ADAM and ADAMTS family proteins and their role in the colorectal cancer etiopathogenesis

The ADAM and ADAMTS families, also called adamalysins belong to an important group of extracellular matrix proteins. The ADAMs family belong to both the transmembrane and secreted proteins, while ADAMTS family only contains secreted forms. Adamalysins play an important role in the cell phenotype regulation via their activities in signaling pathways, cell adhesion and migration. The human proteome contains 21 ADAM, and 19 ADAMTS proteins, which are involved in extracellular matrix remodeling, shedding of various substrates such as: adhesion ligands, growth factors, their receptors and diverse cytokines. Recent studies provide evidence that adamalysins play a crucial role in colorectal cancer (CRC) etiopathogenesis. It seems possible that adamalysins might be used as CRC prediction markers or potential pharmaceutical targets. [BMB Reports 2013; 46(3): 139-150]     

The contribution of adhesion signaling to lactogenesis

The mammary gland undergoes hormonally controlled cycles of pubertal maturation, pregnancy, lactation, and involution, and these processes rely on complex signaling mechanisms, many of which are controlled by cell–cell and cell–matrix adhesion. The adhesion of epithelial cells to the extracellular matrix initiates signaling mechanisms that have an impact on cell proliferation, survival, and differentiation throughout lactation. The control of integrin expression on the mammary epithelial cells, the composition of the extracellular matrix and the presence of secreted matricellular proteins all contribute to essential adhesion signaling during lactogenesis. In vitro and in vivo studies, including the results from genetically engineered mice, have shed light on the regulation of these processes at the cell and tissue level and have led to increased understanding of the essential signaling components that are regulated in temporal and cell specific manner during lactogenesis. Recent studies suggest that a secreted matricellular protein, CTGF/CCN2, may play a role in lactogenic differentiation through binding to β1 integrin complexes, enhancing the production of extracellular matrix components and contributions to cell adhesion signaling.     

Extracellular acidosis accelerates bone resorption by enhancing osteoclast survival, adhesion, and migration

Acidic extracellular pH promotes osteoporotic bone loss by osteoclast activation. However, the change of osteoclastic cell behavior in acidosis-stimulated bone resorption process is unknown. We found that lowering extracellular pH induced an increase in the survival, adhesion, and migration of mature osteoclasts with a full actin ring, leading to enhanced pit formation on dentine slices. Acidosis upregulated osteopontin, which is an Arg-Gly-Asp (RGD) motif-containing matrix protein secreted from osteoclasts and acts as a common modulator for their survival, adhesion, and migration. A synthetic RGD peptide treatment blocked acidosis-induced osteoclast adhesion and migration, likely by competing with the RGD motif-containing extracellular matrix proteins for cell surface integrin binding. We finally observed that acidosis was associated with activation of osteoclast survival/adhesion/migration-related Pyk2, Cbl-b, and Src signals. Collectively, the findings indicate that extracellular acidosis stimulates bone resorption by extending osteoclast survival and facilitating osteoclast adhesion and migration.     

Transforming Growth Factor-β1 Increases the Adhesion of MDA-MB-231 Mammary Adenocarcinoma Cells to the Microvascular Subendothelium

The increase of tumor cell adhesion to the Subendothelium in the presence of TGF-β1 is thought to be mediated by two major events: an enrichment of extracellular matrix proteins secreted by endothelial cells and an increase of the integrins on the surface of tumor cells. In this study, we analyzed the effect of TGF-β1 on the adhesion of a mammary adenocarcinoma cell line (MDA-MB-231) to the matrix of human microvascular endothelial cells (HMEC-1). The adhesion of TGF-β1 -treated tumor cells to a non-treated matrix or to purified matrix proteins was enhanced, white no increase was observed when non-treated tumor cells were let to adhere to a matrix secreted by HMEC-1 in the presence of the cytokine. Thus, the increase of cell adhesion was due to the effect of TGF-β1 on tumor cells and not to the matrix enrichment induced by this cytokine. The hyper-adhesion was inhibited by the RGD peptide and EDTA indicating that integrins were involved. Integrin subunits concentrations (α5, αv and β1) on the surface of TGF-β1-treated tumor cells were not modified, while confocal microscopy showed a reorganization of β1 integrin subunits on the cell surface and in the cytoplasm resulting in actin fibers reorganization in the cytoskeleton. This indicates that the enhanced adhesion of TGF-β1-treated MDA-MB-231 cells to the subendothelium is due to a qualitative change of integrins.     

