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Results for “Integrin alpha2beta1”

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PubMed2000

Integrin alpha2beta1 mediates the cell attachment of the rotavirus neuraminidase-resistant variant nar3.

It was previously reported that integrins alpha2beta1, alpha4beta1, and alphaXbeta2 are involved in rotavirus cell infection. In this work we studied the role of integrin subunits alpha2, alpha4, and beta2 on the attachment of rotaviruses RRV and nar3 to MA104 cells. Integrin alpha2beta1 was found to serve as the binding receptor for the neuraminidase-resistant virus nar3, whereas the neuraminidase-sensitive strain RRV interacted with this integrin at a postattachment step. It was shown that nar3 binds alpha2beta1 through the DGE integrin-recognition motif located in the virus surface protein VP5. Integrin subunits alpha4 and beta2 do not seem to be involved in the initial cell binding of either virus.

Antibodies, Monoclonal↗

PubMed1997

Proteolytic cleavage of the beta1 subunit of platelet alpha2beta1 integrin by the metalloproteinase jararhagin compromises collagen-stimulated phosphorylation of pp72.

Early signaling events in the stimulation of platelets by collagen include the tyrosine phosphorylations of FcR gamma-chain, pp72(syk) and phospholipase Cgamma2. These events are dependent on the main platelet collagen receptor, alpha2beta1 integrin (glycoprotein Ia-IIa complex). We recently found that jararhagin, a 52-kDa snake venom metalloproteinase, selectively inhibits collagen-induced platelet secretion and aggregation in parallel with the cleavage of the beta1 subunit of the alpha2beta1 integrin. The present study demonstrates that jararhagin also interferes with collagen-induced phosphorylation of the protein-tyrosine kinase pp72(syk). This effect is not observed when the platelet aggregation response to collagen is inhibited by two venom RGD-containing disintegrins, contortrostatin and echistatin. These disintegrins inhibit platelet aggregation through their high affinity binding to the platelet alphaIIbbeta3 integrin (glycoprotein IIb-IIIa complex). We also show that mild stimulation by ADP of jararhagin-treated platelets, but not of platelets treated with the RGD-containing disintegrins, restores the collagen-induced platelet aggregation. ADP also restored both pp72(syk) and pleckstrin phosphorylation of jararhagin-treated platelets in response to collagen, presumably via interaction of collagen with ADP-activated alphaIIbbeta3 integrin. Thus, RGD-containing disintegrins do not interfere with agonist-induced pp72(syk) phosphorylation but inhibit aggregation through occupancy of the alphaIIbbeta3 integrin. Conversely, jararhagin affects early platelet signaling events in response to collagen through its effects on the alpha2beta1 integrin without interfering with the function of the alphaIIbbeta3 integrin. Our demonstration that the degradation of the beta1 subunit of alpha2beta1 by jararhagin results in the loss of pp72(syk) phosphorylation, suggests that this subunit is critically involved in collagen-induced platelet signaling.

Collagen↗

PubMed2003

Vascular smooth muscle cells orchestrate the assembly of type I collagen via alpha2beta1 integrin, RhoA, and fibronectin polymerization.

Assembly of collagen into fibrils is widely studied as a spontaneous and entropy-driven process. To determine whether vascular smooth muscle cells (SMCs) impact the formation of collagen fibrils, we microscopically tracked the conversion of soluble to insoluble collagen in human SMC cultures, using fluorescent type I collagen at concentrations less than that which supported self-assembly. Collagen microaggregates were found to form on the cell surface, initially as punctate collections and then as an increasingly intricate network of fibrils. These fibrils displayed 67-nm periodicity and were found in membrane-delimited cellular invaginations. Fibril assembly was inhibited by an anti-alpha2beta1 integrin antibody and accelerated by an alpha2beta1 integrin antibody that stimulates a high-affinity binding state. Newly assembled collagen fibrils were also found to co-localize with newly assembled fibronectin fibrils. Moreover, inhibition of fibronectin assembly with an anti-alpha5beta1 integrin antibody completely inhibited collagen assembly. Collagen fibril formation was also linked to the cytoskeleton. Fibrils formed on the stretched tails of SMCs, ran parallel to actin microfilament bundles, and formed poorly on SMCs transduced with retrovirus containing cDNA for dominant-negative RhoA and robustly on SMCs expressing constitutively active RhoA. Lysophosphatidic acid, which activates RhoA and stimulates fibronectin assembly, stimulated collagen fibril formation, establishing for the first time that collagen polymerization can be regulated by soluble agonists of cell function. Thus, collagen fibril formation is under close cellular control and is dynamically integrated with fibronectin assembly, opening new possibilities for modifying collagen deposition.

