GCN2 regulates pancreatic β cell mass by sensing intracellular amino acid levels
Ayumi Kanno, … , Masato Kasuga, Yoshiaki Kido
Ayumi Kanno, … , Masato Kasuga, Yoshiaki Kido
Published May 7, 2020
Citation Information: JCI Insight. 2020;5(9):e128820. https://doi.org/10.1172/jci.insight.128820.
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Research Article Endocrinology Metabolism

GCN2 regulates pancreatic β cell mass by sensing intracellular amino acid levels

Abstract

EIF2AK4, which encodes the amino acid deficiency–sensing protein GCN2, has been implicated as a susceptibility gene for type 2 diabetes in the Japanese population. However, the mechanism by which GCN2 affects glucose homeostasis is unclear. Here, we show that insulin secretion is reduced in individuals harboring the risk allele of EIF2AK4 and that maintenance of GCN2-deficient mice on a high-fat diet results in a loss of pancreatic β cell mass. Our data suggest that GCN2 senses amino acid deficiency in β cells and limits signaling by mechanistic target of rapamycin complex 1 to prevent β cell failure during the consumption of a high-fat diet.

Authors

Ayumi Kanno, Shun-ichiro Asahara, Ayuko Furubayashi, Katsuhisa Masuda, Risa Yoshitomi, Emi Suzuki, Tomoko Takai, Maki Kimura-Koyanagi, Tomokazu Matsuda, Alberto Bartolome, Yushi Hirota, Norihide Yokoi, Yuka Inaba, Hiroshi Inoue, Michihiro Matsumoto, Kenichi Inoue, Takaya Abe, Fan-Yan Wei, Kazuhito Tomizawa, Wataru Ogawa, Susumu Seino, Masato Kasuga, Yoshiaki Kido

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Figure 3

mTORC1 signaling is enhanced in the islets of GCN2–/– mice fed a HFD.

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mTORC1 signaling is enhanced in the islets of GCN2–/– mice fed a HFD. (A...
(A and B) Immunoblot analysis of mTORC1 (A) and insulin (B) signaling in pancreatic islets of 24-week-old HFD-fed GCN2+/+ or GCN2–/– mice. Duplicate samples in A and B were run on the same blot; the samples in A share the same loading control as in B. Representative blots and quantitative data for 3–5 independent experiments are shown. (C) Immunostaining of insulin and E-cadherin in pancreatic sections from mice as in A. Scale bars: 20 μm. (D) Size of individual β cells was determined from the insulin-positive area divided by the number of nuclei in insulin-positive cells (n = 6 each). The number of β cells was determined from the number of β cells divided by the total pancreatic area (n = 5 each). (E) The number of Ki67+ β cells per islet in 16-week-old HFD-fed GCN2+/+ (n = 7) and GCN2–/– (n = 8) mice. (D) The number of apoptotic β cells per islet in mice as in D (n = 5 each) was determined with the TUNEL assay. (G and H) Immunoblot analysis (G) and RT-PCR analysis (H) (n = 5 each) of GCN2 in INS-1 cells transfected with a scramble siRNA (control) or GCN2 siRNA (GCN2 KD). (I and J) Immunoblot analysis of mTORC1 (I) and insulin (J) signaling in cells as in G following 24-hour deprivation of leucine, lysine, and arginine. Representative blots and quantitative data from 3–5 independent experiments are shown. All quantitative data are the mean ± SEM. *P < 0.05, **P < 0.01 (2-tailed Student’s t test).