GPR179 interacts with TRPM1 in retinal depolarizing bipolar cells

Abstract

BackgroundComplete congenital stationary night blindness (cCSNB) is a heterogeneous disorder of the retina characterized by impairment of low light vision and loss of the b‐wave of the electroretinogram. Mutations in GRM6, TRPM1and NYX, which encode proteins critical to signal transmission in one class of retinal interneurons called depolarizing bipolar cells (DBCs) cause cCSNB. We have shown that an orphan G‐protein coupled receptor, GPR179, also plays a vital role in DBC function.Methods/ResultsImmunochemical staining of retinal cross‐sections demonstrates that TRPM1 and GPR179 co‐localize on the dendritic tips of DBCs. Further, TRPM1 is lost from GPR179 mutant mice (Nob5 ) indicating they may interact. We used a yeast two‐hybrid analyses and co‐immunoprecipitation (co‐IP) assays after expression in HEK293T cells to examine interactions. Both methods show that GPR179 and TRPM1 interact. Furthermore, antibodies to GPR179 could co‐IP TRPM1 from retinal lysates, confirming the interaction.ConclusionsThis is the first study to demonstrate the interaction of TRPM1 and a previously uncharacterized orphan G protein receptor, GPR179. This result was confirmed by three independent methods suggesting that the interaction of GPR179 and TRPM1 is a critical component of the G protein signal transduction cascade in DBCs.