title: Combined defect in membrane expression and activation of platelet GPIIb--IIIa complex without primary sequence abnormalities in myeloproliferative disease.
abstract: Defects in glycoprotein (GP)IIb-IIIa or in its activation may cause abnormal platelet aggregation and a bleeding diathesis. We report studies in a 67-year-old man with a myeloproliferative disease and markedly abnormal platelet responses. By flow cytometry, platelet binding of two complex-specific anti-GPIIb-IIIa monoclonal antibodies (mAbs), A2A9 and 10E5, was approximately 50% of normal. An enzyme-linked immunosorbent assay (ELISA) using immobilized kistrin showed 18% of normal membrane GPIIb-IIIa complex. By immunoblot analysis, GPIIb and GPIIIa levels in platelet lysates and membranes were near normal. Activation of GPIIb-IIIa, monitored with mAb PAC-1, was markedly decreased (< 20% of normal) in response to ADP, thrombin and platelet-activating factor (PAF); expression of ligand-induced binding sites (LIBS) was < or = 30% of normal. Signal transduction-independent LIBS expression, induced by echistatin, was approximately 60% of normal, suggesting that the integrin present had intact ligand-binding capability. Sequence analysis of GPIIb and GPIIIa cDNA, and platelet mRNA levels for both subunits, were normal. These findings document an acquired combined defect in membrane expression (secondary to a defect in post-translational processing of the complex) and inside-out signalling-dependent activation of the GPIIb-IIIa complex.
authors: Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA.
authors: R
authors: R
authors: Kaplan
authors: J
authors: J
authors: Gabbeta
authors: L
authors: L
authors: Sun
authors: G F
authors: GF
authors: Mao
authors: A K
authors: AK
authors: Rao
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000368:Aged; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001665:Binding Sites; D001792:Blood Platelets / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D004075:Diglycerides / Q000494:pharmacology; D020536:Enzyme Activators / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D036341:Intercellular Signaling Peptides and Proteins; D007476:Ionophores / Q000494:pharmacology; D016177:Macrophage-1 Antigen / Q000032:analysis; D008297:Male; D009196:Myeloproliferative Disorders / Q000097:blood* / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D010455:Peptides / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000494:pharmacology; D010974:Platelet Aggregation; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000032:analysis / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D018179:Receptors, Thrombin / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000911:Antibodies, Monoclonal; D018076:DNA, Complementary; D004075:Diglycerides; D020536:Enzyme Activators; D036341:Intercellular Signaling Peptides and Proteins; D007476:Ionophores; D016177:Macrophage-1 Antigen; D010455:Peptides; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D012333:RNA, Messenger; D018179:Receptors, Thrombin; C044295:1,2-dioctanoylglycerol; C057986:echistatin; D012701:Serotonin; D000001:Calcimycin; D000244:Adenosine Diphosphate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D011493:Protein Kinase C