The recently identified histone modification lysine lactylation can be stimulated by L-lactate and glycolysis. Although the chemical group added upon lysine lactylation was originally proposed to be the L-enantiomer of lactate (K _L-la ), two isomeric modifications, lysine D-lactylation (K _D-la ) and N-ε-(carboxyethyl) lysine (K _ce ), also exist in cells, with their precursors being metabolites of glycolysis. The dynamic regulation and differences among these three modifications in response to hypoxia remain poorly understood. In this study, we demonstrate that intracellular K _L-la , but not K _D-la or K _ce , is up-regulated in response to hypoxia. Depletion of glyoxalase enzymes, GLO1 and GLO2, had minimal impact on K _D-la , K _ce , or hypoxia-induced K _L-la . Conversely, blocking glycolytic flux to L-lactate under hypoxic conditions by knocking out lactate dehydrogenase A/B completely abolished the induction of K _L-la but increased K _D-la and K _ce . We further observed a correlation between the level of K _L-la and hypoxia-inducible factor 1 alpha (HIF-1α) expression under hypoxic conditions and when small molecules were used to stabilize HIF-1α in the normoxia condition. Our result demonstrated that there is a strong correlation between HIF-1α and K _L-la in lung cancer tissues and that patient samples with higher grade tend to have higher K _L-la levels. Using a proteomics approach, we quantified 66 K _L-la sites that were up-regulated by hypoxia and demonstrated that p300/CBP contributes to hypoxia-induced K _L-la . Collectively, our study demonstrates that K _L-la , rather than K _D-la or K _ce , is the prevailing lysine lactylation in response to hypoxia. Our results therefore demonstrate a link between K _L-la and the hypoxia-induced adaptation of tumor cells.

Communication between infected cells and cells in the surrounding tissue is a determinant of viral spread. However, it remains unclear how cells in close or distant proximity to an infected cell respond to primary or secondary infections. We establish a cell-based system to characterize a virus microenvironment, distinguishing infected, neighboring, and distal cells. Cell sorting, microscopy, proteomics, and cell cycle assays allow resolving cellular features and functional consequences of proximity to infection. We show that human cytomegalovirus (HCMV) infection primes neighboring cells for both subsequent HCMV infections and secondary infections with herpes simplex virus 1 and influenza A. Neighboring cells exhibit mitotic arrest, dampened innate immunity, and altered extracellular matrix. Conversely, distal cells are poised to slow viral spread due to enhanced antiviral responses. These findings demonstrate how infection reshapes the microenvironment through intercellular signaling to facilitate spread and how spatial proximity to an infection guides cell fate.

Ketone bodies have long been known as a group of lipid‐derived alternative energy sources during glucose shortages. Nevertheless, the molecular mechanisms underlying their non‐metabolic functions remain largely elusive. This study identified acetoacetate as the precursor for lysine acetoacetylation (Kacac), a previously uncharacterized and evolutionarily conserved histone post‐translational modification. This protein modification is comprehensively validated using chemical and biochemical approaches, including HPLC co‐elution and MS/MS analysis using synthetic peptides, Western blot, and isotopic labeling. Histone Kacac can be dynamically regulated by acetoacetate concentration, possibly via acetoacetyl‐CoA. Biochemical studies show that HBO1, traditionally known as an acetyltransferase, can also serve as an acetoacetyltransferase. In addition, 33 Kacac sites are identified on mammalian histones, depicting the landscape of histone Kacac marks across species and organs. In summary, this study thus discovers a physiologically relevant and enzymatically regulated histone mark that sheds light on the non‐metabolic functions of ketone bodies.

Shotgun proteomics has been widely used to identify histone marks. Conventional database search methods rely on the “target-decoy” strategy to calculate the false discovery rate (FDR) and distinguish true peptide-spectrum matches (PSMs) from false ones. This strategy has a caveat of inaccurate FDR caused by the small data size of histone marks. To address this challenge, we developed a tailored database search strategy, named “Comprehensive Histone Mark Analysis (CHiMA).” Instead of target-decoy–based FDR, this method uses “50% matched fragment ions” as the key criterion to identify high-confidence PSMs. CHiMA identified twice as many histone modification sites as the conventional method in benchmark datasets. Reanalysis of our previous proteomics data using CHiMA led to the identification of 113 new histone marks for four types of lysine acylations, almost doubling the number of previously reported marks. This tool not only offers a valuable approach for identifying histone modifications but also greatly expands the repertoire of histone marks.

Male and female disease states differ in their prevalence, treatment responses, and survival rates. In cardiac disease, women almost uniformly fare far worse than men. Though sex plays a critical role in cardiac disease, the mechanisms underlying sex differences in cardiac homeostasis and disease remain unexplained. Here, in adult and embryonic hearts we reveal sex-specific transcriptomes and proteomes and show that cardiac sex differences are predominately accounted for by post-transcriptional mechanisms. We found differential expression of male-female proteins in the cardiomyocytes. Using a quantitative proteomics-based approach, we characterized differential sex-specific enriched cardiac proteins, protein complexes, and biological sex processes in the context of global genetic diversity of the Collaborative Cross, an established surrogate for human diversity. We also found that sex differences in cardiac protein expression are established by both hormonal and sex chromosomal mechanisms. We have demonstrated the onset of sex-biased protein expression and discovered that sex disparities in heart tissue occur at the earliest stages of heart development at a period that preceeds mammalian gonadal development. Collectively, these findings may explain why congenital heart disease, a leading cause of death whose origin is often developmental, is sex biased. Our results reveal molecular foundations for differences in cardiac tissue that underlie sex disparities in health, disease, and treatment outcomes.

Membrane proteins are involved in various cellular processes. However, purification of membrane proteins has long been a challenging task, as membrane protein stability in detergent is the bottleneck for purification and subsequent analyses. Therefore, the optimization of detergent conditions is critical for the preparation of membrane proteins. Here, we utilize analytical ultracentrifugation (AUC) to examine the effects of different detergents (OG, Triton X-100, DDM), detergent concentrations, and detergent supplementation on the behavior of membrane protein TmrA. Our results suggest that DDM is more suitable for the purification of TmrA compared with OG and TritonX-100; a high concentration of DDM yields a more homogeneous protein aggregation state; supplementing TmrA purified with a low DDM concentration with DDM maintains the protein homogeneity and aggregation state, and may serve as a practical and cost-effective strategy for membrane protein purification.