PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Integrin alpha2”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1997

Arginine-glycine-aspartic acid mimics can identify a transitional activation state of recombinant alphaIIb beta3 in human embryonic kidney 293 cells.

The platelet-specific integrin alphaIIb beta3 achieves a high affinity binding state in response to extracellular agonists such as thrombin, ADP, or collagen. During this activation, the receptor undergoes a number of conformational changes. To characterize the different conformations of alphaIIb beta3, we expressed recombinant alphaIIb beta3 in human embryonic kidney (HEK) 293 cells. Antigenic and peptide recognition specificities of the full-length recombinant receptor resembled those of the native receptor in platelets. We used an array of peptidic and nonpeptidic arginine-glycine-aspartic acid (RGD) mimics that specifically bind to human platelet alphaIIb beta3 to determine the affinity state of the receptor. Some of these RGD mimics were previously shown to clearly discriminate between resting and activated alphaIIb beta3. Solution-phase binding of these RGD mimics to the recombinant cells suggested that in HEK 293 cells the full-length alphaIIb beta3 is expressed in a "transitional" activation state. This observation was confirmed by the binding of the activation-specific, monoclonal anti-alphaIIb beta3 antibody PAC1 to cells expressing the full-length recombinant alphaIIb beta3. Deletion of the entire cytoplasmic domain of the beta subunit was sufficient to convert the receptor in HEK 293 cells to a fully active form, as found in activated platelets. In addition, the full-length receptor was capable of mediating agonist-independent aggregation of cells in the presence of fibrinogen. Thus, by using RGD mimics, we have identified a functional transitional activation state of alphaIIb beta3 that is capable of mediating fibrinogen-dependent cell aggregation.

Antigens, CD↗
PubMed2002

Laminins and TGF-beta maintain cell polarity and functionality of human gastric glandular epithelium.

The human gastric glandular epithelium produces a gastric lipase enzyme (HGL) that plays an important role in digestion of dietary triglycerides. To assess the involvement of extracellular matrix components and transforming growth factor-beta1 (TGF-beta1) in the regulation of this enzymic function, normal gastric epithelial cells were cultured on collagen type I, Matrigel, and laminins (LN)-1 and -2 with or without TGF-beta1. Epithelial morphology and HGL expression were evaluated using microscopy techniques, enzymic assays, Western blot, Northern hybridization, and RT-PCR. A correlation was observed between the cell polarity status and the level of HGL expression. TGF-beta1 alone or individual matrix components stimulated cell spreading and caused a downfall of HGL activity and mRNA. By contrast, Matrigel preserved the morphological features of differentiated epithelial cells and maintained HGL expression. The combination of LNs with TGF-beta1 (two constituents of Matrigel) exerted similar beneficial effects on epithelial cell polarity and evoked a 10-fold increase of HGL levels that was blunted by a neutralizing antibody against the alpha(2)-integrin subunit and by mitogen-activated protein kinase (MAPK) inhibitors PD-98059 (p42/p44) or SB-203580 (p38). This investigation demonstrates for the first time that a powerful synergism between a growth factor and basement membrane LNs positively influences cell polarity and functionality of the human gastric glandular epithelium through an activation of the alpha(2)beta(1)-integrin and effectors of two MAPK pathways.

Antigens, CD↗
PubMed2006

Enhanced frequency of CD18- and CD49b-expressing T cells in peripheral blood of asthmatic patients correlates with disease severity.

