Subtype-Selective Positive Modulation of K(Ca)2.3 Channels Increases Cilia Length

[Image: see text] Small-conductance Ca(2+)-activated potassium (K(Ca)2.x) channels are gated exclusively by intracellular Ca(2+). The activation of K(Ca)2.3 channels induces hyperpolarization, which augments Ca(2+) signaling in endothelial cells. Cilia are specialized Ca(2+) signaling compartments. Here, we identified compound 4 that potentiates human K(Ca)2.3 channels selectively. The subtype selectivity of compound 4 for human K(Ca)2.3 over rat K(Ca)2.2a channels relies on an isoleucine residue in the HA/HB helices. Positive modulation of K(Ca)2.3 channels by compound 4 increased flow-induced Ca(2+) signaling and cilia length, while negative modulation by AP14145 reduced flow-induced Ca(2+) signaling and cilia length. These findings were corroborated by the increased cilia length due to the expression of Ca(2+)-hypersensitive K(Ca)2.3_G351D mutant channels and the reduced cilia length resulting from the expression of Ca(2+)-hyposensitive K(Ca)2.3_I438N channels. Collectively, we were able to associate functions of K(Ca)2.3 channels and cilia, two crucial components in the flow-induced Ca(2+) signaling of endothelial cells, with potential implications in vasodilation and ciliopathic hypertension.