Transforming growth factor-beta 1 increases the adhesion of MDA-MB-231 mammary adenocarcinoma cells to the microvascular subendothelium

The increase of tumor cell adhesion to the subendothelium in the presence of TGF-beta 1 is thought to be mediated by two major events: an enrichment of extracellular matrix proteins secreted by endothelial cells and an increase of the integrins on the surface of tumor cells. In this study, we analyzed the effect of TGF-beta 1 on the adhesion of a mammary adenocarcinoma cell line (MDA-MB-231) to the matrix of human microvascular endothelial cells (HMEC-1). The adhesion of TGF-beta 1-treated tumor cells to a non-treated matrix or to purified matrix proteins was enhanced, while no increase was observed when non-treated tumor cells were let to adhere to a matrix secreted by HMEC-1 in the presence of the cytokine. Thus, the increase of cell adhesion was due to the effect of TGF-beta 1 on tumor cells and not to the matrix enrichment induced by this cytokine. The hyper-adhesion was inhibited by the RGD peptide and EDTA indicating that integrins were involved. Integrin subunits concentrations (alpha 5, alpha v and beta 1) on the surface of TGF-beta 1-treated tumor cells were not modified, while confocal microscopy showed a reorganization of beta 1 integrin subunits on the cell surface and in the cytoplasm resulting in actin fibers reorganization in the cytoskeleton. This indicates that the enhanced adhesion of TGF-beta 1-treated MDA-MB-231 cells to the subendothelium is due to a qualitative change of integrins.     

The CCN family of genes: a perspective on CCN biology and therapeutic potential

The CCN family of genes currently comprises six secreted proteins (designated CCN1-6 after Cyr61/CCN1; ctgf/CCN2; Nov/CCN3; WISP1/CCN4; WISP2/CCN5, WISP3/CCN6) with a similar mosaic primary structure. It is now well accepted that CCN proteins are not growth factors but matricellular proteins that modify signaling of other molecules, in particular those associated with the extracellular matrix. CCN proteins are involved in mitosis, adhesion, apoptosis, extracellular matrix production, growth arrest and migration of multiple cell types. Since their first identification as matricellular factors, the CCN proteins now figure prominently in a variety of major diseases and are now considered valid candidates for therapeutic targeting. Dissection of the molecular mechanisms governing the biological properties of these proteins is being actively pursued by an expanding network of scientists around the globe who will meet this year at the 5th International Workshop on the CCN family of Genes, organized by the International CCN Society ( http://ccnsociety.com ), home for an international cadre of collaborators working in the CCN field.     

Molecular mechanisms of node of Ranvier formation

Action potential propagation along myelinated nerve fibers requires high-density protein complexes that include voltage-gated Na(+) channels at the nodes of Ranvier. Several complementary mechanisms may be involved in node assembly including: (1) interaction of nodal cell adhesion molecules with the extracellular matrix; (2) restriction of membrane protein mobility by paranodal junctions; and (3) stabilization of ion channel clusters by axonal cytoskeletal scaffolds. In the peripheral nervous system, a secreted glial protein at the nodal extracellular matrix interacts with axonal cell adhesion molecules to initiate node formation. In the central nervous system, both glial soluble factors and paranodal axoglial junctions may function in a complementary manner to contribute to node formation.     

Emerging roles of ADAM and ADAMTS metalloproteinases in cancer

A disintegrin and metalloproteinases (ADAMs) are a recently discovered family of proteins that share the metalloproteinase domain with matrix metalloproteinases (MMPs). Among this family, structural features distinguish the membrane-anchored ADAMs and the secreted ADAMs with thrombospondin motifs referred to as ADAMTSs. By acting on a large panel of membrane-associated and extracellular substrates, they control several cell functions such as adhesion, fusion, migration and proliferation. The current review addresses the contribution of these proteinases in the positive and negative regulation of cancer progression as mainly mediated by the regulation of growth factor activities and integrin functions.     

