title: C-terminal threonines and serines play distinct roles in the desensitization of rhodopsin, a G protein-coupled receptor.
abstract: Rod photoreceptors generate measurable responses to single-photon activation of individual molecules of the G protein-coupled receptor (GPCR), rhodopsin. Timely rhodopsin desensitization depends on phosphorylation and arrestin binding, which quenches G protein activation. Rhodopsin phosphorylation has been measured biochemically at C-terminal serine residues, suggesting that these residues are critical for producing fast, low-noise responses. The role of native threonine residues is unclear. We compared single-photon responses from rhodopsin lacking native serine or threonine phosphorylation sites. Contrary to expectation, serine-only rhodopsin generated prolonged step-like single-photon responses that terminated abruptly and randomly, whereas threonine-only rhodopsin generated responses that were only modestly slower than normal. We show that the step-like responses of serine-only rhodopsin reflect slow and stochastic arrestin binding. Thus, threonine sites play a privileged role in promoting timely arrestin binding and rhodopsin desensitization. Similar coordination of phosphorylation and arrestin binding may more generally permit tight control of the duration of GPCR activity.
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, United States.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Azevedo
authors.affiliation: Department of Ophthalmology, University of Washington, Seattle, United States.
authors.forename: Thuy
authors.initials: T
authors.lastname: Doan
authors.affiliation: Departments of Cell & Neurobiology and Ophthalmology, Zilkha Neurogenetic Institute, Keck School of Medicine of University of Southern California, Los Angeles, United States.
authors.forename: Hormoz
authors.initials: H
authors.lastname: Moaven
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, United States.
authors.forename: Iza
authors.initials: I
authors.lastname: Sokal
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, United States.
authors.forename: Faiza
authors.initials: F
authors.lastname: Baameur
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, United States.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Vishnivetskiy
authors.affiliation: Life Sciences Institute, Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, United States.
authors.forename: Kristoff T
authors.initials: KT
authors.lastname: Homan
authors.affiliation: Life Sciences Institute, Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, United States.
authors.forename: John J G
authors.initials: JJ
authors.lastname: Tesmer
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, United States.
authors.forename: Vsevolod V
authors.identifier: http://orcid.org/0000-0002-3950-5351
authors.initials: VV
authors.lastname: Gurevich
authors.affiliation: Departments of Cell & Neurobiology and Ophthalmology, Zilkha Neurogenetic Institute, Keck School of Medicine of University of Southern California, Los Angeles, United States.
authors.forename: Jeannie
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, United States.
authors.forename: Fred
authors.initials: F
authors.lastname: Rieke
mesh_terms: D000818:Animals; D019393:Arrestin / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism*
chemical_list: D019393:Arrestin; D043562:Receptors, G-Protein-Coupled; D013912:Threonine; D012694:Serine; D012243:Rhodopsin
keywords: G-protein-coupled receptor; G-protein-coupled receptor kinase; arrestin; biophysics; mouse; neuroscience; single-photon response; structural biology