title: Interaction and localization of the retinitis pigmentosa protein RP2 and NSF in retinal photoreceptor cells.
abstract: RP2 is a ubiquitously expressed protein encoded by a gene associated with X-linked retinitis pigmentosa (XLRP), a retinal degenerative disease that causes severe vision loss. Previous in vitro studies have shown that RP2 binds to ADP ribosylation factor-like 3 (Arl3) and activates its intrinsic GTPase activity, but the function of RP2 in the retina, and in particular photoreceptor cells, remains unclear. To begin to define the role of RP2 in the retina and XLRP, we have conducted biochemical studies to identify proteins in retinal cell extracts that interact with RP2. Here, we show that RP2 interacts with N-ethylmaleimide sensitive factor (NSF) in retinal cells as well as cultured embryonic kidney (HEK293) cells by mass spectrometry-based proteomics and biochemical analysis. This interaction is mediated by the N-terminal domain of NSF. The E138G and DeltaI137 mutations of RP2 known to cause XLRP abolished the interaction of RP2 with the N-terminal domain of NSF. Immunofluorescence labeling studies further showed that RP2 colocalized with NSF in photoreceptors and other cells of the retina. Intense punctate staining of RP2 was observed close to the junction between the inner and outer segments beneath the connecting cilium, as well as within the synaptic region of rod and cone photoreceptors. Our studies indicate that RP2, in addition to serving as a regulator of Arl3, interacts with NSF, and this complex may play an important role in membrane protein trafficking in photoreceptors and other cells of the retina.
authors.affiliation: Department of Ophthalmology,University of Helsinki, Helsinki, Finland.
authors.forename: Juha M
authors.initials: JM
authors.lastname: Holopainen
authors.forename: Christiana L
authors.initials: CL
authors.lastname: Cheng
authors.forename: Laurie L
authors.initials: LL
authors.lastname: Molday
authors.forename: Gurp
authors.initials: G
authors.lastname: Johal
authors.forename: Jonathan
authors.initials: J
authors.lastname: Coleman
authors.forename: Frank
authors.initials: F
authors.lastname: Dyka
authors.forename: Theresa
authors.initials: T
authors.lastname: Hii
authors.forename: Jinhi
authors.initials: J
authors.lastname: Ahn
authors.forename: Robert S
authors.initials: RS
authors.lastname: Molday
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002923:Cilia / Q000378:metabolism; D005136:Eye Proteins / Q000032:analysis / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis / Q000378:metabolism*; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D051379:Mice; D052066:N-Ethylmaleimide-Sensitive Proteins / Q000032:analysis / Q000378:metabolism*; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D012160:Retina / Q000378:metabolism; D012174:Retinitis Pigmentosa / Q000378:metabolism; D014162:Transfection
chemical_list: D005136:Eye Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C072178:RP2 protein, human; D019204:GTP-Binding Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins