Editors' ChoiceCellular Metabolism

Modifying Mitochondrial Metabolism

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Sci. Signal.  29 Apr 2014:
Vol. 7, Issue 323, pp. ec114
DOI: 10.1126/scisignal.2005423

Protein posttranslational modifications regulate diverse cellular functions. Lysine residues are subject to methylation, ubiquitylation, and sumoylation, as well as acylation involving acetyl-coenzyme A (CoA), succinyl-CoA, or malonyl-CoA. Sirtuin 5 (SIRT5) is a member of class III histone deacetylases (HDACs) that has desuccinylase and demalonylase activity. Glutaryl-CoA is an intermediate in the catabolism of lysine and tryptophan. Tan et al. reported the discovery of lysine glutarylation and deglutarylation and showed that glutarylation of mitochondrial metabolic proteins was altered by diet and disease. Western blot analysis with an antibody that specifically recognized glutaryl-lysine revealed glutarylation of proteins in several prokaryotic and eukaryotic species. Mass spectrometry–based comparison of synthetic glutarylated peptides and glutaryl-lysine–enriched peptides derived from bacteria and HeLa cells, as well as analysis of glutarylated peptides from HeLa cells grown in the presence of isotopically labeled glutarate, confirmed the existence of glutarylation. In vitro assays identified SIRT5 as the only HDAC with deglutarylation activity. The livers of Sirt5 knockout mice had globally increased glutarylation, including 683 lysines in 191 proteins that were enriched for proteins that function in cellular metabolism and localize in the mitochondria. The protein with the greatest number of glutarylated lysines was carbamoyl-phosphate synthetase1 (CPS1), a long-chain enoyl-CoA hydratase in the urea cycle. Sirt5 knockout mice and the media of HeLa cells with SIRT5 knockdown had more ammonia, a result consistent with inhibition of CPS1. The livers of fasted wild-type mice showed different patterns of glutarylation than those of mice fed a normal diet, and fruit flies fed with tryptophan showed globally increased glutarylation. Protein glutarylation was increased in samples from patients with glutaric acidemia caused by mutation in the gene encoding glutaryl-CoA dehydrogenase (GCDH), which converts glutaryl-CoA to crotonyl-CoA, and in those from GCDH knockout mice. CPS1 activity was reduced in hepatocytes of both Sirt5 and GCDH knockout mice. Thus, glutarylation is among a growing number of lysine posttranslational modifications important for the cellular metabolic homeostasis.

M. Tan, C. Peng, K. A. Anderson, P. Chhoy, Z. Xie, L. Dai, J. Park, Y. Chen, H. Huang, Y. Zhang, J. Ro, G. R. Wagner, M. F. Green, A. S. Madsen, J. Schmiesing, B. S. Peterson, G. Xu, O. R. Ilkayeva, M. J. Muehlbauer, T. Braulke, C. Mühlhausen, D. S. Backos, C. A. Olsen, P. J. McGuire, S. D. Pletcher D. B. Lombard, M. D. Hirschey, Y. Zhao, Lysine glutarylation is a protein posttranslational modification regulated by SIRT5. Cell Metab. 19, 605–617 (2014). [PubMed]