Abstract
Abstract: :
Purpose: TULP1, a member of a family of four proteins with unknown function designated tubby–like proteins or TULPs, is expressed specifically in photoreceptor cells. Mutations in TULP1 are associated with autosomal recessive retinitis pigmentosa and Tulp1 knockout mice develop an early–onset, progressive photoreceptor degeneration involving both rods and cones. As an approach to determining the physiologic function of TULP1, we are pursuing the identification of interacting proteins. Methods: Immunoprecipitation experiments were performed with bovine retinal homogenates and a polyclonal anti–TULP1 antibody. Immunoprecipitation products were separated by SDS–PAGE, protein bands excised, digested in situ with trypsin and identified by LC MS/MS. Reciprocal pull–down and immunohistochemistry analyses were performed to corroborate protein interactions. Results: Dynamin–1, a neuronal specific GTPase that mediates vesicle formation and movement, was identified by mass spectrometry and western blotting in anti–TULP1 retinal immunoprecipitates. In reciprocal immunoprecipitations, GST–Dynamin–1 was able to pull down TULP–1 from retinal lysate. Immunohistochemistry indicates that TULP1 and Dynamin–1 co–localize to the outer plexiform layer in the retina. Conclusions: Dynamin–1 appears to interact with TULP1 in the retina. This result suggests that TULP1 may be involved in vesicular trafficking of proteins and offers insight into possible mechanisms underlying photoreceptor degeneration caused by mutations in TULP1.
Keywords: protein structure/function • retinal degenerations: cell biology • photoreceptors