Dataset Information

A non-canonical tricarboxylic acid cycle underlies cellular identity.

ABSTRACT: The tricarboxylic acid (TCA) cycle is a central hub of cellular metabolism, oxidizing nutrients to generate reducing equivalents for energy production and critical metabolites for biosynthetic reactions. Despite the importance of the products of the TCA cycle for cell viability and proliferation, mammalian cells display diversity in TCA-cycle activity^1,2. How this diversity is achieved, and whether it is critical for establishing cell fate, remains poorly understood. Here we identify a non-canonical TCA cycle that is required for changes in cell state. Genetic co-essentiality mapping revealed a cluster of genes that is sufficient to compose a biochemical alternative to the canonical TCA cycle, wherein mitochondrially derived citrate exported to the cytoplasm is metabolized by ATP citrate lyase, ultimately regenerating mitochondrial oxaloacetate to complete this non-canonical TCA cycle. Manipulating the expression of ATP citrate lyase or the canonical TCA-cycle enzyme aconitase 2 in mouse myoblasts and embryonic stem cells revealed that changes in the configuration of the TCA cycle accompany cell fate transitions. During exit from pluripotency, embryonic stem cells switch from canonical to non-canonical TCA-cycle metabolism. Accordingly, blocking the non-canonical TCA cycle prevents cells from exiting pluripotency. These results establish a context-dependent alternative to the traditional TCA cycle and reveal that appropriate TCA-cycle engagement is required for changes in cell state.

SUBMITTER: Arnold PK

PROVIDER: S-EPMC8934290 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

A non-canonical tricarboxylic acid cycle underlies cellular identity.

Arnold Paige K PK Jackson Benjamin T BT Paras Katrina I KI Brunner Julia S JS Hart Madeleine L ML Newsom Oliver J OJ Alibeckoff Sydney P SP Endress Jennifer J Drill Esther E Sullivan Lucas B LB Finley Lydia W S LWS

Nature 20220309 7901

The tricarboxylic acid (TCA) cycle is a central hub of cellular metabolism, oxidizing nutrients to generate reducing equivalents for energy production and critical metabolites for biosynthetic reactions. Despite the importance of the products of the TCA cycle for cell viability and proliferation, mammalian cells display diversity in TCA-cycle activity<sup>1,2</sup>. How this diversity is achieved, and whether it is critical for establishing cell fate, remains poorly understood. Here we identify ...[more]

PMID: 35264789

Similar Datasets

Project description:Methylmalonic acidemia (MMA) is a propionate pathway disorder caused by dysfunction of the mitochondrial enzyme methylmalonyl-CoA mutase (MMUT). MMUT catalyzes the conversion of methylmalonyl-CoA to succinyl-CoA, an anaplerotic reaction which feeds into the tricarboxylic acid (TCA) cycle. As part of the pathological mechanisms of MMA, previous studies have suggested there is decreased TCA activity due to a "toxic inhibition" of TCA cycle enzymes by MMA related metabolites, in addition to reduced anaplerosis. Here, we have utilized mitochondria isolated from livers of a mouse model of MMA (Mut-ko/ki) and their littermate controls (Ki/wt) to examine the amounts and enzyme functions of most of the TCA cycle enzymes. We have performed mRNA quantification, protein semi-quantitation, and enzyme activity quantification for TCA cycle enzymes in these samples. Expression profiling showed increased mRNA levels of fumarate hydratase in the Mut-ko/ki samples, which by contrast had reduced protein levels as detected by immunoblot, while all other mRNA levels were unaltered. Immunoblotting also revealed decreased protein levels of 2-oxoglutarate dehydrogenase and malate dehydrogenase 2. Interesting, the decreased protein amount of 2-oxoglutarate dehydrogenase was reflected in decreased activity for this enzyme while there is a trend towards decreased activity of fumarate hydratase and malate dehydrogenase 2. Citrate synthase, isocitrate dehydrogenase 2/3, succinyl-CoA synthase, and succinate dehydrogenase are not statistically different in terms of quantity of enzyme or activity. Finally, we found decreased activity when examining the function of methylmalonyl-CoA mutase in series with succinate synthase and succinate dehydrogenase in the Mut-ko/ki mice compared to their littermate controls, as expected. This study demonstrates decreased activity of certain TCA cycle enzymes and by corollary decreased TCA cycle function, but it supports decreased protein quantity rather than "toxic inhibition" as the underlying mechanism of action. SUMMARY: Methylmalonic acidemia (MMA) is an inborn metabolic disorder of propionate catabolism. In this disorder, toxic metabolites are considered to be the major pathogenic mechanism for acute and long-term complications. However, despite optimized therapies aimed at reducing metabolite levels, patients continue to suffer from late complications, including metabolic stroke and renal insufficiency. Since the propionate pathway feeds into the tricarboxylic acid (TCA) cycle, we investigated TCA cycle function in a constitutive MMA mouse model. We demonstrated decreased amounts of the TCA enzymes, Mdh2 and Ogdh as semi-quantified by immunoblot. Enzymatic activity of Ogdh is also decreased in the MMA mouse model compared to controls. Thus, when the enzyme amounts are decreased, we see the enzymatic activity also decreased to a similar extent for Ogdh. Further studies to elucidate the structural and/or functional links between the TCA cycle and propionate pathways might lead to new treatment approaches for MMA patients.

Dataset Information

A non-canonical tricarboxylic acid cycle underlies cellular identity.

Publications

A non-canonical tricarboxylic acid cycle underlies cellular identity.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets