Cellular Basis Of Action Of Gastrointestinal Peptides/Growth factors

最近的研究表明，胃肠激素/生长因子可能通过刺激细胞内多个酪氨酸磷酸化(TyrP)信号通路以及反式激活生长因子受体而导致细胞生长。然而，目前对许多胃肠激素/生长因子激活这些级联反应的能力知之甚少。在对肺癌细胞的研究中，我们研究了PACAP/VIP的G蛋白偶联受体刺激其生长的能力。我们发现，其机制包括EGF受体的反式激活，以及刺激粘着斑激酶、PXLIN和PYK2的激活，以及活性氧物种、基质金属蛋白酶和Src的激活。类似的研究目前正在进行中，研究胃肠神经肽神经降压素以自分泌方式刺激这些细胞生长的能力，以及孤儿受体BRS-3，蛙皮素受体家族(BN-R)的成员。蛙皮素相关多肽是这些肿瘤中特别重要的自分泌生长因子，但许多肿瘤细胞具有多种BN-R受体亚型，BRS-3受体的作用至今未见研究。有了高度选择性的BRS-3激动剂/拮抗剂(在药理学部分讨论)，我们现在能够进行这些研究。来自这些研究的许多见解导致了这些癌症的新疗法。 与西班牙马德里的N.Gonzalez博士合作，我们探索了BNR受体BRS-3调节脂肪和胰岛素代谢的细胞机制。对正常、肥胖或糖尿病受试者分散的心肌细胞中的BRS-3信号进行了研究。在这些不同的心肌细胞中，BRS-3激动剂刺激GLUT-4水平、葡萄糖转运和激活PI3K信号级联的能力存在显著差异，表明BRS-3信号的变化在糖尿病和肥胖症的变化中具有重要意义。 胰腺星状细胞在胰腺炎和胰腺癌中都具有重要作用，它们可被多种细胞因子和G蛋白偶联受体激活，但对它们在胰腺炎发病中的作用和信号转导机制知之甚少。与日本福冈的伊藤教授合作进行了三项研究，调查它们在胰腺炎中的信号转导。在一项即将完成的研究中，在星状细胞上发现了GLP1的受体。这一点可能特别重要，因为这些药物被广泛用于治疗糖尿病，而它们不想要的副作用之一是胰腺炎，其机制尚不清楚。我们发现GLP1R受体在胰腺炎过程中数量增加，在星状细胞中，它们激活MAPK级联并导致这些细胞的生长，提示它们可能参与了GLP1-R的这种副作用。在另一项研究中，研究了细胞因子Fractalkine(CXCL1)在胰腺炎中的作用，发现它是由星状细胞通过涉及金属蛋白酶的MPK机制分泌的，这可能有助于星状细胞信号在胰腺炎发病中的作用。在最后一项研究中，细胞质双链DNA显示了一种损伤相关的分子模式，诱导了胰腺星状细胞的炎症反应，并可能是组织损伤相关性胰腺炎的机制。。

Recent studies show that gastrointestinal hormones/growth factors may cause cell growth by stimulating multiple intracellular tyrosine phosphorylation (TyrP) signaling cascades as well as by transactivating growth factor receptors. However at present little is known about the ability of many gastrointestinal hormones/growth factors to activate these cascades. In a study on lung cancer cells we investigated the ability of the G-protein coupled receptors for PACAP/VIP to stimulate their growth. We found that the mechanism involved transactivation of the EGF receptor as well as stimulating activation of focal adhesion kinase, paxillin and PYK2, in addition to activation of reactive oxygen species, matrix metalloproteinases and Src. Similar studies are now underway investigating the ability of the GI-neural peptide neurotensin, to stimulate growth of these cells in an autocrine manner as well as the orphan receptor BRS-3, a member of the bombesin receptor family (BN-R). Bombesin-related peptides are particularly important autocrine growth factors for these cancers, and many others, however, many tumor cells posses multiple BN-R receptor subtypes, and the role of the BRS-3 receptor has not be studied until now. With the availability highly selective BRS-3 agonists/antagonists (discussed in pharmacology section) we are now able to perform these studies. Insights from these studies many lead to novel treatments for these cancers. In collaboration with Dr N.Gonzalez(Madrid, Spain) we explored the cellular mechanisms by which the BnR receptor, BRS-3 regulates fat and insulin metabolism. BRS-3 signaling was investigated in dispersed myocytes form normal, obese, or diabetic subjects. Marked differences were found in these different myocytes in the ability of BRS-3 agonists to stimulate GLUT-4 levels, glucose transport, and activate the PI3K signaling cascades, demonstrating alterations in BRS-3 signaling are important in the changes seen in diabetes and obesity. Pancreatic stellate cells are important in both pancreatitis and pancreatic cancer and they are activated by a number of cytokines and G-protein coupled receptors however little is known of their signaling or importance in causing pancreatitis. Three studies in collaboration with Prof Ito, Fukuoka, Japan were performed investigating their signaling in pancreatitis. In one study almost completed, receptors for the GLP1 were found on stellate cells. This could be particularly important because these agents are widely used to treat diabetes and one of their unwanted side-effect is pancreatitis, the mechanism of which is unknown. We found GLP1R receptor increase in number during pancreatitis, in the stellate cells, they activate the MAPK cascade and can cause growth of these cells suggesting they may be involve in this side-effect of GLP1-R usage In another study, the role of the cytokine fractalkine (CXCL1) in pancreatitis was investigate and it was found to be secreted by stellate cells though a MPK mechanism involving metalloproteinase, and this could contribute to the role of stellate cells signaling in causing pancreatitis. In a final study cytosolic double-stranded DNA was shown to show a damage-associated molecular pattern that induced the inflammatory response in pancreatic stellate cells and to be a plausible mechanism for tissue injury-associated pancreatitis. .