Actins↗

PubMed1998

Alpha2beta1 integrin recognition of the carboxyl-terminal propeptide of type I procollagen: integrin recognition and feed-back regulation of matrix biosynthesis are mediated by distinct sequences.

It has recently been established that the carboxyl-terminal propeptide of type I collagen exert a feedback regulatory effect on extracellular matrix biosynthesis and that the propeptide bind to the alpha2beta1 integrin. This raises the intriguing hypothesis that the regulatory propeptide sequences exert their effects as a consequence of binding to the integrin. We show that recombinant alpha1(I) collagen chain C-terminal propeptide contains a binding site for the intact alpha2beta1 integrin and for a recombinant alpha2 integrin I domain, but not for the alpha1beta1 integrin, a structurally and functionally related collagen/laminin receptor. Additional studies employing a series of recombinant N-terminal and C-terminal deletion mutants, internal fragments of the propeptide, synthetic peptides, recombinant alpha2 integrin I domain and inhibitory monoclonal antibodies established that the previously identified sequences within the alpha1(I) C-terminal propeptide that mediate regulation of matrix biosynthesis are neither necessary nor sufficient for alpha2beta1 integrin binding. In contrast, the integrin recognition site is composed of a conformationally complex determinant located within a structurally distinct 115 amino acid region of the propeptide.

Animals↗

PubMed2006

hnRNP L regulates differences in expression of mouse integrin alpha2beta1.

There is a 2-fold variation in platelet integrin alpha2beta1 levels among inbred mouse strains. Decreased alpha2beta1 in 4 strains carrying Itga2 haplotype 2 results from decreased affinity of heterogeneous ribonucleoprotein L (hnRNP L) for a 6 CA repeat sequence (CA6) within intron 1. Seven strains bearing haplotype 1 and a 21 CA repeat sequence at this position (CA21) express twice the level of platelet alpha2beta1 and exhibit an equivalent gain of platelet function in vitro. By UV crosslinking and immunoprecipitation, hnRNP L binds more avidly to CA21, relative to CA6. By cell-free, in vitro mRNA splicing, decreased binding of hnRNP L results in decreased splicing efficiency and an increased proportion of alternatively spliced product. The splicing enhancer activity of CA21 in vivo is abolished by prior treatment with hnRNP L-specific siRNA. Thus, decreased surface alpha2beta1 results from decreased Itga2 pre-mRNA splicing regulated by hnRNP L and depends on CA repeat length at a specific site in intron 1.

Alternative Splicing↗

PubMed2006

The alpha2beta1 integrin mediates the malignant phenotype on type I collagen in pancreatic cancer cell lines.

Pancreatic cancer is characterised by a hallmark desmoplastic response that includes upregulated expression of the extracellular matrix, and type I collagen in particular. Recent studies indicate that pancreatic cancer cells stimulate type I collagen synthesis in adjacent stellate cells, and that this upregulated type I collagen expression promotes the malignant phenotype in tumour cells as defined by increased proliferation, resistance to chemically induced apoptosis, and increased tumorigenesis. The integrin specificity of this interaction between type I collagen and tumour cells was not identified, however. In the present study, we examined eight pancreatic cancer cell lines for adhesion, proliferation, and migration, on types I and IV collagen, fibronectin, laminin, and vitronectin, as well as integrin expression. Our results indicate, for the overwhelming majority of cell lines, that type I collagen promotes the strongest adhesion, proliferation, and migration relative to the other substrates tested. Utilising function-blocking monoclonal antibodies directed against particular integrin subunits in cell adhesion and migration inhibition assays, we demonstrate further that the malignant phenotype on type I collagen is mediated specifically by the alpha2beta1 integrin. These results identify alpha2beta1 integrin-mediated adhesion to type I collagen as a potential therapeutic target in the treatment of pancreatic cancer.

