Calcium store depletion in dimethyl BAPTA-loaded human platelets increases protein tyrosine phosphorylation in the absence of a rise in cytosolic calcium.
The endomembrane Ca(2+)-ATPase inhibitor, thapsigargin, was used to deplete the intracellular Ca2+ stores of fura-2-loaded human platelets. In control cells, thapsigargin evoked a rise in cytosolic [Ca2+] and a substantial increase in protein tyrosine phosphorylation. Thapsigargin also evoked an increase in tyrosine phosphorylation in cells co-loaded with fura-2 and the Ca2+ chelator dimethyl BAPTA, such that the rise in cytosolic [Ca2+] was abolished. These data support the existence of a tyrosine phosphatase regulated by the Ca2+ content of the intracellular store, a requirement of the putative model for reciprocal control of Ca2+ entry by cytosolic and store [Ca2+] via protein tyrosine phosphorylation.
Sargeant
P
P
Physiological Laboratory, University of Cambridge.
Farndale
R W
RW
Sage
S O
SO
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D016257:Fura-2; D006801:Humans; D010766:Phosphorylation; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014443:Tyrosine / Q000378:metabolism*
D002614:Chelating Agents; D013729:Terpenes; D014443:Tyrosine; D004533:Egtazic Acid; D019284:Thapsigargin; C058180:5,5'-dimethyl-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate; D002118:Calcium; D016257:Fura-2; D004121:Dimethyl Sulfoxide