Transducin: A Signaling Switch Regulated by Guanine Nucleotides

Ho, Yee-Kin; Hingorani, Vijay N.; Navon, Samuel E.; Fung, Bernard K.-K.

doi:10.1016/b978-0-12-152830-0.50008-6

Cited by 27 publications

(10 citation statements)

References 76 publications

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“…Gat is a member of the Gai/Gao family [31,32], which are all substrates for ADP ribosylation and thereby inactivation by pertussis toxin. Although both Gats are heterotrimeric, their b subunit composition also varies from rods to cones.…”

Section: Ga At the G Protein Of The Visual Pathwaymentioning

confidence: 99%

Wnt-frizzled signaling to G-protein-coupled effectors

Wang

Malbon

2004

Cellular and Molecular Life Sciences (CMLS)

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Wnt proteins signal via cell surface receptors termed Frizzleds. Frizzleds display many properties characteristic of members of the superfamily of G-protein-coupled receptors, including heptihelical hydropathy plots; an exofacial N-terminal region that is glycosylated; a cytoplasmic C-terminal region that includes canonical motifs for phosphorylation by protein kinase A, protein kinase C and casein kinase II; cytoplasmic domains that couple to heterotrimeric G proteins, as evidenced by a GTP-shift in receptor affinity; receptor-mediated responses sensitive to depletion of specific G protein subunits and receptor-mediated responses sensitive to bacterial toxins that target G proteins. Evidence from a variety of developmental systems demonstrates Wnt-Frizzled (Fz) signaling via pathways other than the Wnt/beta-catenin pathway linked to transcription controlled by Lef/Tcf. Prominent among these additional pathways is a Wnt-Fz pathway regulating intracellular [Ca(++)] and cyclic GMP levels. The essential role of heterotrimeric G proteins in Wnt-Fz signaling is highlighted.

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Section: Ga At the G Protein Of The Visual Pathwaymentioning

confidence: 99%

Wnt-frizzled signaling to G-protein-coupled effectors

Wang

Malbon

2004

Cellular and Molecular Life Sciences (CMLS)

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“…In vertebrate rod photoreceptors, rhodopsin phosphorylation has been studied extensively as a mechanism terminating the light-activated biochemical processes (1)(2)(3)6). In addition, phosphorylation of some proteins has been investigated, although little is known about the molecular roles of these proteins in the process of visual transduction.…”

mentioning

confidence: 99%

“…The hydrolysis of cGMP by phosphodiesterase (PDE) appears directly involved in the process of visual transduction in vertebrate photoreceptor rod outer segments (ROS) (1)(2)(3). Illumination of rhodopsin leads to activation of transducin, a G protein in ROS.…”

mentioning

confidence: 99%

“…The resulting fall in cytoplasmic cGMP concentration leads to the closure of cGMP-sensitive cation channels, causing the hyperpolarization of rod plasma membranes. PDE is composed of catalytic subunits (Pa, , 3) with Mr values of 89,000 and 87,000 and two inhibitory subunits (Pys) with Mr of 13,000 (1)(2)(3). The activation cascade offrog PDE has been described (4,5).…”

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confidence: 99%

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Phosphatidylinositol-stimulated phosphorylation of an inhibitory subunit of cGMP phosphodiesterase in vertebrate rod photoreceptors.

Hayashi

Lin

Matsumoto

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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An inhibitory subunit (Py) of cGMP phosphodiesterase from vertebrate rod photoreceptors (frog, toad, and bovine) was phosphorylated by cytosolic protein kinase(s) derived from intact frog rod outer segments. The phosphorylation offrog Py was stimulated by phosphatidylinositol but not by cAMP or cGMP. One-and two-dimensional gel electrophoresis revealed that 70-80% of Py was phosphorylated with 1 mol of phosphate per frog Py under optimal conditions. A peptide that derived from an active domain of bovine Py was also phosphorylated. Phosphorylation of frog Py was inhibited by addition of the peptide to the reaction mixture. Phosphorylation of frog Py was also inhibited by addition of transducin subunits or active (Py-less) cGMP phosphodiesterase. Okadaic acid, on the other hand, enhanced Py phosphorylation, suggesting the presence of protein phosphatase(s) in the cytosolic fraction. These data suggest another mechanism for the regulation of cGMP phosphodiesterase in vertebrate rod photoreceptors.

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“…The rod (GNAT1) and the cones (GNAT2) express differing, but homologous, forms of Gαt. Gαt is a member of the Gαi/Gαo family [28,29], which are all substrates for ADP ribosylation and are inactivated by treatment with pertussis toxin. After activation by rhodopsin, the GDP of the heterotrimer is exchanged for GTP and the Gαt-GTP diffuses and binds to a membrane-associated photoreceptorspecific cGMP PDE.…”

Section: Gαt 2 Cgmp Pdes (Phosphodiesterases) and The Visual Pathwaymentioning

confidence: 99%

PDE6 is an effector for the Wnt/Ca2+/cGMP-signalling pathway in development

Wang

Lee

Malbon

2004

Biochemical Society Transactions

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Wnt signalling in development operates via members of the Frizzleds, G-protein-coupled receptors that bind specific Wnt ligands and mediate signalling via distinct pathways. The Wnt/Ca(2+)/cGMP pathway mediated by Frizzled-2 was discovered recently. Activation of this pathway leads to increased intracellular concentrations of Ca(2+) and decreased intracellular concentrations of cGMP. The nature of the phosphodiesterase responsible for this Frizzled-2-mediated effect on cGMP levels was identified based on three separate criteria: (i) sensitivity to selective enzyme inhibitors, (ii) behaviour on chromatographic separation, and (ii) isolation by two-dimensional gels in tandem with direct mapping by MS of tryptic digests of the activity. On the basis of results from these three analyses, the cGMP-specific phosphodiesterase, PDE6, is demonstrated to be an effector for the Wnt/Ca(2+)/cGMP signalling pathway of development, which is mediated by Frizzled-2.

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Transducin: A Signaling Switch Regulated by Guanine Nucleotides

Cited by 27 publications

References 76 publications

Wnt-frizzled signaling to G-protein-coupled effectors

Wnt-frizzled signaling to G-protein-coupled effectors

Phosphatidylinositol-stimulated phosphorylation of an inhibitory subunit of cGMP phosphodiesterase in vertebrate rod photoreceptors.

PDE6 is an effector for the Wnt/Ca2+/cGMP-signalling pathway in development

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