title: Differential light-induced responses in sectorial inherited retinal degeneration.
abstract: Retinitis pigmentosa (RP) is a group of genetically and clinically heterogeneous inherited degenerative retinopathies caused by abnormalities of photoreceptors or retinal pigment epithelium in the retina leading to progressive sight loss. Rhodopsin is the prototypical G-protein-coupled receptor located in the vertebrate retina and is responsible for dim light vision. Here, novel M39R and N55K variants were identified as causing an intriguing sector phenotype of RP in affected patients, with selective degeneration in the inferior retina. To gain insights into the molecular aspects associated with this sector RP phenotype, whose molecular mechanism remains elusive, the mutations were constructed by site-directed mutagenesis, expressed in heterologous systems, and studied by biochemical, spectroscopic, and functional assays. M39R and N55K opsins had variable degrees of chromophore regeneration when compared with WT opsin but showed no gross structural misfolding or altered trafficking. M39R showed a faster rate for transducin activation than WT rhodopsin with a faster metarhodopsinII decay, whereas N55K presented a reduced activation rate and an altered photobleaching pattern. N55K also showed an altered retinal release from the opsin binding pocket upon light exposure, affecting its optimal functional response. Our data suggest that these sector RP mutations cause different protein phenotypes that may be related to their different clinical progression. Overall, these findings illuminate the molecular mechanisms of sector RP associated with rhodopsin mutations.
authors.affiliation: From the Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Rambla de Sant Nebridi 22, 08222 Terrassa, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Ramon
authors.affiliation: the Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
authors.forename: Arnau
authors.initials: A
authors.lastname: Cordomí
authors.affiliation: the University College London Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, United Kingdom, and.
authors.forename: Mònica
authors.initials: M
authors.lastname: Aguilà
authors.affiliation: From the Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Rambla de Sant Nebridi 22, 08222 Terrassa, Spain.
authors.forename: Sundaramoorthy
authors.initials: S
authors.lastname: Srinivasan
authors.affiliation: From the Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Rambla de Sant Nebridi 22, 08222 Terrassa, Spain.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Dong
authors.affiliation: the University College London Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, United Kingdom, and the Moorfields Eye Hospital, London EC1V 2PD, United Kingdom.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Moore
authors.affiliation: the University College London Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, United Kingdom, and the Moorfields Eye Hospital, London EC1V 2PD, United Kingdom.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Webster
authors.affiliation: the University College London Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, United Kingdom, and.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Cheetham
authors.affiliation: From the Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Rambla de Sant Nebridi 22, 08222 Terrassa, Spain, pere.garriga@upc.edu.
authors.forename: Pere
authors.initials: P
authors.lastname: Garriga
mesh_terms: D000328:Adult; D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D005260:Female; D006801:Humans; D007700:Kinetics; D008875:Middle Aged; D020125:Mutation, Missense; D055550:Protein Stability / Q000528:radiation effects; D021381:Protein Transport; D012174:Retinitis Pigmentosa / Q000235:genetics*; D012243:Rhodopsin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D012243:Rhodopsin
keywords: G-protein-coupled Receptor; Light Exposure; Protein Stability; Protein Structure; Retinal Degeneration; Rhodopsin; Signal Transduction; Transducin; Visual Pigments