Acetate is a key regulator of cellular metabolic dynamics. As a precursor for acetyl-CoA, acetate influences cellular energy production, modulates histone acetylation, and contributes to lipid biosynthesis, underscoring its central roles in metabolic and epigenetic regulation [1,2]. While ATP citrate lyase (ACLY) and the pyruvate dehydrogenase complex (PDC) generate acetyl-CoA from citrate and pyruvate under nutrient- and oxygen-rich conditions [[3], [4], [5]], acyl-CoA synthetase short-chain family member 2 (ACSS2) provides an alternative pathway by converting acetate into acetyl-CoA. In contrast to PDC and ACLY, ACSS2 has been shown to function under hypoxic and low-glucose conditions, often associated with cellular stress and pathology [1,6].

ACSS2 has emerged as a potential therapeutic target, particularly in the area of oncology [6], including its investigation in clinical trials (i.e., MTB-9655), highlighting an increasing need to define its broader regulatory functions beyond lipid metabolism [7]. Through its unique role in acetate metabolism, ACSS2 contributes to diverse biological processes including lipid homeostasis [8,9], lysosomal biogenesis [10,11] memory and learning [[12], [13], [14], [15], [16]], and cancer pathology [[17], [18], [19], [20]]. Notably, ACSS2 is highly abundant in lipid-synthesizing tissues, such as the liver, brain, and adipose [8]. Supporting this, ACSS2-deficient mice exhibit reduced expression of lipogenic proteins, along with decreased triglyceride accumulation, and protection from hepatic steatosis under high-fat diet exposure [9], highlighting the enzyme's fundamental role in coordinating lipid metabolism.

Recent work has also revealed broader regulatory functions of ACSS2 beyond its established roles in lipid metabolism. A key advancement in understanding ACSS2's regulatory role came with the discovery that under conditions of nutritional stress, ACSS2 translocates to the nucleus where it interacts directly with transcription factor EB (TFEB), promoting autophagy and lysosomal biogenesis [9]. Complementary findings in Saccharomyces cerevisiae demonstrated that ACSS2 participates in recycling acetate derived from histone deacetylation to generate nuclear acetyl-CoA, directly influencing chromatin acetylation and transcriptional regulation [21]. Expanding on these mechanistic insights, recent transcriptomic profiling of ACSS2-deficient male mice revealing broader impacts on tissue-specific regulation at baseline [22], pointing toward previously undefined roles for ACSS2 beyond lipid metabolism and epigenetic regulation.

Despite insights from recent transcriptomic profiling in male mice, the impact of ACSS2 loss on the basal proteome remains poorly understood, particularly with respect to sex differences. While transcriptomics provides valuable information in regard to gene regulation, proteomic approaches better capture functional outcomes, offering a clearer view of tissue- and sex-specific regulatory mechanisms driven by ACSS2. Here, we performed deep proteomic phenotyping on livers and hearts from male and female ACSS2 knockout (KO) mice and age-matched wild-type (WT) controls to assess basal proteomic divergences and explore sex-differences in the context of global ACSS2 loss. The liver, a major site of detoxification and lipid metabolism, and the heart, which relies heavily on fatty acid oxidation to sustain high energetic demand, provide complementary models for understanding the function of ACSS2 in distinct tissue types [9,23]. This study expands on transcriptomic findings by delivering the first proteomic characterization of ACSS2-deficient female mice. Our analysis revealed minimal overlap between tissues and clear sex-specific proteomic signatures, reaffirming the highly tissue-dependent regulatory role of ACSS2. Together, these findings highlight novel insights into the tissue- and sex-specific proteomic landscapes shaped by ACSS2, offering a deeper understanding of its role in metabolic regulation in the heart and liver.