BACKGROUND: Results from a transcriptome analysis of human CD4+ T regulatory type 1 (Tr1) clones have indicated that transcripts for the integrins CD18 and CD49b are overexpressed in these cells. The aim of this study was to investigate whether the presence of T cells concomitantly expressing these molecules could be detected in asthmatic patients and represent Tr1 cells. METHODS: Expression of CD18 and CD49b was analyzed by flow cytometry on peripheral blood mononuclear cells from asthmatic patients of various severity and healthy subjects. The cytokine production profile of purified CD4+ CD18(high) CD49b+ T cells was analyzed by ELISA. The effect of glucocorticoid treatment on the expression of CD18 and CD49b was determined. RESULTS: The frequency of peripheral blood CD18(high) CD49b+ T cells was significantly elevated in severe asthmatic patients, as compared with both mild asthmatic and healthy donors, and was diminished in asthmatic patients with a controlled status of the disease. Neither short-course oral glucocorticoid treatment of asthmatic patients ex vivo, nor culture of their peripheral blood mononuclear cells with dexamethasone in vitro, increased the frequency of CD18(high) CD49b+ T cells, indicating that their presence seems to be independent from recent anti-inflammatory treatment. However, purified CD4+ CD18(high) CD49b+ T cells from these patients, in contrast to those from healthy donors, lacked the production of the immunosuppressive cytokine interleukin-10. CONCLUSION: In contrast to healthy donors, peripheral blood CD18(high) CD49b+ T cells of asthmatic patients do not fulfill the phenotypic criteria of Tr1 cells. Nevertheless, the presence of elevated numbers of peripheral blood CD18(high) CD49b+ T cells is characteristic for patients with severe and uncontrolled asthma.

Adult↗
PubMedDate not supplied

Analysis of glycoprotein Ia, Ib, IIb and IV RNA in platelets: quantitative determination using fluorescence-based polymerase chain reaction.

The aim of this study was to analyze the RNA level of glycoprotein (GP) receptors in platelets. We have therefore established a quantitative fluorescence-based polymerase chain reaction (PCR) to analyze GP Ia, Ib, IIb, and IV RNA. Isolation of platelet RNA was performed by guanidium isothiocyanate/phenol chloroform extraction. An internal standard consisting of cRNA copies from plasmid pAW109 was included before reverse transcription in each RNA sample and PCR amplification was performed using fluorescence-labeled primers. Subsequently, PCR fragments were separated by gel electrophoresis and quantitation of the GP-specific fragments was done by measuring the fluorescence intensities in comparison to the internal standard. Relative amount of GP RNA/platelet were calculated taking into account the number of platelets used for isolation of platelet RNA and the platelet size as determined by flow-cytometric analysis. Using this method we analyzed the GPIa, Ib, IIb and IV RNA content of platelets in healthy blood donors. In parallel experiments the number of GP cell surface receptors was measured by flow-cytometric analysis and correlated with the GP-specific RNA content. This method may be useful to study the GP-specific RNA content in platelets as well as in other tissues, such as megakaryocytes, especially in patients with congenital or acquired platelet function disorders.

Antigens, CD↗
PubMed2006

Autosomal dominant thrombocytopenias with reduced expression of glycoprotein Ia.

We have recently studied a case series of 46 unrelated patients with inherited thrombocytopenias and identified 18 cases that did not fit any known platelet disorder. In two unrelated families, a mild thrombocytopenia with normal platelet size was transmitted in an autosomal dominant fashion. Bleeding time was prolonged in 5 investigated patients. In all of them, flow cytometry and SDS-PAGE of platelet glycoproteins (GP) showed a reduced content of GPIa, a subunit of the GPIa-IIa complex (also known as integrin alpha 2 beta(1)) that is a major collagen receptor on platelets. All other membrane GPs were within the normal range. GPIa deficiency was associated with severely reduced in vitro platelet adhesion to molecules known to interact selectively with GPIa. In vitro platelet aggregation was normal in all subjects, except for a suboptimal platelet response to fibrillar collagen in two patients. A mild defect of alpha-granules was observed in all affected subjects. No mutation was identified in the genes encoding for GPIa or GPIIa. Since no other similar cases have been reported in the literature, we suggest that an autosomal dominant thrombocytopenia associated with GPIa deficiency and alpha-granule defect represents a new form of inherited thrombocytopenia.

Adult↗
PubMed2006

Vascular risk factors in sudden hearing loss.

