P-Rex1 Mediates Glucose-Stimulated Rac1 Activation and Insulin Secretion in Pancreatic β-Cells.
P-Rex1 Mediates Glucose-Stimulated Rac1 Activation and Insulin Secretion in Pancreatic β-Cells.
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DOI：
10.33594/000000310
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发表时间：
2020-12-12
影响因子：
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通讯作者：
Kowluru, Anjaneyulu
中科院分区：
文献类型：
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作者：
Thamilselvan, Vijayalakshmi;Gamage, Suhadinie;Harajli, Ali;Chundru, Sri Aneesha;Kowluru, Anjaneyulu
尽管已发表的证据表明磷酸肌醇3-激酶（PI 3-激酶）参与胰岛功能的调节，但关于其下游信号步骤（包括胰岛β细胞中的磷脂酰肌醇-3，4，5-三磷酸依赖性Rac交换因子1（P-Rex 1）信号通路）的推定贡献作用的信息有限。因此，我们研究了P-Rex 1在胰岛素分泌（INS-1 832/13）β细胞中葡萄糖刺激的Rac 1活化和胰岛素分泌中的潜在作用。通过ELISA定量葡萄糖刺激的胰岛素分泌（GSIS）。内源性P-Rex 1和RhoG的表达通过使用DharmaFect 1试剂的siRNA转染而被抑制。使用Mem-PER Plus膜提取试剂盒分离总膜和胞质组分。Rac 1的活化程度通过下拉测定来确定。P-Rex 1在INS-1 832/13细胞、正常大鼠胰岛和人胰岛中表达。siRNA介导的P-Rex 1敲低减弱了葡萄糖诱导的Rac 1活化、膜结合和胰岛素分泌。RhoG与其他细胞类型中PI 3激酶介导的Rac 1活化有关，但似乎对GSIS没有贡献，因为siRNA介导的RhoG敲低未能对GSIS产生显著影响。LY 294002是一种已知的PI 3激酶抑制剂，可增强GSIS，而不影响葡萄糖诱导的Rac 1激活。基于这些发现，我们得出结论，P-Rex 1在葡萄糖诱导的Rac 1激活和胰岛素分泌中起着新的调节作用。
Despite the published evidence implicating phosphoinositide 3-kinase (PI3-kinase) in the regulation of islet function, limited information is available on the putative contributory roles of its downstream signaling steps, including the phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 1 (P-Rex1) signaling pathway in the islet β-cell. Therefore, we investigated potential roles for P-Rex1 in glucose-stimulated Rac1 activation and insulin secretion in insulin-secreting (INS-1 832/13) β-cells. Glucose-stimulated Insulin secretion (GSIS) was quantified by ELISA. Expression of endogenous P-Rex1 and RhoG was suppressed by siRNA transfection using the DharmaFect1 reagent. Total membrane and cytosolic fractions were isolated using the Mem-PER Plus Membrane Extraction Kit. The degree of activation of Rac1 was determined by the pull-down assay. P-Rex1 is expressed in INS-1 832/13 cells, normal rat islets and human islets. siRNA-mediated knockdown of P-Rex1 attenuated glucose-induced Rac1 activation, membrane association and insulin secretion. RhoG, which has been implicated in PI3-kinase-mediated Rac1 activation in other cell types, appears not to contribute to GSIS since the siRNA-mediated knockdown of RhoG failed to exert significant effects on GSIS. LY294002, a known inhibitor of PI3-kinase, potentiated GSIS without affecting glucose-induced Rac1 activation. Based on these findings, we conclude that P-Rex1 plays a novel regulatory role in glucose-induced Rac1 activation and insulin secretion.