ROLE OF MITOGEN-ACTIVATED PROTEIN KINASES IN GI PEPTIDE HORMONE RECEPTOR SIGNALIN

丝裂原激活蛋白激酶在胃肠道肽激素受体信号中的作用

• 批准号: 6907126
• 负责人: Courtney M Townsend
• 金额: $ 23.99万
• 依托单位: UNIVERSITY OF TEXAS MED BR GALVESTON
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6907126
• 关键词: apoptosis; biological signal transduction; bombesin; calcium; calcium flux; cell differentiation; cell growth regulation; cell proliferation; gastrointestinal hormones; gastrointestinal system; gene expression; genetic regulatory element; hormone receptor; hormone regulation /control mechanism; inositol phosphates; mitogen activated protein kinase; pancreas; peptide hormone; phospholipase C; prostaglandin endoperoxide synthase; protein kinase; tissue /cell culture; voltage /patch clamp

Transactivation of receptor tyrosine kinase (RTK)-regulated signaling pathways following G protein-coupled receptor (GPCR) activation has recently been described and can occur through intracellular and extracellular mediators. Activation of RTK signaling pathways by GPCR has explained some of the cell proliferative effects associated with GPCR agonists. We have discovered a novel mechanism by which an RTK agonist potentiates GPCR-mediated signal transduction; specifically, pretreatment of rat intestinal epithelial cells with epidermal growth factor (EGF) increases bombesin (BBS)-stimulated Ca2+ release from intracellular Ca2+ stores in a dose-dependent manner. BBS stimulates Ca2+ release from the inositol 1,4,5-triphosphate (lnsP3)-sensitive Ca2+ stores mediated by the gastrin-releasing peptide receptor (GRP-R), a member of the GPCR superfamily. The stimulatory effect of EGF on GRP-R-mediated Ca2+ release requires activation of the mitogen-activated kinase kinase (MEK)-1,2/extracellular signal-regulated kinase (ERK)-1,2 pathway. Reduction of basal MEK-1,2/ERK-l ,2 activity by either serum starvation, treatment with selective MEK-1,2 inhibitors or expression of a dominant-negative mutant form of MEK-1 decrease BBS-stimulated Ca2+ release from intracellular stores. Conversely, increasing basal activity of the MEK-1,2/ERK-1,2 pathway reversed the inhibitory effects of serum starvation on G17-stimulated Ca2+ release. These data demonstrate a novel role for basal MAPK activity in the regulation of Gl peptide hormone-mediated Ca2+mobilization and suggest a potentially important mechanism for "cross-talk" between the GPCR-regulated pathways and regulators of MAPK activity, such as EGF. We hypothesize that MAPKs play a central role in signal integration, in part, by modulating the sensitivity of Gl peptide hormone receptor-mediated response to agonist stimulation and by coupling growth factor receptor kinases to Gl peptide hormone-regulated signaling pathways. Our Specific Aims are: 1) To determine the molecular mechanisms by which mitogen-activate protein kinases (MAPKs) modulate Gl peptide hormone-mediated increases in [Ca2+]j. 2) To determine the effects of modulating basal MAPK activity on GRP-R-regulated gene expression, cell proliferation and peptide secretion. Uncovering the molecular mechanisms involved in MAPK sensitization of Gl peptide hormone receptor-mediated signal transduction will get us closer to realizing the full therapeutic potential of Gl peptide hormones in human disease.

最近已经描述了G蛋白偶联受体（GPCR）激活后受体酪氨酸激酶（RTK）调节的信号传导途径的反式激活，并且可以通过细胞内和细胞外介体发生。 GPCR通过GPCR激活RTK信号通路已解释了与GPCR激动剂相关的一些细胞增殖作用。我们发现了一种新型机制，RTK激动剂会增强GPCR介导的信号转导。具体而言，用表皮生长因子（EGF）对大鼠肠上皮细胞的预处理增加了bombesin（BBS）刺激的Ca2+从细胞内CA2+释放 以剂量依赖性方式存储。 BBS刺激了肌醇1,4,5-三磷酸（LNSP3）敏感的Ca2+储存的Ca2+释放，这是由GPCR超级家庭的成员介导的胃链释放肽受体（GRP-R）介导的。 EGF对GRP-R介导的Ca2+释放的刺激作用需要激活有丝分裂原激活的激酶激酶（MEK）-1,2/细胞外信号调节激酶（ERK）-1,2途径。减少基底MEK-1,2/ERK-L，2通过血清饥饿，有选择性MEK-1,2的治疗 MEK-1的显性阴性突变体形式的抑制剂或表达降低了BBS刺激的Ca2+从细胞内存储中释放。相反，增加MEK-1,2/ERK-1,2途径的基础活性逆转了血清饥饿对G17刺激的Ca2+释放的抑制作用。这些数据表明，基底MAPK活性在调节GL肽激素介导的Ca2+动员中的新作用，并提出了GPCR调节途径和MAPK活性调节剂（例如EGF）之间“串扰”的潜在重要机制。我们假设MAPK通过调节GL肽受体受体介导的对激动剂刺激的反应以及将生长因子受体激酶对GL肽激素调节的信号通路的敏感性进行调节，在某种程度上在信号整合中起着核心作用。我们的具体目的是：1）确定有丝分裂原活化的分子机制 蛋白激酶（MAPKS）调节[Ca2+] J中的GL肽激素介导的增加的增加。 2）确定调节基底MAPK活性对GRP-R调节基因表达，细胞增殖和肽分泌的影响。揭示GL肽受体介导的信号转导的MAPK敏化涉及的分子机制将使我们更接近实现人类疾病中GL肽激素的全部治疗潜力。