Genetic encoding of ε-N-L-lactyllysine for detecting delactylase activity in living cells

Development of a urea-bond cleavage reaction induced by nitric oxide for fluorescence imaging

Nitric oxide (NO) is a multifunctional signalling molecule with indispensable roles in physiological processes, but its abnormal production is implicated in various disease conditions. Detecting NO is crucial for interrogating its biological roles. Although many o-phenylenediamine-based fluorescent probes have been developed, only a small fraction has been employed in vivo. Moreover, these probes largely require direct modifications of the fluorophore backbones to render NO responsiveness, which restricts the general applicability of o-phenylenediamine-based probe designs to other types of fluorophores. Here, we report the rational development, optimization, and application of a NO-induced urea-bond cleavage reaction for selective fluorescence detection and imaging of NO in living systems. Through rational design and extensive screening, we identified a 2-aminophenylurea-derived functionality that can react with NO through N-nitrosation, acyltriazole formation, and hydrolysis to induce the cleavage of the urea bond and release of the amino-containing coumarin fluorophore. By caging different amino-containing fluorophore scaffolds with the 2-aminophenylurea-derived functionality, we modularly developed a series of NO fluorescent probes with different excitation and emission profiles for the detection of NO in aqueous solutions and live cells. Among these probes, the near-infrared probe has been demonstrated to enable in vivo fluorescence visualization of elevated endogenous levels of NO in a murine inflammation model. Overall, this study provides a NO-induced urea-bond cleavage reaction and establishes the utility of this reaction for the general and modular development of NO fluorescent probes, thus opening new opportunities for studying and manipulating NO in biological systems.

Lactylated Apolipoprotein C-II Induces Immunotherapy Resistance by Promoting Extracellular Lipolysis

Mortality rates due to lung cancer are high worldwide. Although PD-1 and PD-L1 immune checkpoint inhibitors boost the survival of patients with non-small-cell lung cancer (NSCLC), resistance often arises. The Warburg Effect, which causes lactate build-up and potential lysine-lactylation (Kla), links immune dysfunction to tumor metabolism. The role of non-histone Kla in tumor immune microenvironment and immunotherapy remains to be clarified. Here, global lactylome profiling and metabolomic analyses of samples from patients with NSCLC is conducted. By combining multi-omics analysis with in vitro and in vivo validation, that intracellular lactate promotes extracellular lipolysis through lactyl-APOC2 is revealed. Mechanistically, lactate enhances APOC2 lactylation at K70, stabilizing it and resulting in FFA release, regulatory T cell accumulation, immunotherapy resistance, and metastasis. Moreover, the anti-APOC2K70-lac antibody that sensitized anti-PD-1 therapy in vivo is developed. This findings highlight the potential of anti lactyl-APOC2-K70 approach as a new combination therapy for sensitizing immunotherapeutic responses.

Lactate and Lactylation in Sepsis: A Comprehensive Review

Sepsis is a disorder of the immune response to infection or infectious factors with high morbidity and mortality in clinical settings. The lactylation of lysine residues, fueled by lactate, plays a pivotal role in its pathophysiology. In conducting a literature review on sepsis-related research, we employed a systematic approach to ensure comprehensiveness and accuracy. Initially, we conducted an extensive literature search through the PubMed database, utilizing a range of keywords including "sepsis", "lactate", "lactylation", and "epigenetic modification". The aim was to capture the most recent research related to the pathophysiological mechanisms of sepsis, metabolic disorders, and the role of lactylation. The results of the literature review revealed a close link between sepsis and metabolic dysfunction, particularly the pivotal role of lactylation in regulating immune responses and inflammatory processes. Lactate, not only an energy metabolic byproduct produced during glycolysis, affects the activity of various proteins, including those involved in immune regulation and cell signaling, through lactylation. In the context of sepsis, changes in the levels of lactylation may be closely associated with the severity and prognosis of the disease. In summary, lactylation, as an emerging type of epigenetic modification, provides a new perspective for the diagnosis and treatment of sepsis. Future research needs to further elucidate the exact mechanisms of lactylation in sepsis and explore its potential as a therapeutic target.

