Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Integrin beta3”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,441 records · Page 80Linked to original sources
PubMed2003

Adenosine diphosphate-induced platelet aggregation is associated with P2Y12 gene sequence variations in healthy subjects.

BACKGROUND: The adenosine diphosphate (ADP) receptor P2Y12 plays a pivotal role in platelet aggregation, as demonstrated by the benefit conferred by its blockade in patients with cardiovascular disease. Some studies have shown interindividual differences in ADP-induced platelet aggregation responses ex vivo, but the mechanisms underlying this variability are unknown. METHODS AND RESULTS: We examined ADP-induced platelet aggregation responses in 98 healthy volunteers, and we identified 2 phenotypic groups of subjects with high and low responsiveness to 2 micromol/L ADP. This prompted us to screen the recently identified Gi-coupled ADP receptor gene P2Y12 for sequence variations. Among the 5 frequent polymorphisms thus identified, 4 were in total linkage disequilibrium, determining haplotypes H1 and H2, with respective allelic frequencies of 0.86 and 0.14. The number of H2 alleles was associated with the maximal aggregation response to ADP in the overall study population (P=0.007). Downregulation of the platelet cAMP concentration by ADP was more marked in 10 selected H2 carriers than in 10 noncarriers. CONCLUSIONS: In healthy subjects, ADP-induced platelet aggregation is associated with a haplotype of the P2Y12 receptor gene. Given the crucial role of the P2Y12 receptor in platelet functions, carriers of the H2 haplotype may have an increased risk of atherothrombosis and/or a lesser clinical response to drugs inhibiting platelet function.

Adenosine Diphosphate↗
PubMed2000

Estrogen attenuates integrin-beta(3)-dependent adventitial fibroblast migration after inhibition of osteopontin production in vascular smooth muscle cells.

BACKGROUND: Previous in vitro studies have suggested that estrogen attenuates the vascular injury response by modulating vascular smooth muscle cell (VSMC) expression of soluble factor(s) directing migration of adventitial fibroblasts. Previous in vivo studies have established a role for osteopontin (OPN) and its integrin receptors after vascular injury. In this study, we examined OPN expression in activated VSMCs, its modulation by estrogen, and its effects on adventitial fibroblast migration. In addition, the relative functional roles of beta(1)- and beta(3)-integrin-matrix interactions were examined. METHODS AND RESULTS: Primary cultures of VSMCs and adventitial fibroblasts were derived from female Sprague-Dawley rats. Serum-activated VSMCs expressed high levels of OPN mRNA and secreted protein that was effectively inhibited by estrogen treatment (10(-7) mol/L). Compared with VSMCs, fibroblasts expressed similar levels of integrins alphanu and beta(1) and higher levels of integrin-beta(3). Exogenous OPN (5.0 to 40 microg/mL) directed fibroblast migration in a dose-dependent fashion. Anti-beta(3)-integrin antibody (F11) pretreatment markedly inhibited adventitial fibroblast migration directed by exogenous OPN or VSMC-conditioned medium in a dose-dependent manner. In contrast, anti-beta(1)-integrin antibody (Ha2/5) did not affect fibroblast migration. Similarly, pretreatment with either linear or cyclic RGD peptides (10 to 1000 micromol/L) inhibited fibroblast migration directed by OPN or VSMC-conditioned medium in a dose-dependent manner. CONCLUSIONS: These observations suggest that estrogen indirectly attenuates integrin-beta(3)-dependent adventitial fibroblast migration after inhibition of OPN expression in VSMCs.

Animals↗
PubMed2001

Beta(3)-integrin-deficient mice but not P-selectin-deficient mice develop intimal hyperplasia after vascular injury: correlation with leukocyte recruitment to adherent platelets 1 hour after injury.

