Department of Pharmacology, University of Illinois, Chicago, 60612, United States.
Cell Signal. 2010 May;22(5):770-82. doi: 10.1016/j.cellsig.2010.01.001. Epub 2010 Jan 13.
P-Rex1 (phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchanger 1) is a Rac-specific guanine nucleotide exchange factor activated by Gbetagamma subunits and by PtdIns((3,4,5))P(3). Recent studies indicate that P-Rex1 plays an important role in signaling downstream of neutrophil chemoattractant receptors. Here we report that heterologous expression of P-Rex1, but not Vav1, reconstitutes formyl peptide receptor 1 (FPR1)-mediated NADPH oxidase activation in the transgenic COS(phox) cells expressing gp91(phox), p22(phox), p67(phox) and p47(phox). A successful reconstitution requires the expression of a full-length P-Rex1 with intact DH and PH domains, and is accompanied by P-Rex1 membrane localization as well as Rac1 activation. P-Rex1-dependent superoxide generation in the reconstituted COS(phox) cells was further enhanced by expression of the novel PKC isoform PKCdelta and by overexpression of Akt. Heterologous expression of P-Rex1 in COS(phox) cells potentiated fMet-Leu-Phe-induced Akt phosphorylation, whereas expression of a constitutively active form of Akt enhanced Rac1 activation. In contrast, a dominant negative Akt mutant reduced the fMet-Leu-Phe stimulated superoxide generation as well as Rac1 activation. These results demonstrate that in COS(phox) cells, P-Rex1 is a critical component for FPR1-mediated signaling leading to NADPH oxidase activation, and there is a crosstalk between the P-Rex1-Rac pathway and Akt in superoxide generation.
P-Rex1（磷酸肌醇 3,4,5-三磷酸依赖性 Rac 交换因子 1）是一种 Rac 特异性鸟苷酸交换因子，由 Gbetagamma 亚基和 PtdIns((3,4,5))P(3)激活。最近的研究表明，P-Rex1 在中性粒细胞趋化因子受体下游信号转导中发挥重要作用。在这里，我们报告 P-Rex1 的异源表达，但不是 Vav1，可重建表达 gp91(phox)、p22(phox)、p67(phox)和 p47(phox)的转基因 COS(phox)细胞中 formyl peptide receptor 1 (FPR1)介导的 NADPH 氧化酶激活。成功的重建需要表达全长的 P-Rex1，其 DH 和 PH 结构域完整，并且伴随着 P-Rex1 的膜定位以及 Rac1 的激活。在重建的 COS(phox)细胞中，P-Rex1 依赖性超氧化物生成进一步增强了新型 PKC 同工型 PKCdelta 的表达和 Akt 的过表达。在 COS(phox)细胞中异源表达 P-Rex1 增强了 fMet-Leu-Phe 诱导的 Akt 磷酸化，而 Akt 的组成性激活形式增强了 Rac1 的激活。相比之下，显性负性 Akt 突变体减少了 fMet-Leu-Phe 刺激的超氧化物生成以及 Rac1 的激活。这些结果表明，在 COS(phox)细胞中，P-Rex1 是 FPR1 介导的信号转导导致 NADPH 氧化酶激活的关键组成部分，并且在超氧化物生成中存在 P-Rex1-Rac 途径和 Akt 之间的串扰。
