title: Endocytosis of the seven-transmembrane RGS1 protein activates G-protein-coupled signalling in Arabidopsis.
abstract: Signal transduction typically begins by ligand-dependent activation of a concomitant partner that is otherwise in its resting state. However, in cases where signal activation is constitutive by default, the mechanism of regulation is unknown. The Arabidopsis thaliana heterotrimeric Gα protein self-activates without accessory proteins, and is kept in its resting state by the negative regulator, AtRGS1 (regulator of G-protein signalling 1), which is the prototype of a seven-transmembrane receptor fused with an RGS domain. Endocytosis of AtRGS1 by ligand-dependent endocytosis physically uncouples the GTPase-accelerating activity of AtRGS1 from the Gα protein, permitting sustained activation. Phosphorylation of AtRGS1 by AtWNK8 kinase causes AtRGS1 endocytosis, required for both G-protein-mediated sugar signalling and cell proliferation. In animals, receptor endocytosis results in signal desensitization, whereas in plants, endocytosis results in signal activation. These findings reveal how different organisms rearrange a regulatory system to result in opposite outcomes using similar phosphorylation-dependent endocytosis mechanisms.
authors.affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Urano
authors.forename: Nguyen
authors.initials: N
authors.lastname: Phan
authors.forename: Janice C
authors.initials: JC
authors.lastname: Jones
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Jirong
authors.initials: J
authors.lastname: Huang
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Grigston
authors.forename: J Philip
authors.initials: JP
authors.lastname: Taylor
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D049109:Cell Proliferation; D004705:Endocytosis / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020710:RGS Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D020710:RGS Proteins; C477755:RGS1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; C508913:WNK8 protein, Arabidopsis; D019204:GTP-Binding Proteins