Slo2.1 (Slick), but not Slo2.2 (Slack), is regulated by changes in cell volume

Abstract

A number of physiological processes, such as nerve activity, epithelial transport and apoptosis, involve changes in cell volume. The KCa1.1 ‐ (Slo, BK, MaxiK) ‐ related potassium channels Slo2.1 (Slick) and Slo2.2 (Slack) are activated by intracellular Na+ and Cl– and inhibited by intracellular ATP. Both channels are widely expressed in different tissues, including dura mater, middle cerebral artery and basilar artery confirmed by RT‐PCR. In this study we examined the possible regulation of Slo2.1 and Slo2.2 by small, fast changes in cell volume in Xenopus oocytes after co‐expression with aquaporins (AQP1) to ensure high water permeability. Our results show that Slo2.1 is dramatically stimulated (to 196% of control) by cell swelling of approximately 5%, and inhibited (to 44% of control) by a similar decrease in cell volume. In contrast, changes in cell volume did not affect the Slo2.2 channels. Therefore it is suggested that cell volume is a significant regulatory parameter for Slo2.1 and that these channels may play an important role in regulating intracellular potassium concentration during changes in cell volume.