Regulation of Glutamine Carrier Proteins by RNF5 Determines Breast Cancer Response to ER Stress-Inducing Chemotherapies

Many tumor cells are fueled by altered metabolism and increased glutamine (Gln) dependence. We identify regulation of the L-glutamine carrier proteins SLC1A5 and SLC38A2 (SLC1A5/38A2) by the ubiquitin ligase RNF5. Paclitaxel-induced ER stress to breast cancer (BCa) cells promotes RNF5 association, ubiquitination, and degradation of SLC1A5/38A2. This decreases Gln uptake, levels of TCA cycle components, mTOR signaling, and proliferation while increasing autophagy and cell death. Rnf5-deficient MMTV-PyMT mammary tumors were less differentiated and showed elevated SLC1A5 expression. Whereas RNF5 depletion in MDA-MB-231 cells promoted tumorigenesis and abolished paclitaxel responsiveness, SLC1A5/38A2 knockdown elicited opposing effects. Inverse RNF5hi/SLC1A5/38A2lo expression was associated with positive prognosis in BCa. Thus, RNF5 control of Gln uptake underlies BCa response to chemotherapies. [Display omitted] •Gln carrier proteins SLC1A5 and SLC38A2 are regulated by ubiquitin ligase RNF5•Glutamine uptake and mTOR activity following ERS is RNF5-SLC1A5 dependent•RNF5 inhibition of SLC1A5 is required for paclitaxel-induced apoptosis of BCa cells•Low SLC1A5 expression in BCa TMA and RPPA associates with good prognosis Jeon et al. show that paclitaxel-induced ER stress in BCa cells promotes the ubiquitin ligase RNF5 to associate with, ubiquitinate, and degrade the Gln carriers SLC1A5 and SLC38A2, thereby leading to decreased Gln uptake and increased autophagy and cell death.