Cell Wall and Secreted Proteins of Candida albicans: Identification, Function, and Expression

The cell wall is essential to nearly every aspect of the biology and pathogenicity of Candida albicans. Although it was intially considered an almost inert cellular structure that protected the protoplast against osmotic offense, more recent studies have demonstrated that it is a dynamic organelle. The major components of the cell wall are glucan and chitin, which are associated with structural rigidity, and mannoproteins. The protein component, including both mannoprotein and nonmannoproteins, comprises some 40 or more moieties. Wall proteins may differ in their expression, secretion, or topological location within the wall structure. Proteins may be modified by glycosylation (primarily addition of mannose residues), phosphorylation, and ubiquitination. Among the secreted enzymes are those that are postulated to have substrates within the cell wall and those that find substrates in the extracellular environment. Cell wall proteins have been implicated in adhesion to host tissues and ligands. Fibrinogen, complement fragments, and several extracellular matrix components are among the host proteins bound by cell wall proteins. Proteins related to the hsp70 and hsp90 families of conserved stress proteins and some glycolytic enzyme proteins are also found in the cell wall, apparently as bona fide components. In addition, the expression of some proteins is associated with the morphological growth form of the fungus and may play a role in morphogenesis. Finally, surface mannoproteins are strong immunogens that trigger and modulate the host immune response during candidiasis.     

Cellular ageing of Alzheimer's disease and Down syndrome cells in culture.

In Alzheimer's disease, the typical clinical symptoms and the pathological findings are restricted to the nervous system. Nevertheless, like in some other neurologic-metabolic disorders, several alterations are found in peripheral tissues. The aim of this study was to examine whether cellular properties which can be studied in vitro on skin fibroblast cultures obtained from Alzheimer's disease patients differ from those of age-matched controls. Down syndrome patients were also included, since the same neuropathological findings are present in nearly 100% of Down syndrome patients. Since Alzheimer's disease is an age-related disorder, we examined the growth characteristics of skin fibroblast cultures. The in vitro senescence of cultured fibroblasts is widely accepted as a model for in vivo ageing. Normal growth properties were found. We can conclude that there is no premature ageing in Alzheimer's disease nor in Down syndrome and that the abnormalities found in peripheral tissues are related to the disease itself. The beta amyloid precursor protein (beta APP) has been shown to have adhesive interactions. We therefore investigated several parameters of adhesion in the skin fibroblast cultures: adhesion to a fibronectin coat, adhesion to extracellular matrix of Alzheimer's disease cultures and semi-quantification of adhesion-related molecules (beta 1-integrin, cell surface proteoglycans, extracellular matrix proteoglycans, extracellular matrix fibronectin). No significant difference was found in the parameters examined.     

Anti-adhesive molecules of the extracellular matrix.

The prototype extracellular matrix glycoproteins had been identified on the basis of their activity in promoting cell adhesion and spreading. Recently, more and more evidence is accumulating that the reverse effect of extracellular matrix proteins, namely the inhibition of cell adhesion and spreading, may be equally important for proper cell function during morphogenesis and development. Several anti-adhesive proteins have been described and their mechanisms of action are being investigated.     

The plant extracellular transglutaminase: what mammal analogues tell

The extracellular transglutaminases (TGs) in eukaryotes are responsible for the post-translational modification of proteins through different reactions, cross-linking being the best known. In higher plants, extracellular TG appears to be involved in roles similar to those performed by the mammalian counterparties. Since TGs are pleiotropic enzymes, to fully understand the role of plant enzymes it is possible to compare them with animal TGs, the most studied being TG of type 2 (TG2). The extracellular form of TG2 stabilizes the matrix and modulates the interaction of the integrin-fibronectin receptor, causing the adhesion of cells to the extracellular matrix; TG2 plays a role also in the pathogenicity. Extracellular TGs have also been identified in the cell wall of fungi, such as Candida and Saccharomyces, where they cross-link structural glycoproteins, and in Phytophthora, where they are involved in pathogenicity; in the alga Chlamydomonas, TGs link polyamines to glycoproteins thereby favouring the strengthening of cell wall. In higher plants, TG localized in the cell wall of flower petals appears to be involved in the structural reinforcement as well as senescence and cell death of the flower corolla. In the pollen cell wall an extracellular TG co-localizes with substrates and cross-linked products; it is required for the apical growth of pollen tubes. The pollen TG is also secreted into the extracellular matrix possibly allowing the migration of pollen tubes during fertilisation. Although pollen TGs seem to be secreted via vesicles transported along actin filaments, a different mechanism from the classical ER-Golgi pathway is possible, similar to TG2.     

