title: Platelet adhesion to collagen activates a phosphoprotein complex of heat-shock proteins and protein phosphatase 1.
abstract: Rapid activation of blood platelets is required for effective haemostasis, with shape change, aggregation, secretion of granule contents and cell adhesion occurring in seconds or even milliseconds. Signal-transduction events, evidenced by changes in protein phosphorylation and calcium levels, also take place in this time domain. We have now shown that platelet adhesion to collagen via the alpha 2 beta 1 integrin under arterial shear forces initiated the rapid dephosphorylation of a 67 kDa protein "band" which contained the 70 kDa constitutive heat-shock protein, hsc70. Immunoprecipitation with hsc70 antibodies revealed a large phosphoprotein complex in resting platelets and adhesion caused dissociation of the complex along with dephosphorylation of hsc70. The complex also contained the hsp90 heat-shock protein, protein phosphatase IC, alpha, delta and M subunits, and some 7-8 unidentified phosphoproteins. The data suggest that heat-shock proteins and protein phosphatases are actively involved in integrin-mediated platelet adhesion.
authors.affiliation: Department of Biochemistry, University of Virginia, Charlottesville, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Gear
authors.forename: C G
authors.initials: CG
authors.lastname: Simon
authors.forename: R
authors.initials: R
authors.lastname: Polanowska-Grabowska
mesh_terms: D001711:Biotransformation / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D007700:Kinetics; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010973:Platelet Adhesiveness / Q000187:drug effects*; D011233:Precipitin Tests; D054645:Protein Phosphatase 1; D015398:Signal Transduction / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology
chemical_list: D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010750:Phosphoproteins; D003094:Collagen; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D013917:Thrombin