Participation of calpain I activation in the ATP release reaction of platelets stimulated with thrombin.
Proteolytic activation of calpain (calcium-dependent neutral protease) I in thrombin-stimulated platelets was determined by following the production of the 76- and 78-kDa forms from the 80-kDa subunit of calpain I as measured by immunoblotting using monospecific antibody to human calpain I, and the correlation between the extents of calpain I activation and ATP release was investigated. When platelets were stimulated with thrombin in the range from 0.01 to 0.5 U/ml, the maximal 60% activation of calpain I was achieved within 15 s after the stimulation, and ATP release began after the maximal activation had been reached. The extent of ATP release decreased in parallel with the decrease in activation ratio of calpain I on treatment of platelets with EGTA or EST, a membrane-permeable inhibitor of calpain. Although pretreatment of platelets with EST did not affect the thrombin-dependent elevation of the cytosolic Ca2+ concentration, both the inhibition of calpain I activation and the reduction of ATP release were observed as a function of EST concentration. These results suggest that calpain I participates in one of the processes leading to the ATP release reaction of platelets stimulated with thrombin.
Ishii
H
H
Department of Clinical Biochemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa, Japan.
Suzuki
Y
Y
Horie
S
S
Nakagawa
M
M
Kazama
M
M
D000255:Adenosine Triphosphate / Q000032:analysis*; D000906:Antibodies; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002154:Calpain / Q000276:immunology / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D015539:Platelet Activation / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors
D000906:Antibodies; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D013917:Thrombin; D002154:Calpain