BACKGROUND: Intimal hyperplasia contributes to restenosis after percutaneous vascular interventions. Both beta(3)-integrins, alpha(V)beta(3) and alpha(IIb)beta(3) (glycoprotein IIb/IIIa), and leukocytes have been implicated in neointimal formation, based in part on the results obtained using antagonists to 1 or both receptors in animal models. METHODS AND RESULTS: The responses in wild-type mice, beta(3)-integrin-deficient mice, and P-selectin-deficient mice were studied in a model of transluminal endothelial injury of the femoral artery. At 4 weeks, beta(3)-integrin-deficient mice were not protected from developing intimal hyperplasia, whereas P-selectin-deficient mice were protected. Within 1 hour of injury, several layers of platelets deposited on the arteries of wild-type mice and a single layer of platelets deposited on the vessels of beta(3)-integrin-deficient mice; in both cases, leukocytes were recruited to the platelet layer. In P-selectin-deficient mice, the platelet layer was less compact and extended further into the lumen but did not recruit leukocytes. CONCLUSIONS: In a model of transluminal arterial injury, absence of early leukocyte recruitment and not deficiency of beta(3)-integrins correlated with a reduction in neointimal formation. Blockade of P-selectins may be an effective therapeutic strategy to decrease restenosis after percutaneous vascular interventions.

Animals↗
PubMed2001

Platelet glycoprotein IIIa Pl(a) polymorphism, fibrinogen, and platelet aggregability: The Framingham Heart Study.

BACKGROUND: Recent data suggest that the Pl(A2) allele of the platelet glycoprotein IIIa receptor may be a genetic risk factor for cardiovascular disease. We previously reported that the Pl(A2) allele was associated with increased platelet aggregability, as indicated by lower epinephrine threshold concentrations. Paradoxically, however, it has been reported that Pl(A2)-positive platelets have reduced fibrinogen binding. Because fibrinogen mediates platelet aggregability, we hypothesized that plasma fibrinogen levels may interact with Pl(A) genotype in modulating platelet aggregability. Methods and Results-- Glycoprotein IIIa Pl(A) genotype, fibrinogen level, and platelet aggregability were ascertained in 1340 subjects enrolled into the Framingham Offspring Study. Platelet aggregability was evaluated by the Born method. Higher fibrinogen levels were associated with increased epinephrine-induced aggregation (P=0.002) and a trend for ADP-induced aggregation (P=0.07). The fibrinogen effect was genotype specific, however, in that the increase in platelet aggregability with higher fibrinogen was present for the Pl(A1/A1) genotype (P=0.0005 and P=0.03 for epinephrine- and ADP-induced aggregation, respectively) but not for the Pl(A2)-positive genotype (P>0.90). CONCLUSION: Higher fibrinogen levels were associated with increased platelet aggregability. However, the association between fibrinogen and platelet aggregability was genotype specific. This interaction may be responsible for the conflicting findings regarding Pl(A) genotype and platelet aggregability. Further study of this gene-environment interaction may provide insight into cardiovascular disease risk.

Adenosine Diphosphate↗
PubMed2002

Outside-in signals delivered by matrix metalloproteinase-1 regulate platelet function.

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade extracellular matrix proteins. These enzymes are implicated in a variety of physiological and pathological events characterized by extracellular matrix remodeling. Recent studies suggest that MMPs may have a signaling capacity, but direct evidence supporting this concept is lacking. In the present study, we demonstrate that outside-in signals delivered by exogenous MMP-1 (interstitial collagenase) markedly increase the number of tyrosine-phosphorylated proteins in platelets. Active MMP-1 also targets beta(3) integrins to areas of cell contact and primes platelets for aggregation. Examination of the endogenous enzyme demonstrated that activated platelets process latent MMP-1 into its active form. Neutralization of MMP-1 activity with MMP inhibitors or specific blocking antibodies markedly attenuates agonist-induced phosphorylation of intracellular proteins, movement of beta(3) integrins to cell contact points, and intercellular aggregation. The finding that MMP-1 is rapidly activated in platelets and controls functional responses identifies a new role for this metalloproteinase as a signaling molecule that regulates thrombotic events.

Antigens, CD↗
PubMed1995

Osteopontin and beta 3 integrin are coordinately expressed in regenerating endothelium in vivo and stimulate Arg-Gly-Asp-dependent endothelial migration in vitro.

