Insulin control of GLUT4 traffic to the plasma membrane of adipocytes

葡萄糖转运到脂肪和肌肉中，这是严格调节的，由质膜（PM）中GLUT 4葡萄糖转运蛋白的量决定。在空腹状态下，当胰岛素水平低时，GLUT 4通过快速内吞作用和缓慢再循环在细胞内主动隔离。餐后状态下胰岛素升高诱导GLUT 4重新分布到PM，主要是通过加速GLUT 4再循环。在胰岛素升高的餐后期间，通过快速GLUT 4再循环积极维持PM GLUT 4水平升高。当循环胰岛素水平降低时，GLUT 4 PM水平恢复到刺激前的水平。因此，脂肪和肌肉细胞对葡萄糖摄取的控制依赖于GLUT 4在细胞内部和PM之间运输的调节。受损的GLUT 4重新分布到PM有助于与胰岛素抵抗和2型糖尿病相关的高血糖症。阐明GLUT 4运输及其受胰岛素调节的分子机制将显著影响我们对胰岛素抵抗的理解，从而为未来治疗干预的发展提供基础。 虽然GLUT 4运输的现象被很好地描述，但关于该过程的分子机制还有很多东西要学。GLUT 4主要分布在2个细胞内膜区室中：胰岛素应答囊泡（IRV），专门用于GLUT 4的运输和GLUT 4 TGN核周区室。IRV已被深入研究，因为它们在未刺激的（基础）和胰岛素刺激的细胞中将GLUT 4转运到PM。核周区室在基底脂肪细胞中GLUT 4的细胞内隔离和GLUT 4的动员中具有关键作用，以支持胰岛素刺激细胞中增加的需求。控制GLUT 4运输到核周位点和从核周位点运输的分子机制尚未详细描述。在这里，我建议填补这一知识空白。该工作计划以我的实验室过去的成就为基础，解决了GLUT 4贩运领域的几个关键问题。该项目的主要目标是：定义核周区室蛋白质组，从而识别在GLUT 4运输调节中起作用的蛋白质，以及识别除GLUT 4以外的货物蛋白质;发现和表征负责调节GLUT 4通过核周区室的通量的蛋白质机制。为了实现这些目标，我们将使用国家的最先进的质谱分析方法，和功能完整的细胞检测的全面电池，以表征的分子机制，调节贩运到和从核周区室。

Glucose transport into fat and muscle, which is tightly regulated, is determined by the amount of the GLUT4 glucose transporter in the plasma membrane (PM). In the fasted state, when insulin levels are low, GLUT4 is actively sequestered intracellularly by rapid endocytosis and slow recycling. Elevated insulin in the postprandial state induces a redistribution of GLUT4 to the PM, predominantly by accelerating GLUT4 recycling. Increased levels of PM GLUT4 are actively maintained by rapid GLUT4 recycling during the postprandial period of elevated insulin. GLUT4 PM levels return to pre-stimulation amounts when circulating insulin levels decrease. Thus, the control of glucose uptake by fat and muscle cells is dependent upon regulation of GLUT4 trafficking between the interior and PM of cells. Compromised GLUT4 redistribution to the PM contributes to hyperglycemia associated with insulin-resistance and type 2 diabetes. Elucidating the molecular mechanism underlying GLUT4 traffic and its regulation by insulin will significantly impact our understanding of insulin resistance and thereby provide a foundation for the future development of therapeutic interventions. Although the phenomenon of GLUT4 trafficking is well described, there is much to be learned about the molecular mechanisms of the process. GLUT4 is largely distributed among 2 intracellular membrane compartments: insulin-responsive vesicles (IRVs) that are specialized for the traffic of GLUT4 and the GLUT4 TGN perinuclear compartment. IRVs have been intensively studied because they ferry GLUT4 to the PM in both unstimulated (basal) and insulin-stimulated cells. The perinuclear compartment has a pivotal role in the intracellular sequestration of GLUT4 in basal adipocytes and in the mobilization of GLUT4 to support the increased demand in insulin-stimulated cells. The molecular mechanisms controlling GLUT4 trafficking to and from the perinuclear site have not been described in detail. Here I propose to address that gap in knowledge. The workplan, building on my labs past accomplishments, addresses several key questions in the field of GLUT4 trafficking. The major objectives of the project are to: define the perinuclear compartment proteome, thereby identifying proteins that function in the regulation of GLUT4 traffic as well as identifying cargo proteins other than GLUT4 that are stored their; discover and characterize the protein machinery responsible for regulating flux of GLUT4 through this perinuclear compartment. To accomplish these objectives, we will use state-of-the-art mass spectrometry profiling methods, and a comprehensive battery of functional intact cell assays to characterize the molecular mechanism regulating trafficking to and from the perinuclear compartment.