Purchase this article with an account.
X. Lu, M. Guruju, P.A. Ferreira; Molecular, Functional and Mutation Analysis of RPGRIP1 Isoforms . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2995.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The Retinitis Pigmentosa GTPase Regulator–Interacting Protein 1 (RPGRIP1) was found as an interacting substrate of Retinitis Pigmentosa GTPase Regulator (RPGR), thus implicating RPGRIP1 in the molecular pathogenesis of X–linked retinitis pigmentosa type 3 (XlRP3). Mutations in RPGRIP1 lead to Leber congenital amaurosis (LCA). We have shown that the products of RPGRIP1 undergoe extensive processing at the transcriptional and posttranslational levels in the retina. In addition, there are species–specific differences between RPGRIP1 isoforms. Yet, the functional, cellular and pathological implications of the processing of RPGRIP1s, the diversity of RPGRIP1s among species, and the effect of mutations in these isoforms are not known. The current study aims at understanding the functional implications of the molecular diversity of RPGRIP1s and proteolytic products thereof. Methods: We employed a combination of cell–based, genetic, biochemical and quantitative imaging analysis assays to determine the functional diversity of RPGRIP1 isoforms and byproducts thereof. Results:Transfection of COS7 cells with various and species–specific RPGRIP1 isoforms lead to distinct subcellular distribution of epitope–tagged RPGRIP1s and byproducts thereof. We found a novel domain in RPGRIP1 that is transported to the nucleus. The nuclear import of the processed RPGRIP1 is completely dependent on the presence of the RPGR–interacting domain (RID) in RPGRIP1. A murine–specific RPGRIP1 isoform, mRPGRIP1b, lacking the RID domain was identified with pan–retinal expression. This is the most abundant RPGRIP1 retinal isoform in the murine. mRPGRIP1b localization in the retina and cell culture is distinct from all other isoforms and it colocalizes partially with a subpopulation of lysosomes. The LCA mutations, D1114G and ΔE1279, in the RID of RPGRIP1 lead to distinct molecular and subcellular phenotypes. The homozygous D1114G is a loss–of–function mutation that has a cis–acting effect on an upstream domain of RPGRIP1, while the monoallelic ΔE1279 is a gain–of–function mutation without such effect. Finally, novel interacting partners of RPGRIP1 were identified from yeast two–hybrid screens that will provide clues of the role of RPGR, RPGRIP1 and domains thereof in retinal function and allied dystrophies. Conclusions: RPGRIP1s play multiple roles in retinal function by sequestering multiple molecular partners and their isoform–dependent subcellular localization. Moreover, a subset of RPGRIP1s and allied mutations are implicated likely in the pathogenesis of XlRP3 and LCA by distinct molecular mechanisms and pathways.
This PDF is available to Subscribers Only