Osteopontin is an Arg-Gly-Asp (RGD)-containing acidic glycoprotein postulated to mediate cellular adhesion and migration in a growing number of normal and pathological conditions through interaction with integrin molecules. In this report, we have investigated the potential contributions of osteopontin and one of its receptors, the alpha v beta 3 integrin, to endothelial regenerative processes by using both in vivo and in vitro models. In vivo, uninjured rat arterial endothelium had undetectable levels of osteopontin and beta 3-integrin mRNA by in situ hybridization. After balloon catheter denudation, osteopontin mRNA levels correlated temporally and spatially with active endothelial proliferation and migration, with the highest levels observed at the wound edge between 8 hours and 2 weeks after injury, declining to uninjured levels at 6 weeks, when regeneration was complete. Osteopontin protein levels, as determined by immunocytochemistry, paralleled the time course of mRNA expression. Likewise, beta 3-integrin mRNA and protein levels were substantially elevated in regenerating endothelial cells but were not detectable in uninjured or healed endothelium. In vitro, rat smooth muscle cell-derived and bacterial expressed mouse recombinant osteopontins both stimulated the adhesion and directed migration of bovine aortic endothelial cells through interactions with the alpha v beta 3 receptor. Structural mutants of osteopontin confirmed the importance of the RGD domain for both adhesion and migration of endothelial cells through alpha v beta 3. These data suggest important roles for osteopontin and beta 3 integrin in regenerating endothelium.

Animals↗
PubMed2004

A2 alelle of GpIIIa gene is a risk factor for stroke caused by large-vessel disease in males.

BACKGROUND AND PURPOSE: Glycoprotein IIIa (GpIIIa) is a platelet membrane receptor for fibrinogen and von Willebrand factor. It plays a key role in platelet aggregation. Previous studies in stroke patients, without analysis based on specific subtypes of stroke cause, have not shown any link between GpIIIa A1/A2 polymorphism and stroke risk. We studied the significance of the GpIIIa gene A1/A2 polymorphism in stroke patients with different stroke causes. METHODS: We genotyped 92 patients with stroke caused by large-vessel disease (LVD stroke) and 184 matched controls; 103 patients with stroke caused by small-vessel disease (SVD stroke) and 206 controls; and 182 patients with cardioembolic stroke (CE stroke) and 182 controls (TOAST criteria). The GpIIIa A1/A2 polymorphism was analyzed by polymerase chain reaction followed by restriction enzyme digestion and electrophoresis. RESULTS: The genotype distribution of the GpIIIa gene in patients with LVD stroke (A1/A1, 63%; A1/A2, 34.8%; A2/A2, 2.2%) differed significantly from their controls (A1A1, 79.3%; A1/A2, 20.1%; A2/A2, 0.6%). The distribution of the GpIIIa A1/A2 polymorphism in patients with SVD stroke and CE stroke was similar to that of their controls. In contrast to females with LVD stroke, we found that males with LVD stroke presented with an overrepresentation of at least 1 A2 allele of the GpIIIa gene when compared with their controls (39.7% versus 23.0%; P=0.003). Conditional logistic regression analysis showed that possession of at least 1 A2 allele of the GpIIIa gene was an independent risk factor for LVD stroke in males (OR, 2.51; 95% CI, 1.21 to 5.20). CONCLUSIONS: A2 allele of the GpIIIa gene is an independent risk factor for LVD stroke in males.

Aged↗
PubMed2004

Platelet GP IIIa polymorphism HPA-1 (PlA) protects against subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Few genetic modifications have been identified to be associated with subarachnoid hemorrhage (SAH), most of them playing a role in the formation or size of aneurysms. METHODS: We evaluated the role of common and functional polymorphisms affecting the main platelet adhesive glycoproteins (GP) (GPIIIa: HPA-1; GPIa: HPA-5 and C807T; GPIbalpha: HPA-2 and VNTR) in the risk for development of the disease and in the severity of the onset. The study was performed in 103 patients with SAH, 103 matched controls, and 473 subjects from the general population. RESULTS: The HPA-1b (PlA2) allele significantly protected against SAH (OR, 0.48; 95% CI, 0.24 to 0.96; P=0.037). Interestingly, patients carrying this allele displayed larger aneurysms, but the extension of their hemorrhage and the clinical grade at presentation was significantly lower when compared with patients HPA-1 a/a (11.9+/-2.8 mm versus 8.8+/-2.2 mm, P=0.0001. Fisher grade < or =2: 68.4% versus 20%; P=0.0001; Hunt and Hess score <IV; 84.2% versus 53.8%; P=0.0187, respectively). The protection of the HPA-1b allele seemed to be exacerbated by the simultaneous presence of the HPA-2b allele. Thus, no patient carried this combination, which was present in 7.8% of controls (P=0.007). CONCLUSIONS: We present the first evidence suggesting a protective role for the platelet GPIIIa HPA-1b allele in SAH. The suggested platelet hyper-reactivity determined by this allele could reduce the risk to suffer SAH, specially if the aneurysm is small, attenuate the severity of the hemorrhage, and reduce the clinical grade at presentation. This effect might be amplified by the simultaneous combination with the GPIbalpha HPA-2b allele.

