Disruption and stabilization of β-cell actin microfilaments differently influence insulin secretion triggered by intracellular Ca2+ mobilization or store-operated Ca2+ entry

AbstractLatrunculin depolymerizes and jasplakinolide polymerizes β-cell actin microfilaments. Both increase insulin secretion when Ca2+ enters β-cells during depolarization by glucose, sulfonylureas or potassium. Mouse islets were held hyperpolarized with diazoxide, and stimulated with acetylcholine to test the role of microfilaments in insulin secretion triggered by intracellular Ca2+ mobilization and store-operated Ca2+ entry (SOCE).Jasplakinolide slightly attenuated Ca2+ mobilization and did not affect SOCE, but consistently inhibited the attending insulin secretion. Latrunculin did not affect Ca2+ changes induced by acetylcholine, but consistently increased insulin secretion, its effect being larger in response to Ca2+ entry than to Ca2+ mobilization. Microfilaments have thus a distinct impact on exocytosis of insulin granules depending on the source of triggering Ca2+