Involvement of phosphoprotein phosphatase 1 in collagen-platelet interaction.
The binding of type I collagen to its receptor initiates platelet aggregation, but the relationship of the receptor to other signal transduction components is not yet established. Correlation of platelet aggregation and anti-type I collagen receptor antibody immunoprecipitation of type I collagen treated [32PO4]-labeled platelets showed that there are two phosphoproteins (M(r) 53 kDa and 21 kDa) that coprecipitated with the 65 kDa platelet type I collagen receptor. In the present investigation, we have identified one of the phosphoproteins. A soluble component the 100,000x g supernatant fraction of 53 kDa protein is recognized by polyclonal anti-PP1 antibody. The activity of the precipitated phosphatase is inhibited by okadaic acid and inhibitor 1, suggesting that it is protein phosphatase 1 (PP 1). Phosphorylation decreases PP 1 activity as was found with [32PO4]-phosphorylase b as the substrate. The immunocoprecipitation of the type-1 collagen receptor and PP 1 inot the result of cross reactivity of the anti-type I collagen receptor antibody with the PP I protein. These results indicate that the platelet type I collagen receptor, PP 1, and unidentified 21 kDa protein are in close association with the platelet type I collagen receptor upon the binding of type I collagen by the receptor.
Chiang
T M
TM
Research Service, VA Medical Center, Memphis, TN 38104, USA.
Kang
E S
ES
Kang
A H
AH
D001792:Blood Platelets / Q000502:physiology*; D003094:Collagen / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D010974:Platelet Aggregation; D054645:Protein Phosphatase 1; D038981:Receptors, Collagen
D016023:Integrins; D038981:Receptors, Collagen; D003094:Collagen; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1