Antigens, Human Platelet↗
PubMed1997

Polymorphisms of the human platelet antigens HPA-1, HPA-2, HPA-3, and HPA-5 on the platelet receptors for fibrinogen (GPIIb/IIIa), von Willebrand factor (GPIb/IX), and collagen (GPIa/IIa) are not correlated with an increased risk for stroke.

BACKGROUND AND PURPOSE: A recent study has described a high incidence of the human platelet antigen (HPA)-1b alloantigen in patients with myocardial infarction. We investigated the distribution of gene polymorphisms of platelet glycoproteins (GPs) in patients with cerebrovascular disease (CVD) and stroke. The polymorphic systems we have studied are HPA-1 and HPA-3 on the fibrinogen receptor (GPIIb/IIIa), HPA-2 on the von Willebrand factor receptor (GPIb/IX), and HPA-5 on one of the platelet collagen receptors (GPIa/IIa). METHODS: DNA was isolated from peripheral blood collected from 218 consecutive stroke patients, 165 neurological inpatients without signs of CVD, and 321 healthy blood donors. The genotypes of HPA-1, HPA-2, HPA-3, and HPA-5 were determined by sequence specific primer polymerase chain reactions. RESULTS: The calculated allele frequencies were as follows: for CVD patients, HPA-1a/b 0.81/0.19, HPA-2a/b 0.91/0.09, HPA-3a/b 0.61/0.39, and HPA-5a/b 0.92/0.08; for inpatient HPA-1a/b 0.83/0.17, HPA-2a/b 0.91/0.09, HPA-3a/b 0.62/0.3 and HPA-5a/b 0.93/0.07; and for blood donors, HPA-1a 0.85/0.15, HPA-2a/b 0.94/0.06, HPA-3a/b 0.60/0.40, and HPA 5a/b 0.92/0.08. There were no statistically significant difference for the analyzed HPA polymorphism frequencies either between the CVD patients and the non-CVD inpatients or the CVD patients and blood donors. However, the HPA-1b genotype was slightly more frequent in patients (CVD and non-CVD) than in the healthy blood donors. CONCLUSIONS: Our results indicate that the HPA-1, HPA-2, HPA-3, and HPA-5 polymorphisms are not associated with an increased risk for stroke.

Adolescent↗
PubMed1998

Platelet glycoprotein receptor IIIa polymorphism P1A2 and ischemic stroke risk: the Stroke Prevention in Young Women Study.

BACKGROUND AND PURPOSE: Platelet glycoprotein IIb/IIa (GpIIb-IIIa), a membrane receptor for fibrinogen and von Willebrand factor, has been implicated in the pathogenesis of acute coronary syndromes but has not been previously investigated in relation to stroke in young adults. METHODS: We used a population-based case-control design to examine the association of the GpIIIa polymorphism P1A2 with stroke in young women. Subjects were 65 cerebral infarction cases (18 patients with and 47 without an identified probable etiology) 15 to 44 years of age from the Baltimore-Washington region and 122 controls frequency matched by age from the same geographic area. A face-to-face interview for vascular disease risk factors and a blood sample for the P1A2 allele and serum cholesterol were obtained from each participant. Logistic regression was used to estimate the odds ratio for one or more P1A2 alleles after adjustment for other risk factors. RESULTS: Among cases and controls, the prevalence rates of one or more P1A2 alleles were 21% and 22% among blacks and 36% and 28% among whites, respectively. This genotype was significantly associated with hypertension only in black control subjects but otherwise not with any of the established vascular risk factors. The adjusted odds ratio for cerebral infarction of one or more P1A2 alleles was 1.1 (confidence interval [CI], 0.6 to 2.3) overall, 0.5 (CI, 0.1 to 7.1) among blacks, and 1.4 (CI, 0.5 to 3.7) among whites. For the cases with an identified probable etiology, the corresponding odds ratios were 3.0 (CI, 0.9 to 10.4) overall, 0.7 (CI, 0.1 to 7.1) among blacks, and 12.8 (CI, 1.2 to 135.0) among whites. CONCLUSIONS: No association was found between the P1A2 polymorphism of GpIIIa and young women with stroke. However, subgroup analyses showed that the P1A2 polymorphism of GpIIIa appeared to be associated with stroke risk among white women, particularly those with a clinically identified probable etiology for their stroke. Further work with an emphasis on stroke subtypes and with multiracial populations is warranted.

