HIF2α-dependent inhibition of mitochondrial clustering of glutaminase suppresses clear cell renal cell carcinoma

Abstract

Clear cell renal cell carcinomas (ccRCC) are largely driven by HIF2 and are avid consumers of glutamine. However, inhibitors of glutaminase1 (GLS1), the first step in glutaminolysis, have not shown benefit in phase III trials, and HIF2 inhibition, recently FDA-approved for treatment of ccRCC, shows great but incomplete benefits, underscoring the need to better understand the roles of glutamine and HIF2 in ccRCC. Here, we report that glutamine deprivation rapidly redistributes GLS1 into isolated clusters within mitochondria across diverse cell types, but not in ccRCC. GLS1 clustering is rapid (1-3 hours) and reversible, is specifically driven by reduced intracellular glutamate, and is mediated by mitochondrial fission. Clustered GLS1 markedly enhances glutaminase activity and promotes cell death under glutamine-deprived conditions. HIF2 prevents GLS1 clustering, independently of its transcriptional activity, thereby protecting ccRCC cells from cell death induced by glutamine deprivation. Reversing this protection, by genetic expression of GLS1 mutants that constitutively cluster, enhances ccRCC cell death in culture and suppresses ccRCC growth in vivo. These findings provide multiple insights into cellular glutamine handling, including a novel metabolic pathway by which HIF2 promotes ccRCC, and reveals a potential therapeutic avenue to synergize with HIF2 inhibition in the treatment of ccRCC.