Cybulsky A V, McTavish A J, Papillon J
Department of Medicine, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
Am J Physiol. 1996 Sep;271(3 Pt 2):F579-87. doi: 10.1152/ajprenal.1996.271.3.F579.
Adhesion of rat glomerular epithelial cells (GEC) to collagen stimulates production of D-myo-inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol. This process is mediated via beta 1-integrins, and it modulates GEC proliferation. In this study, we address the changes in inositol-lipid turnover induced by GEC adhesion to extracellular matrix (ECM). The masses of both phosphatidylinositol 4,5-bisphosphate (PIP2) and IP3, as well as [3H]inositol phosphates, were increased in GEC adherent to collagen, compared with plastic substratum. Phosphatidylinositol-4-phosphate (PIP) 5-kinase activity was predominantly membrane associated and was enhanced in GEC on collagen. Phospholipase C (PLC) activity and PLC-gamma 1 protein were increased in membrane fractions of GEC adherent to collagen, compared with plastic. Stable overexpression of PLC-gamma 1 in GEC amplified the effect of ECM on the production of [3H]inositol phosphates. In addition, the PLC-gamma 1 that was membrane associated in collagen-adherent GEC was tyrosine phosphorylated. Thus production of IP3 in GEC adherent to ECM is associated with increased production of PIP2. Moreover, adhesion to ECM increases tyrosine phosphorylation and membrane association of PLC-gamma 1, which may facilitate PIP2 hydrolysis by increasing the catalytic activity of PLC-gamma 1 and the proximity of PLC-gamma 1 and its substrate. Understanding the process of ECM-induced inositol lipid production and breakdown in GEC may provide insights into the regulation of GEC proliferation and differentiated functions in normal conditions and during glomerular injury.
大鼠肾小球上皮细胞（GEC）与胶原蛋白的黏附刺激了D-肌醇1,4,5-三磷酸（IP3）和1,2-二酰甘油的产生。这一过程由β1整合素介导，并调节GEC的增殖。在本研究中，我们探讨了GEC与细胞外基质（ECM）黏附所诱导的肌醇脂质周转变化。与塑料基质相比，黏附于胶原蛋白的GEC中磷脂酰肌醇4,5-二磷酸（PIP2）、IP3以及[3H]肌醇磷酸的量均增加。磷脂酰肌醇-4-磷酸（PIP）5-激酶活性主要与膜相关，且在黏附于胶原蛋白的GEC中增强。与塑料相比，黏附于胶原蛋白的GEC膜组分中的磷脂酶C（PLC）活性和PLC-γ1蛋白增加。GEC中PLC-γ1的稳定过表达放大了ECM对[3H]肌醇磷酸产生的影响。此外，黏附于胶原蛋白的GEC中与膜相关的PLC-γ1发生了酪氨酸磷酸化。因此，黏附于ECM的GEC中IP3的产生与PIP2产生的增加相关。此外，与ECM的黏附增加了PLC-γ1的酪氨酸磷酸化和膜结合，这可能通过增加PLC-γ1的催化活性以及PLC-γ1与其底物的接近度来促进PIP2的水解。了解ECM诱导的GEC中肌醇脂质产生和分解的过程，可能有助于深入了解正常条件下以及肾小球损伤期间GEC增殖和分化功能的调节。