Adolescent↗
PubMed2001

Pl(A2) polymorphism of beta(3) integrins is associated with enhanced thrombin generation and impaired antithrombotic action of aspirin at the site of microvascular injury.

BACKGROUND: Mechanisms by which the Pl(A2) (Leu33Pro) polymorphism of beta(3) integrins could lead to an increased risk for coronary events are unclear. This study was designed to examine the effect of this polymorphism on blood coagulation. METHODS AND RESULTS: In normal subjects (12 with Pl(A1A1), 9 with Pl(A1A2), and 3 with Pl(A2A2)), we evaluated the activation of prothrombin, factor V, and factor XIII and fibrinogen removal by quantitative immunoblotting; thrombin-antithrombin III complex generation using ELISA; and levels of fibrinopeptide A and B by high-performance liquid chromatography in blood collected every 30 seconds at sites of standardized microvascular injury before and after 7 days of aspirin ingestion (75 mg/d). Compared with the Pl(A1A1) subjects, the Pl(A2) carriers exhibited higher maximum rates of thrombin B-chain generation (by 31.6%; P=0.005), thrombin-antithrombin III complex generation (by 30.7%; P=0.003), fibrinogen consumption (by 31.3%; P=0.002), prothrombin consumption (by 26.1%; P=0.011), and activation of factor V (by 14.1%; P=0.033) and factor XIII (by 27.0%; P=0.012). In the Pl(A1A1) homozygotes, aspirin ingestion resulted in reductions in the velocity of thrombin B-chain formation (by 32.1%; P=0.007), prothrombin consumption (by 30.4%; P=0.018), factor Va generation (by 28.9%; P=0.014), fibrinogen removal (by 41.2%; P=0.001), and factor XIII activation (by 22.6%; P=0.026). In the Pl(A2) carriers, aspirin did not alter the velocity of all these processes. After aspirin ingestion, fibrinopeptide A and B concentrations in the last 30-second interval were significantly reduced, but only in the Pl(A1A1) subjects. CONCLUSIONS: The presence of the Pl(A2) allele is associated with enhanced thrombin formation and an impaired antithrombotic action of aspirin, which might favor coronary thrombosis in the Pl(A2) carriers.

Adult↗
PubMed2001

Disordered cellular migration and angiogenesis in cd39-null mice.

BACKGROUND: Nucleoside triphosphate diphosphohydrolase-1 (NTPDase1)/CD39 is the major ectonucleotidase of endothelial cells and monocytes and catalyzes phosphohydrolysis of extracellular nucleoside diphosphates (NDP) and triphosphates (NTP, eg, ATP and UTP). Deletion of cd39 causes perturbations in the hydrolysis of NTP and NDP in the vasculature. Activation of P2 receptors appears to influence endothelial cell chemotactic and mitogenic responses in vitro. Therefore, aberrant regulation of nucleotide P2 receptors may influence angiogenesis in cd39-null mice. Methods and Results- In control mice, implanted Matrigel plugs containing growth factors were rapidly populated by monocyte/macrophages, endothelial cells, and pericytes, with the development of new vessels over days. In cd39-null mice, migrating cells were completely confined to the tissue-Matrigel interface in a clearly stratified manner. Absolute failure of new vessel ingrowth was consistently observed in the mutant mice. Linked to these findings, chemotaxis of cd39-null monocyte/macrophages to nucleotides was impaired in vitro. This abnormality was associated with desensitization of nucleotide receptor P2Y-mediated signaling pathways. CONCLUSIONS: Our findings demonstrate a role for NTPDase1 and phosphohydrolysis of extracellular nucleotides in the regulation of the cellular infiltration and new vessel growth in a model of angiogenesis.

Acid Anhydride Hydrolases↗
PubMed2001

Cerebrovascular events in patients with significant stenosis of the carotid artery are associated with hyperhomocysteinemia and platelet antigen-1 (Leu33Pro) polymorphism.

