Mitochondrial Ca2+ uptake 1 (MICU1) and mitochondrial ca2+ uniporter (MCU) contribute to metabolism-secretion coupling in clonal pancreatic β-cells.
Mitochondrial Ca2+ uptake 1 (MICU1) and mitochondrial ca2+ uniporter (MCU) contribute to metabolism-secretion coupling in clonal pancreatic β-cells.
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DOI：
10.1074/jbc.m112.392084
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发表时间：
2012-10-05
期刊：
影响因子：
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通讯作者：
Graier WF
中科院分区：
文献类型：
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作者：
Alam MR;Groschner LN;Parichatikanond W;Kuo L;Bondarenko AI;Rost R;Waldeck-Weiermair M;Malli R;Graier WF
背景：线粒体Ca2+摄取的分子贡献者是未知的，这是β细胞代谢-分泌耦合所必需的。结果：MICU1和MCU的下调减少了激动剂和去极化诱导的线粒体Ca2+封存、ATP产生和d-葡萄糖刺激的胰岛素分泌。结论：MICU1和MCU是β-细胞代谢-分泌偶联的重要组成部分。意义：本研究发现MICU1和MCU是胰腺β细胞功能的重要贡献者。在胰腺β细胞中，Ca2+进入线粒体通过激活各种基质酶促进代谢-分泌耦合，从而通过氧化磷酸化促进ATP生成，进而增加胰岛素释放。我们采用了一种基于sirna的方法来评估最近被描述为参与克隆INS-1 832/13胰腺β细胞线粒体Ca2+隔离的四种蛋白质的个体贡献：线粒体Ca2+摄取1 (MICU1)，线粒体Ca2+单转运蛋白（MCU），解偶联蛋白2 （UCP2）和亮氨酸拉链含fe -手跨膜蛋白1 （LETM1）。使用基于fret的基因编码Ca2+传感器靶向线粒体，我们发现MICU1或MCU的瞬时敲低减少了线粒体Ca2+摄取细胞内Ca2+释放和Ca2+通过l型通道进入。相比之下，UCP2和LETM1的敲低分别在响应细胞内Ca2+释放或Ca2+进入时特异性地减少了线粒体Ca2+摄取。因此，我们进一步研究了MICU1和MCU在代谢-分泌耦合中的作用。MICU1或MCU的减少减少了线粒体对d-葡萄糖的Ca2+摄取，而d-葡萄糖引发的细胞质Ca2+振荡不受影响。此外，在MICU1或mcu沉默的细胞中，d-葡萄糖引起的胞质ATP增加和d-葡萄糖刺激的胰岛素分泌减少。我们的数据强调了MICU1和MCU在胰腺β细胞线粒体Ca2+摄取中的关键作用，以及它们参与持续胰岛素分泌所需的正反馈。
Background: The molecular contributors of the mitochondrial Ca2+ uptake, which is essential for metabolism-secretion coupling in β-cells, are unknown. Results: Knockdown of MICU1 and MCU reduced agonist- and depolarization-induced mitochondrial Ca2+ sequestration, ATP production, and d-glucose-stimulated insulin secretion. Conclusion: MICU1 and MCU are integral to metabolism-secretion coupling in β-cells. Significance: The presented data identify MICU1 and MCU as important contributors to pancreatic β-cell function. In pancreatic β-cells, uptake of Ca2+ into mitochondria facilitates metabolism-secretion coupling by activation of various matrix enzymes, thus facilitating ATP generation by oxidative phosphorylation and, in turn, augmenting insulin release. We employed an siRNA-based approach to evaluate the individual contribution of four proteins that were recently described to be engaged in mitochondrial Ca2+ sequestration in clonal INS-1 832/13 pancreatic β-cells: the mitochondrial Ca2+ uptake 1 (MICU1), mitochondrial Ca2+ uniporter (MCU), uncoupling protein 2 (UCP2), and leucine zipper EF-hand-containing transmembrane protein 1 (LETM1). Using a FRET-based genetically encoded Ca2+ sensor targeted to mitochondria, we show that a transient knockdown of MICU1 or MCU diminished mitochondrial Ca2+ uptake upon both intracellular Ca2+ release and Ca2+ entry via L-type channels. In contrast, knockdown of UCP2 and LETM1 exclusively reduced mitochondrial Ca2+ uptake in response to either intracellular Ca2+ release or Ca2+ entry, respectively. Therefore, we further investigated the role of MICU1 and MCU in metabolism-secretion coupling. Diminution of MICU1 or MCU reduced mitochondrial Ca2+ uptake in response to d-glucose, whereas d-glucose-triggered cytosolic Ca2+ oscillations remained unaffected. Moreover, d-glucose-evoked increases in cytosolic ATP and d-glucose-stimulated insulin secretion were diminished in MICU1- or MCU-silenced cells. Our data highlight the crucial role of MICU1 and MCU in mitochondrial Ca2+ uptake in pancreatic β-cells and their involvement in the positive feedback required for sustained insulin secretion.