title: A ras-related protein is phosphorylated and translocated by agonists that increase cAMP levels in human platelets.
abstract: The antigenicity of platelet proteins was assayed against various monoclonal antibodies (mAbs) that recognize specific epitopes of the ras-encoded p21 protein. mAb M90, which detects the region of p21 protein within amino acids 107-130 and inhibits its GTP-binding activity, strongly reacted with a 22-kDa protein present in the particulate fraction of human platelets. Other mAbs against ras-encoded proteins, including Y13-259, which efficiently detects ras proteins from a variety of organisms, did not recognize the platelet 22-kDa protein. Transfer of the platelet 22-kDa protein to nitrocellulose paper showed that the protein binds [alpha-32P]GTP. Moreover, preincubation of the transferred protein with mAb M90 drastically reduced its GTP-binding activity. Treatment of platelets with iloprost, a prostacyclin analog, caused (i) a time-dependent increase of a 24-kDa protein that is recognized by mAb M90 in particulate and cytosolic fractions and (ii) the gradual decrease of the 22-kDa protein from the particulate fraction. When platelets were labeled with 32P and then treated with iloprost, the 24-kDa protein was found to be phosphorylated. The 32P-labeled 24-kDa protein was specifically immunoprecipitated by mAb M90. These results suggest that appearance of the 24-kDa protein results from phosphorylation of the 22-kDa protein, which shifts its mobility to a higher molecular mass area.
authors: Division of Cell Biology, Burroughs Wellcome Company, Research Triangle Park, NC 27709.
authors: E G
authors: EG
authors: Lapetina
authors: J C
authors: JC
authors: Lacal
authors: B R
authors: BR
authors: Reep
authors: L
authors: L
authors: Molina y Vedia
mesh_terms: D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D001665:Binding Sites; D001692:Biological Transport; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000097:blood*; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000276:immunology; D011464:Epoprostenol / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000097:blood; D006801:Humans; D016285:Iloprost; D007163:Immunosorbent Techniques; D008565:Membrane Proteins; D008970:Molecular Weight; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood; D011518:Proto-Oncogene Proteins / Q000097:blood*; D016283:Proto-Oncogene Proteins p21(ras)
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D006160:Guanosine Triphosphate; D011464:Epoprostenol; D000242:Cyclic AMP; D011494:Protein Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D016285:Iloprost