PI KINASES, CANALICULAR TRANSPORTERS AND CHOLESTASIS

负责细胞内胆汁淤积和ATP依赖性小管转运蛋白spgp（牛磺胆酸盐）、mrp 2（非胆汁酸有机阴离子）、mdr 1（有机阳离子）、mdr 3（磷脂酰胆碱移位酶）和新描述的mrp 3（甘氨胆酸盐）的细胞内转运的调节机制知之甚少。需要完整的微管网络和起源于跨高尔基体网络并终止于胆小管膜的囊泡运输。两者都与PI 3-激酶活性相关，并被PI 3-激酶抑制剂Wortmannin和LY 294002阻断。完整细胞中PI 3-激酶的激活促进胆汁酸分泌。我们建议PI 3-激酶脂质产品是必不可少的囊泡贩运的ATP依赖性小管转运蛋白，以及为他们的活动在小管膜。我们还假设，这些磷脂的产生是有缺陷的某些形式的胆汁淤积。使用生物化学，分子和共聚焦荧光显微镜技术和新的试剂和实验模型，包括基因工程p85-/- PI 3-激酶小鼠，小管转运蛋白的特定运输和PI 3-激酶及其脂质生产者在胆汁分泌中的作用将被确定。这些研究应阐明胆汁淤积的细胞内机制。此外，特定PI 3-激酶功能的激活可能选择性地增强小管转运，并在胆汁淤积中具有治疗潜力。

Mechanisms responsible for intracellular cholestasis and regulation of intracellular trafficking of the ATP-dependent canalicular transporters spgp (taurocholate), mrp2 (nonbile acid organic anions), mdr1 (organic cations), mdr3 (phosphatidylcholine translocase) and newly described mrp3 (glycocholate) are poorly understood. An intact microtubular network and vesicular trafficking originating in the trans-Golgi network and concluding in the bile canalicular membrane are required. Both are associated with PI 3-kinase activity and are blocked by Wortmannin and LY294002, which are PI 3-kinase inhibitors. Activation of PI 3- kinase in intact cells accelerates bile acid secretion. We propose that PI 3-kinase lipid products are essential for vesicular trafficking of the ATP-dependent canalicular transporters as well as for their activity in the canalicular membrane. We also postulate that generation of these phospholipids is defective in certain forms of cholestasis. Using biochemical, molecular and confocal fluorescence microscopic techniques and novel reagents and experimental models, including genetically engineered p85-/- PI 3- kinase mice, the specific trafficking of canalicular transporters and the role of PI 3-kinase and its lipid producers in bile secretion will be determined. These studies should elucidate intracellular mechanisms of cholestasis. Furthermore, activation of specific PI 3-kinase functions may selectively enhance canalicular transport and have therapeutic potential in cholestasis.