Cellular and Biophysical Applications of Genetic Code Expansion

Despite their diverse functions, proteins are inherently constructed from a limited set of building blocks. These compositional constraints pose significant challenges to protein research and its practical applications. Strategically manipulating the cellular protein synthesis system to incorporate novel building blocks has emerged as a critical approach for overcoming these constraints in protein research and application. In the past two decades, the field of genetic code expansion (GCE) has achieved significant advancements, enabling the integration of numerous novel functionalities into proteins across a variety of organisms. This technological evolution has paved the way for the extensive application of genetic code expansion across multiple domains, including protein imaging, the introduction of probes for protein research, analysis of protein-protein interactions, spatiotemporal control of protein function, exploration of proteome changes induced by external stimuli, and the synthesis of proteins endowed with novel functions. In this comprehensive Review, we aim to provide an overview of cellular and biophysical applications that have employed GCE technology over the past two decades.

Deacetylase Sirtuin 1 mitigates type I IFN- and type II IFN-induced signaling and antiviral immunity

Type I and type II IFNs are important immune modulators in both innate and adaptive immunity. They transmit signaling by activating JAK-STAT pathways. Sirtuin 1 (SIRT1), a class III NAD+-dependent deacetylase, has multiple functions in a variety of physiological processes. Here, we characterized the novel functions of SIRT1 in the regulation of type I and type II IFN-induced signaling. Overexpression of SIRT1 inhibited type I and type II IFN-induced interferon-stimulated response element activation. In contrast, knockout of SIRT1 promoted type I and type II IFN-induced expression of ISGs and inhibited viral replication. Treatment with SIRT1 inhibitor EX527 had similar positive effects. SIRT1 physically associated with STAT1 or STAT3, and this interaction was enhanced by IFN stimulation or viral infection. By deacetylating STAT1 at K673 and STAT3 at K679/K685/K707/K709, SIRT1 downregulated the phosphorylation of STAT1 (Y701) and STAT3 (Y705). Sirt1+/- primary peritoneal macrophages and Sirt1+/- mice exhibited enhanced IFN-induced signaling and antiviral activity. Thus, SIRT1 is a novel negative regulator of type I and type II IFN-induced signaling through its deacetylase activity.IMPORTANCESIRT1 has been reported in the precise regulation of antiviral (RNA and DNA) immunity. However, its functions in type I and type II IFN-induced signaling are still unclear. In this study, we deciphered the important functions of SIRT1 in both type I and type II IFN-induced JAK-STAT signaling and explored the potential acting mechanisms. It is helpful for understanding the regulatory roles of SIRT1 at different levels of IFN signaling. It also consolidates the notion that SIRT1 is an important target for intervention in viral infection, inflammatory diseases, or even interferon-related therapies.

Lactoylglutathione promotes inflammatory signaling in macrophages through histone lactoylation

Chronic, systemic inflammation is a pathophysiological manifestation of metabolic disorders. Inflammatory signaling leads to elevated glycolytic flux and a metabolic shift towards aerobic glycolysis and lactate generation. This rise in lactate corresponds with increased generation of lactoylLys modifications on histones, mediating transcriptional responses to inflammatory stimuli. Lactoylation is also generated through a non-enzymatic S-to-N acyltransfer from the glyoxalase cycle intermediate, lactoylglutathione (LGSH). Here, we report a regulatory role for LGSH in mediating histone lactoylation and inflammatory signaling. In the absence of the primary LGSH hydrolase, glyoxalase 2 (GLO2), RAW264.7 macrophages display significant elevations in LGSH and histone lactoylation with a corresponding potentiation of the inflammatory response when exposed to lipopolysaccharides. An analysis of chromatin accessibility shows that lactoylation is associated with more compacted chromatin than acetylation in an unstimulated state; upon stimulation, however, regions of the genome associated with lactoylation become markedly more accessible. Lastly, we demonstrate a spontaneous S-to-S acyltransfer of lactate from LGSH to CoA, yielding lactoyl-CoA. This represents the first known mechanism for the generation of this metabolite. Collectively, these data suggest that LGSH, and not intracellular lactate, is the primary driving factor facilitating histone lactoylation and a major contributor to inflammatory signaling.

A multi-dimensional approach to unravel the intricacies of lactylation related signature for prognostic and therapeutic insight in colorectal cancer

BACKGROUND

Lactylation, a novel contributor to post-translational protein modifications, exhibits dysregulation across various tumors. Nevertheless, its intricate involvement in colorectal carcinoma, particularly for non-histone lactylation and its intersection with metabolism and immune evasion, remains enigmatic.

