title: Phosphorylation of G protein-coupled receptor kinase 1 (GRK1) is regulated by light but independent of phototransduction in rod photoreceptors.
abstract: Phosphorylation of rhodopsin by G protein-coupled receptor kinase 1 (GRK1, or rhodopsin kinase) is critical for the deactivation of the phototransduction cascade in vertebrate photoreceptors. Based on our previous studies in vitro, we predicted that Ser(21) in GRK1 would be phosphorylated by cAMP-dependent protein kinase (PKA) in vivo. Here, we report that dark-adapted, wild-type mice demonstrate significantly elevated levels of phosphorylated GRK1 compared with light-adapted animals. Based on comparatively slow half-times for phosphorylation and dephosphorylation, phosphorylation of GRK1 by PKA is likely to be involved in light and dark adaptation. In mice missing the gene for adenylyl cyclase type 1, levels of phosphorylated GRK1 were low in retinas from both dark- and light-adapted animals. These data are consistent with reports that cAMP levels are high in the dark and low in the light and also indicate that cAMP generated by adenylyl cyclase type 1 is required for phosphorylation of GRK1 on Ser(21). Surprisingly, dephosphorylation was induced by light in mice missing the rod transducin α-subunit. This result indicates that phototransduction does not play a direct role in the light-dependent dephosphorylation of GRK1.
authors.affiliation: Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina 27599-7090, USA.
authors.forename: Shoji
authors.initials: S
authors.lastname: Osawa
authors.forename: Rebecca
authors.initials: R
authors.lastname: Jo
authors.forename: Yubin
authors.initials: Y
authors.lastname: Xiong
authors.forename: Boris
authors.initials: B
authors.lastname: Reidel
authors.forename: Nomingerel
authors.initials: N
authors.lastname: Tserentsoodol
authors.forename: Vadim Y
authors.initials: VY
authors.lastname: Arshavsky
authors.forename: P Michael
authors.initials: PM
authors.lastname: Iuvone
authors.forename: Ellen R
authors.initials: ER
authors.lastname: Weiss
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D003623:Dark Adaptation / Q000502:physiology* / Q000528:radiation effects; D051606:G-Protein-Coupled Receptor Kinase 1 / Q000235:genetics / Q000378:metabolism*; D008027:Light; D055537:Light Signal Transduction / Q000502:physiology* / Q000528:radiation effects; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation / Q000528:radiation effects; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*; D015293:Transducin / Q000235:genetics / Q000378:metabolism
chemical_list: D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D051606:G-Protein-Coupled Receptor Kinase 1; C496762:Grk1 protein, mouse; D015293:Transducin; D000262:Adenylyl Cyclases; C106670:adenylyl cyclase 1