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Identity and Function of a Cardiac Mitochondrial Small Conductance Ca 2+ ‐Activated K + Channel Splice variant
Author(s) -
Yang Meiying,
Camara Amadou K.S.,
Kwok WaiMeng,
Aldakkak Mohammed,
Stowe David F
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1081.10
Subject(s) - mitochondrion , mitochondrial apoptosis induced channel , inner mitochondrial membrane , membrane potential , microbiology and biotechnology , chemistry , calmodulin , voltage dependent anion channel , biology , biophysics , biochemistry , bacterial outer membrane , escherichia coli , gene , enzyme
Small conductance Ca 2+ ‐activated K + channels (SK Ca ) have three isoforms, SK1, 2 and 3, with small unit conductance of 3–30 pS; Ca 2+ binding to calmodulin initiates opening of SK Ca channels. SK Ca channel activator DCEBIO protects against ischemia and reperfusion (IR) injury in isolated hearts but protection is abolished by reactive O 2 species scavenger MnTBAP, indicating SK Ca channels play an important role in mitochondrial function during IR injury. Here we provide further evidence by showing that: SK Ca channel opening via i.v. infusion in intact rats reduces regional infarct size induced by coronary artery occlusion and reperfusion; agonists of SK Ca channels improve mitochondrial respiration after IR injury; and CaCl 2 applied to isolated mitochondria (m) increases K + influx. Moreover, we confirm the presence of mSK Ca isoform 3 (mSK3) in heart mitochondria of guinea pig, rat and human using Western blotting of inner mitochondrial membrane proteins, immunocytochemical staining of cardiomyocytes, and immunogold labeling of isolated mitochondria. We identify mSK3 splice variants in guinea pig (SK3.1, aka SK3a) and human ventricular cells (SK3.2). Overexpression of full length, N‐terminal truncated and C‐terminal truncated guinea pig SK3.1 in HL‐1 cells demonstrated that N‐terminus is not required for mitochondrial trafficking but the C‐terminus beyond the Ca 2+ calmodulin binding domain is required for Ca 2+ sensing to induce mK + influx and to promote mitochondrial localization. Silencing of SK3.1 with siRNA in HL‐1 cells induced a greater fall in membrane potential (DY m ), and enhanced cell death with simulated IR injury. Together, these molecular and physiological experiments support the presence of, and a prominent role for, SK Ca channel splice variants in mitochondria that afford cardiac protection against oxidative stress injury. Support or Funding Information This research study was supported in part by the Veterans Administration (BX‐002539‐01) and the National Institutes of Health (R01 HL089514 and P01‐GM066730).