Abstract 3720: Cysteine palmitoylation of astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) regulates its biological and immunological activity

Abstract Non-alcoholic steatohepatitis (NASH) is a major risk factor for hepatocellular carcinoma (HCC). Astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) augments steatosis, inflammation, and tumorigenesis, thereby promoting the whole spectrum of this disease process. Targeting AEG-1 is a potential interventional strategy for NASH and HCC. Thus, proper understanding of the regulation of this molecule is essential. We found that AEG-1 is palmitoylated at residue Cysteine75 (Cys75). Mutation of Cys75 to Serine (Ser) completely abolished AEG-1 palmitoylation.Systematic knockdown studies identified zinc finger DHHC-type palmitoyltransferase 6 (ZDHHC6) as the palmitoyltransferase catalyzing the process. To obtain insight into how palmitoylation regulates AEG-1 function, we generated a knock-in mouse by CRISPR/Cas9 in which Cys75 of AEG-1 was mutated to Ser (AEG-1-C75S). No developmental or anatomical abnormality was observed between AEG-1-wild type (AEG-1-WT) and AEG-1-C75S littermates. However, global gene expression analysis by RNA-sequencing unraveled that signaling pathways and upstream regulators, which contribute to cell proliferation, motility, inflammation,angiogenesis, and lipid accumulation, are activated in AEG-1-C75S hepatocytes compared toAEG-1-WT. Feeding these mice with high fat/high sugar diet for 20 weeks showed accumulation of T-regulatory cells and exhausted CD8 T-cells in the livers of AEG-1-C75S mice vs AEG-1-WT, and only in females, suggesting that inhibition of AEG-1 palmitoylation creates an immunosuppressive milieu favoring tumorigenesis. Collectively, these findings suggest that AEG-1-C75S functions as dominant positive, and palmitoylation restricts oncogenic and NASH-promoting functions of AEG-1. Studies are ongoing to unravel the mechanism by which palmitoylation restricts AEG-1 function, and to understand the sex-specific immune-modulatory role of AEG-1 palmitoylation in hepatocarcinogenesis. Citation Format: Maria Del Carmen Camarena, Garrison Komaniecki, Debashri Manna, Rachel Mendoza, Mark A. Subler, Jolene J. Windle, Mikhail G. Dozmorov, Hening Lin, Devanand Sarkar. Cysteine palmitoylation of astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) regulates its biological and immunological activity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3720.