title: Silencing the KCNK9 potassium channel (TASK-3) gene disturbs mitochondrial function, causes mitochondrial depolarization, and induces apoptosis of human melanoma cells.
abstract: TASK-3 (KCNK9 or K2P9.1) channels are thought to promote proliferation and/or survival of malignantly transformed cells, most likely by increasing their hypoxia tolerance. Based on our previous results that suggested mitochondrial expression of TASK-3 channels, we hypothesized that TASK-3 channels have roles in maintaining mitochondrial activity. In the present work we studied the effect of reduced TASK-3 expression on the mitochondrial function and survival of WM35 and A2058 melanoma cells. TASK-3 knockdown cells had depolarized mitochondrial membrane potential and contained a reduced amount of mitochondrial DNA. Compared to their scrambled shRNA-transfected counterparts, they demonstrated diminished responsiveness to the application of the mitochondrial uncoupler [(3-chlorophenyl)hydrazono]malononitrile (CCCP). These observations indicate impaired mitochondrial function. Further, TASK-3 knockdown cells presented reduced viability, decreased total DNA content, altered cell morphology, and reduced surface area. In contrast to non- and scrambled shRNA-transfected melanoma cell lines, which did not present noteworthy apoptotic activity, almost 50 % of the TASK-3 knockdown cells exhibited strong Annexin-V-specific immunofluorescence signal. Sequestration of cytochrome c from the mitochondria to the cytosol, increased caspase 3 activity, and translocation of the apoptosis-inducing factor from mitochondria to cell nuclei were also demonstrated in TASK-3 knockdown cells. Interference with TASK-3 channel expression, therefore, induces caspase-dependent and -independent apoptosis of melanoma cells, most likely via causing mitochondrial depolarization. Consequently, TASK-3 channels may be legitimate targets of future melanoma therapies.
authors.affiliation: Department of Physiology, Faculty of General Medicine, University of Debrecen, Nagyerdei krt 98, PO Box 22, 4012, Debrecen, Hungary.
authors.forename: Dénes
authors.initials: D
authors.lastname: Nagy
authors.forename: Mónika
authors.initials: M
authors.lastname: Gönczi
authors.forename: Beatrix
authors.initials: B
authors.lastname: Dienes
authors.forename: Árpád
authors.initials: Á
authors.lastname: Szöőr
authors.forename: János
authors.initials: J
authors.lastname: Fodor
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Nagy
authors.forename: Adrienn
authors.initials: A
authors.lastname: Tóth
authors.forename: Tamás
authors.initials: T
authors.lastname: Fodor
authors.forename: Péter
authors.initials: P
authors.lastname: Bai
authors.forename: Géza
authors.initials: G
authors.lastname: Szücs
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Rusznák
authors.forename: László
authors.initials: L
authors.lastname: Csernoch
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015536:Down-Regulation; D004734:Energy Metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D024683:Potassium Channels, Tandem Pore Domain / Q000172:deficiency* / Q000235:genetics; D034622:RNA Interference; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors; D014162:Transfection; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; C498655:KCNK9 protein, human; D024683:Potassium Channels, Tandem Pore Domain; D014475:Uncoupling Agents