Low density lipoprotein (LDL) and fibrinogen apheresis was recently reported to be an effective therapy in sudden hearing loss (SHL). In this study, we investigated whether lipoprotein and/or fibrinogen plasma concentrations, related gene polymorphisms and other cardiovascular risk factors are also risk factors for SHL. Total cholesterol, HDL and LDL cholesterol plasma concentrations, fibrinogen levels, and two functionally relevant fibrinogen polymorphisms were determined in 142 consecutive patients and in 84 age- and sex-matched control subjects of the same ethnic background, using routine laboratory methods and PCR analysis. In addition, we determined the platelet glycoprotein Ia (GPIa) C807T polymorphism, which was recently proposed to be a genetic risk factor for SHL, and we compared the patients' and controls' clinical characteristics. Total and LDL cholesterol concentrations were not different between patients and controls. Fibrinogen plasma levels were significantly increased in SHL patients (260+/-57 vs. 239+/-110 mg/dl, p=0.002). However, fibrinogen was not related to SHL in multivariate analysis, and none of the investigated fibrinogen polymorphisms was associated with SHL. By contrast, T allele carriers of the GPIa 807 polymorphic site had an increased risk to develop SHL (OR 1.81) and were more likely not to recover from SHL, compared to C allele carriers (OR 3.0). Moreover, significantly more SHL patients were current smokers (56.3% vs. 19.3% in the control group, p<0.0001). In conclusion, there is a partial overlap between classical coronary risk factors and risk factors for SHL. Hypercholesterolemia and hypoalphalipoproteinemia (low HDL cholesterol levels) are apparently no major risk factors for SHL, whereas the GPIa C807T polymorphism, elevated fibrinogen levels, and smoking are associated with an increased risk for SHL. Altogether these findings suggest a vascular involvement in the pathogenesis of SHL and may have important implications for the development of therapeutic and preventive strategies.

Adolescent↗
PubMed1994

Chimeric 7E3 prevents carotid artery thrombosis in cynomolgus monkeys.

BACKGROUND AND PURPOSE: We compared the current antithrombotic strategy of antiplatelet therapy with aspirin, and anticoagulant therapy with heparin, with a specific genetically engineered chimeric antibody (c7E3 Fab) directed against the human glycoprotein IIb/IIIa receptor in an animal model of arterial thrombosis. METHODS: Anesthetized cynomolgus monkeys (Macaca fascicularis) were instrumented for monitoring of arterial blood pressure, heart rate, and carotid artery flow velocity. Animals were treated with saline (n = 6), aspirin (25 mg PO daily for 3 days; n = 6), heparin (100 U/kg i.v. plus infusion adjusted to maintain activated partial thromboplastin time at 2 to 3 times baseline; n = 6), aspirin plus heparin (as administered separately, n = 6), or c7E3 Fab (0.10 mg/kg i.v., n = 7; 0.15 mg/kg i.v., n = 6; 0.20 mg/kg i.v., n = 6; 0.25 mg/kg i.v., n = 6). Thrombus formation via anodal electrolytic stimulation (100 microA) to the intimal surface of the right carotid artery was initiated 15 minutes after drug administration and continued for 180 minutes. Electrolytic injury to the left carotid artery began 210 minutes after drug administration and continued for 180 minutes. Whole blood cell counts, glycoprotein IIb/IIIa receptor blockade, ex vivo platelet aggregation, template bleeding time, and activated partial thromboplastin time were assessed at various time points throughout the experimental protocol. RESULTS: Hemodynamic and hematologic parameters were comparable among groups at baseline. Treatment with c7E3 Fab inhibited ex vivo platelet aggregation, increased bleeding time, decreased thrombus weight, and increased time to occlusion in a dose-dependent manner in both vessels. Treatment with aspirin, heparin, or the combination of aspirin plus heparin was ineffective for the prevention of carotid artery thrombosis in this model. CONCLUSIONS: Inhibition of the platelet glycoprotein IIb/IIIa receptor with c7E3 Fab was found to be safe and effective for the prevention of primary thrombus formation, whereas treatment with either aspirin or heparin or the combination of the two agents failed to protect against occlusive thrombus formation in cynomolgus monkeys.

