Effect of Casein Kinase 1α Activator Pyrvinium Pamoate on Erythrocyte Ion Channels

Pharmacological modification of protein kinase CK1 (casein kinase 1) has previously been shown to influence suicidal erythrocyte death or eryptosis, which is triggered by activation of Cl--sensitive Ca2+-permeable cation channels. Ca2+ entering through those channels stimulates cell membrane scrambling and opens Ca2+-activated K+-channels resulting in KCl exit and thus cell shrinkage. The specific CK1-inhibitor D4476 (1 µM) blunted, whereas the specific CK1 αactivator pyrvinium pamoate (10 µM) enhanced cell membrane scrambling. The substances were at least partially effective through modification of cytosolic Ca2+-activity. The present study explored, whether pyrvinium pamoate indeed influences Cl--sensitive cation-channels in erythrocytes. As a result, removal of Cl-increased Fluo3-fluorescence (reflecting cytosolic Ca2+-activity), triggered cell membrane scrambling (apparent from annexin-V-binding), and decreased forward scatter (pointing to cell shrinkage). Pyrvinium pamoate significantly augmented the effect of Cl--removal on Fluo3 fluorescence and annexin-V-binding, but blunted the effect on forward scatter. According to whole cell patch clamp recording, Cl-removal activated a cation current, which was significantly enhanced by pyrvinium pamoate. Pyrvinium pamoate inhibited Ca2+-activated K+-channels. Ca2+-ionophore ionomycin (1 µM) decreased forward scatter, an effect significantly blunted by pyrvinium pamoate. In conclusion, pyrvinium pamoate activates Cl--sensitive Ca2+-permeable cation channels with subsequent Ca2+-entry and inhibits Ca2+-activated K+-channels thus blunting the stimulating effect of Ca2+ on those channels, K+-exit and thus cell shrinkage.