miR‐181c Activates Mitochondrial Calcium Uptake by Regulating MICU1 in the Heart

Abstract

Background Translocation of miR‐181c into cardiac mitochondria downregulates the mitochondrial gene, mt‐ COX 1. miR‐181c/d −/− hearts experience less oxidative stress during ischemia/reperfusion (I/R) and are protected against I/R injury. Additionally, miR‐181c overexpression can increase mitochondrial matrix Ca 2+ ([Ca 2+ ] m ), but the mechanism by which miR‐181c regulates [Ca 2+ ] m is unknown. Methods and Results By RNA sequencing and analysis, here we show that hearts from miR‐181c/d −/− mice overexpress nuclear‐encoded Ca 2+ regulatory and metabolic pathway genes, suggesting that alterations in miR‐181c and mt‐ COX 1 perturb mitochondria‐to‐nucleus retrograde signaling and [Ca 2+ ] m regulation. Quantitative polymerase chain reaction validation of transcription factors that are known to initiate retrograde signaling revealed significantly higher Sp1 (specificity protein) expression in the miR‐181c/d −/− hearts. Furthermore, an association of Sp1 with the promoter region of MICU 1 was confirmed by chromatin immunoprecipitation‐quantitative polymerase chain reaction and higher expression of MICU 1 was found in the miR‐181c/d −/− hearts. Conversely, downregulation of Sp1 by small interfering RNA decreased MICU 1 expression in neonatal mouse ventricular myocytes. Changes in PDH activity provided evidence for a change in [Ca 2+ ] m via the miR‐181c/ MICU 1 axis. Moreover, this mechanism was implicated in the pathology of I/R injury. When MICU 1 was knocked down in the miR‐181c/d −/− heart by lentiviral expression of a short‐hairpin RNA against MICU 1, cardioprotective effects against I/R injury were abrogated. Furthermore, using an in vitro I/R model in miR‐181c/d −/− neonatal mouse ventricular myocytes, we confirmed the contribution of both Sp1 and MICU 1 in ischemic injury. Conclusions miR‐181c regulates mt‐ COX 1, which in turn regulates MICU 1 expression through the Sp1‐mediated mitochondria‐to‐nucleus retrograde pathway. Loss of miR‐181c can protect the heart from I/R injury by modulating [Ca 2+ ] m through the upregulation of MICU 1.

Protective effect of HINT2 on mitochondrial function via repressing MCU complex activation attenuates cardiac microvascular ischemia–reperfusion injury

“…MICU1 and MICU2 form heterodimers and act as MCU gatekeepers to keep the channel closed by sensing the [Ca 2+ ] i concentration [38]. Restraining [Ca 2+ ] m influx via the upregulation of MICU1 protected the heart from I/R injury [3,50]. MCUb was not expressed at baseline, but was upregulated when sensing calcium elevation in the cytoplasm [21].…”

MicroRNAs Regulating Mitochondrial Function in Cardiac Diseases

“…In addition, the nuclear-encoded miR-181c can be transported to the mitochondria to form an AGO/mt-COX1 complex, which regulates mtROS. The activation of the transcription factor Sp1 can directly upregulate the transcription of MICU1 by binding to the MICU1 promoter region, clarifying the regulatory role of the miR-181c→mt-COX 1→ROS→Sp1→MICU1 signaling pathway in the regulation of mitochondrial calcium uptake in the model; however, the article did not identify the specific target of miR-181c (Banavath et al, 2019). Similarly, in both in vivo and in vitro models induced by anoxia reoxygenation (AR), HR, or IR, miR-30a, and miR-486 can target p53 transcription, restore the mitochondrial membrane potential and ATP production, improve mitochondrial damage, and inhibit myocardial apoptosis (Forini et al, 2014;Sun et al, 2017;Zhang C. et al, 2019).…”

“…Many miRNAs are thought to be involved in the development of CVDs, such as miR-20b, which promotes cardiac hypertrophy by targeting the inhibition of mitofusin 2 (MFN2)-mediated intercellular Ca 2+ interactions in cardiomyocytes (Qiu et al, 2020). The knockout of miR-181c upregulated the expression of mitochondrial calcium uptake 1 (MICU1), and the regulation of mitochondrial calcium uptake in the myocardium has been shown to protect against heart injury (Banavath et al, 2019). Therefore, understanding the crosstalk between miRNAs and mitochondrial function is important for the study of cardiac diseases and the development of potential drug interventions.…”

Mitochondrial microRNAs: A Putative Role in Tissue Regeneration

“…While forced overexpression of miR-181c altered mitochondrial metabolism and ROS generation, contributing to heart failure, its inhibition may be enough to balance mitochondrial bioenergetics, potentiating cardiac remodeling or at least controlling cardiac damages. Recently, Banavath et al showed that the loss of miR-181c, through MICU1 upregulation, a specific promoter of Sp1, may protect the heart from injury [ 81 ]. Mitochondrial miR-338-5p in neural cell culture systems was demonstrated to modulate the expression of COX-IV and subunits of the ATP synthase complex [ 82 , 83 ].…”

“…Recently, Banavath et al showed that the loss of miR-181c, through MICU1 upregulation, a specific promoter of Sp1, may protect the heart from injury [81]. Mitochondrial miR-338-5p in neural cell culture systems was demonstrated to modulate the expression of COX-IV and subunits of the ATP synthase complex [82,83].…”