Potential of lysine succinylation as a therapeutic target for gallstone formation: An insightful strategy

Abstract

Cholelithiasis has a complex pathogenesis, necessitating better therapeutic and preventive strategies. We recently read with interest Wang et al’s study on lysine acetyltransferase 2A (KAT2A)-mediated adenosine monophosphate-activated protein kinase (AMPK) succinylation in cholelithiasis. Using mouse models and gallbladder mucosal epithelial cells, they found that KAT2A inhibits gallstones through AMPK K170 succinylation, thereby activating the AMPK/silent information regulator 1 pathway to reduce inflammation and pyroptosis. This study is the first to connect lysine succinylation with cholelithiasis, offering new insights and identifying succinylation as a potential therapeutic target. Future research should confirm these findings using patient samples, investigate other post-translational modifications, and use structural biology to clarify succinylation-induced conformational changes, thereby bridging basic research to clinical applications.

Key Words: Cholelithiasis; Gallstone formation; Lysine succinylation; Inflammation; Adenosine monophosphate-activated protein kinase; Post-translational modification; Gallbladder

Core Tip: The mechanisms of cholelithiasis are incompletely understood. The study by Wang et al is the first to demonstrate that lysine acetyltransferase 2A-mediated succinylation of adenosine monophosphate-activated protein kinase (AMPK) inhibits gallstone formation by activating the AMPK/silent information regulator 1 pathway and suppressing inflammation and pyroptosis in gallbladder mucosal epithelial cells. This finding provides a novel therapeutic target, filling a gap in succinylation research in cholelithiasis. After obtaining meaningful conclusions from basic research, more work is needed, specifically horizontal and vertical research expansions and verification using real-world patient specimens, to bridge the gap from basic research to clinical practice.

TO THE EDITOR

We write to express our sincere appreciation for the insightful study by Wang et al[1]. recently published in World Journal of Gastroenterology. This work addresses a long-standing gap in cholelithiasis research by uncovering the role of lysine succinylation, an understudied post-translational modification (PTM), in gallstone formation. The study further delineates the molecular mechanism by highlighting the lysine acetyltransferase 2A (KAT2A)-mediated succinylation of adenosine monophosphate-activated protein kinase (AMPK) at K170.

CHOLELITHIASIS

Cholelithiasis is a common hepatobiliary disease with variations in stone types. Cholesterol stones, the most common type, result from cholesterol supersaturation in bile, whereas pigment stones, which are less common, are associated with conditions such as hemolysis and chronic intrahepatic cholestasis[2]. Despite similar clinical symptoms, the underlying mechanisms and risk factors for these stones can differ substantially.

The formation of gallbladder cholesterol stones is influenced by various physiological and pathological factors. Gallbladder motility, regulated by interstitial cells of Cajal (ICC), is crucial, and alterations in the quantity and function of ICCs can lead to stone formation[3]. High-cholesterol diets reduce ICC density and increase apoptosis, thereby weakening motility and promoting stones[3]. Additionally, gut microbiota imbalance affects bile acid metabolism, impacting cholesterol processing and stone development[4]. Studies have found that patients with gallstones have reduced microbial diversity and altered bacterial abundance, which might disrupt bile acid metabolism and accelerate stone formation[4]. Estrogen receptors, particularly G protein-coupled estrogen receptor 1 (GPER1), are crucial in cholesterol stone formation. Research has found that estrogen significantly increase cholesterol stone risk by activating the GPER1 pathway[5]. In animal studies, GPER1 antagonists successfully decreased estrogen-induced gallstones, suggesting a new therapeutic target[5].

Pigment stones, mainly made of calcium bilirubinate, result from altered bile composition, biliary tract infections, and bile stasis. Changes in bile composition, such as reduced bile acid levels and imbalances in phospholipids and cholesterol, can destabilize bile and create unfavorable conditions within the biliary tract that hinder bile flow, leading to stone formation[6]. Additionally, biliary tract infections increase bilirubin levels, with studies revealing a strong link between the biliary microbiota, particularly gram-positive bacteria, and stone calcification[7]. Bile stasis, often attributable to duct stricture or obstruction, raises bilirubin levels, thereby promoting pigment stone development.

