K49 acetylation of ACSL4 antagonizes its ubiquitination degradation and promotes tumorigenesis in hepatocellular carcinoma

Lysine acetylation affects hepatocellular carcinoma (HCC) malignancy through multiple pathways. Evidence from our laboratory and other groups indicates that long chain acyl CoA synthetase 4 (ACSL4) is a crucial oncoprotein in HCC. However, the precise mechanisms underlying the post-translational regulation of ACSL4 acetylation remains unknown. Here, we report a previously unknown mechanism of ACSL4 regulation involving acetylation at the lysine 49 (K49) site by the acetyltransferase MOF. ACSL4 acetylation hindered its degradation via the ubiquitin-proteasome pathway. Using mass spectrometry and subsequent verification, we demonstrated that TRIM21 is an E3 ubiquitin ligase responsible for ACSL4 proteasomal degradation. Further mechanistic studies revealed that MOF-mediated ACSL4-K49 acetylation counteracted the TRIM21-mediated degradation of ACSL4. Functionally, we demonstrated that acetylated ACSL4 promotes lipid accumulation and HCC progression, both in vitro and in vivo. Clinically, ACSL4-K49 acetylation is frequently increased in HCC samples, and elevated ACSL4-K49 acetylation is associated with poor prognosis in patients with HCC. Together, these findings unveil a novel regulatory mechanism of ACSL4, highlighting its pivotal role in modulating HCC progression.