Rac1/PAK1 signaling promotes epithelial-mesenchymal transition of podocytes in vitro via triggering β-catenin transcriptional activity under high glucose conditions.

Ras-related C3 botulinum toxin substrate 1 (Rac1), together with its major downstream effector p21-activated kinase 1 (PAK1), has been identified a central role in cellular events such as cell cytoskeletal remodeling that contributed to cell migration and epithelial-mesenchymal transition (EMT). And there are data implicating that podocytes underwent EMT under pathological conditions. However, little is known about mechanisms of podocytes undergoing EMT. To address this, we assessed the cellular changes of podocytes after high glucose stimulation in vitro, detected the effects of Rac1/PAK1 signaling on podocytes in response to the stimuli, and investigated interactions of Rac1/PAK1 axis with β-catenin and Snail under high glucose conditions. We found that in vitro high glucose treatment led to remarkable down-regulation of nephrin and P-cadherin, as well as significant up-regulation of α-SMA and FSP-1, suggesting that in the presence of high glucose, podocytes underwent EMT, during which Rac1/PAK1 signaling was activated. And these were notably ameliorated by Rac1 gene knockdown. Furthermore, β-catenin and Snail nuclear translocation were triggered by Rac1/PAK1 axis, which were both markedly reversed via Rac1 gene knockdown or pretreatment of IPA-3, a PAK1 inhibitor. These findings elaborated that Rac1/PAK1 signaling contributed to high glucose-induced podocyte EMT via promoting β-catenin and Snail transcriptional activities, which could be a potential mechanism involved in podocytes injury in response to stimuli under diabetic conditions.

Lv Z ，Hu M ，Zhen J ，Lin J ，Wang Q ，Wang R ... -  《-》

GSK-3β and vitamin D receptor are involved in β-catenin and snail signaling in high glucose-induced epithelial-mesenchymal transition of mouse podocytes.

Epithelial-mesenchymal transition (EMT) is recognized to play an important role in diabetic nephropathy (DN). To analyze the roles of glycogen synthase kinase 3β (GSK-3β), β-catenin and Snail signaling in high glucose (HG)-induced mouse podocytes EMT. Differentiated podocytes were divided into: the normal glucose group (NG: glucose 5.6mM), the HG groups (12.5HG: 12.5mM; 25HG: 25mM; and 50HG: 50mM of glucose), and the osmotic control group (NG+M: glucose 5.6mM and mannitol 44.4mM). GSK-3β, β-catenin and Snail were assessed using semi-quantitative RT-PCR, western blot and immunofluorescence. β-catenin and Snail pathways were assessed after down-regulating GSK-3β expression using an inhibitor (LiCl) or a small-interfering RNA (siRNA). HG increased GSK-3β, β-catenin and Snail expressions, and promoted EMT, as shown by decreased nephrin expression (epithelial marker), and increased α-SMA expression (mesenchymal marker). GSK-3β inhibitor and GSK-3β siRNA decreased β-catenin and Snail expressions, and reversed HG-induced EMT. Immunofluorescence showed that GSK-3β and β-catenin did not completely overlap; β-catenin was transferred to the nucleus in the 25HG group. VDR seems to be involved in HG-induced β-catenin nuclear translocation. Down-regulating GSK-3β expression decreased β-catenin and Snail expression and reversed HG-induced podocytes EMT. Thus, modulating GSK-3β might be a target to slow or prevent DN. © 2014 S. Karger AG, Basel.

Guo J ，Xia N ，Yang L ，Zhou S ，Zhang Q ，Qiao Y ，Liu Z ... -  《-》

P21 activated kinase-1 mediates transforming growth factor β1-induced prostate cancer cell epithelial to mesenchymal transition.

Transforming growth factor beta (TGFβ) is believed to play a dual role in prostate cancer. Molecular mechanism by which TGFβ1 suppresses early prostate tumor growth and induces epithelial-to-mesenchymal transition (EMT) in advanced stages is not known. We determined if P21-activated kinase1 (Pak1), which mediates cytoskeletal remodeling is necessary for the TGFβ1 induced prostate cancer EMT. Effects of TGFβ1 on control prostate cancer PC3 and DU145 cells and those with IPA 3 and siRNA mediated Pak1 inhibition were tested for prostate tumor xenograft in vivo and EMT in vitro. TGFβ1 inhibited PC3 tumor xenograft growth via activation of P38-MAPK and caspase-3, 9. Long-term stimulation with TGFβ1 induced PC3 and DU145 cell scattering and increased expression of EMT markers such as Snail and N-cadherin through tumor necrosis factor receptor-associated factor-6 (TRAF6)-mediated activation of Rac1/Pak1 pathway. Selective inhibition of Pak1 using IPA 3 or knockdown using siRNA both significantly inhibited TGFβ1-induced prostate cancer cell EMT and expression of mesenchymal markers. Our study demonstrated that TGFβ1 induces apoptosis and EMT in prostate cancer cells via activation of P38-MAPK and Rac1/Pak1 respectively. Our results reveal the potential therapeutic benefits of targeting TGFβ1-Pak1 pathway for advanced-stage prostate cancer.

Al-Azayzih A ，Gao F ，Somanath PR 《-》

Podocyte-specific Rac1 deficiency ameliorates podocyte damage and proteinuria in STZ-induced diabetic nephropathy in mice.

Lv Z ，Hu M ，Fan M ，Li X ，Lin J ，Zhen J ，Wang Z ，Jin H ，Wang R ... -  《Cell Death & Disease》

Troglitazone ameliorates high glucose-induced EMT and dysfunction of SGLTs through PI3K/Akt, GSK-3β, Snail1, and β-catenin in renal proximal tubule cells.

Lee YJ ，Han HJ 《-》