The TASK-2 channel belongs to the family of two-pore domain potassium channels, the so-called background or leak channels. TASK-2 has been implicated in cell volume regulation in several cell types among them the Ehrlich Ascites Tumor (EAT) cells. Withholding a constant cell volume is important for maintaining cell homeostasis. For that purpose the cell has several regulating mechanisms including regulatory volume increase and regulatory volume decrease (RVD) which both are seen in response to acute changes in cell volume. When experiencing an extracellular decrease or an intracellular increase in osmolarity, the cell swells and activates the RVD mechanisms, which includes efflux of KCl followed by osmotically obliged water through specific channels (see 1;2). The details of the activation of these channels has so far remained unknown, though it seems that tyrosine phosphorylation is somehow involved in the activation of TASK-2 in EAT cells, thus the purpose of this study was to investigate the role of tyrosine phosphorylation in the activation of the volume sensitive TASK-2 channel in EAT cells. When studying the effect of over-expressing the TASK-2 channel in HEK-293 cells we found that the over-expression resulted in an increased RVD (faster and with a greater ion loss) compared to what was seen in wild type cells. Furthermore we found that the tyrosine kinase inhibitor genistein impaired the RVD in response to swelling as if the channels remained closed and that the tyrosine phosphatase inhibitor mpV(pic) potentiated RVD as if the channel was kept open for a longer period of time. When precipitating the hypotonically stimulated channel (1, 5 and 10 min) and using western blotting together with antibodies against TASK-2 as well as against phospho-tyrosines we found that there was a significantly and time dependent increase in the tyrosine phosphorylation of the channel itself. Netphos prediction programme gave us 5 possible tyrosine phosphorylation sites, which are to be further analysed using mass spectrometry.

Hoffmann EK, Lambert IH and Pedersen SF( 2009) Physiol Rev 89:193–277.

Okada Y (2004) Cell Biochemistry and Biophysics 41:233-258.