Poulsen C R, Bokvist K, Olsen H L, Høy M, Capito K, Gilon P, Gromada J
Department of Islet Cell Physiology, Islet Discovery Research, Novo Nordisk A/S, Bagsvaerd, Denmark.
Diabetes. 1999 Nov;48(11):2171-81. doi: 10.2337/diabetes.48.11.2171.
In mouse pancreatic beta-cells, extracellular ATP (0.1 mmol/l) effectively reduced glucose-induced insulin secretion. This inhibitory action resulted from a direct interference with the secretory machinery, and ATP suppressed depolarization-induced exocytosis by 60% as revealed by high-resolution capacitance measurements. Suppression of Ca2+-dependent exocytosis was mediated via binding to P2Y1 purinoceptors but was not associated with inhibition of the voltage-dependent Ca2+ currents or adenylate cyclase activity. Inhibition of exocytosis by ATP resulted from G-protein-dependent activation of the serine/threonine protein phosphatase calcineurin and was abolished by cyclosporin A and deltamethrin. In contrast to the direct inhibitory action on exocytosis, ATP reduced the whole-cell ATP-sensitive K+ (K(ATP)) current by 30% (via activation of cytosolic phospholipase A2), leading to membrane depolarization and stimulation of electrical activity. The stimulatory effect of ATP also involved mobilization of Ca2+ from thapsigargin-sensitive intracellular stores. We propose that the inhibitory action of ATP, by interacting with the secretory machinery at a level downstream to an elevation in [Ca2+]i, is important for autocrine regulation of insulin secretion in mouse beta-cells.
在小鼠胰腺β细胞中，细胞外ATP（0.1 mmol/L）可有效降低葡萄糖诱导的胰岛素分泌。这种抑制作用源于对分泌机制的直接干扰，高分辨率电容测量显示，ATP可使去极化诱导的胞吐作用抑制60%。Ca2+依赖性胞吐作用的抑制是通过与P2Y1嘌呤受体结合介导的，但与电压依赖性Ca2+电流或腺苷酸环化酶活性的抑制无关。ATP对胞吐作用的抑制是由丝氨酸/苏氨酸蛋白磷酸酶钙调神经磷酸酶的G蛋白依赖性激活引起的，环孢素A和溴氰菊酯可消除这种抑制作用。与对胞吐作用的直接抑制作用相反，ATP可使全细胞ATP敏感性钾（K(ATP)）电流降低30%（通过激活胞质磷脂酶A2），导致膜去极化并刺激电活动。ATP的刺激作用还涉及从毒胡萝卜素敏感的细胞内储存库中动员Ca2+。我们认为，ATP通过在[Ca2+]i升高下游的水平与分泌机制相互作用，其抑制作用对小鼠β细胞中胰岛素分泌的自分泌调节很重要。
