The Expression of Whirlin and Cav1.3α1 is Mutually Independent in Photoreceptors

摘要

Whirlin is a gene responsible for Usher syndrome type II (USH2) and congenital deafness. In photoreceptors, it organizes a protein complex through binding to proteins encoded by other USH2 genes, usherin (USH2A) and G-protein-coupled receptor 98 (GPR98). Recently, Cav1.3α1 (α1D) has been discovered to interact with whirlin in vitro and these two proteins are localized to the same subcellular compartments in photoreceptors. Accordingly, it is proposed that Cav1.3α1 is in the USH2 protein complex and that the USH2 protein complex is involved in regulating Ca²⁺ in photoreceptors. To test this hypothesis, we investigated the interdependence of Cav1.3α1 and whirlin expression in photoreceptors. We found that lack of Cav1.3α1 did not change the whirlin distribution or expression level in photoreceptors. In the retina, several Cav1.3α1 splice variants were found at the RNA level. Among them, the whirlin-interacting Cav1.3α1 long variant had no change in its protein expression level in the absence of whirlin. The localization of Cav1.3α1 in photoreceptors, published previously, cannot be confirmed. Therefore, the mutual independence of whirlin and Cav1.3α₁ expressions in photoreceptors suggests that Ca_v1.3α₁ may not be a key member of the USH2 protein complex at the periciliary membrane complex.