METHODS

Employing immunohistochemistry on tissue microarray with clinical information and immunofluorescence on colorectal cell lines, we investigated the presence of global lactylation and its association with development and progression in colorectal cancer as well as its functional location. Leveraging the AUCell algorithm alongside correlation analysis in single-cell RNA sequencing data, as well as cox-regression and lasso-regression analysis in TCGA dataset and confirmed in GEO dataset, we identified a 23-gene signature predicting colorectal cancer prognosis. Subsequently, we analyzed the associations between the lactylation related gene risk and clinical characteristics, mutation landscapes, biological functions, immune cell infiltration, immunotherapy responses, and drug sensitivity. Core genes were further explored for deep biological insights through bioinformatics and in vitro experiments.

RESULTS

Our study innovatively reveals a significant elevation of global lactylation in colorectal cancer, particularly in malignant tumors, confirming it as an independent prognostic factor for CRC. Through a comprehensive analysis integrating tumor tissue arrays, TCGA dataset, GEO dataset, combining in silico investigations and in vitro experiments, we identified a 23-gene Lactylation-Related Gene risk model capable of predicting the prognosis of colorectal cancer patients. Noteworthy variations were observed in clinical characteristics, biological functions, immune cell infiltration, immune checkpoint expression, immunotherapy responses and drug sensitivity among distinct risk groups.

CONCLUSIONS

The Lactylation-Related Gene risk model exhibits significant potential for improving the management of colorectal cancer patients and enhancing therapeutic outcomes, particularly at the intersection of metabolism and immune evasion. This finding underscores the clinical relevance of global lactylation in CRC and lays the groundwork for mechanism investigation and targeted therapeutic strategies given the high lactate concentration in CRC.

Histone lactylation regulates cancer progression by reshaping the tumor microenvironment

As a major product of glycolysis and a vital signaling molecule, many studies have reported the key role of lactate in tumor progression and cell fate determination. Lactylation is a newly discovered post-translational modification induced by lactate. On the one hand, lactylation introduced a new era of lactate metabolism in the tumor microenvironment (TME), and on the other hand, it provided a key breakthrough point for elucidation of the interaction between tumor metabolic reprogramming and epigenetic modification. Studies have shown that the lactylation of tumor cells, tumor stem cells and tumor-infiltrating immune cells in TME can participate in the development of cancer through downstream transcriptional regulation, and is a potential and promising tumor treatment target. This review summarized the discovery and effects of lactylation, as well as recent research on histone lactylation regulating cancer progression through reshaping TME. We also focused on new strategies to enhance anti-tumor effects via targeting lactylation. Finally, we discussed the limitations of existing studies and proposed new perspectives for future research in order to further explore lactylation targets. It may provide a new way and direction to improve tumor prognosis.

Lactylation of METTL16 promotes cuproptosis via m6A-modification on FDX1 mRNA in gastric cancer

Cuproptosis, caused by excessively high copper concentrations, is urgently exploited as a potential cancer therapeutic. However, the mechanisms underlying the initiation, propagation, and ultimate execution of cuproptosis in tumors remain unknown. Here, we show that copper content is significantly elevated in gastric cancer (GC), especially in malignant tumors. Screening reveals that METTL16, an atypical methyltransferase, is a critical mediator of cuproptosis through the m6A modification on FDX1 mRNA. Furthermore, copper stress promotes METTL16 lactylation at site K229 followed by cuproptosis. The process of METTL16 lactylation is inhibited by SIRT2. Elevated METTL16 lactylation significantly improves the therapeutic efficacy of the copper ionophore- elesclomol. Combining elesclomol with AGK2, a SIRT2-specific inhibitor, induce cuproptosis in gastric tumors in vitro and in vivo. These results reveal the significance of non-histone protein METTL16 lactylation on cuproptosis in tumors. Given the high copper and lactate concentrations in GC, cuproptosis induction becomes a promising therapeutic strategy for GC.

