Post-translational modifications of Hsp90

Division Of Basic Sciences - Nci

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Abstract

TRAP1, the mitochondrial isoform of HSP90, has emerged as a key regulator of cancer cell metabolism, yet the mechanisms by which it rewires nutrient utilization remain poorly understood. We previously reported that TRAP1 loss increases glutamine dependency of mitochondrial respiration following glucose withdrawal. Here, we investigate how TRAP1 deletion impacts glucose metabolism and the mechanisms enabling glutamine retention to support mitochondrial respiration via reductive carboxylation and the oxidative TCA cycle. TRAP1 knockout (KO) in bladder and prostate cancer cells recapitulates the carbon source-specific metabolic rewiring previously observed. Stable isotope tracing reveals that although glucose oxidation remains functional, TRAP1 KO reduces overall glucose uptake and its contribution to glycolysis and the pentose phosphate pathway. This effect is consistent across multiple cell lines. Concurrently, TRAP1-deficient cells exhibit increased glutamine retention and reliance, potentially due to downregulation of the cystine/glutamate antiporter SLC7A11/xCT. Supporting this, xCT overexpression reduces glutamine-dependent respiration in TRAP1 KO cells. qPCR and proteasome inhibition assays suggest xCT is regulated post-translationally via protein stability. Notably, xCT suppression does not trigger ferroptosis, indicating a selective adaptation rather than induction of cell death. Together, our findings suggest that TRAP1 loss decreases glucose uptake while preserving its metabolic fate, promoting glutamine conservation through xCT downregulation to maintain mitochondrial respiration without inducing ferroptosis. Implications: These results reveal a TRAP1-dependent mechanism of metabolic rewiring in cancer cells and identify xCT-mediated glutamine conservation as a key adaptive response, underscoring TRAP1 as a potential metabolic vulnerability and therapeutic target in tumors with altered nutrient utilization.