities of heparin, while the chemical inhibition of endogenous HSPG sulfation dose-dependently reduced FX-mediated Ad5 cellular uptake. Unlike native heparin, modified heparins lacking O- or N-linked sulfate groups were unable to inhibit Ad5 accumulation in the liver 1h after intravascular administration of adenovirus. Similar results were observed in vitro using Ad5 vectors possessing mutations ablating CAR- and/or α(v) integrin binding, demonstrating that attachment of the Ad5:FX complex to the cell surface involves HSPG sulfation. Interestingly, Ad5 vectors ablated for α(v) integrin binding showed markedly delayed cell entry, highlighting the need for an efficient post-attachment internalisation signal for optimal Ad5 uptake and transport following surface binding mediated through FX. This study therefore integrates the established model of α(v) integrin-dependent adenoviral infection with the high-affinity FX-mediated pathway. This has important implications for mechanisms that define organ targeting following contact of human adenoviruses with blood.