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G. H. Grossman, U. Narendra, G. J. T. Pauer, S. A. Hagstrom; Tulp1 and Dynamin-1 Bind and Co-localize in Photoreceptor Cells. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5441.
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Mutations in TULP1 cause autosomal recessive retinitis pigmentosa in humans and retinal degeneration in mice. Previously, we demonstrated that Tulp1 interacts with Dynamin-1, a neuronal-specific protein involved in vesicle generation and transport. To further investigate the association between Tulp1 and Dynamin-1, we analyzed the binding of the two proteins in retinal tissue and evaluated the localization of Dynamin-1 in tulp1-/- retina as compared to wildtype (wt) retina.
We used immunofluorescence to examine the distribution of Dynamin-1 in tulp1-/- and wt retinas using an antibody specific for Dynamin-1. Results were compared to rd10 retinas, another mouse model with a comparable rate of retinal degeneration. An in situ proximity ligand assay was used to visualize the in-cell binding of Tulp1 and Dynamin-1 at physiological levels of expression in mouse retinal sections.
In the wt retina, Dynamin-1 is localized to the inner and outer plexiform layers. In addition, prominent Dynamin-1 staining is localized and restricted to the apical region of the inner segment and connecting cilium. In this region, there is co-localization with Tulp1 staining. In the tulp1-/- retina, there is a severe attenuation of Dynamin-1 staining in both the photoreceptor terminals and the inner segments. Ligand assays indicate that in wt retinal tissue, Tulp1 and Dynamin1 are endogenous binding partners in both the photoreceptor terminals and inner segments. In the rd10 retina, the localization and binding of Dynamin-1 with Tulp1 is not disrupted.
Our data indicate that Tulp1 endogenously binds and co-localizes with Dynamin-1 in retinal tissue. In the absence of Tulp1, the expression or stability of Dynamin-1 is profoundly diminished, suggesting that the two proteins are involved in the same pathway. No difference in Dynamin-1 localization or binding of Tulp1 was seen in the rd10 retina as compared to wt, indicating that our observations are not associated with a generalized retinal degeneration.
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