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Junhuang Zou, Jun Yang; Whirlin and Cav1.3α1 are Mutually Independent for Their Localization and Expression in Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1613.
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© ARVO (1962-2015); The Authors (2016-present)
Usher syndrome is a condition characterized by retinitis pigmentosa and deafness. Among its three clinical types, Usher syndrome type II (USH2) is the most prevalent. Currently, usherin (USH2A), G-protein-coupled receptor 98 (GPR98), and whirlin have been identified responsible for USH2. Their proteins are known to form a protein complex in vivo, and whirlin plays a role in the organization of this complex. Recently, Cav1.3α1 (α1D) has been discovered to be able to interact with whirlin in vitro, and these two proteins are localized to a similar place in photoreceptors. Here, we further investigate the localization of Cav1.3α1 in photoreceptors and reveal the relationship between whirlin and Cav1.3α1 in vivo.
RT-PCR was utilized to examine the expression of Cav1.3α1 transcripts in the retina. Western blotting, densitometry, statistical analysis, immunofluorescent staining, and confocal laser scanning microscopy were performed to compare the protein expression level and localization between wild-type and various mutant retinas.
Different Cav1.3α1 splice isoforms exist in the retina. They were localized to the multiple regions in photoreceptors. At the apical inner segment, Cav1.3α1 long isoform was in close proximity of whirlin, though their colocalization was limited. Ablation of whirlin did not affect the Cav1.3α1 expression pattern and level in the retina. Similarly, whirlin distribution and expression level were not changed in the Cav1.3α1 deficient retina.
An L-type voltage-gated calcium channel may participate in the biological function of the USH2 proteins complex in photoreceptors. This calcium channel and the USH2 protein complex are mutually independent for their localization and expression.
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