Illumination of the endogenous insulin-regulated TBC1D4 interactome in human skeletal muscle

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Insulin-stimulated muscle glucose uptake is a key process in glycemic control. This process depends on the redistribution of glucose transporters to the surface membrane, a process which involves regulatory proteins such as TBC1D1 and TBC1D4. Accordingly, a TBC1D4 loss-of-function mutation in human skeletal muscle is associated with increased risk of type 2 diabetes, and observations from carriers of a TBC1D1 variant associate this protein to a severe obesity phenotype. Here, we identified interactors of the endogenous TBC1D4 in human skeletal muscle by an unbiased proteomics approach. We detected 76 proteins as candidate TBC1D4 interactors. The binding of 12 of these interactors were regulated by insulin, including proteins known to be involved in glucose metabolism (e.g. 14-3-3 proteins and ACTN4). TBC1D1 also co-precipitated with TBC1D4 and vice versa in both human and mouse skeletal muscle. This interaction was not regulated by insulin nor exercise in young, healthy, lean individuals. Similarly, the exercise- and insulin-regulated phosphorylation of the TBC1D1-TBC1D4 complex was intact. In contrast, we observed an altered interaction as well as compromised insulin-stimulated phospho-regulation of the TBC1D1-TBC1D4 complex in muscle of obese individuals with type 2 diabetes. Altogether, we provide a repository of TBC1D4 interactors in human and mouse skeletal muscle, which serve as potential regulators of TBC1D4 function and, thus, insulin-stimulated glucose uptake in human skeletal muscle.

Original languageEnglish
Issue number5
Pages (from-to)906-920
Publication statusPublished - 2022

Bibliographical note

Funding Information:
Acknowledgments. The authors would like to thank Dr. Laurie J. Goodyear (Joslin Diabetes Center and Harvard Medical School, Boston, MA) for the donation of phosphospecific TBC1D4-Ser711 antibody. The authors acknowledge the mass spectrometry platform staff (University of Copenhagen, Novo Nordisk Foundation Center for Protein Research, Clinical Proteomics) for their support with the proteomics analysis. The authors also thank Professor Erik A. Richter and Professor Bente Kiens (Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark) for their expertise and assistance during several of the clinical experiments. Funding. This work was supported by grants from the Danish Council for Independent Research (FSS: 610-00498B) and the Novo Nordisk Foundation (NNF21OC0070370) given to J.F.P.W. This work was also supported by a postdoctoral research fellow grant to R.K. from the Danish Diabetes Academy, which is funded by the Novo Nordisk Foundation (grant number NNF17SA0031406). The proteomics analysis and A.S.D. were supported by the Novo Nordisk Foundation (NNF14CC001 and NNF18CC0034900). Duality of Interest. J.F.P.W. has ongoing collaborations with Pfizer Inc. and Novo Nordisk Inc., unrelated to the current study. No other potential conflicts of interest relevant to this article were reported. Author Contributions. J.K.L., J.F.P.W., and R.K. conceived and designed the study. J.K.L., M.R.L., and J.B.B. conducted laboratory analyses. J.K.L. and A.S.D. analyzed mass spectrometry data. J.F.P.W., J.K.L., D.E.S., J.R.H., K.H., and J.F.P.W. conducted clinical experiments. A.C. and H.A.-H. contributed animal resources. J.K.L., J.F.P.W., and R.K. drafted the manuscript. All authors wrote, reviewed, edited, and approved the manuscript. J.F.P.W. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Publisher Copyright:
© 2022 by the American Diabetes Association.

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