Abciximab↗
PubMed2002

Association of the platelet glycoprotein Ia C807T/G873A gene polymorphism and thrombosis in Behçet patients.

Thrombosis is a common complication of Behçet disease and the pathogenic mechanism of thrombotic tendency in Behçet disease is not well known. Several platelet membrane glycoprotein gene polymorphisms have been identified as risk factors for thrombosis. This study aimed to evaluate the possible role of the GP Ia C807T/G873A polymorphism as a risk factor for thrombosis in Behçet disease. We determined the prevalence of platelet glycoprotein Ia C807T/G873A gene polymorphism in Behçet patients. Genomic DNA was obtained from 20 patients with Behçet disease and 61 controls. All individuals were of Turkish ancestry and were genotyped for the GP Ia C807T/G873A polymorphism with real-time PCR method by LightCycler system. The 807 CC, CT and TT genotypes corresponded with 873 GG, GA and AA genotypes, respectively. Complete linkage between the 807 and 873 sites was found in all samples. The 807CC(873 GG), 807CT(873GA), 807TT(873AA) genotypes found to be 45.9%, 45.9% and 8.1% in controls and 30.0%, 55.0% and 15.0% in patients with Behçet disease, respectively. The Odds Ratio for BD (OR = 1.97; 95% confidence interval (CI): 0.42-9.13) is high for the 807 TT genotype compared with controls. Thrombosis was found in 7 cases of Behçet disease group: five cases have 807CT, one case has 807TT genotype and one case has 807CC genotype. Our data indicate hat patients with BD are affected by the glycoprotein Ia gene 807TT genotypes and carrying 807T allele. The risk of thrombosis is significantly higher in patients who have 807TT and 807CT genotypes than in patients who have 807CC genotype.

Behcet Syndrome↗
PubMed2000

Different expression of TNF-alpha receptors and prostaglandin E(2 )Production in normal and fibrotic lung fibroblasts: potential implications for the evolution of the inflammatory process.

Normal human lung fibroblasts downregulate the production of tumor necrosis factor (TNF)-alpha by activated monocytes through the production of prostaglandin E(2) (PGE(2)), contributing to the local control of the inflammatory process. In this study, we provide evidence that fibroblasts derived from diseased tissue, such as fibrotic lung fibroblasts, exhibit different functional features compared with normal cells, with particular regard to their modulatory role. Indeed, fibrotic fibroblasts (FF) spontaneously produced less PGE(2) (3,300 +/- 410 pg/ml) compared with normal fibroblasts (NF) (7,500 +/- 270 pg/ml) and, as a consequence, they showed a reduced ability to downregulate the production of TNF-alpha by lipopolysaccharide (LPS)- activated monocytes. The percentage of inhibition induced by normal cells on the production of TNF-alpha by LPS-activated monocytes was 61 +/- 5.9%, whereas the inhibitory effect exerted by fibrotic cells was reduced to 32 +/- 4% (P < 0.01). We have also observed that the ability of TNF-alpha to induce PGE(2) was impaired in FF and was related to a reduced expression of cyclooxygenase 2. This was possibly due to the reduction of the expression of TNF receptors (TNFRs) in fibrotic cell lines compared with normal cell lines. Flow cytometry revealed that the mean fluorescence intensity (MFI) of both isoforms of TNFR was significantly lower in FF compared with NF. The MFI of TNFR1 was 3. 55 +/- 0.12 for NF and 1.78 +/- 0.35 for FF (P < 0.001). The MFI of TNFR2 was 1.95 +/- 0.27 for NF and 0.99 +/- 0.16 for FF (P < 0.01). The analysis of the effect of TNF-alpha on some functions associated with collagen metabolism in NF and FF showed an increase of the expression of the receptor for collagen type I (alpha(2)beta(1) integrin) in NF (42 +/- 10%) and an even larger increase in FF (102 +/- 23%) (P < 0.05). Interestingly, unlike NF, TNF-alpha failed to increase matrix metalloproteinase 1 levels in FF and did not cause any growth inhibition in these cells. The reduced capability of fibrotic cells to produce PGE(2) either spontaneously or after TNF-alpha treatment may lead to an unrestrained release of TNF-alpha from activated monocytes and, as a result of the reduced expression of TNFRs, to a different response of these cells to TNF-alpha. These changes may be important in the evolution of the inflammatory process, potentially contributing to its transformation into a chronic and self-perpetuating process.

