Inhibition of Glucose-Stimulated Insulin Secretion by KCNJ15, a Newly Identified Susceptibility Gene for Type 2 Diabetes
- Koji Okamoto1,2,
- Naoko Iwasaki3,4,5⇓,
- Kent Doi2,
- Eisei Noiri2,
- Yasuhiko Iwamoto3,
- Yasuko Uchigata3,
- Toshiro Fujita2 and
- Katsushi Tokunaga1⇓
- 1Department of Human Genetics, Graduate School of Tokyo University, Tokyo, Japan
- 2Department of Nephrology and Endocrinology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
- 3Diabetes Center, Tokyo Women’s Medical University, Tokyo, Japan
- 4Institute of Integrated Medical Science, Tokyo Women’s Medical University, Tokyo, Japan
- 5Institute of Medical Genetics, Tokyo Women’s Medical University, Tokyo, Japan
- Corresponding authors: Katsushi Tokunaga, , and Naoko Iwasaki, .
Potassium inwardly rectifying channel, subfamily J, member 15 (KCNJ15) is a type 2 diabetes–associated risk gene, and Kcnj15 overexpression suppresses insulin secretion in rat insulinoma (INS1) cells. The aim of the current study was to characterize the role of Kcnj15 by knockdown of this gene in vitro and in vivo. Human islet cells were used to determine the expression of KCNJ15. Expression of KCNJ15 mRNA in islets was higher in subjects with type 2 diabetes. In INS1 cells, Kcnj15 expression was induced by high glucose–containing medium. Regulation of Kcnj15 by glucose and its effect on insulin secretion were analyzed in INS1 cells and in normal mice and diabetic mice by the inactivation of Kcnj15 using small interfering RNA. Knockdown of Kcnj15 increased the insulin secretion in vitro and in vivo. KCNJ15 and Ca2+-sensing receptor (CsR) interact in the kidney. Binding of Kcnj15 with CsR was also detected in INS1 cells. In conclusion, downregulation of Kcnj15 leads to increased insulin secretion in vitro and in vivo. The mechanism to regulate insulin secretion involves KCNJ15 and CsR.
- Received September 5, 2011.
- Accepted February 27, 2012.
- © 2012 by the American Diabetes Association.
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