Heparan sulfate proteoglycans and their binding proteins in embryo implantation and placentation

Complex interactions occur among embryonic, placental and maternal tissues during embryo implantation. Many of these interactions are controlled by growth factors, extracellular matrix and cell surface components that share the ability to bind heparan sulfate (HS) polysaccharides. HS is carried by several classes of cell surface and secreted proteins called HS proteoglycan that are expressed in restricted patterns during implantation and placentation. This review will discuss the expression of HS proteoglycans and various HS binding growth factors as well as extracellular matrix components and HS-modifying enzymes that can release HS-bound proteins in the context of implantation and placentation.     

Secretogranin I/Chromogranin B Is a Heparin-Binding Adhesive Protein

The major heparin-binding protein secreted by PC12 cells was purified from conditioned medium. Amino-terminal sequencing of the purified protein identified it as secretogranin I/chromogranin B (SgI/ChmB). The protein showed the same electrophoretic mobility and biochemical characteristics as previously reported for SgI/ChmB and could be purified in high yield using a simple procedure. In vitro experiments demonstrated that SgI/ChmB effectively promoted cell-substratum adhesion of NIH 3T3 and PC12 cells and supported neurite outgrowth in primary hippocampal neurons. Thus, SgI/ChmB may be a new member of the family of heparin-binding extracellular matrix proteins that mediate cell adhesion and support neurite outgrowth.     

Mapping of the secretome of primary isolates of mammalian cells, stem cells and derived cell lines

Within a mammalian organism, the interaction among cells both at short and long distances is mediated by soluble factors released by cells into the extracellular environment. The secreted proteins may involve extracellular matrix proteins, proteinases, growth factors, protein hormones, immunoregulatory cytokines, chemokines or other bioactive molecules that have a direct impact on target cell phenotype. Stem cells of mesenchymal, adipose, neural and embryonic origin, fibroblast feeder cells as well as primary isolates of astrocytes, endothelial and muscle cells have recently become targets of intensive secretome profiling with the search for proteins regulating cell survival, proliferation, differentiation or inflammatory response. Recent advances and challenges of the stem cell and primary cell secretome analysis together with the most relevant results are discussed in this review.     

The netrin protein family

The name netrin is derived from the Sanskrit Netr, meaning ''guide''. Netrins are a family of extracellular proteins that direct cell and axon migration during embryogenesis. Three secreted netrins (netrins 1, 3 and 4), and two glycosylphosphatidylinositol (GPI)-anchored membrane proteins, netrins G1 and G2, have been identified in mammals. The secreted netrins are bifunctional, acting as attractants for some cell types and repellents for others. Receptors for the secreted netrins include the Deleted in Colorectal Cancer (DCC) family, the Down''s syndrome cell adhesion molecule (DSCAM), and the UNC-5 homolog family: Unc5A, B, C and D in mammals. Netrin Gs do not appear to interact with these receptors, but regulate synaptic interactions between neurons by binding to the transmembrane netrin G ligands NGL1 and 2. The chemotropic function of secreted netrins has been best characterized with regard to axon guidance during the development of the nervous system. Extending axons are tipped by a flattened, membranous structure called the growth cone. Multiple extracellular guidance cues direct axonal growth cones to their ultimate targets where synapses form. Such cues can be locally derived (short-range), or can be secreted diffusible cues that allow target cells to signal axons from a distance (long-range). The secreted netrins function as short-range and long-range guidance cues in different circumstances. In addition to directing cell migration, functional roles for netrins have been identified in the regulation of cell adhesion, the maturation of cell morphology, cell survival and tumorigenesis.     

Parathyroid hormone-related protein overexpression in the human colon cancer cell line HT-29 enhances adhesion of the cells to collagen type I

The present experiments examined the potential ability of parathyroid hormone-related protein (PTHrP) to influence growth of the human colon cancer cell HT-29 and the ability of the cell to adhere to several extracellular matrix (ECM) proteins found in normal tissues. Addition of PTHrP analogs, PTHrP (1-34), PTHrP (67-86), or PTHrP (107-139), to HT-29 cells in culture did not influence cell growth or the adhesion of the cells to wells coated with fibronectin, laminin, or collagen type I. Likewise, in HT-29 cells induced to overexpress PTHrP by stable transfection with PTHrP cDNA, compared to vector-transfected control HT-29 cells, no effect on cell growth occurred. However, in the transfected cells, the increased production of PTHrP significantly enhanced cell adhesion to type I collagen but not to fibronectin or laminin. The results raise the possibility that PTHrP might play a role in colon tumor invasion and metastasis by influencing cell adhesion to specific extracellular matrix proteins.     

