Oncoprotein DJ-1 interacts with mTOR complexes to effect transcription factor Hif1α-dependent expression of collagen I (α2) during renal fibrosis

Proximal tubular epithelial cells respond to transforming growth factor beta (TGF beta) to synthesize collagen I (alpha 2) during renal fibrosis. The oncoprotein DJ-1 has previously been shown to promote tumorigenesis and prevent apoptosis of dopami-nergic neurons; however, its role in fibrosis signaling is unclear. Here, we show TGF beta-stimulation increased expression of DJ-1, which promoted noncanonical mTORC1 and mTORC2 activ-ities. We show DJ-1 augmented the phosphorylation/activation of PKC beta II, a direct substrate of mTORC2. In addition, coim-munoprecipitation experiments revealed association of DJ-1 with Raptor and Rictor, exclusive subunits of mTORC1 and mTORC2, respectively, as well as with mTOR kinase. Inter-estingly, siRNAs against DJ-1 blocked TGF beta-stimulated expression of collagen I (alpha 2), while expression of DJ-1 increased expression of this protein. In addition, expression of dominant negative PKC beta II and siRNAs against PKC beta II significantly inhibited TGF beta-induced collagen I (alpha 2) expres-sion. In fact, constitutively active PKC beta II abrogated the effect of siRNAs against DJ-1, suggesting a role of PKC beta II down-stream of this oncoprotein. Moreover, we demonstrate expression of collagen I (alpha 2) stimulated by DJ-1 and its target PKC beta II is dependent on the transcription factor hypoxia-inducible factor 1 alpha (Hif1 alpha). Finally, we show in the renal cor-tex of diabetic rats that increased TGF beta was associated with enhanced expression of DJ-1 and activation of mTOR and PKC beta II, concomitant with increased Hif1 alpha and collagen I (alpha 2). Overall, we identified that DJ-1 affects TGF beta-induced expres-sion of collagen I (alpha 2) via an mTOR-, PKC beta II-, and Hif1 alpha- dependent mechanism to regulate renal fibrosis.

Automated summary

This study demonstrates that DJ-1 regulates the expression of collagen I (alpha 2) induced by TGF beta through an mTOR- and PKC beta II-dependent mechanism, and identifies Hif1 alpha as an important transcription factor in this regulation.