瘦素通过涉及 AMP 激活的蛋白激酶 (AMPK) 和 cAMP 依赖性蛋白激酶 (PKA) 的信号机制调节胰腺β细胞中的 KATP 通道转运。

Leptin regulates KATP channel trafficking in pancreatic β-cells by a signaling mechanism involving AMP-activated protein kinase (AMPK) and cAMP-dependent protein kinase (PKA).

机构信息

Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239.

Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239.

出版信息

J Biol Chem. 2013 Nov 22;288(47):34098-34109. doi: 10.1074/jbc.M113.516880. Epub 2013 Oct 7.

Abstract

Pancreatic β-cells secrete insulin in response to metabolic and hormonal signals to maintain glucose homeostasis. Insulin secretion is under the control of ATP-sensitive potassium (KATP) channels that play key roles in setting β-cell membrane potential. Leptin, a hormone secreted by adipocytes, inhibits insulin secretion by increasing KATP channel conductance in β-cells. We investigated the mechanism by which leptin increases KATP channel conductance. We show that leptin causes a transient increase in surface expression of KATP channels without affecting channel gating properties. This increase results primarily from increased channel trafficking to the plasma membrane rather than reduced endocytosis of surface channels. The effect of leptin on KATP channels is dependent on the protein kinases AMP-activated protein kinase (AMPK) and PKA. Activation of AMPK or PKA mimics and inhibition of AMPK or PKA abrogates the effect of leptin. Leptin activates AMPK directly by increasing AMPK phosphorylation at threonine 172. Activation of PKA leads to increased channel surface expression even in the presence of AMPK inhibitors, suggesting AMPK lies upstream of PKA in the leptin signaling pathway. Leptin signaling also leads to F-actin depolymerization. Stabilization of F-actin pharmacologically occludes, whereas destabilization of F-actin simulates, the effect of leptin on KATP channel trafficking, indicating that leptin-induced actin reorganization underlies enhanced channel trafficking to the plasma membrane. Our study uncovers the signaling and cellular mechanism by which leptin regulates KATP channel trafficking to modulate β-cell function and insulin secretion.

摘要

胰岛β细胞响应代谢和激素信号分泌胰岛素,以维持血糖稳态。胰岛素分泌受三磷酸腺苷(ATP)敏感性钾(KATP)通道的控制,该通道在设定β细胞膜电位方面发挥着关键作用。瘦素是脂肪细胞分泌的一种激素,通过增加β细胞中 KATP 通道的电导来抑制胰岛素分泌。我们研究了瘦素增加 KATP 通道电导的机制。我们表明,瘦素会导致 KATP 通道的表面表达短暂增加,而不影响通道门控特性。这种增加主要是由于通道向质膜的运输增加,而不是表面通道的内吞作用减少。瘦素对 KATP 通道的作用依赖于蛋白激酶 AMP 激活的蛋白激酶(AMPK)和蛋白激酶 A(PKA)。AMPK 或 PKA 的激活模拟了瘦素的作用,而 AMPK 或 PKA 的抑制则消除了瘦素的作用。瘦素通过增加 AMPK 在苏氨酸 172 位的磷酸化来直接激活 AMPK。PKA 的激活导致通道表面表达增加,即使存在 AMPK 抑制剂,这表明 AMPK 在瘦素信号通路中位于 PKA 的上游。瘦素信号还导致 F-肌动蛋白解聚。F-肌动蛋白的稳定药理学上阻碍了,而 F-肌动蛋白的不稳定模拟了,瘦素对 KATP 通道运输的影响,表明瘦素诱导的肌动蛋白重排是增强通道向质膜运输的基础。我们的研究揭示了瘦素调节 KATP 通道运输以调节β细胞功能和胰岛素分泌的信号转导和细胞机制。

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