Cellular Basis Of Action Of Gastrointestinal Peptides/Gr

最近的研究表明，胃肠道激素/生长因子可能通过刺激多种细胞内酪氨酸磷酸化（TyrP）信号级联反应来刺激细胞生长。然而，目前对许多胃肠道激素/生长因子激活胃肠道组织中这些级联反应的能力知之甚少。在这一年中，我们报道了Src激酶Lyn、接头蛋白Gab1、蛋白激酶c δ和接头蛋白CRK11的激活在介导胰腺腺泡细胞对激素、生长因子和活性氧引起的应激反应中的重要性。我们证明了接头蛋白GAB1的激活对于生长因子，肝细胞生长因子（HGF）改变胰腺腺泡细胞的能力是重要的。然而，不同的g蛋白偶联受体（包括CCK受体、胆碱能受体、VIP受体、分泌素或bombesin受体）在腺泡细胞上的细胞信号传导中不起作用。据报道，HGF在胰腺腺泡细胞的生长和损伤恢复中发挥重要作用，并作为重要的生长因子在胰腺癌中发挥作用。我们的研究表明，HGF在GAB1的Y307和Y627 Tyr位点快速有效地刺激GAB1 TyrP。这不仅导致GAB1重新分布到膜上，还刺激了GAB1与许多下游效应物的关联，包括SHP2、PI3K、Shc和Crk亚型，但不包括PLC γ。这种刺激并不依赖于HGF刺激细胞钙变化或激活PKC的能力。这些结果表明，GAB1在HGF而不是其他G蛋白偶联受体改变胰腺腺泡细胞功能的能力中起核心作用。我们证明了激活腺苷酸环化酶和磷脂酶C的激素以及已知的胰腺生长因子都能引起Src激酶的快速激活。这种激活导致随后大量细胞内级联的激活，证明了Src激酶的激活在腺泡细胞信号传导中起着核心作用。

Recent studies show that gastrointestinal hormones/growth factors may stimulate cell growth by stimulating multiple intracellular tyrosine phosphorylation (TyrP) signaling cascades. However at present little is known about the ability of many gastrointestinal hormones/growth factors to activate these cascades in GI tissues. During this year we have reported the importance of activation of the Src kinase Lyn, the adaptor protein Gab1, protein kinase c delta and the adaptor protein CRK11 in mediating response of pancreatic acini to hormones, growth factors and stress caused by reactive oxygen species. We demonstrated that activation of the adaptor protein, GAB1 is important for the ability of the growth factor, hepatocyte growth factor (HGF) to alter pancreatic acinar cells. However it played no role in the cellular signaling by different G-protein-coupled receptors present on acinar cells including receptors for CCK, cholinergic agents, VIP, secretin or bombesin. HGF has been reported to play an important role in growth as well as the recovery from injury of acinar cells as well as function as an important growth factor in pancreatic cancer. Our studies show HGF stimulates GAB1 TyrP rapidly and potently at both the Y307 and Y627 Tyr loci of GAB1. This not only caused a redistribution of GAB1 to the membrane it also stimulated the association of GAB1 with numerous downstream effectors including SHP2, PI3K, Shc and Crk isoforms, but not PLC gamma. This stimulation did not depend on the ability of HGF to stimulate changes in cellular calcium or activate PKC. These results show GAB1 plays a central role in the ability of HGF but not different G protein coupled receptors to alter pancreatic acinar cell function. We demonstrated both hormones activating adenylate cyclase as well as phospholipase C and known pancreatic growth factors, all caused rapid activation of the Src kinase, lyn. This activation resulted in subsequent\ activation of a large number of intracellular cascades demonstrating the central role activation of the Src kinase plays in acinar cell signaling.