We believe this study makes two notable contributions to the field. First, this is the first study to link lysine succinylation to the pathogenesis of cholelithiasis. By integrating in vivo experiments using a high-fat diet-induced murine model and in vitro studies using gallbladder mucosal epithelial cells (GMECs) combined with RNA-seq, co-immunoprecipitation, and flow cytometry, the authors convincingly demonstrate that KAT2A downregulation impairs AMPK succinylation, thereby suppressing the AMPK/silent information regulator 1 (SIRT1) pathway, exacerbating GMEC pyroptosis and inflammation, and ultimately promoting gallstone formation. This finding expands our understanding of cholelithiasis beyond classical cholesterol homeostasis and bilirubin metabolism, highlighting PTMs as key regulatory nodes. Second, the identification of AMPK K170 as a critical succinylation site provides a precise molecular target. The authors’ use of site-directed mutagenesis (K154R/K154E) and a KAT2A catalytic mutant (Y645A) to validate the functional importance of this site is methodologically rigorous, laying the groundwork for future targeted intervention strategies.

Wang et al[1] employed a well-established method to induce cholesterol gallstones through cholesterol supplementation and high-fat diet feeding. This approach disrupted the solubility equilibrium of cholesterol in bile, resulting in the precipitation of cholesterol crystals and the subsequent formation of gallstones. Future studies should investigate the role of lysine succinylation in pigment and mixed gallstones, expanding from animal models to patient-derived samples. Additionally, examining KAT2A expression, AMPK succinylation, and AMPK/SIRT1 pathway activity in human gallbladder tissues will help clarify whether KAT2A-induced AMPK succinylation is conserved across species or specific to murine models.

Although Wang et al’s research[1] focused on succinylation, other PTMs such as ubiquitination and acetylation might also hold significant roles in cholelithiasis. Ubiquitination is crucial in cholecystitis, impacting disease progression by regulating proteins involved in inflammation, apoptosis, and immune evasion. This process modifies the intensity and duration of inflammatory responses via the nuclear factor-kappa B pathway, influences apoptosis by affecting the stability and activity of proteins such as p53, and aids immune evasion by controlling the degradation of immune checkpoint proteins, thus affecting the immune system’s ability to identify and clear pathological cells[8,9]. Previous research demonstrated that cholinergic metabolites, especially phosphatidylcholine and sphingomyelin, protect against acute non-gallstone cholecystitis[10]. Acetylation might regulate these metabolites, affecting the development of cholecystitis. Future research should investigate the primary and secondary relationships among PTMs in the pathogenesis of cholecystitis and their interconnections, particularly whether KAT2A-mediated succinylation dominates the regulation of AMPK in GMECs. Exploring such crosstalk could provide a more comprehensive view of multi-layered regulatory networks in gallstone formation.

The authors revealed that succinylation of AMPK at K154 enhances its binding with live kinase B1 (LKB1), although the structural mechanism, such as the effects of succinylation on the confirmation of AMPK to enable LKB1 docking, is unclear. Techniques such as cryo-EM or X-ray crystallography could provide atomic-level insights, but they do not capture the kinetic processes of intermolecular interactions such as binding and dissociation rates. Real-time kinetic methods and molecular simulations are needed to understand the mechanism by which succinylation dynamically regulates AMPK–LKB1 binding. Additionally, functional studies and experiments in cells and animals are necessary to validate and translate these findings from in vitro experiments to in vivo applications. Further research is anticipated to elucidate the mechanism by which succinylation at K170 influences the local and global conformation of AMPK, including the examination of amino acid interactions at the binding interface and domain arrangements. Such studies are expected to uncover the mechanism by which these conformational modifications enhance the binding affinity between AMPK and LKB1. Additionally, understanding this conformation-dependent interaction will shed light on the phosphorylation-mediated activation of AMPK by LKB1, which in turn might inhibit inflammation and pyroptosis, ultimately reducing the formation of gallstones.

CONCLUSION

Cholelithiasis develops through complicated processes. Wang et al's study[1] marks a major breakthrough in understanding the disease by proposing the novel use of lysine succinylation to prevent gallstones. Future research should validate these results in patient samples, explore other PTMs, and use structural biology to clarify succinylation-related changes, linking basic research with clinical applications.

ACKNOWLEDGEMENTS

We sincerely thank Ye WY for her inspiration and encouragement.