title: Phosrestin I undergoes the earliest light-induced phosphorylation by a calcium/calmodulin-dependent protein kinase in Drosophila photoreceptors.
abstract: Activation of PI-PLC initiates two independent branches of protein phosphorylation cascades catalyzed by either PKC or Ca2+/calmodulin-dependent protein kinase (CaMK). We find that phosrestin I (PRI), a Drosophila homolog of vertebrate photoreceptor arrestin, undergoes light-induced phosphorylation on a subsecond time scale which is faster than that of any other protein in vivo. We determine that a CaMK activity is responsible for in vitro PRI phosphorylation at Ser366 in the C-terminal tryptic segment, MetLysSer(P)IleGluGlnHisArg, in which Ser(P) represents phosphoserine366. We also demonstrate that Ser366 is the phosphorylation site of PRI in vivo by identifying the molecular species resulting from in-gel tryptic digestion of purified phospho-PRI using HPLC-electrospray ionization tandem quadrupole mass spectroscopy. From these data, we conclude that the CaMK pathway, not the PKC pathway, is responsible for the earliest protein phosphorylation event following activation of PI-PLC in living Drosophila photoreceptors.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
authors.forename: H
authors.initials: H
authors.lastname: Matsumoto
authors.forename: B T
authors.initials: BT
authors.lastname: Kurien
authors.forename: Y
authors.initials: Y
authors.lastname: Takagi
authors.forename: E S
authors.initials: ES
authors.lastname: Kahn
authors.forename: T
authors.initials: T
authors.lastname: Kinumi
authors.forename: N
authors.initials: N
authors.lastname: Komori
authors.forename: T
authors.initials: T
authors.lastname: Yamada
authors.forename: F
authors.initials: F
authors.lastname: Hayashi
authors.forename: K
authors.initials: K
authors.lastname: Isono
authors.forename: W L
authors.initials: WL
authors.lastname: Pak
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000737:chemistry; D019390:Arrestins; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D003624:Darkness; D004330:Drosophila; D005136:Eye Proteins / Q000737:chemistry; D007301:Insect Hormones / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism* / Q000528:radiation effects; D011489:Protein Denaturation; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid; D000071557:beta-Arrestins
chemical_list: D000941:Antigens; D019390:Arrestins; D005136:Eye Proteins; D007301:Insect Hormones; D010446:Peptide Fragments; D010750:Phosphoproteins; D000071557:beta-Arrestins; D010768:Phosphoserine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase