Epac1-mediated, high glucose-induced renal proximal tubular cells hypertrophy via the Akt/p21 pathway.
Epac1-mediated, high glucose-induced renal proximal tubular cells hypertrophy via the Akt/p21 pathway.
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DOI：
10.1016/j.ajpath.2011.06.035
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发表时间：
2011-10
期刊：
影响因子：
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通讯作者：
Lin Sun;V. Kondeti;P. Xie;Kirtee Raparia;Y. Kanwar
中科院分区：
文献类型：
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作者：
Lin Sun;V. Kondeti;P. Xie;Kirtee Raparia;Y. Kanwar
糖尿病肾病小管肥大的机制尚不清楚。我们研究了cAMP 1激活的交换蛋白（Epac1）在细胞肥大中的作用，Epac1激活rap家族G蛋白。Epac1在心脏、肾小管和HK-2细胞系中表达。在糖尿病小鼠中，Epac1表达增加，在高糖环境（HGA）下，HK-2细胞也表现出Epac1表达增加。我们在fepac1基因起始密码子上游分离了一个1614 bp的DNA片段，包括葡萄糖反应元件（GREs）。转染Epac1启动子的HK-2或COS7细胞在HGA作用下显示其活性呈剂量依赖性增加。GRE基序突变导致启动子活性降低。在HGA作用下，HK-2细胞表现出肥厚反应和增加的蛋白质合成，Epac1-siRNA或-突变体可以减少蛋白质合成，而使用蛋白激酶a抑制剂则影响很小。Epac1转染导致细胞肥大和蛋白质合成增加，HGA加重了这一现象。HGA增加了G0/G1细胞周期期的细胞比例，增加了pAkt和周期蛋白依赖性激酶抑制剂p21和p27的表达，降低了周期蛋白依赖性激酶4的活性。用Epac1-siRNA或-突变体转染细胞后，这些效应被逆转。这些数据表明，HGA增加了gr依赖的Epac1转录，导致细胞周期阻滞和细胞肥大。
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 ofEpac1gene, 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.