title: Peripherin-2 differentially interacts with cone opsins in outer segments of cone photoreceptors.
abstract: Peripherin-2 is a glycomembrane protein exclusively expressed in the light-sensing compartments of rod and cone photoreceptors designated as outer segments (OS). Mutations in peripherin-2 are associated with degenerative retinal diseases either affecting rod or cone photoreceptors. While peripherin-2 has been extensively studied in rods, there is only little information on its supramolecular organization and function in cones. Recently, we have demonstrated that peripherin-2 interacts with the light detector rhodopsin in OS of rods. It remains unclear, however, if peripherin-2 also binds to cone opsins. Here, using a combination of co-immunoprecipitation analyses, transmission electron microscopy (TEM)-based immunolabeling experiments, and quantitative fluorescence resonance energy transfer (FRET) measurements in cone OS of wild type mice, we demonstrate that peripherin-2 binds to both, S-opsin and M-opsin. However, FRET-based quantification of the respective interactions indicated significantly less stringent binding of peripherin-2 to S-opsin compared to its interaction with M-opsin. Subsequent TEM-studies also showed less co-localization of peripherin-2 and S-opsin in cone OS compared to peripherin-2 and M-opsin. Furthermore, quantitative FRET analysis in acutely isolated cone OS revealed that the cone degeneration-causing V268I mutation in peripherin-2 selectively reduced binding to M-opsin without affecting the peripherin-2 interaction to S-opsin or rhodopsin. The differential binding of peripherin-2 to cone opsins and the mutant-specific interference with the peripherin-2/M-opsin binding points to a novel role of peripherin-2 in cones and might contribute to understanding the differential penetrance of certain peripherin-2 mutations in rods and cones. Finally, our results provide a proof-of-principle for quantitative FRET measurements of protein-protein interactions in cone OS.
authors.affiliation: Munich Center for Integrated Protein Science CIPS , 81377 München, Germany, elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.|Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: O N Phuong
authors.initials: ON
authors.lastname: Nguyen
authors.affiliation: Munich Center for Integrated Protein Science CIPS , 81377 München, Germany, elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.|Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: Sybille
authors.initials: S
authors.lastname: Böhm
authors.affiliation: Department of Biology, Animal Physiology, Friedrich-Alexander Universität Erlangen-Nürnberg, 91058 Erlangen, Germany and elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Gießl
authors.affiliation: Munich Center for Integrated Protein Science CIPS , 81377 München, Germany, elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.|Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: Elisabeth S
authors.initials: ES
authors.lastname: Butz
authors.affiliation: Cell and Matrix Biology, Institute of Zoology, Johannes-Gutenberg Universität Mainz, 55128 Mainz, Germany elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Wolfrum
authors.affiliation: Department of Biology, Animal Physiology, Friedrich-Alexander Universität Erlangen-Nürnberg, 91058 Erlangen, Germany and elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.
authors.forename: Johann H
authors.initials: JH
authors.lastname: Brandstätter
authors.affiliation: Munich Center for Integrated Protein Science CIPS , 81377 München, Germany, elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.|Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wahl-Schott
authors.affiliation: Munich Center for Integrated Protein Science CIPS , 81377 München, Germany, elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.|Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Biel
authors.affiliation: Munich Center for Integrated Protein Science CIPS , 81377 München, Germany, elvir.becirovic@cup.uni-muenchen.de martin.biel@cup.uni-muenchen.de.|Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: Elvir
authors.initials: E
authors.lastname: Becirovic
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D055358:Cone Opsins / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D051379:Mice; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D011485:Protein Binding; D012160:Retina / Q000378:metabolism / Q000473:pathology; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism* / Q000473:pathology; D012162:Retinal Degeneration / Q000235:genetics* / Q000473:pathology; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D055358:Cone Opsins; C546952:periphilin protein, mouse; D012243:Rhodopsin