Ryanodine receptors in human pancreatic β cells:: localization and effects on insulin secretion
Ryanodine receptors in human pancreatic β cells:: localization and effects on insulin secretion
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DOI：
10.1096/fj.03-1280fje
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发表时间：
2004-03-01
期刊：
影响因子：
4.8
通讯作者：
Polonsky, KS
中科院分区：
文献类型：
--
作者：
Johnson, JD;Kuang, SH;Polonsky, KS
很明显，胰腺β细胞功能障碍，包括基础高胰岛素血症和响应葡萄糖的胰岛素释放减少，是2型糖尿病疾病进展的关键决定因素，但潜在的分子缺陷尚不清楚。在糖尿病中，兰尼碱受体 (RyR) Ca2+ 释放通道的表达和功能降低。目前的研究旨在确定 RyR 在控制人胰腺 β 细胞刺激和基础胰岛素释放中的亚细胞位置和作用。使用共聚焦显微镜，我们观察到囊泡模式中的 RyR 免疫反应性。 RyRs 不与胰岛素分泌颗粒共定位，但部分与内体共定位。用纳摩尔浓度的兰尼定直接激活会引起胞质 Ca2+ 增加，并与短暂的胰岛素释放相结合。 1 nM ryanodine 刺激的胰岛素释放对 BAPTA-AM 预孵育敏感，但与毒胡萝卜素敏感的内质网 (ER) Ca2+ 库无关。用微摩尔浓度的兰尼碱阻断 RyRs 会导致 BAPTA 抗性胰岛素释放，但与胞质 Ca2+ 的增加无关，而胞浆 Ca2+ 的增加涉及管腔 Ca2+ 的变化。然而，10-50 muM ryanodine 既不能阻断 Ca2+ 信号，也不能阻断葡萄糖刺激的胰岛素释放，这表明 CD38/环 ADP-核糖/RyR 途径不是非转化 β 细胞中葡萄糖作用的主要机制。我们提供了第一个证据表明 RyR 直接控制原代 β 细胞中的胰岛素分泌。出乎意料的是，兰尼碱对胰岛素分泌的刺激独立于葡萄糖并通过两种机制发生，包括一种新的胞质 Ca2+ 独立机制，可能涉及非 ER 细胞器（如内体）管腔内 Ca2+ 的变化。
It is clear that pancreatic beta-cell dysfunction, including basal hyperinsulinemia and reduced insulin release in response to glucose, is a key determinant of disease progression in type 2 diabetes, but the underlying molecular defects are not known. In diabetes, the expression and function of ryanodine receptor (RyR) Ca2+ release channels are reduced. The present studies were undertaken to define the subcellular location and role of RyR in the control of stimulated and basal insulin release from human pancreatic beta cells. Using confocal microscopy, we observed RyR immunoreactivity in a vesicular pattern. RyRs did not colocalize with insulin secretory granules but partially colocalized with endosomes. Direct activation with nanomolar concentrations of ryanodine evoked increases in cytosolic Ca2+ that were coupled to transient insulin release. Insulin release stimulated by 1 nM ryanodine was sensitive to BAPTA-AM preincubation but independent of thapsigargin-sensitive endoplasmic reticulum ( ER) Ca2+ pools. Blocking RyRs with micromolar concentrations of ryanodine led to BAPTA-resistant insulin release that was not associated with an increase in cytosolic Ca2+, which implicated alterations in luminal Ca2+. However, neither Ca2+ signals nor insulin release stimulated by glucose was blocked by 10-50 muM ryanodine, which suggests that the CD38/cyclic ADP-ribose/RyR pathway is not a primary mechanism of glucose action in nontransformed beta cells. We provide the first evidence that RyRs directly control insulin secretion in primary beta cells. Unexpectedly, stimulation of insulin secretion by ryanodine occurs independently of glucose and by two mechanisms, including a novel cytosolic Ca2+-independent mechanism likely involving changes in Ca2+ within the lumens of non-ER organelles, such as endosomes.