TY - JOUR
T1 - Disease-causing mutations associated with four bestrophinopathies exhibit disparate effects on the localization, but not the oligomerization, of Bestrophin-1
AU - Johnson, Adiv A.
AU - Lee, Yong Suk
AU - Chadburn, Andrew J.
AU - Tammaro, Paolo
AU - Manson, Forbes D.
AU - Marmorstein, Lihua Y.
AU - Marmorstein, Alan D.
N1 - Funding Information:
This work was supported by grants from the NIH ( EY13160 to ADM, EY014465 to LYM, and NIGMS 5T32 GM08400 to Graduate Training in Systems and Integrative Physiology at the University of Arizona, Tucson, AZ), the Macula Vision Research Foundation , and unrestricted grants from Research to Prevent Blindness to the Departments of Ophthalmology at the University of Arizona, Tucson, AZ, and the Mayo Clinic, Rochester, MN.
PY - 2014/4
Y1 - 2014/4
N2 - 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.
AB - 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.
KW - Bestrophin
KW - Fluorescence resonance energy transfer
KW - MDCK
KW - Retinal pigment epithelium
KW - Retinitis pigmentosa
KW - Vitelliform dystrophy
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U2 - 10.1016/j.exer.2014.02.006
DO - 10.1016/j.exer.2014.02.006
M3 - Article
C2 - 24560797
AN - SCOPUS:84895965121
SN - 0014-4835
VL - 121
SP - 74
EP - 85
JO - Experimental Eye Research
JF - Experimental Eye Research
ER -