Faculty Collaboration Database

Identity and function of a cardiac mitochondrial small conductance Ca²⁺-activated K⁺ channel splice variant. Biochim Biophys Acta Bioenerg 2017 Jun;1858(6):442-458

Date

03/28/2017

Pubmed ID

28342809

Pubmed Central ID

PMC5749404

DOI

10.1016/j.bbabio.2017.03.005

Scopus ID

2-s2.0-85017126810 (requires institutional sign-in at Scopus site)   26 Citations

Abstract

We provide evidence for location and function of a small conductance, Ca²⁺-activated K⁺ (SK_Ca) channel isoform 3 (SK3) in mitochondria (m) of guinea pig, rat and human ventricular myocytes. SK_Ca agonists protected isolated hearts and mitochondria against ischemia/reperfusion (IR) injury; SK_Ca antagonists worsened IR injury. Intravenous infusion of a SK_Ca channel agonist/antagonist, respectively, in intact rats was effective in reducing/enhancing regional infarct size induced by coronary artery occlusion. Localization of SK3 in mitochondria was evidenced by Western blot of inner mitochondrial membrane, immunocytochemical staining of cardiomyocytes, and immunogold labeling of isolated mitochondria. We identified a SK3 splice variant in guinea pig (SK3.1, aka SK3a) and human ventricular cells (SK3.2) by amplifying mRNA, and show mitochondrial expression in mouse atrial tumor cells (HL-1) by transfection with full length and truncated SK3.1 protein. We found that the N-terminus is not required for mitochondrial trafficking but the C-terminus beyond the Ca²⁺ calmodulin binding domain is required for Ca²⁺ sensing to induce mK⁺ influx and/or promote mitochondrial localization. In isolated guinea pig mitochondria and in SK3 overexpressed HL-1 cells, mK⁺ influx was driven by adding CaCl₂. Moreover, there was a greater fall in membrane potential (ΔΨ_m), and enhanced cell death with simulated cell injury after silencing SK3.1 with siRNA. Although SK_Ca channel opening protects the heart and mitochondria against IR injury, the mechanism for favorable bioenergetics effects resulting from SK_Ca channel opening remains unclear. SK_Ca channels could play an essential role in restraining cardiac mitochondria from inducing oxidative stress-induced injury resulting from mCa²⁺ overload.

Author List

Yang M, Camara AKS, Aldakkak M, Kwok WM, Stowe DF

Authors

Amadou K. Camara PhD Professor in the Anesthesiology department at Medical College of Wisconsin
Wai-Meng Kwok PhD Professor in the Anesthesiology department at Medical College of Wisconsin
David F. Stowe MD, PhD Professor in the Anesthesiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

1-Naphthylamine
Amino Acid Sequence
Animals
Benzimidazoles
Calcium Chloride
Cell Hypoxia
Cell Line
Guinea Pigs
Humans
Membrane Potential, Mitochondrial
Mice
Mitochondria, Heart
Myocardial Reperfusion Injury
Myocytes, Cardiac
Potassium
Potassium Channel Blockers
Protein Isoforms
RNA Interference
RNA, Messenger
Rats
Recombinant Fusion Proteins
Sequence Alignment
Sequence Homology, Amino Acid
Small-Conductance Calcium-Activated Potassium Channels