Functional expression of mitochondrial K Ca 3.1 channels in non-small cell lung cancer cells.

Lung cancer is one of the leading causes of cancer-related deaths worldwide. The Ca2+ -activated K+ channel KCa 3.1 contributes to the progression of non-small cell lung cancer (NSCLC). Recently, KCa 3.1 channels were found in the inner membrane of mitochondria in different cancer cells. Mitochondria are the main sources for the generation of reactive oxygen species (ROS) that affect the progression of cancer cells. Here, we combined Western blotting, immunofluorescence, and fluorescent live-cell imaging to investigate the expression and function of KCa 3.1 channels in the mitochondria of NSCLC cells. Western blotting revealed KCa 3.1 expression in mitochondrial lysates from different NSCLC cells. Using immunofluorescence, we demonstrate a co-localization of KCa 3.1 channels with mitochondria of NSCLC cells. Measurements of the mitochondrial membrane potential with TMRM reveal a hyperpolarization following the inhibition of KCa 3.1 channels with the cell-permeable blocker senicapoc. This is not the case when cells are treated with the cell-impermeable peptidic toxin maurotoxin. The hyperpolarization of the mitochondrial membrane potential is accompanied by an increased generation of ROS in NSCLC cells. Collectively, our results provide firm evidence for the functional expression of KCa 3.1 channels in the inner membrane of mitochondria of NSCLC cells.