Antigens, CD↗
PubMed1992

A new variant of Glanzmann's thrombasthenia (Strasbourg I). Platelets with functionally defective glycoprotein IIb-IIIa complexes and a glycoprotein IIIa 214Arg----214Trp mutation.

We describe a new variant of Glanzmann's thrombasthenia (variant Strasbourg I). The patient (M.S.) showed an absence of platelet aggregation to ADP, thrombin, and collagen, and a decreased clot retraction. Platelet fibrinogen was approximately 20% of normal levels. ADP-stimulated platelets bound markedly reduced amounts of soluble fibrinogen and platelet adhesion to surface-bound fibrinogen was defective. Normal to subnormal amounts of glycoprotein (GP) IIb-IIIa (alpha IIb beta 3) complexes, the platelet fibrinogen receptor, were revealed by SDS-PAGE, crossed immunoelectrophoresis, and antibody binding. However, the complexes were unusually sensitive to dissociation with EDTA at room temperature. Furthermore, flow cytometry showed that the platelets failed to bind the activation-dependent monoclonal antibody, PAC-1, after stimulation. In contrast, an RGDS-containing peptide induced significant binding of the anti-ligand-induced binding site antibody, D3GP3, suggesting the presence of a functional RGD binding domain on the patient's GPIIb-IIIa complex. Sequence analysis was performed after polymerase chain reaction amplification of selected patient's GPIIIa exons, and of the patient's platelet GPIIb and GPIIIa mRNAs. A point mutation (C to T) was localized in exon D (iv) of GPIIIa that resulted in an 214Arg to 214Trp amino acid substitution. The defect has been inherited from the parents who are heterozygous for the same mutation. This substitution points to an essential amino acid in a region of GPIIIa involved in the binding of fibrinogen and influencing the Ca(2+)-dependent stability of the GPIIb-IIIa complex.

Adult↗
PubMedDate not supplied

Perfusion enhances functions of bone marrow stromal cells in three-dimensional culture.

Perfusion of medium through three-dimensional (3D) collagen sponges enhanced viability and function of cocultivated marrow stromal and hematopoietic cell lines. Cells of the murine bone marrow stromal cell line GPIa were cultured in novel 3D collagen sponges, made from pepsin-digested bovine skin. Static cultures of sponges were maintained in dishes with media changes every other day. Perfused sponges were contained in a glass column with medium flow set at 1.3 mL/min. In some sponges, the 32D cl3 c-fms(m) (CRX-1) hematopoietic progenitor cell line was added 7 days after GPIa cells. At 7 and 16 days, light microscopic evaluation showed poor viability of cells in static sponge cultures. In perfused sponge cultures, there was greater cellularity throughout the sponge and abundant accumulation of metachromatic extracellular matrix surrounding GPIa cells. Chondroitin 6-sulfate and heparan sulfate were identified as components of the matrix by immunohistochemical methods. DNA synthesis was evaluated by 15-h exposure of cultures to bromodeoxyuridine (BrdU), with subsequent immunohistochemical localization with monoclonal anti-BrdU antibody. Cells positive for BrdU were identified at the outer surfaces of both static and perfused sponges; however, positive cells were also seen throughout the internal areas of the sponges that were perfused. These results suggest that better nutrient exchange occurred in perfused sponges. In static cocultures of GPIa and CRX-1 cells, there was no detectable viability of the IL-3-dependent CRX-1 cells; however, under perfused conditions, CRX-1 cells flourished within the sponges as documented by BrdU incorporation. Thus, medium perfusion enhanced GPIa stromal cell line viability and function in 3D collagen sponge cultures, as demonstrated by BrdU incorporation, matrix production, and support of CRX-1 cells. This novel culture system may be useful for examining the interactions of bone marrow stromal cells with extracellular matrix molecules, soluble and matrix-bound factors, and with other cell types.

