GI HORMONES IN NORMAL AND NEOPLASTIC GUT AND PANCREAS

蛙皮素（BBS）及其哺乳动物对应物胃泌素释放肽 (GRP)是重要的肽，影响肠道的许多方面， 功能包括：1）刺激肽释放，2）增加 基因表达，和3）刺激正常和肿瘤性肠道生长。 结合BBS的受体是G蛋白受体超家族的成员 并且包括GRP-受体（GRP-R）和神经调节素-B受体（NMB-1）。 R）。关键问题仍然是理解生物学的关键 BBS的影响，特别是，和所有的GI激素，一般。他们 包括，调节不同细胞的机制是什么， 肽与受体结合时产生的功能， 负责肽相同或分开的第二信使途径 释放，基因表达和细胞生长的改变？主要重点 这个项目的目的是确定细胞内的机制， BBS在肠道中的多种生物学效应。完成这一目标 我们通过转染功能性BBS建立了一种独特的细胞模型， 受体植入到我们先前描述的人类内分泌细胞系中， BON，产生神经降压素（NT）、嗜铬粒蛋白A（CGA） 和胰蛋白酶抑制剂。我们的初步研究结果表明，BBS 增加肽释放，改变NT基因表达并刺激细胞 这些BON转染子的生长。此外，我们表明，BBS 刺激人胃癌细胞系SIIA的生长， 除GRP-R或NMB-R以外的受体。此外，我们的体内研究 表明BBS影响正常和肿瘤性肠道组织， 差异和细胞特异性方式。综合来看，这些结果 表明BBS通过多个细胞特异性信号转导起作用 调节细胞功能的途径。根据我们的调查结果， 这个建议的中心假设是胃肠道激素调节肽 通过特定的受体和后- 受体机制为了验证这个假设，我们计划 具有以下具体目的的实验：1）我们将描述 BBS调节激素的信号转导途径 分泌物为了实现这一目标，我们将使用我们转染的BON细胞， 克隆，以系统的方式进一步描绘特定的信号 负责BBS介导的激素释放的转导途径。（二） 我们将确定对BBS介导的变化重要的细胞因子 在肽基因表达中。为了实现这一目标，我们将确定 负责BBS介导的NT基因表达增加的机制。 3)我们将研究受体和细胞内机制负责 BBS的营养效应。为了实现这一目标，我们将评估 BBS对我们建立的BBS介导的细胞模型的影响 细胞增殖该提案的长期目标是 系统地定义细胞内的机制，调节 BBS的细胞效应利用新的细胞模型系统， 建立在我们的实验室。对信号的深入识别 转导系统和分子机制，负责 这些多种细胞功能对我们的整体 了解胃肠道激素产生的各种生物效应。

Bombesin (BBS) and its mammalian counterpart, gastrin-releasing peptide (GRP) are important peptides that affect numerous aspects of intestinal function that include: 1) stimulation of peptide release, 2) increase in gene expression, and 3) stimulation of normal and neoplastic gut growth. Receptors that bind BBS are members of the G protein receptor superfamily and include the GRP-receptor (GRP-R) and the neuromedin-B receptor (NMB- R). Key questions remain that are crucial for understanding the biologic effects of BBS, in particular, and all GI hormones, in general. They include, what are the mechanisms that regulate the diverse cellular functions produced by a peptide when it binds to its receptor and are identical or separate second messenger pathways responsible for peptide release, alterations in gene expression and cell growth? The major focus of this project is to define the intracellular mechanisms that regulate the multiple biologic effects of BBS in the gut. To accomplish this goal we have established a unique cell model by transfection of functional BBS receptors into our previously-characterized human endocrine cell line, BON, which produces the hormones neurotensin (NT), chromogranin A (CGA) and pancreastatin. Our preliminary findings demonstrate that BBS increases peptide release, alters NT gene expression and stimulates cell growth of these BON transfectants. In addition, we show that BBS stimulates the growth of the human gastric cancer cell line SIIA through a receptor other than GRP-R or NMB-R. Furthermore, our in vivo studies demonstrate that BBS affects normal and neoplastic gut tissues in a differential and cell-specific fashion. Taken together, these results indicate that BBS acts through multiple cell-specific signal transduction pathways to regulate cellular function. Based upon our findings, the central hypothesis of this proposal is that GI hormones regulate peptide release, gene expression and growth through specific receptors and post- receptor mechanisms. To examine this hypothesis we have planned experiments with the following Specific Aims: 1) We will characterize signal transduction pathways through which BBS regulates hormone secretion. To accomplish this goal, we will use our transfected BON cell clones to further delineate, in a systematic fashion, the specific signal transduction pathways responsible for BBS-mediated hormone release. 2) We will determine the cellular factors important for BBS-mediated changes in peptide gene expression. To accomplish this goal, we will identify the mechanisms responsible for BBS-mediated increases in NT gene expression. 3) We will examine the receptors and intracellular mechanisms responsible for the trophic effects of BBS. To accomplish this goal, we will assess the effects of BBS on our cell-established models of BBS-mediated cellular proliferation. The long-term goal of this proposal is to systematically define the intracellular mechanisms that regulate the cellular effects of BBS utilizing novel cell model systems that have been established in our laboratory. An in-depth identification of the signal transduction systems and molecular mechanisms that are responsible for these multiple cellular functions are crucial to our overall understanding of the diverse biologic effects exerted by the GI hormones.