Inter-organelle crosstalk supports acetyl-coenzyme A homeostasis and lipogenesis under metabolic stress

Proliferating cells rely on acetyl-CoA to support membrane biogenesis and acetylation. Several organelle-specific pathways are available for provision of acetyl-CoA as nutrient availability fluctuates, so understanding how cells maintain acetyl-CoA flux under such stresses is critically important. To this end we applied 13 C isotope tracing cell lines deficient in these mitochondrial (ATP-citrate lyase; ACLY-), cytosolic, (acetyl-CoA synthetase (ACSS2-), and peroxisomal (peroxisomal biogenesis factor 5; PEX5-) dependent pathways. ACLY knockout in multiple cell lines reduced fatty acid synthesis and increased reliance on extracellular lipids or acetate. Knockout of both ACLY and ACSS2 (DKO) severely stunted but did not entirely block proliferation, suggesting alternate pathways can support acetyl-CoA homeostasis. Metabolic tracing and PEX5 knockout studies link peroxisomal oxidation of exogenous lipids as a major source of acetyl-CoA for lipogenesis and histone acetylation, highlighting a role for inter-organelle crosstalk in supporting cell survival in response to nutrient fluctuations. Teaser We quantify how acetyl-CoA metabolism is supported by distinct pathways spanning mitochondria, cytosol, and peroxisomes using comprehensive tracing applied to knockout cells.