Uncoupling protein-2 contributes significantly to high mitochondrial proton leak in INS-1E insulinoma cells and attenuates glucose-stimulated insulin secretion
Uncoupling protein-2 contributes significantly to high mitochondrial proton leak in INS-1E insulinoma cells and attenuates glucose-stimulated insulin secretion
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DOI：
10.1042/bj20070954
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发表时间：
2008-01-01
影响因子：
4.1
通讯作者：
Brand, Martin D.
中科院分区：
文献类型：
--
作者：
Affourtit, Charles;Brand, Martin D.
由于 INS-1E 线粒体的质子传导性较高，质子泄漏对克隆胰腺 β 细胞 (INS-1E) 线粒体中的 ATP/ADP 的控制比大鼠骨骼肌线粒体中的 ATP/ADP 更强 [Affourtit 和 Brand (2006) Biochem. J. 393, 151-159]。在本研究中，我们证明高质子泄漏也表现在细胞水平上：INS-1E 细胞的泄漏率（以粘噻唑敏感、寡霉素抗性呼吸测量）几乎是成肌细胞的四倍。通过 RNAi（RNA 干扰）敲低 UCP2（解偶联蛋白 2）后，这种相对较高的渗漏活性降低了 30% 以上。 UCP2 对泄漏的高贡献表明通过 UCP2 的质子电导约占 10%。 INS-1E 呼吸的 20%。 UCP2 敲除增强了 GSIS（葡萄糖刺激的胰岛素分泌），这与 UCP2 在 β 细胞生理学中的作用一致。我们认为，β 细胞中线粒体质子高泄漏是一种放大生理 UCP2 调节剂对细胞质 ATP/ADP 的影响的机制，从而放大胰岛素分泌的影响。
Proton leak exerts stronger control over ATP/ADP in mitochondria from clonal pancreatic beta-cells (INS-1E) than in those from rat skeletal muscle, due to the higher proton conductance of INS-1E mitochondria [Affourtit and Brand (2006) Biochem. J. 393, 151-159]. In the present study, we demonstrate that high proton leak manifests itself at the cellular level too: the leak rate (measured as myxothiazol-sensitive, oligomycin-resistant respiration) was nearly four times higher in INS-1E cells than in myoblasts. This relatively high leak activity was decreased more than 30% upon knock-down of UCP2 (uncoupling protein-2) by RNAi (RNA interference). The high contribution of UCP2 to leak suggests that proton conductance through UCP2 accounts for approx. 20% of INS-1E respiration. UCP2 knock-down enhanced GSIS (glucose-stimulated insulin secretion), consistent with a role for UCP2 in beta-cell physiology. We propose that the high mitochondrial proton leak in beta-cells is a mechanism which amplifies the effect of physiological UCP2 regulators on cytoplasmic ATP/ADP and hence on insulin secretion.