Antibodies, Monoclonal↗

PubMed2000

Engagement of the alpha2beta1 integrin inhibits Fas ligand expression and activation-induced cell death in T cells in a focal adhesion kinase-dependent manner.

T-cell receptor (TCR)-mediated apoptosis, also known as activation-induced cell death (AICD), plays an important role in the control of immune response and in the development of T-cell repertoire. Mechanistically, AICD has been largely attributed to the interaction of Fas ligand (Fas-L) with its cell surface receptor Fas in activated T cells. Signal transduction mediated by the integrin family of cell adhesion receptors has been previously shown to modulate apoptosis in a number of different cell types; in T cells, integrin signaling is known to be important in cellular response to antigenic challenge by providing a co-stimulatory signal for TCR. In this study we demonstrate that signaling via the collagen receptor alpha2beta1 integrin specifically inhibits AICD by inhibiting Fas-L expression in activated Jurkat T cells. Engagement of the alpha2beta1 integrin with monoclonal antibodies or with type I collagen, a cognate ligand for alpha2beta1, reduced anti-CD3 and PMA/ionomycin-induced cell death by 30% and 40%, respectively, and the expression of Fas-L mRNA by 50%. Further studies indicated that the alpha2beta1-mediated inhibition of AICD and Fas-L expression required the focal adhesion kinase FAK, a known component in the integrin signaling pathways. These results suggest a role for the alpha2beta1 integrin in the control of homeostasis of immune response and T-cell development. (Blood. 2000;95:2044-2051)

Apoptosis↗

PubMed2004

Integrin alpha2beta1 affects mechano-transduction in slowly and rapidly adapting cutaneous mechanoreceptors in rat hairy skin.

The role of a transmembrane protein, integrin alpha2beta1, to modulate the neural responses of cutaneous mechanoreceptors to mechanical indentation was examined using an isolated skin-nerve preparation in a rat model. Skin and its intact innervation were harvested from the medial thigh of the hindlimb and placed in a dish containing synthetic interstitial fluid. Using a standard teased nerve preparation, the neural responses of single slowly or rapidly adapting mechanoreceptors (SA or RA, respectively) were identified and the afferents categorized according to standard protocols (i.e. response to constant stimuli). The most sensitive spot of a mechanoreceptor's receptive field was identified and then stimulated using controlled compressive stress (constant or dynamic loads between threshold and saturation load for SAs and RAs, respectively). Loads were applied before, during, and after passive diffusion into the skin of a function-blocking anti-integrin alpha2 monoclonal antibody (FBmAb) or one of two types of control antibodies (immunoglobulin G or a FBmAb conjugated with a secondary antibody). The sensitivities of both SA and RA mechanoreceptors were profoundly reduced in the presence of the FBmAb, while not changing the waveforms of their action potentials or their adaptation properties. Both control antibodies had no significant effect on mechanoreceptors' sensitivities. Following removal of the FBmAb, the effects in some neurons were partially reversible. Taken together, the data from this study support the hypothesis that integrin alpha2beta1 plays a significant role in modulating mechanoreceptive response to compressive indentation.

Adaptation, Physiological↗

PubMed2004

Endorepellin causes endothelial cell disassembly of actin cytoskeleton and focal adhesions through alpha2beta1 integrin.