Lactoylglutathione promotes inflammatory signaling in macrophages

Chronic, systemic inflammation is a pathophysiological manifestation of metabolic disorders. Inflammatory signaling leads to elevated glycolytic flux and a metabolic shift towards aerobic glycolysis and lactate generation. This rise in lactate corresponds with increased generation of lactoylLys modifications on histones, mediating transcriptional responses to inflammatory stimuli. Lactoylation is also generated through a non-enzymatic S-to-N acyltransfer from the glyoxalase cycle intermediate, lactoylglutathione (LGSH). Here, we report a regulatory role for LGSH in inflammatory signaling. In the absence of the primary LGSH hydrolase, glyoxalase 2 (GLO2), RAW264.7 macrophages display significant elevations in LGSH, while demonstrating a potentiated inflammatory response when exposed to lipopolysaccharides, corresponding with a rise in histone lactoylation. Interestingly, our data demonstrate that lactoylation is associated with more compacted chromatin than acetylation in an unstimulated state, however, upon stimulation, regions of the genome associated with lactoylation become markedly more accessible. Lastly, we demonstrate a spontaneous S-to-S acyltransfer of lactate from LGSH to CoA, yielding lactoyl-CoA. This represents the first known mechanism for the generation of this metabolite. Collectively, these data suggest that LGSH, and not intracellular lactate, is a primary contributing factor facilitating the inflammatory response.

A global view of the human post-translational modification landscape

Post-translational modifications (PTMs) provide a rapid response to stimuli, finely tuning metabolism and gene expression and maintain homeostasis. Advances in mass spectrometry over the past two decades have significantly expanded the list of known PTMs in biology and as instrumentation continues to improve, this list will surely grow. While many PTMs have been studied in detail (e.g. phosphorylation, acetylation), the vast majority lack defined mechanisms for their regulation and impact on cell fate. In this review, we will highlight the field of PTM research as it currently stands, discussing the mechanisms that dictate site specificity, analytical methods for their detection and study, and the chemical tools that can be leveraged to define PTM regulation. In addition, we will highlight the approaches needed to discover and validate novel PTMs. Lastly, this review will provide a starting point for those interested in PTM biology, providing a comprehensive list of PTMs and what is known regarding their regulation and metabolic origins.

Functional analysis of protein post-translational modifications using genetic codon expansion

Post-translational modifications (PTMs) of proteins not only exponentially increase the diversity of proteoforms, but also contribute to dynamically modulating the localization, stability, activity, and interaction of proteins. Understanding the biological consequences and functions of specific PTMs has been challenging for many reasons, including the dynamic nature of many PTMs and the technical limitations to access homogenously modified proteins. The genetic code expansion technology has emerged to provide unique approaches for studying PTMs. Through site-specific incorporation of unnatural amino acids (UAAs) bearing PTMs or their mimics into proteins, genetic code expansion allows the generation of homogenous proteins with site-specific modifications and atomic resolution both in vitro and in vivo. With this technology, various PTMs and mimics have been precisely introduced into proteins. In this review, we summarize the UAAs and approaches that have been recently developed to site-specifically install PTMs and their mimics into proteins for functional studies of PTMs.

Research progress of abnormal lactate metabolism and lactate modification in immunotherapy of hepatocellular carcinoma

Tumors meet their energy, biosynthesis, and redox demands through metabolic reprogramming. This metabolic abnormality results in elevated levels of metabolites, particularly lactate, in the tumor microenvironment. Immune cell reprogramming and cellular plasticity mediated by lactate and lactylation increase immunosuppression in the tumor microenvironment and are emerging as key factors in regulating tumor development, metastasis, and the effectiveness of immunotherapies such as immune checkpoint inhibitors. Reprogramming of glucose metabolism and the "Warburg effect" in hepatocellular carcinoma (HCC) lead to the massive production and accumulation of lactate, so lactate modification in tumor tissue is likely to be abnormal as well. This article reviews the immune regulation of abnormal lactate metabolism and lactate modification in hepatocellular carcinoma and the therapeutic strategy of targeting lactate-immunotherapy, which will help to better guide the medication and treatment of patients with hepatocellular carcinoma.

Targeting lactate-related cell cycle activities for cancer therapy

Lactate has long been considered as a metabolic by-product of aerobic glycolysis for cancer. However, more and more studies have shown that lactate can regulate cancer progression via multiple mechanisms such as cell cycle regulation, immune suppression, energy metabolism and so on. A recent discovery of lactylation attracted a lot of attention and is already a hot topic in the cancer field. In this review, we summarized the latest functions of lactate and its underlying mechanisms in cancer. We also included our analysis of protein lactylation in different rat organs and compared them with other published lactylation data. The unresolved challenges in this field were discussed, and the potential application of these new discoveries of lactate-related cell cycle activities for cancer target therapy was speculated.