title: The inhibitory gamma subunit of the type 6 retinal cGMP phosphodiesterase functions to link c-Src and G-protein-coupled receptor kinase 2 in a signaling unit that regulates p42/p44 mitogen-activated protein kinase by epidermal growth factor.
abstract: The inhibitory gamma subunit of the retinal photoreceptor type 6 cGMP phosphodiesterase (PDEgamma) is phosphorylated by G-protein-coupled receptor kinase 2 on threonine 62 and regulates the epidermal growth factor- dependent stimulation of p42/p44 mitogen-activated protein kinase in human embryonic kidney 293 cells. We report here that PDEgamma is in a pre-formed complex with c-Src and that stimulation of cells with epidermal growth factor promotes the association of GRK2 with this complex. c-Src has a critical role in the stimulation of the p42/p44 mitogen-activated protein kinase cascade by epidermal growth factor, because c-Src inhibitors block the activation of this kinase by the growth factor. Mutation of Thr-62 (to Ala) in PDEgamma produced a GRK2 phosphorylation-resistant mutant that was less effective in associating with GRK2 in response to epidermal growth factor and did not potentiate the stimulation of p42/p44 mitogen-activated protein kinase by this growth factor. The transcript for a short splice variant version of PDEgamma lacking the Thr-62 phosphorylation site is also expressed in certain mammalian cells and, in common with the Thr-62 mutant, failed to potentiate the stimulatory effect of epidermal growth factor on p42/p44 mitogen-activated protein kinase. The mutation of Thr-22 (to Ala) in PDEgamma, which is a site for phosphorylation by p42/p44 mitogen-activated protein kinase, resulted in a prolonged activation of p42/p44 mitogen-activated protein kinase by epidermal growth factor, suggesting a role for this phosphorylation event in the negative feedback control of PDEgamma.
authors.affiliation: Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 ONR, Scotland, United Kingdom.
authors.forename: Kah Fei
authors.initials: KF
authors.lastname: Wan
authors.forename: Balwinder S
authors.initials: BS
authors.lastname: Sambi
authors.forename: Rothwelle
authors.initials: R
authors.lastname: Tate
authors.forename: Catherine
authors.initials: C
authors.lastname: Waters
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Pyne
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000737:chemistry* / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D017398:Alternative Splicing; D001665:Binding Sites; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; D004815:Epidermal Growth Factor / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D006801:Humans; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013917:Thrombin / Q000378:metabolism; D014162:Transfection; D051552:beta-Adrenergic Receptor Kinases; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D011506:Proteins; D011994:Recombinant Proteins; D004815:Epidermal Growth Factor; D019061:src-Family Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; C517431:PDE6B protein, human; D013917:Thrombin