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Updated: Jan 2, 2026
In Vivo Nanovector Delivery of a Heart-specific MicroRNA-sponge
Published on: June 15, 2018
miR-181c Activates Mitochondrial Calcium Uptake by Regulating MICU1 in the Heart
Hemanth N Banavath1, Barbara Roman1, Nathan Mackowski2
1Department of Pathology Johns Hopkins School of Medicine Baltimore MD.
Abstract:
Background Translocation of miR-181c into cardiac mitochondria downregulates the mitochondrial gene, mt-COX1. 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 Ca2+ ([Ca2+]m), but the mechanism by which miR-181c regulates [Ca2+]m is unknown. Methods and Results By RNA sequencing and analysis, here we show that hearts from miR-181c/d-/- mice overexpress nuclear-encoded Ca2+ regulatory and metabolic pathway genes, suggesting that alterations in miR-181c and mt-COX1 perturb mitochondria-to-nucleus retrograde signaling and [Ca2+]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 MICU1 was confirmed by chromatin immunoprecipitation-quantitative polymerase chain reaction and higher expression of MICU1 was found in the miR-181c/d-/- hearts. Conversely, downregulation of Sp1 by small interfering RNA decreased MICU1 expression in neonatal mouse ventricular myocytes. Changes in PDH activity provided evidence for a change in [Ca2+]m via the miR-181c/MICU1 axis. Moreover, this mechanism was implicated in the pathology of I/R injury. When MICU1 was knocked down in the miR-181c/d-/- heart by lentiviral expression of a short-hairpin RNA against MICU1, 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 MICU1 in ischemic injury. Conclusions miR-181c regulates mt-COX1, which in turn regulates MICU1 expression through the Sp1-mediated mitochondria-to-nucleus retrograde pathway. Loss of miR-181c can protect the heart from I/R injury by modulating [Ca2+]m through the upregulation of MICU1.
Insights
MicroRNA-181c (miR-181c) regulates mitochondrial function and calcium levels, impacting cardiac ischemia/reperfusion (I/R) injury. Loss of miR-181c protects the heart by upregulating MICU1 via the Sp1-mediated retrograde pathway.
Area of Science:
- Cardiovascular Biology
- Mitochondrial Medicine
- Molecular Cardiology
Background:
- MicroRNA-181c (miR-181c) translocates to cardiac mitochondria, downregulating mt-COX1.
- miR-181c/d knockout hearts show reduced oxidative stress and protection against ischemia/reperfusion (I/R) injury.
- The mechanism by which miR-181c regulates mitochondrial calcium ([Ca2+]m) remains unclear.
Purpose of the Study:
- To elucidate the mechanism by which miR-181c influences mitochondrial calcium regulation.
- To investigate the role of miR-181c in cardiac I/R injury through mitochondria-to-nucleus retrograde signaling.
- To identify key molecular players in the miR-181c-mediated regulation of cardiac mitochondrial function.
Main Methods:
- RNA sequencing and quantitative polymerase chain reaction (qPCR) in miR-181c/d knockout mouse hearts.
- Chromatin immunoprecipitation-qPCR to assess transcription factor binding to gene promoters.
- Small interfering RNA (siRNA) and short-hairpin RNA (shRNA) for gene knockdown in neonatal mouse ventricular myocytes.
- Assessment of pyruvate dehydrogenase (PDH) activity to infer mitochondrial calcium changes.
- In vitro ischemia/reperfusion (I/R) models.
Main Results:
- Hearts lacking miR-181c/d overexpressed nuclear-encoded calcium regulatory and metabolic genes, including MICU1.
- Specificity protein 1 (Sp1) expression was significantly higher in knockout hearts, with Sp1 binding to the MICU1 promoter.
- Downregulation of Sp1 reduced MICU1 expression, and changes in PDH activity indicated altered [Ca2+]m via the miR-181c/MICU1 axis.
- Knockdown of MICU1 abrogated the cardioprotective effects of miR-181c deficiency against I/R injury.
- Both Sp1 and MICU1 were confirmed to contribute to I/R injury in an in vitro model.
Conclusions:
- miR-181c regulates mt-COX1, which subsequently controls MICU1 expression via the Sp1-mediated mitochondria-to-nucleus retrograde pathway.
- Loss of miR-181c confers cardioprotection against I/R injury by upregulating MICU1 and modulating mitochondrial calcium levels.
- This pathway represents a novel therapeutic target for mitigating cardiac I/R injury.
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