title: Farnesylation of retinal transducin underlies its translocation during light adaptation.
abstract: G proteins are posttranslationally modified by isoprenylation: either farnesylation or geranylgeranylation. The gamma subunit of retinal transducin (Talpha/Tbetagamma) is selectively farnesylated, and the farnesylation is required for light signaling mediated by transducin in rod cells. However, whether and how this selective isoprenylation regulates cellular functions remain poorly understood. Here we report that knockin mice expressing geranylgeranylated Tgamma showed normal rod responses to dim flashes under dark-adapted conditions but exhibited impaired properties in light adaptation. Of note, geranylgeranylation of Tgamma suppressed light-induced transition of Tbetagamma from membrane to cytosol, and also attenuated its light-dependent translocation from the outer segment to the inner region, an event contributing to retinal light adaptation. These results indicate that, while the farnesylation of transducin is interchangeable with the geranylgeranylation in terms of the light signaling, the selective farnesylation is important for visual sensitivity regulation by providing sufficient but not excessive membrane anchoring of Tbetagamma.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kassai
authors.forename: Atsu
authors.initials: A
authors.lastname: Aiba
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nakao
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakamura
authors.forename: Motoya
authors.initials: M
authors.lastname: Katsuki
authors.forename: Wei-Hong
authors.initials: WH
authors.lastname: Xiong
authors.forename: King-Wai
authors.initials: KW
authors.lastname: Yau
authors.forename: Hiroo
authors.initials: H
authors.lastname: Imai
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Shichida
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Satomi
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Takao
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Okano
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Fukada
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D015350:Contrast Sensitivity / Q000235:genetics; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010775:Photic Stimulation; D017368:Protein Prenylation / Q000235:genetics*; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*; D015293:Transducin / Q000235:genetics / Q000378:metabolism*; D014785:Vision, Ocular / Q000502:physiology*
chemical_list: D017261:Glycosylphosphatidylinositols; D021122:Protein Subunits; D015293:Transducin