Endorepellin, the COOH-terminal domain of the heparan sulfate proteoglycan perlecan, inhibits several aspects of angiogenesis. We provide evidence for a novel biological axis that links a soluble fragment of perlecan protein core to the major cell surface receptor for collagen I, alpha2beta1 integrin, and provide an initial investigation of the intracellular signaling events that lead to endorepellin antiangiogenic activity. The interaction between endorepellin and alpha2beta1 integrin triggers a unique signaling pathway that causes an increase in the second messenger cAMP; activation of two proximal kinases, protein kinase A and focal adhesion kinase; transient activation of p38 mitogen-activated protein kinase and heat shock protein 27, followed by a rapid down-regulation of the latter two proteins; and ultimately disassembly of actin stress fibers and focal adhesions. The end result is a profound block of endothelial cell migration and angiogenesis. Because perlecan is present in both endothelial and smooth muscle cell basement membranes, proteolytic activity during the initial stages of angiogenesis could liberate antiangiogenic fragments from blood vessels' walls, including endorepellin.

Actins↗

PubMed1997

A collagen-like peptide stimulates tyrosine phosphorylation of syk and phospholipase C gamma2 in platelets independent of the integrin alpha2beta1.

Activation of platelets by collagen is mediated through a tyrosine kinase-dependent pathway that is associated with phosphorylation of the Fc receptor gamma chain, the tyrosine kinase syk, and phospholipase C gamma2 (PLC gamma2). We recently described a collagen-related triple-helical peptide (CRP) with the sequence GCP*(GPP*)GCP*G (single letter amino acid code: P* = hydroxyproline; Morton et al, Biochem J306:337, 1995). The cross-linked peptide is a potent stimulus of platelet activation but, unlike collagen, does not support alpha2beta1-mediated, Mg2+-dependent adhesion, suggesting that its action is independent of the integrin alpha2beta1. This finding suggests the existence of a platelet receptor other than alpha2beta1 that underlies activation. In the present study, we show that CRP stimulates tyrosine phosphorylation of the same pattern of proteins in platelets as collagen, including syk and PLC gamma2. Protein tyrosine phosphorylation induced by CRP is not altered in the absence of Mg2+ or the presence of monoclonal antibodies (MoAbs) to the integrin alpha2beta1 (MoAb 6F1 and MoAb 13), conditions that prevent the interaction of collagen with the integrin. In contrast, phosphorylation of syk and PLC gamma2 by collagen is partially reduced by MoAb 6F1 and MoAb 13 or by removal of Mg2+. This may reflect a direct role of alpha2beta1 in collagen-induced signaling events or an indirect role in which the integrin facilitates the binding of collagen to its signaling receptor. The results show an alpha2beta1-independent pathway of platelet activation by CRP that involves phosphorylation of syk and PLC gamma2. This pathway appears to contribute to platelet activation by collagen.

Collagen↗

PubMed2004

Differential roles of integrins alpha2beta1 and alphaIIbbeta3 in collagen and CRP-induced platelet activation.

Collagen and collagen-related peptide (CRP) activate platelets by interacting with glycoprotein (GP)VI. In addition, collagen binds to integrin alpha2beta1 and possibly to other receptors. In this study, we have compared the role of integrins alpha2beta1 and alphaIIbbeta3 in platelet activation induced by collagen and CRP. Inhibitors of ADP and thromboxane A2 (TxA2) substantially attenuated collagen-induced platelet aggregation and dense granule release, whereas CRP-induced responses were only partially inhibited. Under these conditions, a proportion of platelets adhered to the collagen fibres resulting in dense granule release and alphaIIbbeta3 activation. This adhesion was substantially mediated by alpha2beta1. The alphaIIbbeta3 antagonist lotrafiban potentiated CRP-induced dense granule release, suggesting that alphaIIbbeta3 outside-in signalling may attenuate GPVI signals. By contrast, lotrafiban inhibited collagen-induced dense granule release. These results emphasise the differential roles of alpha2beta1 and alphaIIbbeta3 in platelet activation induced by collagen and CRP. Further, they show that although ADP and TxA2 greatly facilitate collagen-induced platelet activation, collagen can induce full activation of those platelets to which it binds in the absence of these mediators, via a mechanism that is dependent on adhesion to alpha2beta1.

