The role of phosphatidylinositol turnover on insulin-induced GLUT4 translocation and glucose uptake.

胰岛素刺激导致磷脂酰肌醇3-激酶（pi3 -激酶）的快速激活，随后形成磷脂酰肌醇（PI） 3,4 - p_2和PI 3,4,5 - p_3，被认为参与胰岛素依赖性葡萄糖转运体GLUT4易位和葡萄糖摄取的信号传导。然而，这些pi在胰岛素信号传导中的具体作用仍然存在争议。因此，我们评估了野生型含sh2的肌醇5′-磷酸酶（wt-SHIP）表达对这些生物学效应的影响，该表达有望降低PI 3,4,5 - p3的细胞水平。此外，我们比较了肉豆蔻酰基化SHIP（myr-SHIP）和wt-SHIP的作用，因为PI的转换被认为发生在质膜上，myr-SHIP具有膜靶向部分。利用重组腺病毒系统将LacZ（作为对照）、wild-SHIP或myr-SHIP过表达到3T3-L1脂肪细胞中。免疫印迹法证实了各蛋白的过表达，并证实了其5′-磷酸酶活性。体外将[3′-^<32>P]PI 3,4,5 - p3去磷酸化为[3′-^<32>P]PI 3,4 - p2证实了所表达的SHIP。在胰岛素浓度为10^<-7> M时，3T3-L1脂肪细胞中wt-SHIP和myr-SHIP的过表达非但没有抑制胰岛素诱导的葡萄糖摄取，反而刺激了胰岛素诱导的葡萄糖摄取，分别是LacZ过表达时的1.7倍和2.7倍。过表达wt-SHIP和myr-SHIP对GLUT4的总表达没有显著影响，但确实增强了胰岛素诱导的GLUT4易位。总之，我们的研究结果表明，wt-SHIP和myr-SHIP的表达增强了胰岛素诱导的GLUT4易位和葡萄糖摄取，表明pi3,4 - p_2而不是pi3,4,5 - p_3是介导这些生物作用的主要磷脂产物。此外，我们还报道了显性阴性突变型肝细胞核因子(HNF)-1α影响胰岛素分泌，曲格列酮增加血浆血管内皮生长因子水平，这可能导致水肿和血管并发症。少

Insulin stimulation leads to rapid activation of phosphatidylinositol 3-kinase(PI3-kinase)and the subsequent formation of phosphatidylinositol(PI)3, 4-P_2 and PI 3, 4, 5-P_3, which are thought to be involved in signaling for insulin-dependent glucose transporter GLUT4 translocation and glucose uptake. However, the specific role of each of these PIs in insulin signaling is still controversial. Therefore, we assessed the effects of wild type SH2-containing inositol 5'-phosphatase(wt-SHIP)expression, which is expected to decrease the cellular levels of PI 3, 4, 5-P_3, on these biological effects. Moreover, we compared the effects of myristoylated SHIP(myr-SHIP), which has a membrane targeting moiety, to those of wt-SHIP, because PI turnover is thought to occur at plasma membrane.LacZ(as control), wild-SHIP or myr-SHIP is overexpressed into 3T3-L1 adipocytes using recombinant adenovirus system. Overexpression of each protein was confirmed with immunoblotting, and 5'-phosphatase activity of … More the expressed SHIP was verified by dephosphorylation of[3'-^<32>P]PI 3, 4, 5-P_3 to[3'-^<32>P]PI 3, 4-P_2 in vitro. At 10^<-7> M insulin concentration overexpression of wt-SHIP and myr-SHIP did not inhibit but rather stimulated insulin-induced glucose uptake by 1.7-fold and 2.7-fold above the value obtained with overexpression of LacZ, respectively, in 3T3-L1 adipocytes. Overexpression of wt-SHIP and myr-SHIP did not have any significant effect on total GLUT4 expression, but did potentiate insulin-induced GLUT4 translocation.In summary, our results demonstrated that expression of wt-SHIP and myr-SHIP potentiated insulin-induced GLUT4 translocation and glucose uptake, suggesting that PI 3, 4-P_2, rather than PI 3, 4, 5-P_3, is the major phospholipid product mediating these biological actions.In addition, we also repored that dominant negative mutant hepatocyte nuclear factor(HNF)-1α influenced insulin secretion, and that troglitazone increased plasma vascular endothelial growth factor levels, which might cause edema and vascular complications. Less