title: Treatment of human platelets with trypsin, thrombin, or collagen inhibits the pertussis toxin-induced ADP-ribosylation of a 41-kDa protein.
abstract: Permeabilization of human platelets with saponin (15-25 micrograms/ml) allows the determination of the ADP-ribosylation of a 41-kDa protein by pertussis toxin. The ADP-ribosylated protein is present in the particulate fraction. ADP-ribosylation of the 41-kDa protein increases for 20 min; it is not affected by indomethacin, prostacyclin, and 1,2-diacylglycerols but is inhibited by 1 mM Ca2+ and phorbol esters. Treatment of platelets with trypsin, thrombin, or collagen before saponin addition precludes subsequent pertussis toxin-induced ADP-ribosylation of the 41-kDa protein. The effect of trypsin or thrombin is blocked by soybean trypsin inhibitor and leupeptin. Trypsin proteolytically cleaves the ADP-ribosylated 41-kDa protein to an ADP-ribosylated fragment slightly smaller than 20 kDa. The results suggest that a modification of a guanine nucleotide-binding regulatory protein is associated with the actions of trypsin, thrombin, and collagen on platelet activation.
authors.forename: E G
authors.initials: EG
authors.lastname: Lapetina
authors.forename: B
authors.initials: B
authors.lastname: Reep
authors.forename: K J
authors.initials: KJ
authors.lastname: Chang
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D002463:Cell Membrane Permeability; D003094:Collagen / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D037342:Pertussis Toxin; D013917:Thrombin / Q000502:physiology*; D014357:Trypsin / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D001798:Blood Proteins; D009702:Nucleoside Diphosphate Sugars; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D003094:Collagen; D037342:Pertussis Toxin; D014357:Trypsin; D013917:Thrombin