| First Author | Lambert JP | Year | 2019 |
| Journal | Circulation | Volume | 140 |
| Issue | 21 | Pages | 1720-1733 |
| PubMed ID | 31533452 | Mgi Jnum | J:298046 |
| Mgi Id | MGI:6478843 | Doi | 10.1161/CIRCULATIONAHA.118.037968 |
| Citation | Lambert JP, et al. (2019) MCUB Regulates the Molecular Composition of the Mitochondrial Calcium Uniporter Channel to Limit Mitochondrial Calcium Overload During Stress. Circulation 140(21):1720-1733 |
| abstractText | BACKGROUND: The mitochondrial calcium uniporter (mtCU) is an approximately 700-kD multisubunit channel residing in the inner mitochondrial membrane required for mitochondrial Ca(2+) (mCa(2+)) 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 Ca(2+) 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 mCa(2+) uptake. Furthermore, we show that MCUB incorporation into the mtCU is a stress-responsive mechanism to limit mCa(2+) 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 mCa(2+) uptake impair mitochondrial energetics and contractile function. CONCLUSIONS: We detail a new regulatory mechanism to modulate mtCU function and mCa(2+) uptake. Our results suggest that MCUB-dependent changes in mtCU stoichiometry are a prominent regulatory mechanism to modulate mCa(2+) uptake and cellular physiology. |
