Molecular Regulations of Cellular Insulin Signaling and Their Disorders

PI - 3激酶在胰岛素的代谢作用中起重要作用。然而，P1 3激酶的下游效应物及其信号传导机制尚不清楚。为了阐明这些机制，我们利用腺病毒载体在3T3-Li脂肪细胞中表达了Akt和非典型PKC的几个突变体。我们发现两种丝氨酸/苏氨酸激酶Akt （PKB）和非典型PKC是3T3-L1脂肪细胞中P1 3-激酶的下游效应物。也就是说，Akt参与胰岛素刺激的蛋白质合成，但不参与胰岛素刺激的葡萄糖运输。另一方面，非典型PKC参与胰岛素刺激的葡萄糖运输，但不参与胰岛素刺激的蛋白质合成。此外，我们发现Akt和非典型PKC在P1 3激酶的下游独立作用。含glut4的囊泡在胰岛素作用下从细胞内腔室转移到质膜。然而，这种易位的机制尚不清楚。根据SNARE假说，我们分析了3T3-Ll脂肪细胞中含glut4的囊泡与质膜的融合过程。我们发现，在含glut4的囊泡中，VAMP2与质膜中的syntaxin 4的结合对融合过程很重要，而Munc 18c与syntaxin 4的结合阻止了syntaxin 4与VAMP2的结合。

PI 3-kinases were found to have an important roles to transduce metabolic effects of insulin. However, downstream effectors of P1 3-kinases and their signaling mechanisms were unknown. To elucidate these mechanisms, we expressed several mutants of Akt and atypical PKC in 3T3-Li adipocytes using adenovirus vectors. We found that two serine/threonine kinases, Akt (PKB) and atypical PKC are downstream effectors of P1 3-kinases in 3T3-L1 adipocytes. That is, Akt involved in insulin-stimulated protein synthesis, but not in insulin-stimulated glucose transport. On the other hand, atypical PKC is involved in insulin-stimulated glucose transport, but not in insulin-stimulated protein synthesis. Furthermore, we found that Akt and atypical PKC acts independently in the downstream of P1 3-kinases.GLUT4-containg vesicles translocates from intracellular compartments to plasma membranes in response to the insulin. However, mechanisms of this translocation were unknown. According to the SNARE hypothesis, we analysed the fusion process of GLUT4-containg vesicles with plasma membrane in 3T3-Ll adipocytes. We found that the binding of VAMP2 in GLUT4-containg vesicles with syntaxin 4 in the plasma membrane is important for the fusion process and the association of Munc 18c with syntaxin 4 prevents the binding of syntaxin 4 with VAMP2.