Akt and RhoA activation in response to high glucose require caveolin-1 phosphorylation in mesangial cells.
Glomerular matrix accumulation is a hallmark of diabetic renal disease. Serine/threonine kinase PKC-β1 mediates glucose-induced Akt S473 phosphorylation, RhoA activation, and transforming growth factor (TGF)-β1 upregulation and finally leads to matrix upregulation in mesangial cells (MCs). It has been reported that glucose-induced PKC-β1 activation is dependent on caveolin-1 and the presence of intact caveolae in MCs; however, whether activated PKC-β1 regulates caveolin-1 expression and phosphorylation are unknown. Here, we showed that, although the caveolin-1 protein level had no significant change, the PKC-β-specific inhibitor LY-333531 blocked caveolin-1 Y14 phosphorylation in high glucose (HG)-treated MCs and in the renal cortex of diabetic rats. The Src-specific inhibitor SU-6656 prevented the HG-induced association between PKC-β1 and caveolin-1 and PKC-β1 membrane translocation, whereas PKC-β1 small interfering RNA failed to block Src activation, indicating that Src kinase is upstream of PKC-β1 activation. Although LY-333531 blocked PKC-β1 membrane translocation, it had no effect on the PKC-β1/caveolin-1 association, suggesting that PKC-β1 activation requires the interaction of caveolin-1 and PKC-β1. PKC-β1-mediated Akt S473 phosphorylation, RhoA activation, and fibronectin upregulation in response to HG were prevented by SU-6656 and nonphosphorylatable mutant caveolin-1 Y14A. In conclusion, Src activation by HG mediates the PKC-β1/caveolin-1 association and PKC-β1 activation, which assists in caveolin-1 Y14 phosphorylation by Src kinase. The downstream effects, including Akt S473 phosphorylation, RhoA activation, and fibronectin upregulation, require caveolin-1 Y14 phosphorylation. Caveolin-1 is thus an important mediator of the profibrogenic process in diabetic renal disease.
Department of Biochemistry, Wuhan University School of Basic Medical Sciences, Wuhan, People's Republic of China; and.
Su-Zhen
SZ
Wu
Department of Biochemistry, Wuhan University School of Basic Medical Sciences, Wuhan, People's Republic of China; and.
Fang-Fang
FF
Peng
Gannan Medical University, Ganzhou, People's Republic of China; and.
Jia-Lin
JL
Li
Department of Biochemistry, Wuhan University School of Basic Medical Sciences, Wuhan, People's Republic of China; and.
Feng
F
Ye
Department of Biochemistry, Wuhan University School of Basic Medical Sciences, Wuhan, People's Republic of China; and.
Shao-Qing
SQ
Lei
Department of Biochemistry, Wuhan University School of Basic Medical Sciences, Wuhan, People's Republic of China; and Hubei Provincial Key Laboratory of Developmentally Originated Disease, Wuhan, People's Republic of China zbfwq@whu.edu.cn.
Bai-Fang
BF
Zhang
D000818:Animals; D051242:Caveolin 1 / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D008297:Male; D050527:Mesangial Cells / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D051242:Caveolin 1; D051057:Proto-Oncogene Proteins c-akt; D020742:rhoA GTP-Binding Protein; D005947:Glucose
caveolin-1 phosphorylation; extracellular matrix; glomerular sclerosis