Leucine-973 is a crucial residue differentiating insulin and IGF-1 receptor signaling
Hirofumi Nagao, … , Matthias Mann, C. Ronald Kahn
Hirofumi Nagao, … , Matthias Mann, C. Ronald Kahn
Published December 22, 2022
Citation Information: J Clin Invest. 2023;133(4):e161472. https://doi.org/10.1172/JCI161472.
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Leucine-973 is a crucial residue differentiating insulin and IGF-1 receptor signaling

Abstract

Insulin and IGF-1 receptors (IR and IGF1R) are highly homologous and share similar signaling systems, but each has a unique physiological role, with IR primarily regulating metabolic homeostasis and IGF1R regulating mitogenic control and growth. Here, we show that replacement of a single amino acid at position 973, just distal to the NPEY motif in the intracellular juxtamembrane region, from leucine, which is highly conserved in IRs, to phenylalanine, the highly conserved homologous residue in IGF1Rs, resulted in decreased IRS-1/PI3K/Akt/mTORC1 signaling and increased Shc/Gab1/MAPK cell cycle signaling. As a result, cells expressing L973F-IR exhibited decreased insulin-induced glucose uptake, increased cell growth, and impaired receptor internalization. Mice with knockin of the L973F-IR showed similar alterations in signaling in vivo, and this led to decreased insulin sensitivity, a modest increase in growth, and decreased weight gain when mice were challenged with a high-fat diet. Thus, leucine-973 in the juxtamembrane region of the IR acts as a crucial residue differentiating IR signaling from IGF1R signaling.

Authors

Hirofumi Nagao, Weikang Cai, Bruna B. Brandão, Nicolai J. Wewer Albrechtsen, Martin Steger, Arijeet K. Gattu, Hui Pan, Jonathan M. Dreyfuss, F. Thomas Wunderlich, Matthias Mann, C. Ronald Kahn

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Figure 3

Phosphoproteomic signature of WT-IR and L973F-IR cells.

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Phosphoproteomic signature of WT-IR and L973F-IR cells. (A) PCA of the p...
(A) PCA of the phosphosites identified by LC-MS/MS from DKO preadipocytes reconstituted with WT-IR and L973F-IR in the basal and ligand-stimulated (100 nM insulin or IGF-1 for 15 minutes) states. Cells were serum starved for 6 hours in DMEM containing 0.1% BSA before insulin and IGF-1 stimulation. (B) Heatmap showing hierarchical clustering of the differential phosphopeptides in WT-IR and L973F-IR–expressing cells in the basal and ligand-stimulated states. Values are shown as z scores of log2 transformed intensity values. (C) Volcano plot of phosphosites between WT-IR cells and L973F-IR cells using fold changes after ligand stimulation. Changes in phosphorylation between WT-IR cells and L973F-IR cells as fold stimulation, i.e., the ligand-stimulated level divided by the basal level of the phosphosites. Differences were considered significant at P < 0.05. (D) Reactome pathway enrichment analysis of phosphosites upregulated by ligand for fold-change WT-IR > L973F-IR. Plots are –log10 transforms of enrichment FDR value. (E) Reactome pathway enrichment analysis of phosphosites upregulated by ligand for fold change L973F-IR > WT-IR. Plots are –log10 transformed of enrichment FDR value.