Heterologous expression of specific K+ channels in T lymphocytes: functional consequences for volume regulation.

It has been postulated that the K+ channel isoform Kv1.3 plays a role in regulatory volume decrease (RVD) in response to hypotonic shock. We show that a mouse cytotoxic T-lymphocyte line, CTLL-2, is devoid of voltage-dependent K+ channels and is unable to volume regulate. Transient transfection of these cells with Kv1.3 reconstitutes their ability to volume regulate. As predicted by our model, this ability depends critically on volume-induced changes in membrane potential and the isoform of the K+ channel used. When the cells were transfected with Kv3.1, an isoform believed to be expressed in a specific subclass of mouse thymocytes, the CTLL-2 cells did not show RVD. The difference in the ability of the two isoforms to confer the capacity for RVD is expected from differences in the voltage dependence of activation of the channels, according to our proposed model for RVD. The experimental approach that we use, transient transfection and panning to select positive transfectants, is highly effective; it has a > 95% efficiency. This method, and this cell line, may be important tools in studying lymphocyte K+ channels and their function in situ.