BACKGROUND AND PURPOSE: Although risk factors for carotid artery stenosis caused by atherosclerosis are known, it is unclear what triggers "activation" of the atherosclerotic plaques and the ensuing thromboembolic cerebral events. The aim of this study was to evaluate whether thrombophilic factors, platelet glycoprotein (GP) polymorphisms, and homocysteine are associated with a risk of ischemic events in patients with significant carotid stenosis. METHODS: Consecutive patients with >/=50% carotid stenosis, whether symptomatic (with ipsilateral ischemic events) or asymptomatic, who were evaluated and followed in a neurovascular clinic were tested for plasma levels of homocysteine, C677T mutation in methylenetetrahydrofolate reductase, G20210A mutation of factor II, factor V Leiden, antiphospholipid antibodies, and polymorphisms of platelet membrane GP: human platelet antigen (HPA)-1, GP Ia (C807T), and GP Ib (variable number of tandem repeats, Kozak, and HPA-2). RESULTS: Eighty-six asymptomatic and 67 symptomatic patients were evaluated. The former group was older (73.7+/-6.9 versus 69.5+/-9.1 years, P=0.02). Major risk factors for stroke were similar in both groups. In symptomatic patients versus asymptomatic patients, hyperhomocysteinemia was 3-fold more frequent (34.3% versus 12.8%, respectively; P=0.002) and HPA-1a/b was almost 2-fold more common (38.8% versus 20.9%, respectively; P=0.01). All other thrombophilic factors and platelet polymorphisms studied did not differ significantly between the 2 groups. Multivariate analysis revealed that hyperhomocysteinemia and the HPA-1a/b genotype conferred a significant risk of cerebral ischemic events, with odds ratios (95% CI) of 4.07 (1.7 to 9.7) and 3.4 (1.5 to 7.8), respectively. CONCLUSIONS: Hyperhomocysteinemia and HPA-1a/b are independent risk factors for ischemic events in patients with significant carotid stenosis.

Aged↗
PubMed1987

On the association of the platelet-specific alloantigen, Pena, with glycoprotein IIIa. Evidence for heterogeneity of glycoprotein IIIa.

Neonatal alloimmune thrombocytopenic purpura associated with a new platelet-specific alloantigen Pena has been reported. We now provide direct evidence that the Pena determinant is associated with glycoprotein (GP) IIIa, but that it is distinct from epitopes that define the PlA system. By ELISA wherein monoclonal antibodies specific for GPIIb (Tab) and specific for GPIIIa (AP3) were used to capture and hold antigens from a platelet lysate prepared under conditions that generate free GPIIb and GPIIIa, anti-Pena reacted with GPIIIa held by AP3 but not with GPIIb held by Tab. In an alternative ELISA where purified GPIIIa from both PlA1-positive and PlA1-negative platelets were used individually as antigen, anti-Pena reacted with both allelic forms of GPIIIa. By radioimmuno-precipitation, anti-Pena precipitated a single surface-labeled membrane protein with electrophoretic characteristics in sodium dodecyl sulfate-polyacrylamide gels, under nonreduced or reduced conditions, identical to those of GPIIIa. By fluorocytometry, platelets from several donors, regardless of PlA phenotype, bound an amount of anti-Pena roughly equivalent to one-half that amount of anti-PlA1 bound by PlA1 homozygous (A1/A1) platelets and roughly equal to that amount of anti-PlA1 bound by PlA1 heterozygous (A1/A2) platelets. Using platelets from donors typed homozygous for PlA1 and Pena in a quantitative indirect binding assay, 14-24,000 molecules of anti-Pena and 41-51,000 molecules of anti-PlA1 were bound per platelet at saturation. Anti-Pena completely inhibited ADP-induced aggregation of Pena-positive platelets, regardless of PlA phenotype. These results indicate that the Pena determinant is associated with GPIIIa but distinct from PlA.

Antigens, Human Platelet↗
PubMed1989

The human platelet alloantigens, PlA1 and PlA2, are associated with a leucine33/proline33 amino acid polymorphism in membrane glycoprotein IIIa, and are distinguishable by DNA typing.