Animals↗
PubMed2007

Platelet glycoprotein Ia 807C/T and 873G/A polymorphisms in patients with venous thromboembolism.

Two silent polymorphisms (807C/T and 873G/A) within glycoprotein Ia (GPIa) gene have been implicated in increased risk of developing thrombosis and myocardial infarction in affected individuals. The aim of this study was to investigate the GPIa gene polymorphism in patients with venous thromboembolism (VTE). A multiplexed allele specific-polymerase chain reaction (AS-PCR)-based method was used to determine the GPIa 807T/873A allele frequency in 77 patients with VTE and 106 healthy controls. The allelic frequency for 807T/873A was 33% in the patient group and 38% in the control group. The allelic frequency for 807C/873G was 66% in the patient group and 62% in the control group. The genotypic frequencies were 8% for 807TT/873AA, 42% for 807CC/GG, and 50% for 807CT/GA in the patient group. In the control group, the frequencies were 12% for 807TT/873AA, 35% for 807CC/873GG, and 52% for 807CT/873GA. As a result, the glycoprotein Ia 807C/T and 873G/A dimorphisms were not shown as risk factors for VTE.

Adult↗
PubMed2004

Genetic variation responsible for mouse strain differences in integrin alpha 2 expression is associated with altered platelet responses to collagen.

As mouse models have become commonplace for studying hemostasis and thrombosis, we considered whether the mouse system had utility for assessing genetic alterations in platelet receptors. Platelets from 5 mouse strains (C57BL/6 [C57], FVB/N [FVB], BALB/c, C3H/He, and 129Sv) showed only minor differences in the expression of integrin alpha(IIb), integrin beta(3), glycoprotein (GP) Ib alpha, or GPVI across strains. However, FVB platelets expressed approximately 50% the level of integrin alpha(2) as platelets from other strains (P <.0001). We bred FVB mice with C57 and assessed alpha(2) expression in FVB/C57xFVB/C57 (F2) offspring. Linkage analysis demonstrated the gene responsible for alpha(2) levels is tightly linked to the D13mit260 marker (log odds [lod] score 6.7) near the alpha(2) gene. FVB platelets showed reduced aggregation and a longer lag phase to collagen. FVB and C57 platelets aggregated similarly to collagen-related peptide, but FVB platelets showed a reduction in rhodocytin-induced Syk and PLC gamma 2 tyrosine phosphorylation. Thus, FVB platelets express half the level of alpha(2) as other mouse strains, a trait linked to the alpha(2) gene and seemingly responsible for reduced platelet aggregation to collagen. These strain differences serve as a useful model for the 2-fold difference in human platelet alpha(2)beta(1) expression and demonstrate that alpha(2)beta(1) participates in signaling during platelet activation.

Animals↗
PubMed2002

Reconstitution of adhesive properties of human platelets in liposomes carrying both recombinant glycoproteins Ia/IIa and Ib alpha under flow conditions: specific synergy of receptor-ligand interactions.

