VESICLE TRAFFICKING AND PANCREATIC ACINAR CELL SECRETION

本提案的目的是确定参与正常和异常胰酶分泌的分子机制。我们的重点是胰腺腺泡细胞和支持激动剂诱导的酶原颗粒从反式高尔基网络（TGN）形成和运输到顶膜并随后释放酶的机制。使用原代腺泡制剂和我们开发的新型培养胰腺腺泡细胞模型，我们进行了以下新的观察。(1) cck刺激诱导高尔基体的囊泡形成，同时增加酶原颗粒的运输；(2)在激动剂刺激后，特异性囊泡外壳和细胞骨架蛋白被招募到腺泡细胞TGN；(3)微管（Mt）相关的运动酶激酶与酶原颗粒相关，并且与Mt一起，是颗粒运动所必需的。本研究将利用最先进的表达gfp蛋白结构的活的和固定的腺泡细胞的显微成像技术，结合生化和分子方法来验证以下中心假设：腺泡细胞中的特定涂层和运动蛋白在分泌刺激过程中被募集和激活，以介导酶原颗粒从TGN到根尖管的适当形成和运输。我们预测，这种酶原运输机制的破坏将导致腺泡细胞中新生蛋白酶的错误分类和随后的胰腺炎。因此，我们提出了三个具体目标。首先，我们将定义腺泡细胞TGN的结构，并观察其在刺激分泌过程中的变化。将进行抑制运动和外壳功能的机制研究，并随后评估对TGN结构和酶原颗粒形成的影响。其次，我们将确定哪些运动蛋白支持酶原颗粒运输到根尖管腔，并测试这些运动蛋白在分泌过程中是否上调。第三，我们将直接测试外壳和运动蛋白的破坏，或超刺激，是否会导致异常的错分类和随后的酶原释放到细胞质中。据我们所知，这将是第一个在活的腺泡细胞分泌时操纵和观察囊泡形成和运输的研究之一。我们相信这项研究将对理解胰腺腺泡细胞的功能和疾病做出重要贡献。

The objective of this proposal is to define the molecular mechanisms involved in both normal and abnormal pancreatic enzyme secretion. Our focus is on the pancreatic acinar cell and the mechanisms that support the agonist-induced formation and transport of zymogen granules from the trans-Golgi network (TGN) to the apical membrane for subsequent enzyme release. Using both primary acini preparations and a novel cultured pancreatic acinar cell model that we developed, we have made the following novel observations. (i), CCK-stimulation induces vesiculation of the Golgi apparatus while increasing zymogen granule transport, (ii), specific vesicle-coat and cytoskeletal proteins are recruited to the acinar cell TGN following agonist stimulation, and (iii), the microtubule (Mt) associated motor enzyme kinesin is associated with zymogen granules and, along with Mts, is required for granule movement. This study will utilize state-of-the-art microscopic imaging techniques of living and fixed acinar cells expressing GFP-protein constructs, combined with biochemical and molecular methods to test the following CENTRAL HYPOTHESIS: specific coat and motor proteins in the acinar cell are recruited and activated during a secretory stimulus to mediate the appropriate formation and transport of zymogen granules from the TGN to the apical lumen. We predict that disruption of this zymogen transport machinery will lead to missorting of nascent proteases in the acinar cell and subsequent pancreatitis. Thus, we propose three SPECIFIC AIMS. First, we will define the structure of the acinar cell TGN and observe how it changes during stimulated secretion. Mechanistic studies will be conducted to inhibit motor and coat function and subsequently assess the effects on TGN structure and zymogen granule formation. Second, we will define which motor proteins support the transport of zymogen granules to the apical lumen and test whether these motors are upregulated during secretion. Third, we will directly test if a disruption of coat and motor proteins, or suprastimulation, leads to an aberrant missorting and subsequent release of zymogens into the cytoplasm. To our knowledge this will be one of the first studies to manipulate and view vesicle formation and transport in living acinar cells as they secrete. We are confident that this study will make important contributions essential to understanding pancreatic acinar cell function and disease.