Possible anti-proliferative effect of TASK-3 on HEK293 and PANC-1 cells

[Speaker] Yoshihiro Konno:1
[Co-author] Makoto Sato:1, Yutaro Obara:1, Kuniaki Ishii:1
1:Department of Pharmacology, Yamagata University school of Medicine, Japan

Background: TWIK-related acid sensitive K+ channel-3 (TASK-3) is responsible for background potassium currents that regulate cell resting membrane potential and excitability. TASK-3 gene is overexpressed in several types of human carcinomas and is thought to be an oncogenic channel. However, we found that when TASK-3 was co-expressed with GFP in HEK293 cells, GFP-positive cells did not grow well, which suggested that TASK-3 has an anti-proliferative effect. Therefore, we carried out this study to investigate whether TASK-3 does affect cell proliferation. Methods: TASK-3 was overexpressed in HEK293 cells and human pancreatic cancer cell lines, PANC-1, and its influence on the cell proliferation and apoptosis was examined. Cell growth was measured by the WST-8 cell proliferation assay. In addition, β-gal was expressed with or without TASK-3 in the cells and the enzyme activity was measured to estimate the cell viability. Apoptotic cell population was assessed by flow cytometry with DAPI staining. Activation of apoptosis was determined by measuring the activity of effector caspases and detecting the cleavage of PARP. Influence of the TASK-3 mutant (AAA) lacking channel activity was also evaluated. Results: The WST-8 assay showed that the rate of cell proliferation was decreased in HEK293 cells expressing TASK-3, but not in the cells expressing AAA. In HEK293 and PANC-1 cells, co-expression of TASK-3 with β-gal resulted in low β-gal activity, whereas co-expression of AAA with β-gal did not affect the enzyme activity. In TASK-3 expressing cells, flow cytometry data showed an increase in the proportion of apoptotic cells compared to control, and Western blotting revealed an increase in cleaved PARP. In addition, clear activation of caspases was observed in the cells expressing TASK-3 using the Caspase3/7 detection reagent. Conclusions: Overexpression of TASK-3 decreased cell proliferation in HEK293 cells and increased apoptosis in HEK293 and PANC-1 cells. Our results suggest that TASK-3 has an anti-proliferative effect in addition to the well-known oncogenic activity. Further study is necessary to reveal the mechanisms underlying the antitumor effect of this channel.
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