Adenosine Diphosphate↗

PubMed1998

Metastatic dissemination of human ovarian epithelial carcinoma is promoted by alpha2beta1-integrin-mediated interaction with type I collagen.

Metastatic dissemination of epithelial ovarian carcinoma is thought to be mediated via tumor cell exfoliation into the peritoneal cavity, followed by adhesion to and invasion through the mesothelium which overlies the contents of the peritoneal cavity. In this study, we have utilized short-term primary cultures to analyze the effect of specific extracellular matrix proteins on properties of human ovarian epithelial carcinoma cells which contribute to the invasive phenotype. Analysis of cell:matrix adhesive profiles indicated that ovarian carcinoma cells adhere preferentially to type I collagen. Immunoprecipitation analyses demonstrated the presence of the collagen-binding alpha2beta1 integrin in biotin-labeled ovarian carcinoma cell membranes, and cellular adhesion was inhibited by blocking antibodies directed against the alpha2 and beta1 integrin subunits. The alpha2beta1-binding peptide Asp-Gly-Glu-Ala (DGEA) was also moderately effective at blocking adhesion to collagen relative to the control peptide Ala-Gly-Glu-Ala (AGEA). Analysis of cell motility on protein-coated colloidal gold coverslips demonstrated that ovarian carcinoma cells migrate preferentially on type I collagen coated surfaces. Type I collagen promoted migration in a concentration-dependent, saturable manner, with maximal migration observed at a collagen-coating concentration of 50 microg/ml. Migration on collagen was inhibited by antibodies directed against the alpha2 and beta1 integrin subunits and by DGEA peptide, providing evidence for the role of the alpha2beta1 integrin in ovarian carcinoma cell motility. Culturing ovarian carcinoma cells on type I collagen gels led to a significant increase in conversion of the matrix metalloproteinase 2 zymogen to the 66-kD form, suggesting that adhesion to collagen also influences matrix-degrading proteinases. These data suggest that alpha2beta1-integrin-mediated interaction of ovarian carcinoma cells with type I collagen, a protein prevalent both in the mesothelial extracellular matrix and in the peritoneal cavity of ovarian carcinoma patients, may function on multiple levels to promote metastatic dissemination of ovarian carcinoma cells.

Cell Adhesion↗

PubMed2003

Integrin alpha2beta1 inhibits Fas-mediated apoptosis in T lymphocytes by protein phosphatase 2A-dependent activation of the MAPK/ERK pathway.

The mechanisms by which T lymphocytes escape apoptosis during their activation are still poorly defined. In this study, we elucidated the intracellular signaling pathways through which beta1 integrins modulate Fas-mediated apoptosis in T lymphocytes. In experiments done in Jurkat T cells and activated peripheral blood T lymphocytes, engagement of alpha2beta1 integrin with collagen type I (Coll I) was found to significantly reduce Fas-induced apoptosis and caspase-8 activation; Annexin V binding and DNA fragmentation were reduced by approximately 42 and 38%, respectively. We demonstrated that the protective action of Coll I does not require new protein synthesis but was dependent on the activation of the MAPK/Erk pathway. Furthermore, we found that activation of protein phosphatase 2A (PP2A) by Coll I was required for both Coll I-mediated activation of Erk, and inhibition of Fas-induced caspase-8 activation and apoptosis. Other ligands of beta1 integrins, fibronectin (Fbn), and laminin (Lam), did not sustain significant Erk activation and had no effect on Fas-induced apoptosis. Taken together, these results provide the first evidence of a PP2A-dependent activation of the MAPK/Erk pathway downstream of alpha2beta1 integrin, which has a functional role in regulating Fas-mediated apoptosis in T lymphocytes. As such, this study emphasizes the potential importance that Coll I interactions may have on the control of T lymphocyte homeostasis and their persistence in chronic inflammatory diseases.

Apoptosis↗

PubMed2003

Platelet alpha2beta1 integrin activation: contribution of ligand internalization and the alpha2-cytoplasmic domain.

