Identity and Function of a Cardiac Mitochondrial Small Conductance Ca2+‐Activated K+ Channel Splice variant

Small conductance Ca2+‐activated K+ channels (SKCa) have three isoforms, SK1, 2 and 3, with small unit conductance of 3–30 pS; Ca2+ binding to calmodulin initiates opening of SKCa channels. SKCa channel activator DCEBIO protects against ischemia and reperfusion (IR) injury in isolated hearts but protection is abolished by reactive O2 species scavenger MnTBAP, indicating SKCa channels play an important role in mitochondrial function during IR injury. Here we provide further evidence by showing that: SKCa channel opening via i.v. infusion in intact rats reduces regional infarct size induced by coronary artery occlusion and reperfusion; agonists of SKCa channels improve mitochondrial respiration after IR injury; and CaCl2 applied to isolated mitochondria (m) increases K+ influx. Moreover, we confirm the presence of mSKCa 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 Ca2+ calmodulin binding domain is required for Ca2+ 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 (DYm), and enhanced cell death with simulated IR injury. Together, these molecular and physiological experiments support the presence of, and a prominent role for, SKCa channel splice variants in mitochondria that afford cardiac protection against oxidative stress injury.

• Publication year

  2017

• Venue

  Biochimica et Biophysica Acta - Bioenergetics

• Publication date

  2017-04-01

• Fields of study

  Biology, Medicine

• Identifiers
  DOI 10.1016/j.bbabio.2017.03.005PMID 28342809PMCID PMC5749404
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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