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The mitochondrial calcium uniporter regulates breast cancer progression via HIF-1α.

ABSTRACT: Triple-negative breast cancer (TNBC) represents the most aggressive breast tumor subtype. However, the molecular determinants responsible for the metastatic TNBC phenotype are only partially understood. We here show that expression of the mitochondrial calcium uniporter (MCU), the selective channel responsible for mitochondrial Ca(2+) uptake, correlates with tumor size and lymph node infiltration, suggesting that mitochondrial Ca(2+) uptake might be instrumental for tumor growth and metastatic formation. Accordingly, MCU downregulation hampered cell motility and invasiveness and reduced tumor growth, lymph node infiltration, and lung metastasis in TNBC xenografts. In MCU-silenced cells, production of mitochondrial reactive oxygen species (mROS) is blunted and expression of the hypoxia-inducible factor-1α (HIF-1α) is reduced, suggesting a signaling role for mROS and HIF-1α, downstream of mitochondrial Ca(2+) Finally, in breast cancer mRNA samples, a positive correlation of MCU expression with HIF-1α signaling route is present. Our results indicate that MCU plays a central role in TNBC growth and metastasis formation and suggest that mitochondrial Ca(2+) uptake is a potential novel therapeutic target for clinical intervention.

SUBMITTER: Tosatto A

PROVIDER: S-EPMC4864890 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:The mitochondrial calcium uniporter (mtCU) is an ?700-kD multisubunit channel residing in the inner mitochondrial membrane required for mitochondrial Ca2+ (mCa2+) uptake. Here, we detail the contribution of MCUB, a paralog of the pore-forming subunit MCU, in mtCU regulation and function and for the first time investigate the relevance of MCUB to cardiac physiology. METHODS:We created a stable MCUB knockout cell line (MCUB-/-) using CRISPR-Cas9n technology and generated a cardiac-specific, tamoxifen-inducible MCUB mutant mouse (CAG-CAT-MCUB x MCM; MCUB-Tg) for in vivo assessment of cardiac physiology and response to ischemia/reperfusion injury. Live-cell imaging and high-resolution spectrofluorometery were used to determine intracellular Ca2+ exchange and size-exclusion chromatography; blue native page and immunoprecipitation studies were used to determine the molecular function and impact of MCUB on the high-molecular-weight mtCU complex. RESULTS:Using genetic gain- and loss-of-function approaches, we show that MCUB expression displaces MCU from the functional mtCU complex and thereby decreases the association of mitochondrial calcium uptake 1 and 2 (MICU1/2) to alter channel gating. These molecular changes decrease MICU1/2-dependent cooperative activation of the mtCU, thereby decreasing mCa2+ uptake. Furthermore, we show that MCUB incorporation into the mtCU is a stress-responsive mechanism to limit mCa2+ overload during cardiac injury. Indeed, overexpression of MCUB is sufficient to decrease infarct size after ischemia/reperfusion injury. However, MCUB incorporation into the mtCU does come at a cost; acute decreases in mCa2+ uptake impair mitochondrial energetics and contractile function. CONCLUSIONS:We detail a new regulatory mechanism to modulate mtCU function and mCa2+ uptake. Our results suggest that MCUB-dependent changes in mtCU stoichiometry are a prominent regulatory mechanism to modulate mCa2+ uptake and cellular physiology.

Project description:Breast cancer (BC) is a commonly identified life-threatening type of cancer and a major cause of death among women worldwide. Several microRNAs (miRs), including miR-143-5p, have been reported to be vital for regulating hallmarks of cancer; however, the effect of miR-143-5p on BC requires further exploration. The present study performed bioinformatics analysis on GSE42072 and GSE41922 datasets from the National Center for Biotechnology Information Gene Expression Omnibus (GEO) database to identify miR-143-5p expression patterns. Furthermore, miR-143-5p expression was detected in BC cell lines and tissues via reverse transcription-quantitative PCR. Post-transfection with miR-143-5p mimics, Cell Counting Kit-8, colony formation and Transwell assays were performed to explore the effects of miR-143-5p on BC cell proliferation, colony formation, and migration. The association of miR-143-5p with the hypoxia-inducible factor-1α (HIF-1α)-associated glucose transporter 1 (GLUT1) pathway was explored via western blotting, immunofluorescence and dual-luciferase reporter assay. The present study detected high expression of miR-143-5p in BC tissue of the GSE42072 and serum of the GSE41922 datasets by GEO chip analysis. Additionally, the expression levels of miR-143-5p were decreased in BC tissues compared with those in adjacent healthy tissues, and low miR-143-5p expression was associated with a poorer prognosis and shorter survival time in patients with BC. In vitro, miR-143-5p expression levels were decreased in BC cells, and transfection with miR-143-5p mimics suppressed BC cell proliferation, colony formation, migration. Furthermore, miR-143-5p targeted the HIF-1α-related GLUT1 pathway, and inhibited HIF-1α and GLUT1 expression. Additionally, HIF-1α agonists reversed the miR-143-5p-induced inhibition during tumorigenesis. In conclusion, miR-143-5p exhibited low expression in BC tissues, and suppressed BC cell proliferation, colony formation, migration. Moreover, the antitumor effects of miR-143-5p targeted the HIF-1α-related GLUT1 pathway.

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The mitochondrial calcium uniporter regulates breast cancer progression via HIF-1α.

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