TY - JOUR
T1 - Epac1-mediated, high glucose-induced renal proximal tubular cells hypertrophy via the Akt/p21 pathway
AU - Sun, Lin
AU - Kondeti, Vinay K.
AU - Xie, Ping
AU - Raparia, Kirtee
AU - Kanwar, Yashpal S.
N1 - Funding Information:
Supported by the National Institutes of Health (NIH) grant DK60635 and National Foundation Committee of Natural Science of China (NSFC) grants ( 30971379 ).
PY - 2011/10
Y1 - 2011/10
N2 - The mechanisms involved in tubular hypertrophy in diabetic nephropathy are unclear. We investigated the role of exchange protein activated by cAMP 1(Epac1), which activates Rap-family G proteins in cellular hypertrophy. Epac1 is expressed in heart, renal tubules, and in the HK-2 cell line. In diabetic mice, increased Epac1 expression was observed, and under high glucose ambience (HGA), HK-2 cells also exhibited increased Epac1 expression. We isolated a 1614-bp DNA fragment upstream of the initiation codon of Epac1 gene, inclusive of glucose response elements (GREs). HK-2 or COS7 cells transfected with the Epac1 promoter revealed a dose-dependent increase in its activity under HGA. Mutations in GRE motifs resulted in decreased promoter activity. HK-2 cells exhibited a hypertrophic response and increased protein synthesis under HGA, which was reduced by Epac1-siRNA or -mutants, whereas the use of a protein kinase A inhibitor had minimal effect. Epac1 transfection led to cellular hypertrophy and increased protein synthesis, which was accentuated by HGA. HGA increased the proportion of cells in the G0/G1 cell-cycle phase, and the expression of pAkt and the cyclin-dependent kinase inhibitors p21 and p27 was increased while the activity of cyclin-dependent kinase 4 decreased. These effects were reversed following transfection of cells with Epac1-siRNA or -mutants. These data suggest that HGA increases GRE-dependent Epac1 transcription, leading to cell cycle arrest and instigation of cellular hypertrophy.
AB - The mechanisms involved in tubular hypertrophy in diabetic nephropathy are unclear. We investigated the role of exchange protein activated by cAMP 1(Epac1), which activates Rap-family G proteins in cellular hypertrophy. Epac1 is expressed in heart, renal tubules, and in the HK-2 cell line. In diabetic mice, increased Epac1 expression was observed, and under high glucose ambience (HGA), HK-2 cells also exhibited increased Epac1 expression. We isolated a 1614-bp DNA fragment upstream of the initiation codon of Epac1 gene, inclusive of glucose response elements (GREs). HK-2 or COS7 cells transfected with the Epac1 promoter revealed a dose-dependent increase in its activity under HGA. Mutations in GRE motifs resulted in decreased promoter activity. HK-2 cells exhibited a hypertrophic response and increased protein synthesis under HGA, which was reduced by Epac1-siRNA or -mutants, whereas the use of a protein kinase A inhibitor had minimal effect. Epac1 transfection led to cellular hypertrophy and increased protein synthesis, which was accentuated by HGA. HGA increased the proportion of cells in the G0/G1 cell-cycle phase, and the expression of pAkt and the cyclin-dependent kinase inhibitors p21 and p27 was increased while the activity of cyclin-dependent kinase 4 decreased. These effects were reversed following transfection of cells with Epac1-siRNA or -mutants. These data suggest that HGA increases GRE-dependent Epac1 transcription, leading to cell cycle arrest and instigation of cellular hypertrophy.
UR - http://www.scopus.com/inward/record.url?scp=80053254049&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=80053254049&partnerID=8YFLogxK
U2 - 10.1016/j.ajpath.2011.06.035
DO - 10.1016/j.ajpath.2011.06.035
M3 - Article
C2 - 21854750
AN - SCOPUS:80053254049
SN - 0002-9440
VL - 179
SP - 1706
EP - 1718
JO - American Journal of Pathology
JF - American Journal of Pathology
IS - 4
ER -