title: Disease-causing mutations associated with four bestrophinopathies exhibit disparate effects on the localization, but not the oligomerization, of Bestrophin-1.
abstract: BEST1 encodes Bestrophin-1 (Best1), a homo-oligomeric, integral membrane protein localized to the basolateral plasma membrane of the retinal pigment epithelium. Mutations in BEST1 cause five distinct retinal degenerative diseases, including adult vitelliform macular dystrophy (AVMD), autosomal recessive bestrophinopathy (ARB), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and retinitis pigmentosa (RP). The mechanisms underlying these diseases and why mutations cause one disease over another are, for the most part, unknown. To gain insights into these four diseases, we expressed 28 Best1 mutants fused to YFP in polarized MDCK monolayers and, via confocal microscopy and immunofluorescence, live-cell FRET, and reciprocal co-immunoprecipitation experiments, screened these mutants for defects in localization and oligomerization. All 28 mutants exhibited comparable FRET efficiencies to and co-immunoprecipitated with WT Best1, indicating unimpaired oligomerization. RP- and ADVIRC-associated mutants were properly localized to the basolateral plasma membrane of cells, while two AVMD and most ARB mutants were mislocalized. When co-expressed, all mislocalized mutants caused mislocalization of WT Best1 to intracellular compartments. Our current and past results indicate that mislocalization of Best1 is not an absolute feature of any individual bestrophinopathy, occurring in AVMD, BVMD, and ARB. Furthermore, some ARB mutants that do not also cause dominant disease cause mislocalization of Best1, indicating that mislocalization is not a cause of disease, and that absence of Best1 activity from the plasma membrane is tolerated. Lastly, we find that the ARB truncation mutants L174Qfs*57 and R200X can form oligomers with WT Best1, indicating that the first ∼174 amino acids of Best1 are sufficient for oligomerization to occur.
authors.affiliation: Physiological Sciences Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ 85724, USA; Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA. Electronic address: Johnson.Adiv@mayo.edu.
authors.forename: Adiv A
authors.initials: AA
authors.lastname: Johnson
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA. Electronic address: Lee.Yong@mayo.edu.
authors.forename: Yong-Suk
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Faculty of Life Sciences, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom. Electronic address: andrewchadburn@gmail.com.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Chadburn
authors.affiliation: Faculty of Life Sciences, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom. Electronic address: paolo.tammaro@pharm.ox.ac.uk.
authors.forename: Paolo
authors.initials: P
authors.lastname: Tammaro
authors.affiliation: Manchester Centre for Genomic Medicine, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom. Electronic address: Forbes.D.Manson@manchester.ac.uk.
authors.forename: Forbes D
authors.initials: FD
authors.lastname: Manson
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA. Electronic address: Marmorstein.Lihua@mayo.edu.
authors.forename: Lihua Y
authors.initials: LY
authors.lastname: Marmorstein
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA. Electronic address: Marmorstein.Alan@mayo.edu.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Marmorstein
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D000075002:Bestrophins; D015153:Blotting, Western; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism*; D015862:Choroid Diseases / Q000235:genetics / Q000378:metabolism; D004285:Dogs; D004594:Electrophysiology; D015785:Eye Diseases, Hereditary / Q000235:genetics* / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000378:metabolism; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells / Q000378:metabolism; D018613:Microscopy, Confocal; D020125:Mutation, Missense; D018408:Patch-Clamp Techniques; D055503:Protein Multimerization / Q000502:physiology*; D012162:Retinal Degeneration / Q000235:genetics / Q000378:metabolism; D012164:Retinal Diseases / Q000235:genetics* / Q000378:metabolism; D012174:Retinitis Pigmentosa / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D057826:Vitelliform Macular Dystrophy / Q000235:genetics / Q000378:metabolism
chemical_list: C113133:BEST1 protein, human; D001426:Bacterial Proteins; D000075002:Bestrophins; D018118:Chloride Channels; C485182:Cyan Fluorescent Protein; D005136:Eye Proteins; D005456:Fluorescent Dyes; D008164:Luminescent Proteins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins
keywords: MDCK; bestrophin; fluorescence resonance energy transfer; retinal pigment epithelium; retinitis pigmentosa; vitelliform dystrophy