AGEs-RAGE system down-regulates Sirt1 through the ubiquitin-proteasome pathway to promote FN and TGF-β1 expression in male rat glomerular mesangial cells.
We previously demonstrated that advanced glycation-end products (AGEs) promote the pathological progression of diabetic nephropathy by decreasing silent information regulator 2-related protein 1 (Sirt1) expression in glomerular mesangial cells (GMCs). Here, we investigated whether AGEs-receptor for AGEs (RAGE) system down-regulated Sirt1 expression through ubiquitin-proteasome pathway and whether Sirt1 ubiquitination affected fibronectin (FN) and TGF-β1, 2 fibrotic indicators in GMCs. Sirt1 was polyubiquitinated and subsequently degraded by proteasome. AGEs increased Sirt1 ubiquitination and proteasome-mediated degradation, shortened Sirt1 half-life, and promoted FN and TGF-β1 expression. Ubiquitin-specific protease 22 (USP22) reduced Sirt1 ubiquitination and degradation and decreased FN and TGF-β1 expression in GMCs under both basal and AGEs-treated conditions. USP22 depletion enhanced Sirt1 degradation and displayed combined effects with AGEs to further promote FN and TGF-β1 expression. RAGE functioned crucial mediating roles in these processes via its C-terminal cytosolic domain. Inhibiting Sirt1 by EX-527 substantially suppressed the down-regulation of FN and TGF-β1 resulting from USP22 overexpression under both normal and AGEs-treated conditions, eventually leading to their up-regulation in GMCs. These results indicated that the AGEs-RAGE system increased the ubiquitination and subsequent proteasome-mediated degradation of Sirt1 by reducing USP22 level, and AGEs-RAGE-USP22-Sirt1 formed a cascade pathway that regulated FN and TGF-β1 level, which participated in the pathological progression of diabetic nephropathy.
Laboratory of Pharmacology and Toxicology (K.-P.H., C.C., J.H., J.-Y.H., P.-Q.L., H.-Q.H.), School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China; and Department of Pharmacy (K.-P.H.), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China.
Kai-Peng
KP
Huang
Cheng
C
Chen
Jie
J
Hao
Jun-Ying
JY
Huang
Pei-Qing
PQ
Liu
He-Qing
HQ
Huang
D000818:Animals; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D056564:Sirtuin 1 / Q000235:genetics / Q000378:metabolism; D013869:Thiolester Hydrolases / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
D005353:Fibronectins; D017127:Glycation End Products, Advanced; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D053773:Transforming Growth Factor beta1; D013869:Thiolester Hydrolases; D056564:Sirtuin 1