Role of nitric oxide synthase in collagen-platelet interaction: Involvement of platelet nonintegrin collagen receptor nitrotyrosylation

Platelets possess the endothelial isoform of nitric oxide synthase (eNOS), which plays an important role in platelet function. Other laboratories, inc luding ours, have reported that nitric oxide (NO) is released upon exposure of platelets to collagen, but the mechanism of the interaction is not yet established. The objective of this study is to examine the possible role of nonintegrin receptor nitrotyrosylation on collagen-induced platelet aggreg ation. Results of the study show that two platelet proteins with M-r of 65- and 23-kDa proteins are nitrotyrosylated in a time-dependent manner after the addition of type I collagen. The M-r 65-kDa protein is identified as th e platelet receptor for type I collagen. The recombinant protein of the pla telet receptor for type I collagen can also be nitrotyrosylated. The nitrot yrosylated recombinant protein loses its ability to inhibit type I collagen -induced platelet aggregation. In addition, the polyclonal anti-65 kDa immu noprecipitates eNOS suggesting that the platelet nonintegrin receptor for t ype I collagen is closely linked to the eNOS. These results demonstrate tha t the inhibitory effect of NO on collagen-induced platelet aggregation may be mediated by the nitrotyrosylation of the 65-kDa receptor. (C) 2001 Elsev ier Science Ltd. All rights reserved.