MICU1 protects against myocardial ischemia/reperfusion injury and its control by the importer receptor Tom70

Abstract

Mitochondrial Ca2+ overload is a main contributor to mitochondrial damage hence cardiomyocyte death in myocardial ischemia/reperfusion (MI/R) injury. MICU1 has been recently identified as an important regulator of mitochondrial Ca2+ homeostasis. Here we try to identify the role of MICU1 in MI/R, and to investigate whether the mitochondrial importer receptor Tom70 possesses critical roles in the mitochondrial translocation of MICU1 and MI/R. Specific small interfering RNA (20 μg) against MICU1 and Tom70, and lentivirus vectors carrying the Tom70a sequences (3.3 × 107 TU) were delivered through intramyocardial injection. Seventy-two hours after injection, mice were subjected to 30 min of MI followed by 3 h (for cell apoptosis and mitochondrial damage assessment) or 24 h (for cardiac function and infarct size determination) of reperfusion. MI/R had no significant effect on total MICU1 expression, but caused significant reduction of MICU1 in mitochondria. Knockdown of MICU1 significantly aggravated MI/R injury, as evidenced by enlarged infarct size, depressed cardiac function and increased myocardial apoptosis. Moreover, MICU1 deficiency resulted in markedly aggravated mitochondrial Ca2+ overload, consequently destructed mitochondrial morphology and suppressed mitochondrial function (evidenced by decreased ATP production). Interestingly, mitochondrial Tom70 was also decreased in MI/R. Genetic loss-function study revealed that mitochondrial MICU1 expression was depressed by Tom70 ablation. Furthermore, Tom70 deficiency significantly aggravated MI/R injury and worsened mitochondrial Ca2+ overload. However, supplementation of Tom70 significantly attenuated MI/R injury, preserved mitochondrial morphology and function, and inhibited mitochondrial Ca2+ overload, all of which were abolished by MICU1 suppression. Mitochondrial Tom70/MICU1 pathway protects against MI/R injury, in which mitochondrial localization of MICU1 is governed by Tom70, and MICU1 serves as an indispensable factor in Tom70’s cardioprotection.

The Mitochondrial Outer Membrane Protein Tom70-Mediator in Protein Traffic, Membrane Contact Sites and Innate Immunity

“…These findings are in line with a report on a TOM70 deficiency causing mitochondrial damage and ROS overload and thereby aggravated injury after myocardial infarction (post-MI) in mice hearts [ 177 , 201 ]. The authors found that administration of antioxidant N-acetylcysteine (NAC) or melatonin reversed the effects of a TOM70 knockdown.…”

Tom70 enhances mitochondrial preprotein import efficiency by binding to internal targeting sequences

“…TIM22 substrates lack N-terminal presequences but carry internal targeting signals that are recognized on the surface of the mitochondria by a dedicated TOM receptor called Tom70 ( Sirrenberg et al, 1996 ). Tom70, such as its paralog Tom71, has a tetratricopeptide structure and can, together with cytosolic Hsp70 and Hsp90 chaperones, recruit and stabilize its substrate proteins on the mitochondrial surface ( Young et al, 2003 ; Fan et al, 2011 ; Hoseini et al, 2016 ; Zanphorlin et al, 2016 ; Xue et al, 2017 ). Tom70 and Tom20/Tom22 partially overlap in their substrate spectrum so that Tom70 is not essential as long as Tom20/Tom22 receptors are present ( Ramage et al, 1993 ).…”

Ube2s-stabilized β-catenin protects against myocardial ischemia/reperfusion injury by activating HIF-1α signaling

“…The sequences of siRNAs targeting mouse genes are listed as follows: siCtrl GAACUGAUGACAGGGAGGCTT; siUbe2s CUGUC UCUAAGUUAUUUAAAU; siβ-Catenin UAGUCGUG GAAUAGCACCCUG. For Ube2s overexpression in the heart, a volume of 30 μl green fluorescent protein (GFP)-conjugated Ube2s lentivirus (wild-type or C95S mutant) or empty vector control lentivirus were injected into the left ventricle of mice 48 h prior to MI/R surgery as adapted to a previous study [38]. The knockdown and overexpression efficiency was confirmed by Western blot.…”