The alpha2beta1 integrin is a major collagen receptor on platelets. Although it has been proposed that alpha2beta1, like alphaIIbbeta3, undergoes agonist-induced activation, neither the potential contributions of alpha2beta1 receptor/ligand internalization to the increase in ligand binding nor the roles of the alpha2 and beta1 cytoplasmic domains in activation of this integrin have been previously explored. Activation of alpha2beta1 was assessed with fluorescein isothiocyanate-labeled soluble type I collagen binding to platelets by flow cytometry. Although collagen internalization in response to agonist activation of platelets was significant, agonist-induced collagen binding still occurred under conditions that block internalization, with minimal changes in cell surface alpha2beta1 expression. Introduction of cell-permeable peptides containing the alpha2 cytoplasmic tail, and especially the membrane proximal KLGFFKR domain, induced alpha2beta1 activation in resting platelets, whereas a cell-permeable peptide containing the beta1 cytoplasmic tail was without effect. Thus, collagen binding to stimulated platelets is increased due to alpha2beta1 activation, in addition to internalization, and the GFFKR motif appears to play an important role in the activation process.

Amino Acid Sequence↗

PubMed2000

Isolation and characterization of EMS16, a C-lectin type protein from Echis multisquamatus venom, a potent and selective inhibitor of the alpha2beta1 integrin.

We have isolated and characterized EMS16, a potent and selective inhibitor of the alpha2beta1 integrin, from Echis multisquamatus venom. It belongs to the family of C-lectin type of proteins (CLPs), and its amino acid sequence is homologous with other members of this protein family occurring in snake venoms. EMS16 (M(r) approximately 33K) is a heterodimer composed of two distinct subunits linked by S-S bonds. K562 cells transfected with alpha2 integrin selectively adhere to immobilized EMS16, but not to two other snake venom-derived CLPs, echicetin and alboaggregin B. EMS16 inhibits adhesion of alpha2beta1-expressing cells to immobilized collagen I at picomolar concentrations, and the platelet/collagen I interaction in solution at nanomolar concentrations. EMS16 inhibits binding of isolated, recombinant I domain of alpha2 integrin to collagen in an ELISA assay, but not the interaction of isolated I domain of alpha1 integrin with collagen IV. Studies with monoclonal antibodies suggested that EMS16 binds to the alpha2 subunit of the integrin. EMS16 inhibits collagen-induced platelet aggregation, but has no effect on aggregation induced by other agonists such as ADP, thromboxane analogue (U46619), TRAP, or convulxin. EMS16 also inhibits collagen-induced, but not convulxin-induced, platelet cytosolic Ca(2+) mobilization. In addition, EMS16 inhibits HUVEC migration in collagen I gel. In conclusion, we report a new, potent viper venom-derived inhibitor of alpha2beta1 integrin, which does not belong to the disintegrin family.

Amino Acid Sequence↗

PubMed1997

Differentiation and transforming growth factor-beta receptor down-regulation by collagen-alpha2beta1 integrin interaction is mediated by focal adhesion kinase and its downstream signals in murine osteoblastic cells.

Interaction of type I collagen (COL(I)) with alpha2beta1 integrin causes differentiation and transforming growth factor (TGF)-beta receptor down-regulation in osteoblastic cells (Takeuchi, Y., Nakayama, K., and Matsumoto, T. (1996) J. Biol. Chem. 271, 3938-3644). The TGF-beta receptor down-regulation enables cells to escape from the inhibition of differentiation by TGF-beta. To clarify how the cell-matrix interaction regulates these phenotypic changes, signaling pathways were examined in murine MC3T3-E1 cells. Attachment of cells to COL(I) stimulated tyrosine phosphorylation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK), a mitogen-activated protein kinase (MAPK), and enhanced MAPK activity. Inhibition of tyrosine kinase by herbimycin A, destruction of focal adhesion by cytochalasin D, or overexpression of antisense FAK mRNA prevented the activation of ERK/MAPK and the increase in alkaline phosphatase (ALP) activity. Transient expression of a MAPK-specific phosphatase, CL100, also suppressed the elevation of ALP activity. In addition, introduction of a constitutively active MAPK kinase enhanced ALP activity in the absence of collagen production. TGF-beta receptor down-regulation was abrogated by treatments that inactivate FAK, whereas the expression of CL100 had no effect. These results demonstrate that COL(I)-alpha2beta1 integrin interaction facilitates differentiation and down-regulates TGF-beta receptors via the activation of FAK and its diverse downstream signals. These signaling pathways may play an important role in the sequential differentiation of osteoblasts during bone formation.

