The inherited blindness associated protein AIPL1 interacts with the cell cycle regulator protein NUB1

Mutations in the aryl hydrocarbon receptor-interacting protein-like 1 (AlPL1) gene have been found in patients with Leber congenital amaurosis (LCA), a severe, early-onset form of retinal degeneration. To determine the normal function of AlPL1 and to better understand how mutations in this gene cause disease, we performed a yeast two-hybrid screen to identify AlPL1-interacting proteins in the retina. One of the identified interacting proteins corresponds to NUB1 (NEDD8 Ultimate Buster 1), which is thought to control many biological events, especially cell cycle progression, by downregulating NEDD8 expression. The AlPL1-NUB1 interaction was verified by co-immunoprecipitation studies in Y79 retinoblastoma cells, demonstrating that this interaction occurs within cells that share a number of features with retinal progenitor cells. Furthermore, we examined the localization of the AlPL1 protein within developing and adult retinas, and found that AlPL1 is present in the developing photoreceptor layer of the human retina and within the photoreceptors of the adult retina. Similar to AlPL1, NUB1 is also expressed in the developing and adult retina. Therefore, it is possible that the early-onset form of retinal degeneration seen in LCA patients with AlPL1 mutations may be due to a defect in the regulation of cell cycle progression during photoreceptor maturation. These data raise the possibility that AlPL1 is important for appropriate photoreceptor formation during development and/or survival following differentiation.