STRUCTURE AND FUNCTION RELATIONSHIP OF CONE CYCLIC NUCLEOTIDE-GATED CHANNEL

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Photoreceptor cyclic nucleotide-gated (CNG) channel is essential to phototransduction. Mutations in genes encoding cone CNG channel subunits are highly linked to human cone diseases. Mutations in cone CNG channel account for 70% of patients with achromatopsia, early-onset macular degeneration, and progressive cone dystrophy. However, the mechanisms by which mutations result in cone defects are unknown and our current understanding of the structure and functional modulation of cone CNG channel is very limited. This is primarily due to the difficulty of investigating the cone system in a rod dominant mammalian retina. We have shown robust expression of the cone CNG channel and lack of the rod CNG channel in the cone-dominant retina of mice deficient in the transcription factor neural retina leucine zipper (Nrl knockout mice). Thus we have demonstrated that the retina of Nrl knockout mice is a unique tool to study cone CNG channel in mammals. This research program is to utilize this mouse model to determine the biochemical components and properties of the native cone CNG channel by using multiple biochemical approaches. The proposed research is also to understand the modulation of cone CNG channel by evaluating its associations with the calcium binding protein calmodulin and the sodium-potassium-calcium exchanger NCKX2 in retina. The functional modulation of cone CNG channel also will be explored by identifying its interacting proteins. This will be achieved by using multiple affinity purification and mass spectrometry analysis. The long-term goal of this research is to elucidate the mechanism of the mutation-associated cone diseases with the objective of identifying potential therapeutic interventions for the cone diseases.