The human platelet alloantigens, PlA1 and PlA2, comprise a diallelic antigen system located on a component of the platelet fibrinogen receptor, membrane glycoprotein (GP) IIIa. Of the known platelet alloantigens, PlA1, which is carried by 98% of the caucasian population, appears to be the alloantigen that most often provokes neonatal alloimmune thrombocytopenic purpura and posttransfusion purpura. The structural features of the GPIIIa molecule responsible for its antigenicity are as yet unknown. Using the polymerase chain reaction (PcR), we amplified the NH2-terminal region of platelet GPIIIa mRNA derived from PlA1 and PlA2 homozygous individuals. Nucleotide sequence analysis of selected amplified cDNA products revealed a C in equilibrium T polymorphism at base 196 that created a unique Nci I restriction enzyme cleavage site in the PlA2, but not the PlA1 form of GPIIIa cDNA. Subsequent restriction enzyme analysis of cDNAs generated by PcR from 10 PlA1/A1, 5 PlA2/A2, and 3 PlA1/A2 individuals showed that Nci I digestion permitted clear discrimination between the PlA1 and PlA2 alleles of GPIIIa. All PlA2/A2 individuals studied contain a C at base 196, whereas PlA1 homozygotes have a T at this position. This single base change results in a leucine/proline polymorphism at amino acid 33 from the NH2-terminus, and is likely to impart significant differences in the secondary structures of these two allelic forms of the GPIIIa molecule. The ability to perform DNA-typing analysis for PlA phenotype may have a number of useful clinical applications, including fetal testing and determination of the phenotype of severely thrombocytopenic individuals.

Amino Acid Sequence↗
PubMed2003

c-Fms and the alphavbeta3 integrin collaborate during osteoclast differentiation.

beta(3) integrin-null osteoclasts are dysfunctional, but their numbers are increased in vivo. In vitro, however, the number of beta(3)(-/-) osteoclasts is reduced because of arrested differentiation. This paradox suggests cytokine regulation of beta(3)(-/-) osteoclastogenesis differs in vitro and in vivo. In vitro, additional MCSF, but not receptor activator of NF-kappaB ligand (RANKL), completely rescues beta(3)(-/-) osteoclastogenesis. Similarly, activation of extracellular signal-regulated kinases (ERKs) and expression of c-Fos, both essential for osteoclastogenesis, are attenuated in beta(3)(-/-) preosteoclasts, but completely restored by additional MCSF. In fact, circulating and bone marrow cell membrane-bound MCSFs are enhanced in beta(3)(-/-) mice, correlating with the increase in the osteoclast number. To identify components of the MCSF receptor that is critical for osteoclastogenesis in beta(3)(-/-) cells, we retrovirally transduced authentic osteoclast precursors with chimeric c-Fms constructs containing various cytoplasmic domain mutations. Normalization of osteoclastogenesis and ERK activation, in beta(3)(-/-) cells, uniquely requires c-Fms tyrosine 697. Finally, like high-dose MCSF, overexpression of c-Fos normalizes the number of beta(3)(-/-) osteoclasts in vitro, but not their ability to resorb dentin. Thus, while c-Fms and alpha(v)beta(3) collaborate in the osteoclastogenic process via shared activation of the ERK/c-Fos signaling pathway, the integrin is essential for matrix degradation.

Animals↗
PubMed2001

High-resolution CryoFESEM of individual cell adhesion molecules (CAMs) in the glycocalyx of human platelets: detection of P-selectin (CD62P), GPI-IX complex (CD42A/CD42B alpha,B beta), and integrin GPIIbIIIa (CD41/CD61) by immunogold labeling and stereo imaging.

The aim of this study was to develop a model for the detection of individual cell adhesion molecules (CAMs) in the glycocalyx of spread human platelets using high-resolution cryo-field emission scanning electron microscopy (cryoFESEM). Three surface glycoprotein CAMs, P-selectin (CD62P), GPIba in the GPI-IX complex (CD42a/CD42b alpha,b beta), and the integrin GPIIbIIIa (CD41/CD61) in the human platelet were selected on the basis of their unique topographic shape. Spread human platelets were indirectly immunolabeled with 10-nm colloidal gold and then cryoimmobilized. After sublimation of water from the cryoimmobilized sample, partially freeze-dried platelets were coated unidirectionally with Pt, stabilized with carbon, and examined in an in-lens cryoFESEM using high-resolution backscattered electron imaging. CAMs were detected by indirect immunogold labeling and the length of each type of CAM was determined using analysis of differences in parallax as measured in the software program Sterecon. Our results demonstrate the efficacy of using high-resolution cryoFESEM to recognize and detect individual CAMs in the glycocalyx. Further advances in production of metal coatings with finer granularity, together with improvements in imaging (tilting and angle of stereo images), may provide better definition of the topography associated with glycosylation and formation of multimeric CAM complexes. (J Histochem Cytochem 49:809-819, 2001)

Antigens, CD↗