The large-conductance, Ca2+-activated K+ channel from cardiac mitochondria (mitoBKCa) is thought to play a role in cardioprotection. MitoBKCa molecular size is uncertain with reported immunochemical signals at ~55 and ~125 kDa. In addition, mitoBKCa molecular identity and its mitochondrial targeting mechanisms remain unknown, while there is scarce information about its functional properties or direct evidence for their role in cardioprotection. Because cardiac mitoBKCa shares conductance, Ca2+ responsiveness, and sensitivity to pharmacological agents with its plasma membrane counterpart known as BKCa (or MaxiK), we expect that mitoBKCa is assembled like BKCa by four pore-forming a subunits with a monomeric mass of ~125 kDa. We will now test the hypotheses that: 1) mitoBKCa and plasma membrane BKCa are encoded by the same gene and splice variation provides BKCa with intrinsic signals for its preferential mitochondrial targeting; 2) the normal absence of BKCa from the cardiomyocyte plasmalemma and presence in mitochondria is ruled by both an intrinsic signal(s) within mitoBKCa backbone (i.e. splice insert) either directly or indirectly (i.e. via a chaperone), and by cell-specific mechanisms, and ) mitoBKCa contributes to cardioprotection by regulating mitochondrial calcium retention capacity (CRC) and permeability transition pore (mPTP) opening. Preliminary Data shows: 1) the detection of a ~125 kDa protein in mitochondria by specific anti-BKCa antibodies; 2) the detection of all 27 constitutive BKCa exons in isolated cardiomyocyte mRNAs; 3) that BKCa isoform containing splice insert DEC (C-terminal insert of 61 amino acids) but not the constitutive form of BKCa (insertless BKCa) is readily targeted to mitochondria in adult cardiomyocytes; 4) that mitoBKCa subproteome uncovered as a partner Hsp60, a heat shock protein relevant for folding of mitochondrial imported proteins; and 5) that BKCa gene ablation prevents the cardioprotective action of putative BKCa channel opener NS1619. Overall the data support the above hypotheses, which will be tested using multiple approaches and pursuing the following Specific Aims to: 1. Identify the molecular correlate of cardiac mitoBKCa; 2. Functionally validate the identity of cloned putative mitoBKCa; 3. Determine signal mechanisms involved in mitoBKCa mitochondrial targeting; and 4. Directly address the role of mitoBKCa in cardioprotection. The outcomes of this program will open the opportunity to study mitoBKCa at the molecular level and advance the cardiac field by: solving mitoBKCa identity, providing information on its targeting mechanisms, and defining its functional properties and role in cardioprotection. Further understanding of the underlying molecular mechanism(s) of mitoBKCa cardioprotective effects will provide new targets for translation into therapeutics.

Public Health Relevance

One of the mechanisms involved in protecting the heart from lack of oxygen like that occurring during heart infarct is thought to be the opening of a mitochondria potassium channel named mitoBKCa. Here, we propose to unveil mitoBKCa molecular identity, the mechanisms that target it to mitochondria and directly demonstrate its role in protecting the heart from injury by oxygen deprivation. The results of this investigation wll allow the advancement of cardioprotective medicine and provide new molecular targets for therapeutics.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
Program Officer
Wong, Renee P
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California Los Angeles
Schools of Medicine
Los Angeles
United States
Zip Code
Zhang, Jin; Li, Min; Zhang, Zhu et al. (2017) The mitochondrial BKCa channel cardiac interactome reveals BKCa association with the mitochondrial import receptor subunit Tom22, and the adenine nucleotide translocator. Mitochondrion 33:84-101
Singh, H; Li, M; Hall, L et al. (2016) MaxiK channel interactome reveals its interaction with GABA transporter 3 and heat shock protein 60 in the mammalian brain. Neuroscience 317:76-107
Iorga, Andrea; Li, Jingyuan; Sharma, Salil et al. (2016) Rescue of Pressure Overload-Induced Heart Failure by Estrogen Therapy. J Am Heart Assoc 5:
Kundu, Pallob; Li, Min; Lu, Rong et al. (2015) Regulation of transcriptional activation function of rat estrogen receptor ? (ER?) by novel C-terminal splice inserts. Mol Cell Endocrinol 401:202-12
Wu, Xundong; Toro, Ligia; Stefani, Enrico et al. (2015) Ultrafast photon counting applied to resonant scanning STED microscopy. J Microsc 257:31-8
Cao, Qi; Zhong, Xi Zoƫ; Zou, Yuanjie et al. (2015) BK Channels Alleviate Lysosomal Storage Diseases by Providing Positive Feedback Regulation of Lysosomal Ca2+ Release. Dev Cell 33:427-41
Wu, Yong; Wu, Xundong; Toro, Ligia et al. (2015) Resonant-scanning dual-color STED microscopy with ultrafast photon counting: A concise guide. Methods 88:48-56
Wu, Yong; Wu, Xundong; Lu, Rong et al. (2015) Resonant Scanning with Large Field of View Reduces Photobleaching and Enhances Fluorescence Yield in STED Microscopy. Sci Rep 5:14766
Kuntamallappanavar, Guruprasad; Toro, Ligia; Dopico, Alex M (2014) Both transmembrane domains of BK ?1 subunits are essential to confer the normal phenotype of ?1-containing BK channels. PLoS One 9:e109306
Toro, Ligia; Li, Min; Zhang, Zhu et al. (2014) MaxiK channel and cell signalling. Pflugers Arch 466:875-86

Showing the most recent 10 out of 14 publications