3T3 Cells↗

PubMed2006

Laminin alpha1 chain LG4 module promotes cell attachment through syndecans and cell spreading through integrin alpha2beta1.

The laminin alpha1 chain is a subunit of laminin-1, a heterotrimeric basement membrane protein. The LG4-5 module at the C terminus of laminin alpha1 contains major binding sites for heparin, sulfatide, and alpha-dystroglycan and plays a critical role in early embryonic development. We previously identified active synthetic peptides AG73 and EF-1 from the sequence of laminin alpha1 LG4 for binding to syndecan and integrin alpha2beta1, respectively. However, their activity and functional relationship within the laminin-1 and LG4 as well as the functional relation between these sites and alpha-dystroglycan binding sites in LG4 are not clear. To address these questions, we created mutant recombinant LG4 proteins containing alanine substitutions within the AG73 (M1), EF-1 (M2, M3), and alpha-dystroglycan binding sites (M4, M5) and analyzed their activities. We found that recombinant proteins rec-M1 and rec-M5, containing mutations within M1 and M5, respectively, did not bind heparin or lymphoid cell lines expressing syndecans. These results suggest that LG4 binds to heparin and syndecans through M1 and M5. Rec-M1 and rec-M5 reduced fibroblast attachment, whereas mutant rec-M2 and rec-M3 retained cell attachment activity but did not promote cell spreading. Fibroblast attachment to rec-LG4 was inhibited by heparin but not by integrin antibodies. Spreading of fibroblasts on rec-LG4 was inhibited by anti-integrin alpha2 and beta1 but not by anti-integrin alpha1 and alpha6. These results suggest that the M1 and M5 sites are necessary for cell attachment on LG4 through syndecans and that the EF-1 site is for cell spreading activity through integrin alpha2beta1. In contrast, laminin-1-mediated fibroblast attachment and spreading were not inhibited by heparin or anti-integrin alpha2. Our findings indicate that LG4 has a unique function distinct from laminin-1 and suggest that laminin alpha1 LG4-5 may also be produced by a proteolytic cleavage in certain tissues where it exerts its activity.

Alanine↗

PubMed2004

The -455G/A polymorphism of the beta fibrinogen gene and the Bgl II polymorphism of the alpha2beta1 integrin gene and myocardial infarction in patients with type 2 diabetes.

Platelets and fibrinogen might be involved in the pathogenesis of thrombus formation and MI. The Bgl II gene polymorphism of the alpha2beta1 integrin, which is a platelet collagen receptor, and the -455G/A polymorphism in the beta fibrinogen gene have been suggested as genetic risk factors for MI. The aim of this study was to look for a relationship between the -455G/A polymorphism in the beta fibrinogen gene and the development of MI in Caucasians with type 2 diabetes. One hundred and forty-two subjects with type 2 diabetes and MI were compared to 234 diabetic subjects with no history of coronary artery disease. There were no significant differences in the frequency of the Bgl II gene polymorphism or of the -455G/A polymorphism in the beta fibrinogen gene in the patients with MI compared to the patients without MI: Bgl II (+/+) genotype was found in 19.7% of patients with MI and 15.4% of controls and -455GG genotype was found in 58.4% of patients with MI and 57.7% of controls. The present study demonstrates that neither the Bgl II gene polymorphism nor -455G/A polymorphism in the beta fibrinogen gene is a genetic marker for MI in Slovene population (Caucasians) with type 2 diabetes.

Bacterial Proteins↗