Extracellular supply of glutamine regulates nuclear localization of TCA cycle enzymes and epigenetic modifications in myogenic progenitors

Background: Skeletal muscle regeneration depends on the activation of muscle progenitor cells (MPCs), a process highly sensitive to metabolic cues. Glutamine (Gln), though considered non-essential, becomes conditionally essential during catabolic stress and is critical for MPC proliferation. However, the mechanisms through which Gln availability influences myogenesis remain unexplored. Objective: To determine how extracellular Gln regulates subcellular localization of metabolic enzymes and epigenetic modifications during proliferation. Hypothesis: Extracellular Gln availability, during proliferation, may be communicated through spatial regulation of tricarboxylic acid (TCA) cycle enzymes, histone succinylation, and altered chromatin landscape. Methods: Murine myoblasts were cultured in DMEM ± Gln for 5 days. MPC proliferation, cell-cycle dynamics and glutaminase (GLS) inhibition was assessed. Global succinylated-proteins were assessed by mass spectrometry. Nuclear localization of TCA-cycle components (DLST, OGDH) and succinylation regulators (KAT2A [acylase], SIRT5 & 7 [deacylases]) were examined. Chromatin accessibility and gene expression of myogenic markers (Pax7 and MyoD) were analyzed by single-nucleus ATAC-seq and qPCR, respectively. Results: Gln deficiency induced G0/G1 arrest and reduced myogenic markers expression. GLS inhibition retarded proliferation, confirming the necessity of Gln catabolism for proliferation. Gln deficiency (vs. sufficiency) induced TCA-cycle localization in the nucleus, coinciding with increased nuclear KAT2A and no change in SIRT5 & 7 levels. Further, succinyl-proteomics demonstrated enhanced histone succinylation (epigenetic modification) coinciding with reduced chromatin accessibility at myogenic regulatory regions (e.g., MyoD1). Conclusions: Extracellular Gln is critical for sustaining MPC proliferation. Loss of Gln impairs proliferation and leads to nuclear accumulation of TCA-cycle enzymes, histone succinylation, and epigenetic modifications. Significance: The identified metabolic–epigenetic axis is a fundamental mechanism through which nutrient status governs myogenic capacity. Funding: University of Alabama Health Science Foundation. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.