Wang Honghui, Misaki Taro, Taupin Vanessa, Eguchi Akiko, Ghosh Pradipta, Farquhar Marilyn G
Departments of Cellular and Molecular Medicine and.
Medicine, University of California, San Diego, La Jolla, California.
J Am Soc Nephrol. 2015 Feb;26(2):314-27. doi: 10.1681/ASN.2013090985. Epub 2014 Jul 10.
Podocytes are critically involved in the maintenance of the glomerular filtration barrier and are key targets of injury in many glomerular diseases. Chronic injury leads to progressive loss of podocytes, glomerulosclerosis, and renal failure. Thus, it is essential to maintain podocyte survival and avoid apoptosis after acute glomerular injury. In normal glomeruli, podocyte survival is mediated via nephrin-dependent Akt signaling. In several glomerular diseases, nephrin expression decreases and podocyte survival correlates with increased vascular endothelial growth factor (VEGF) signaling. How VEGF signaling contributes to podocyte survival and prevents apoptosis remains unknown. We show here that Gα-interacting, vesicle-associated protein (GIV)/girdin mediates VEGF receptor 2 (VEGFR2) signaling and compensates for nephrin loss. In puromycin aminonucleoside nephrosis (PAN), GIV expression increased, GIV was phosphorylated by VEGFR2, and p-GIV bound and activated Gαi3 and enhanced downstream Akt2, mammalian target of rapamycin complex 1 (mTORC1), and mammalian target of rapamycin complex-2 (mTORC2) signaling. In GIV-depleted podocytes, VEGF-induced Akt activation was abolished, apoptosis was triggered, and cell migration was impaired. These effects were reversed by introducing GIV but not a GIV mutant that cannot activate Gαi3. Our data indicate that after PAN injury, VEGF promotes podocyte survival by triggering assembly of an activated VEGFR2/GIV/Gαi3 signaling complex and enhancing downstream PI3K/Akt survival signaling. Because of its important role in promoting podocyte survival, GIV may represent a novel target for therapeutic intervention in the nephrotic syndrome and other proteinuric diseases.
足细胞对于维持肾小球滤过屏障至关重要,并且是许多肾小球疾病中损伤的关键靶点。慢性损伤会导致足细胞逐渐丧失、肾小球硬化和肾衰竭。因此,在急性肾小球损伤后维持足细胞存活并避免凋亡至关重要。在正常肾小球中,足细胞存活是通过依赖于nephrin的Akt信号传导介导的。在几种肾小球疾病中,nephrin表达降低,且足细胞存活与血管内皮生长因子(VEGF)信号传导增加相关。VEGF信号传导如何促进足细胞存活并防止凋亡仍不清楚。我们在此表明,Gα相互作用、囊泡相关蛋白(GIV)/girdin介导VEGF受体2(VEGFR2)信号传导并补偿nephrin缺失。在嘌呤霉素氨基核苷肾病(PAN)中,GIV表达增加,GIV被VEGFR2磷酸化,且磷酸化的GIV结合并激活Gαi3,并增强下游Akt2、雷帕霉素复合物1(mTORC1)和雷帕霉素复合物2(mTORC2)信号传导。在GIV缺失的足细胞中,VEGF诱导的Akt激活被消除,触发凋亡,且细胞迁移受损。通过引入GIV而非不能激活Gαi3的GIV突变体可逆转这些效应。我们的数据表明,PAN损伤后,VEGF通过触发活化VEGFR2/GIV/Gαi3信号复合物的组装并增强下游PI3K/Akt存活信号传导来促进足细胞存活。由于其在促进足细胞存活中的重要作用,GIV可能代表肾病综合征和其他蛋白尿性疾病治疗干预的新靶点。