Liposomes carrying both recombinant glycoprotein Ia/IIa (rGPIa/IIa) and Ib alpha (rGPIb alpha) (rGPIa/IIa-Ib alpha-liposomes) instantaneously and irreversibly adhered to the collagen surface in the presence of soluble von Willebrand factor (VWF) at high shear rates, in marked contrast with translocation of liposomes carrying rGPIb alpha alone on the VWF surface. In the absence of soluble VWF, the adhesion of rGPIa/IIa-Ib alpha-liposomes to the collagen surface decreased with increasing shear rates, similar to liposomes carrying rGPIa/IIa alone. While adhesion of liposomes with exofacial rGPIa/IIa and rGPIb alpha densities of 2.17 x 10(3) and 1.00 x 10(4) molecules per particle, respectively, was efficient at high shear rates, reduction in rGPIb alpha density to 5.27 x 10(3) molecules per particle resulted in decreased adhesion even in the presence of soluble VWF. A 50% reduction in the exofacial rGPIa/IIa density resulted in a marked decrease in the adhesive ability of the liposomes at all shear rates tested. The inhibitory effect of antibody against GPIb alpha (GUR83-35) on liposome adhesion was greater at higher shear rates. Further, the anti-GPIa antibody (Gi9) inhibited liposome adhesion more than GUR83-35 at all shear rates tested. These results suggest that the rGPIa/IIa-collagen interaction dominates the adhesion of rGPIa/IIa-Ib alpha-liposomes to the collagen surface at low shear rates, while the rGPIa/IIa-collagen and rGPIb alpha-VWF interaction complements each other, and they synergistically provide the needed functional integration required for liposome adhesion at high shear rates. This study thus has confirmed for the first time the proposed mechanisms of platelet adhesion to the collagen surface under flow conditions using the liposome system.

Antigens, CD↗
PubMed2001

Role of 4 platelet membrane glycoprotein polymorphisms on experimental arterial thrombus formation in men.

This study investigates whether the polymorphisms of 3 important platelet receptors affected experimental thrombus formation in men. Forty healthy male volunteers randomly recruited were genotyped for the variable number of tandem repeat (VNTR) of GPIbalpha, the -5T/C polymorphism in the Kozak sequence of GPIbalpha, the 807C/T polymorphism of GPIa, and the PI(A1)/PI(A2) polymorphism of GPIIb/IIIa. Platelet thrombus formation was induced ex vivo by exposing a collagen-coated coverslip in a parallel plate perfusion chamber to native blood for 4 minutes. The shear rates at the collagen surface were 650 and 2600 x s(-1). At 2600 x s(-1) platelet thrombus formation was significantly related only to the 807C/T polymorphism. In contrast, at 650 x s(-1) thrombus formation was significantly altered only by the Kozak sequence polymorphism. The VNTR and the PI(A1)/PI(A2) polymorphisms did not influence thrombus formation. Thus, platelet thrombus formation is significantly influenced by genetic variations of the GPIbalpha and GPIa receptors. The effect of these polymorphisms was dependent on the blood flow rate.

Adult↗
PubMed1995

Alteration of collagen-dependent adhesion, motility, and morphogenesis by the expression of antisense alpha 2 integrin mRNA in mammary cells.

Although integrins are known to mediate adhesive binding of cells to the extracellular matrix, their role in mediating cellular growth, morphology, and differentiation is less clear. To determine more directly the role of the alpha 2 beta 1 integrin, a collagen and laminin receptor, in mediating the collagen-dependent differentiation of mammary cells, we reduced expression of the integrin by the well differentiated human breast carcinoma cell line, T47D, by stably expressing alpha 2 integrin antisense mRNA. Flow cytometry demonstrated that the antisense-expressing clones had levels of alpha 2 beta 1 integrin on their surfaces that were decreased by 30-70%. Adhesion of antisense-expressing clones to both collagens I and IV was decreased relative to controls in a manner that correlated with the level of cell surface alpha 2 beta 1 integrin expression. Adhesion to fibronectin and laminin were not affected. Motility across collagen-coated filters in haptotaxis assays was increased for only those clones that exhibited intermediate levels of adhesion to collagen, suggesting that an intermediate density of cell-surface alpha 2 beta 1 integrin optimally supports cell motility. When cultured in three-dimensional collagen gels, T47D cells organized in a manner suggestive of a glandular epithelium. In contrast, antisense-expressing clones with decreased alpha 2 beta 1 integrin were not able to organize in three-dimensional collagen gels. The growth rate of T47D cells was reduced when the cells were cultured in three-dimensional collagen gels. Unlike adhesion, motility, and morphogenesis, growth rates were unaffected by reduction of alpha 2 beta 1 integrin expression. Our results suggest that adhesive interactions mediated by a critical level of surface alpha 2 beta 1 integrin expression are key determinants of the collagen-dependent morphogenetic capacity of mammary epithelial cells.

Animals↗