| 18439569 |
Lopez JJ, Jardin I, Bobe R, Pariente JA, Enouf J, Salido GM, Rosado JA: STIM1 regulates acidic Ca2+ store refilling by interaction with SERCA3 in human platelets. Biochem Pharmacol. 2008 Jun 1;75(11):2157-64. Epub 2008 Mar 22.
Ca (2+) mobilization regulates a wide variety of cellular functions. Platelets possess agonist-releasable Ca (2+) stores in acidic organelles where sarcoendoplasmic reticulum Ca (2+)-ATPase-3 (SERCA) pump is involved in store refilling. Stromal interaction molecule 1 (STIM1), which has been presented as a central regulator of platelet function, is a Ca (2+) sensor of the intracellular Ca (2+) stores. Here we present that STIM1 is required for acidic store refilling. Electrotransjection of cells with anti-STIM1 (Y (231)-K (243)) antibody, directed towards a cytoplasmic sequence of STIM1, significantly reduced acidic store refilling, which was tested by remobilizing Ca (2+) from the acidic stores using 2,5-di-(t-butyl)-1,4-hydroquinone (TBHQ) after a brief refilling period that followed thrombin stimulation. Platelet treatment with thrombin or thapsigargin in combination with ionomycin, to induce extensive Ca (2+) store depletion, resulted in a transient increase in the interaction between STIM1 and SERCA3, reaching a maximum 30 s after stimulation. The coupling between STIM1 and SERCA3 was abolished by electrotransjection with anti-STIM1 antibody. The interaction between STIM1 and SERCA3 induced by thrombin or by treatment with thapsigargin plus ionomycin is reduced in platelets from type 2 diabetic patients, as well as Ca (2+) reuptake into the acidic Ca (2+) stores. These findings provide evidence for a role of STIM1 in acidic store refilling in platelets probably acting as a Ca (2+) sensor and regulating the activity of SERCA3. This action is impaired in platelets from type 2 diabetics, which might lead to the enhanced cytosolic Ca (2+) concentration observed and, therefore, in platelet hyperactivity. |
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