The effect of the intracellular calcium chelator Quin-2 on the platelet phosphoinositide metabolism, protein phosphorylation and morphology.
When human platelets prelabeled with [32P] orthophosphate were loaded with Quin-2, the 32P-incorporation in phosphatidic acid, phosphatidylinositol-4 phosphate and phosphatidylinositol-4,5 bisphosphate increased, that in phosphatidylinositol decreased. These effects occurred in a Quin-2-concentration-dependent manner. On stimulation of the serotonin-S2 receptor, signal transduction, measured as changes in labeling in phospholipids and phosphoproteins, was altered in the presence of the fluorophore. Microscopic evaluation illustrated that Quin-2 affected platelet morphology as well in resting as in stimulated platelets. A correlation between platelet shape change and myosin light chain phosphorylation was apparent. The data evidence that the Quin-2 that is widely used for fluorometric determination of intracellular Ca2+, affects the metabolism of inositol-containing phospholipids whose breakdown is a key event in Ca2+-mobilization on excitatory platelet activation. These fluorophore-induced alterations might, besides the Ca2-chelating properties, play an important role in the Ca2+-dependent signalling processes in these cells.
de Chaffoy de Courcelles
D
D
Department of Biochemistry, Janssen Pharmaceutica, Beerse, Belgium.
Roevens
P
P
Verheyen
F
F
Van Belle
H
H
De Clerck
F
F
D000634:Aminoquinolines / Q000494:pharmacology*; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D002118:Calcium / Q000097:blood* / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D010716:Phosphatidylinositols / Q000097:blood*; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology
D000634:Aminoquinolines; D001798:Blood Proteins; D010716:Phosphatidylinositols; D011985:Receptors, Serotonin; D012701:Serotonin; C035739:Quin2; D002118:Calcium