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）调节的信号通路的反式激活，并且可以通过细胞内和细胞外介质发生。通过GPCR激活RTK信号传导途径已经解释了与GPCR激动剂相关的一些细胞增殖效应。我们已经发现了一种新的机制，通过这种机制，RTK激动剂增强GPCR介导的信号转导;特别是，用表皮生长因子（EGF）预处理大鼠肠上皮细胞增加蛙皮素（BBS）刺激的细胞内Ca 2+释放。 以剂量依赖性方式储存。BBS刺激Ca 2+从肌醇1，4，5-三磷酸（InsP 3）-敏感的Ca 2+储存中释放，所述Ca 2+储存由GPCR超家族的成员胃泌素释放肽受体（GRP-R）介导。EGF对GRP-R介导的Ca 2+释放的刺激作用需要激活促分裂原活化激酶激酶（MEK）-1，2/细胞外信号调节激酶（ERK）-1，2通路。通过血清饥饿、用选择性MEK-1，2处理或用选择性MEK-1，2处理降低基础MEK-1，2/ERK-1，2活性 MEK-1的显性失活突变体形式的抑制剂或表达降低了BBS刺激的Ca 2+从细胞内储存的释放。相反，增加MEK-1，2/ERK-1，2通路的基础活性逆转了血清饥饿对G17刺激的Ca 2+释放的抑制作用。这些数据证明了基础MAPK活性在G1肽激酶介导的Ca 2+动员的调节中的新作用，并提示了GPCR调节的途径和MAPK活性的调节剂（如EGF）之间的“串扰”的潜在重要机制。我们假设MAPK在信号整合中起着重要作用，部分是通过调节G1肽激素受体介导的对激动剂刺激的反应的敏感性和通过将生长因子受体激酶偶联到G1肽调节的信号传导途径。我们的具体目标是：1）确定丝裂原激活的分子机制， 蛋白激酶（MAPK）调节G1肽激酶介导的[Ca 2 +]增加j.2）确定调节基础MAPK活性对GRP-R调节的基因表达、细胞增殖和肽分泌的影响。揭示参与G1肽激素受体介导的信号转导的MAPK敏化的分子机制将使我们更接近于实现G1肽激素在人类疾病中的全部治疗潜力。