The effect of calcium-store depletion and refilling with various bivalent cations on tyrosine phosphorylation and Mn2+ entry in fura-2-loaded human platelets.
To investigate the possible involvement of tyrosine phosphorylation in the process of store-regulated Ca2+ entry, ionomycin (in the presence of EGTA) was used to deplete the intracellular Ca2+ stores of fura-2-loaded human platelets, and the effect of refilling with Ca2+, Ba2+ or Sr2+ evaluated. Depletion of the intracellular Ca2+ stores resulted in an increase in protein tyrosine phosporylation. This increase is reversed when the stores were refilled in Ca2+ or Sr2+, but not Ba2+. Refilling of the stores with Ca2+ or Sr2+, but not Ba2+, suppressed Mn2+ entry. These findings support the hypothesis that tyrosine phosphorylation plays a role in mediating store-regulated Ca2+ entry in human platelets and provides evidence for tyrosine phosphatase activity regulated by the Ca2+ content of the intracellular stores.
Physiological Laboratory, University of Cambridge, U.K.
S
S
Jenner
R W
RW
Farndale
S O
SO
Sage
D001464:Barium / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D003720:Densitometry; D004533:Egtazic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D016257:Fura-2 / Q000737:chemistry; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D008345:Manganese / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013324:Strontium / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry*
D001464:Barium; D014443:Tyrosine; D008345:Manganese; D004533:Egtazic Acid; D015759:Ionomycin; D017027:Protein Tyrosine Phosphatases; D002118:Calcium; D016257:Fura-2; D013324:Strontium