Development of New Anti-diabetic Peptide Drug

马蜂毒素十四肽能刺激大鼠脂肪细胞摄取葡萄糖。mastoparan的作用呈浓度依赖性，在50 μ M时达到最大刺激，这与胰岛素诱导的作用几乎相同。Mas 7是一种对GTP结合蛋白（如Gi和Go）作用更强的mastoparan类似物，在低于mastoparan的浓度下刺激葡萄糖转运。另一方面，Mas 17，一种无活性的类似物，对葡萄糖转运没有影响。在存在主要组织相容性复合物I类抗原衍生肽D^k-（62-85）（一种GLUT 4内化的强效抑制剂）的情况下，mastoparan效应的浓度-反应关系显著向左偏移，而最大效应没有变化。免疫印迹分析表明，mastoparan促进葡萄糖转运蛋白亚型，GLUT 4，从细胞内池到质膜的易位。Mastoparan对葡萄糖转运的影响不被Wortmannin抑制，Wortmannin是磷脂酰肌醇-3激酶的特异性抑制剂，但被磷脂酶A2抑制剂奎纳克林完全消除。百日咳毒素预处理不影响mastoparn的效果。ATP耗竭KCN预处理取消胰岛素或GTP γ S诱导的葡萄糖转运的刺激，但不是mastoparn。总之，mastoparan通过GTP结合蛋白非依赖性机制刺激葡萄糖转运。磷脂酶A2可能参与了mastoparan对葡萄糖转运的影响。

Mastoparan, a tetradecapeptide from wasp venom, stimulated glucose uptake in isolated rat adipocytes. The effects of mastoparan were concentration-dependent and the maximal stimulation was achieved at 50muM,which was nearly identical to that induced by insulin. Mas 7, a more potent mastoparan analogue on GTP-binding proteins such as Gi and Go, stimulated glucose transport at lower concentrations than mastoparan. On the other hand, Mas 17, an inactive analogue, was without effect on glucose transport. In the presence of the major histocompatibility complex class I antigen-derived peptide, D^k- (62-85), a potent inhibitor of GLUT4 internalization, the concentration-response relationship of mastoparan effects was markedly shifted to the left without change of the maximal effect. Immunoblot analysis revealed that mastoparan promoted translocation of glucose transporter isoform, GLUT4, from intracellular pool to the plasma membrane. The effects of mastoparan on glucose transport were not inhibited by wortmannin, a specific inhibitor of phosphatidylinositol-3 kinase, but were completely abolished by a phospholipase A2 inhibitor quinacrine. Pertussis toxin pretreatment did not affect mastoparn's effect. ATP-depletion by KCN pretreatment abolished stimulation of glucose transport induced by insulin or GTPgammaS but not by mastoparn. In summary, mastoparan stimulates glucose transport via GTP-binding protein-independent mechanism. Phospholipase A2 may be involved in mastoparan effect on glucose transport.