MANF facilitates breast cancer cell survival under glucose-starvation conditions via PRKN-mediated mitophagy regulation

During tumor expansion, breast cancer (BC) cells often experience reactive oxygen species accumulation and mitochondrial damage because of glucose shortage. However, the mechanism by which BC cells deal with the glucose-shortage-induced oxidative stress remains unclear. Here, we showed that MANF (mesencephalic astrocyte derived neurotrophic factor)-mediated mitophagy facilitates BC cell survival under glucose-starvation conditions. MANF-mediated mitophagy also promotes fatty acid oxidation in glucose-starved BC cells. Moreover, during glucose starvation, SENP1-mediated de-SUMOylation of MANF increases cytoplasmic MANF expression through the inhibition of MANF's nuclear translocation and hence renders mitochondrial distribution of MANF. MANF mediates mitophagy by binding to PRKN (parkin RBR E3 ubiquitin protein ligase), a key mitophagy regulator, in the mitochondria. Under conditions of glucose starvation, protein oxidation inhibits PRKN activity; nevertheless, the CXXC motif of MANF alleviates protein oxidation in RING II-domain of PRKN and restores its E3 ligase activity. Furthermore, MANF-PRKN interactions are essential for BC tumor growth and metastasis. High MANF expression predicts poor outcomes in patients with BC. Our results highlight the prosurvival role of MANF-mediated mitophagy in BC cells during glucose starvation, suggesting MANF as a potential therapeutic target.<b>Abbreviation:</b> 2DG, 2-deoxy-D-glucose; 5TG, 5-thio-D-glucose; ACSL4/FACL4, acyl-CoA synthetase long chain family member 4; Baf A1, bafilomycin A₁; BRCA, breast cancer; CHX, cycloheximide; DMF, distant metastasis-free; DMFS, distant metastasis-free survival; ECM, extracellular matrix; ER, endoplasmic reticulum; ERS, endoplasmic reticulum stress; F-1,6-BP, fructose-1,6-bisphosphate; FAO, fatty acid oxidation; GSH, reduced glutathione; GSVA, gene set variation analysis; HCC, hepatocellular carcinoma; ICC, intrahepatic cholangiocarcinoma; IF, immunofluorescence; MANF, mesencephalic astrocyte derived neurotrophic factor; Mdivi-1, mitochondrial division inhibitor 1; MFI, mean fluorescence intensity; NAC, N-acetyl-L-cysteine; OCR, oxygen-consumption rate; OS, overall survival; PMI, SQSTM1/p62-mediated mitophagy inducer; PPP, pentose phosphate pathway; PRKN, parkin RBR E3 ubiquitin protein ligase; RBR, RING in between RING; RFS, relapse-free survival; ROS, reactive oxygen species; SAPLIPs, saposin-like proteins; TCGA, The Cancer Genome Atlas; TNBC, triple-negative breast cancer; WT, wild type.