Rab14 limits the sorting of Glut4 from endosomes into insulin-sensitive regulated secretory compartments in adipocytes
Rab14 limits the sorting of Glut4 from endosomes into insulin-sensitive regulated secretory compartments in adipocytes
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DOI：
10.1042/bcj20160020
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发表时间：
2016-05-15
影响因子：
4.1
通讯作者：
Mastick, Cynthia Corley
中科院分区：
文献类型：
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作者：
Brewer, Paul Duffield;Habtemichael, Estifanos N.;Mastick, Cynthia Corley
胰岛素通过增加促性葡萄糖转运蛋白异构体4 （Glut4）相对于其内吞作用的胞吐率来增加葡萄糖摄取。胰岛素也将Glut4从高度胰岛素调节的分泌室（GSVs或Glut4储存囊泡）释放到组成循环的内体中。先前的研究表明，小gtp结合蛋白Rab14的过表达和敲低都会减少Glut4向质膜（PM）的转运。为了确定这种扰动的机制，我们测量了Rab14敲低对Glut4运输动力学的影响，相对于与Glut4部分共定位的两种蛋白质，转铁蛋白（Tf）受体和低密度脂蛋白受体相关蛋白1 （LRP1）。我们的数据支持Rab14限制蛋白质从分选（或“早期”）内体进入专门的GSV途径的假设，可能是通过调节内体成熟。这一假设与已知的Rab14效应一致。有趣的是，胰岛素敏感的Rab gtpase激活蛋白Akt底物160 kDa （AS160）影响GSVs的分选和胞吐。先前有研究表明，GSVs的胞吐受Rab10的速率限制，Rab10和Rab14都是AS160的体外底物。AS160通过顺序的Rab底物进入和退出GSVs的调控将为在胰岛素浓度增加的反应中观察到的循环Glut4的精细“量”增加提供一种机制。
Insulin increases glucose uptake by increasing the rate of exocytosis of the facilitative glucose transporter isoform 4 (Glut4) relative to its endocytosis. Insulin also releases Glut4 from highly insulin-regulated secretory compartments (GSVs or Glut4 storage vesicles) into constitutively cycling endosomes. Previously it was shown that both overexpression and knockdown of the small GTP-binding protein Rab14 decreased Glut4 translocation to the plasma membrane (PM). To determine the mechanism of this perturbation, we measured the effects of Rab14 knockdown on the trafficking kinetics of Glut4 relative to two proteins that partially co-localize with Glut4, the transferrin (Tf) receptor and low-density-lipoprotein-receptor-related protein 1 (LRP1). Our data support the hypothesis that Rab14 limits sorting of proteins from sorting (or 'early') endosomes into the specialized GSV pathway, possibly through regulation of endosomal maturation. This hypothesis is consistent with known Rab14 effectors. Interestingly, the insulin-sensitive Rab GTPase-activating protein Akt substrate of 160 kDa (AS160) affects both sorting into and exocytosis from GSVs. It has previously been shown that exocytosis of GSVs is rate-limited by Rab10, and both Rab10 and Rab14 are in vitro substrates of AS160. Regulation of both entry into and exit from GSVs by AS160 through sequential Rab substrates would provide a mechanism for the finely tuned 'quantal' increases in cycling Glut4 observed in response to increasing concentrations of insulin.