Splicing factor SF3B4 promotes mitochondrial glutamine metabolism in hepatocellular carcinoma by regulating GLS1 isoform switching.

Metabolic reprogramming is a hallmark of cancer, enabling tumor cells to adapt to nutrient stress and sustain uncontrolled proliferation. In hepatocellular carcinoma (HCC), glutamine metabolism is markedly upregulated and plays a pivotal role in supporting tumor growth and survival. However, the molecular mechanisms underlying this metabolic shift remain poorly understood. Here, we identify the splicing factor SF3B4 as a key regulator of glutamine metabolism in HCC through its control of glutaminase 1 (GLS1) alternative splicing. SF3B4 is highly expressed HCC and is essential for tumor cell proliferation, migration and colony formation. Mechanistically, SF3B4 preferentially promotes the production of the GAC isoform of GLS1, which exhibits higher catalytic activity, while repressing the KGA isoform. Genetic or pharmacological inhibition of SF3B4 leads to reduced GAC expression, decreased GLS enzymatic activity, impaired glutaminolysis, and suppression of glutamine-driven mitochondrial respiration. Moreover, SF3B4 is required for tumor cell survival under glucose-deprived conditions, highlighting its role in supporting metabolic flexibility under nutrient stress. Collectively, these findings uncover a previously unrecognized function of SF3B4 in promoting mitochondrial glutamine metabolism in HCC and suggest that the SF3B4-GAC axis may represent a potential therapeutic target for glutamine-addicted liver cancers.