High glucose couples DJ-1 with PTEN to activate PDGFRβ for renal proximal tubular cell injury

Abstract

High glucose milieu in diabetes induces proximal tubular epithelial cells in the kidney to undergo hypertrophy and matrix protein expansion via Akt/mTORC1 signaling, leading to renal fibrosis. The familial Parkinson’s disease protein DJ-1 acts as a driver of Ras-dependent tumorigenesis and protects dopaminergic neurons from apoptosis. But its function and mechanistic basis to regulate renal fibrosis is not clear. Here, we identify DJ-1 as a high glucose-promoted protein in renal proximal tubular epithelial cells. Mechanistic interrogation revealed that DJ-1 formed complex with the lipid phosphatase PTEN in high glucose-stimulated cells, resulting in phosphorylation/activation of Akt and mTORC1. siRNAs against DJ-1 decreased high glucose-stimulated Akt/mTORC1 activation. In contrast, overexpression of DJ-1 mimicked all effects of high glucose. Interestingly, inhibition of DJ-1 blocked high glucose-induced hypertrophy of proximal tubular epithelial cells and, matrix proteins fibronectin and collagen I (α2) expression while overexpression of DJ-1 mimicked the high glucose effects on these phenomena. Previously, we reported a role of PDGFRβ in proximal tubular cell injury. In exploring the mechanism of DJ-1 function, we found that siDJ-1 inhibited high glucose-induced activating and PI 3 kinase docking site tyrosine phosphorylation of PDGF receptor-β (PDGFRβ) to block phosphorylation of PI 3 kinase. Interestingly, overexpression of PTEN mimicked these effects of siDJ-1. Together, our results reveal an important role of DJ-1-PTEN nodal point for PDGFRβ activation during high glucose-induced proximal tubular epithelial cell injury.