Platelet cell-surface protein disulphide-isomerase mediated S-nitrosoglutathione consumption.
S-nitrosothiols (RSNOs) regulate several aspects of platelet physiology including inhibition of activation, adhesion and aggregation. PDI (protein disulphide-isomerase) has recently been found to be localized to the cell surface, where it exhibits both disulphide-exchange and denitrosation activities. The disulphide-exchange activity of PDI has been linked to aspects of platelet aggregation. The present study suggests that the metabolism of RSNOs by platelets is a function of PDI denitrosation activity. Exposure of washed human platelets to increasing concentrations of GSNO (S-nitrosoglutathione) resulted in saturable denitrosation kinetics. The presence of known PDI inhibitors phenylarsine oxide and anti-PDI antibodies prevented GSNO denitrosation. The fact that, in the presence of GSNO plus the cell-permeable guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxaline-1-one, the initial rates of ADP-induced platelet aggregation and the maximum DeltaOD were diminished by approximately 40% shows that RSNOs have dual inhibitory effects on platelets, which are mediated through PDI. First, PDI denitrosates RSNOs, releasing NO that, via the guanylate cyclase/G-kinase route, attenuates platelet activation. Secondly, RSNOs are denitrosated at the same PDI-active site that catalyses the disulphide bond formation between integrins and their ligands, thereby attenuating irreversible aggregation.
Root
Paul
P
Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Ave., Windsor, ON, Canada N9B 3P4.
Sliskovic
Inga
I
Mutus
Bulent
B
D001792:Blood Platelets / Q000201:enzymology* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology; D019704:Protein Disulfide-Isomerases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D026422:S-Nitrosoglutathione / Q000378:metabolism*
D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D026422:S-Nitrosoglutathione; D019704:Protein Disulfide-Isomerases