title: Association of CIB with GPIIb/IIIa during outside-in signaling is required for platelet spreading on fibrinogen.
abstract: Platelet spreading on immobilized fibrinogen (Fg) involves progression through a number of morphologic stages that, although distinctive, are not well understood mechanistically. Here we demonstrate that an association between GPIIb/IIIa and calcium- and integrin-binding protein (CIB) is required for the process of platelet spreading. Upon platelet adhesion to immobilized Fg, CIB localizes to the transiently formed filopodia and then redistributes diffusely along the membrane periphery of spread platelets. Immunoprecipitation analyses indicate that CIB and glycoprotein IIb/IIIa (GPIIb/IIIa) interact with each other as platelets adhere to immobilized Fg, and together they associate with the platelet cytoskeleton. Introduction of anti-CIB antibody or GPIIb cytoplasmic peptide into platelets blocks lamellipodia but not filopodia formation. GPIIb peptide-induced inhibition of platelet spreading is recovered by the incorporation of recombinant CIB protein, suggesting that interaction between CIB and GPIIb/IIIa is required for progression from filopodial to spread morphologies. Further, anti-CIB- or GPIIb peptide-induced inhibition of platelet spreading can be overcome by the addition of exogenous adenosine diphosphate (ADP). These data suggest that formation of the CIB-GPIIb/IIIa complex may be necessary for initiation of downstream signaling events, such as ADP secretion, that lead to platelet spreading.
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA. unaik@udel.edu
authors.forename: Ulhas P
authors.initials: UP
authors.lastname: Naik
authors.forename: Meghna U
authors.initials: MU
authors.lastname: Naik
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002465:Cell Movement / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D008875:Middle Aged; D010973:Platelet Adhesiveness / Q000502:physiology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011233:Precipitin Tests; D011554:Pseudopodia / Q000378:metabolism / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology
chemical_list: C109198:CIB1 protein, human; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011994:Recombinant Proteins; D000244:Adenosine Diphosphate; D005340:Fibrinogen