Platelet adhesion to collagen activates a phosphoprotein complex of heat-shock proteins and protein phosphatase 1.
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.
Gear
A R
AR
Department of Biochemistry, University of Virginia, Charlottesville, USA.
Simon
C G
CG
Polanowska-Grabowska
R
R
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
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