Regulation of exocrine cell secretion by Rab proteins

描述（由申请方提供）：本提案中描述的研究的长期目标是阐明Rab蛋白和Rab辅助蛋白在外分泌腺中调节胞吐作用的作用。与Ras一样，Rab蛋白也是GTP酶。Rab 3同种型（A、B、C和D）是小的GTP结合蛋白，据信涉及分泌细胞（包括神经元、外分泌和内分泌细胞）中的调节分泌。例如，在腮腺和胰腺腺泡细胞中，Rab 3D定位于分泌颗粒膜。Rab 27 b是另一种被认为在调节分泌中起作用的Rab蛋白。Rab辅助蛋白如rab-GDP-解离抑制剂（GDI）和rab护送蛋白（REP）通过调节鸟嘌呤核苷酸与Rab的结合来调节Rab蛋白的活性。REP还在Rab蛋白的脂质修饰中起作用。本提案中概述的实验旨在检查AR 42 J细胞中Rab蛋白和Rab辅助蛋白之间的相互作用，AR 42 J细胞是一种大鼠胰腺细胞系，在用地塞米松处理后显示腺泡细胞样表型。PI认为，AR 42 J细胞系是研究胞吐作用的有用模型，因为当AR 42 J细胞分化为腺泡样细胞时，可以检查蛋白表达和定位以及颗粒形成的变化。此外，该实验室的工作表明Rab 3D与腮腺中分泌颗粒的密度较低的亚群相关。在本建议中，实验概述了进一步研究这一新发现。该提议的具体目的是：1）检查Rab 3蛋白、Rab 27 b、rab-GDI和REP同种型在AR 42 J细胞中的表达、定位和相互作用，因为它们形成受调节的分泌途径;和2）检查Rab 3D与腮腺和AR 42 J细胞中的分泌颗粒亚群的关联。外分泌腺执行许多重要的功能和外分泌腺功能可能会受到损害的疾病或随着年龄的增长。因此，了解调节外分泌腺分泌的基本机制至关重要。

DESCRIPTION (provided by applicant): The long-term objective of the studies described in the present proposal is to elucidate the role of Rab proteins and Rab accessory proteins in regulated exocytosis in exocrine glands. Like Ras, Rab proteins are GTPases. Rab3 isoforms (A, B, C and D) are small GTP-binding proteins believed to be involved with regulated secretion in secretory cells including neurons, exocrine and endocrine cells. For example, in parotid and pancreatic acinar cells Rab3D is localized to secretory granule membranes. Rab27b is another Rab protein believed to play a role in regulated secretion. Rab accessory proteins like rab-GDP-dissociation inhibitor (GDI) and rab escort protein (REP) regulate Rab protein activity by regulating guanine nucleotide binding to Rabs. REP also plays a role in the lipid modification of Rab proteins. Experiments outlined in this proposal are aimed at examining the interactions between Rab proteins and Rab accessory proteins in AR42J cells, a rat pancreatic cell line that displays an acinar cell-like phenotype upon treatment with dexamethasone. The PI believes that the AR42J cell line is a useful model for studying exocytosis because changes in protein expression and localization, as well as granule formation, can be examined as AR42J cells differentiate into acinar-like cells. In addition, work from this laboratory indicates that Rab3D associates with a less dense subpopulation of secretory granules in parotid. In the present proposal, experiments are outlined to further examine this novel finding. The specific aims of this proposal are to: 1) examine the expression, localization and interactions of Rab3 proteins, Rab27b, rab-GDI and REP isoforms in AR42J cells as they develop a regulated secretory pathway; and 2) examine the association of Rab3D with subpopulations of secretory granules in parotid and AR42J cells. Exocrine glands perform many important functions and exocrine gland function may be compromised by disease or with advancing age. Therefore, an understanding of the basic mechanisms that regulate exocrine gland secretion is essential.