Regulation of axonal outgrowth and pathfinding by integrin-ECM interactions

Developing neurons use a combination of guidance cues to assemble a functional neural network. A variety of proteins immobilized within the extracellular matrix (ECM) provide specific binding sites for integrin receptors on neurons. Integrin receptors on growth cones associate with a number of cytosolic adaptor and signaling proteins that regulate cytoskeletal dynamics and cell adhesion. Recent evidence suggests that soluble growth factors and classic axon guidance cues may direct axon pathfinding by controlling integrin-based adhesion. Moreover, because classic axon guidance cues themselves are immobilized within the ECM and integrins modulate cellular responses to many axon guidance cues, interactions between activated receptors modulate cell signals and adhesion. Ultimately, growth cones control axon outgrowth and pathfinding behaviors by integrating distinct biochemical signals to promote the proper assembly of the nervous system. In this review, we discuss our current understanding how ECM proteins and their associated integrin receptors control neural network formation.     

Acquisition of Anoikis Resistance Up-Regulates Syndecan-4 Expression in Endothelial Cells

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix, behaving as a critical mechanism in preventing adherent-independent cell growth and attachment to an inappropriate matrix, thus avoiding colonization of distant organs. Cell adhesion plays an important role in neoplastic transformation. Tumors produce several molecules that facilitate their proliferation, invasion and maintenance, especially proteoglycans. The syndecan-4, a heparan sulfate proteoglycan, can act as a co-receptor of growth factors and proteins of the extracellular matrix by increasing the affinity of adhesion molecules to their specific receptors. It participates together with integrins in cell adhesion at focal contacts connecting the extracellular matrix to the cytoskeleton. Changes in the expression of syndecan-4 have been observed in tumor cells, indicating its involvement in cancer. This study investigates the role of syndecan-4 in the process of anoikis and cell transformation. Endothelial cells were submitted to sequential cycles of forced anchorage impediment and distinct lineages were obtained. Anoikis-resistant endothelial cells display morphological alterations, high rate of proliferation, poor adhesion to fibronectin, laminin and collagen IV and deregulation of the cell cycle, becoming less serum-dependent. Furthermore, anoikis-resistant cell lines display a high invasive potential and a low rate of apoptosis. This is accompanied by an increase in the levels of heparan sulfate and chondroitin sulfate as well as by changes in the expression of syndecan-4 and heparanase. These results indicate that syndecan-4 plays a important role in acquisition of anoikis resistance and that the conferral of anoikis resistance may suffice to transform endothelial cells.     

Detachment of breast tumor cells induces rapid secretion of exosomes which subsequently mediate cellular adhesion and spreading

Exosomes are nano-vesicles secreted by a wide range of mammalian cell types. These vesicles are abundant in serum and other extracellular fluids and contain a large repertoire of proteins, mRNA and microRNA. Exosomes have been implicated in cell to cell communication, the transfer of infectious agents, and neurodegenerative diseases as well as tumor progression. However, the precise mechanisms by which they are internalized and/or secreted remain poorly understood. In order to follow their release and uptake in breast tumor cells in real time, cell-derived exosomes were tagged with green fluorescent protein (GFP)-CD63 while human serum exosomes were rhodamine isothiocynate-labeled. We show that detachment of adherent cells from various substrata induces a rapid and substantial secretion of exosomes, which then concentrate on the cell surfaces and mediate adhesion to various extracellular matrix proteins. We also demonstrate that disruption of lipid rafts with methyl-beta-cyclodextrin (MβCD) inhibits the internalization of exosomes and that annexins are essential for the exosomal uptake mechanisms. Taken together, these data suggest that cellular detachment is accompanied by significant release of exosomes while cellular adhesion and spreading are enhanced by rapid uptake and disposition of exosomes on the cell surface.