Ship2, a Negative Regulator of the Pi3-Kinase/Akt Signaling Pathway, Promote Angiotensin Ii-Induced Podocytes Injury

Objective: Phosphatidylinositol-3 kinase (PI3-K) has distinct roles in cellular processes spanning from metabolism to cell motility and survival. Angiotensin II (Ang II) promotes the development and progression of proteinuria and renal diseases and induces podocyte endoplasmic reticulum (ER) stress and apoptosis. We investigated the regulating role of PI3-kinase in angiotensin II-induced podocyte injury. Design and method: Mouse podocytes were incubated in media containing Ang II, PI3-kinase modulating agents, such as, 3-methyladenine and AS1949490, and ER stress modulating agents, such as, 4-phenylbutyric acid (PBA). Cell survival/death-modifying reagents and siRNA targeting SHIP2, a negative regulator of the PI3-kinase/Akt signaling pathway, were applied. The changes of podocyte ER stress markers and apoptosis were observed by confocal imaging, western blotting, realtime PCR, and FACS according to the presence of Ang II and PI3-kinase modulating agents. Results: Ang II increased ER stress markers, which were augmented by phosphoinositide 3 (PI3)-kinase inhibition, suggesting that Ang II could induce podocyte ER stress via PI3-kinase pathway. Thereafter, Ang II induced podocyte apoptosis significantly in concentration- and time-dependent manners. PI3-kinase inhibitors, 3-MA and LY294002, further increased Ang II-induced podocyte ER stress and apoptosis. On the other hand, SHIP2 siRNA and AS1949490 improved the mal-location of podocyte proteins and suppressed Ang II-induced podocyte apoptosis and the expression of apoptotic proteins. Conclusions: Our findings suggest that Ang II induces podocyte ER stress and apoptosis, which could be prevented by PI3-kinase activation through the inhibition of SHIP2.