Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
J Biol Chem. 2010 May 7;285(19):14101-8. doi: 10.1074/jbc.M110.110536. Epub 2010 Feb 26.
Recent work has led to the identification of novel endocytic compartments with functional roles in both protein trafficking and growth factor signal transduction. The phosphatidylinositol 3-phosphate binding, FYVE domain-containing protein WDFY2 is localized to a distinct subset of early endosomes, which are localized close to the plasma membrane. Here, we find that the serine/threonine kinase Akt interacts with these endosomes in an isoform-specific manner. Using quantitative fluorescence microscopy we demonstrate specific co-localization of WDFY2 with endogenous Akt2, but not Akt1. Moreover, depletion of WDFY2 leads to impaired phosphorylation of Akt in response to insulin due to isoform specific reduction of Akt2, but not Akt1, protein levels, and to a marked reduction in the insulin-stimulated phosphorylation of numerous Akt substrates. This is accompanied by an impairment in insulin-stimulated glucose transport and, after prolonged silencing, a reduction in the level of expression of adipogenic genes. We propose that WDFY2-enriched endosomes serve as a scaffold that enables specificity of insulin signaling through Akt2.
最近的研究工作导致了新型内吞小体的鉴定，这些内吞小体在蛋白质运输和生长因子信号转导中具有功能作用。磷酸肌醇 3-磷酸结合 FYVE 结构域蛋白 WDFY2 定位于一组独特的早期内涵体，这些内涵体靠近质膜。在这里，我们发现丝氨酸/苏氨酸激酶 Akt 以同种型特异性的方式与这些内涵体相互作用。使用定量荧光显微镜，我们证明了 WDFY2 与内源性 Akt2 的特异性共定位，但与 Akt1 没有共定位。此外，WDFY2 的耗竭导致胰岛素刺激的 Akt 磷酸化受损，这是由于 Akt2 的同种型特异性减少，而不是 Akt1 的蛋白水平减少，并且胰岛素刺激的许多 Akt 底物的磷酸化明显减少。这伴随着胰岛素刺激的葡萄糖转运受损，并且在长时间沉默后，脂肪生成基因的表达水平降低。我们提出，富含 WDFY2 的内涵体充当支架，通过 Akt2 实现胰岛素信号的特异性。
