title: GTPase acceleration as the rate-limiting step in Arabidopsis G protein-coupled sugar signaling.
abstract: Heterotrimeric G protein signaling is important for cell-proliferative and glucose-sensing signal transduction pathways in the model plant organism Arabidopsis thaliana. AtRGS1 is a seven-transmembrane, RGS domain-containing protein that is a putative membrane receptor for d-glucose. Here we show, by using FRET, that d-glucose alters the interaction between the AtGPA1 and AtRGS1 in vivo. AtGPA1 is a unique heterotrimeric G protein alpha subunit that is constitutively GTP-bound given its high spontaneous nucleotide exchange coupled with slow GTP hydrolysis. Analysis of a point mutation in AtRGS1 that abrogates GTPase-accelerating activity demonstrates that the regulation of AtGPA1 GTP hydrolysis mediates sugar signal transduction during Arabidopsis development, in contrast to animals where nucleotide exchange is the limiting step in the heterotrimeric G protein nucleotide cycle.
authors.affiliation: Department of Pharmacology, Lineberger Comprehensive Cancer Center and Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599-7365, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Johnston
authors.forename: J Philip
authors.initials: JP
authors.lastname: Taylor
authors.forename: Yajun
authors.initials: Y
authors.lastname: Gao
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Kimple
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Grigston
authors.forename: Jin-Gui
authors.initials: JG
authors.lastname: Chen
authors.forename: David P
authors.initials: DP
authors.lastname: Siderovski
authors.forename: Alan M
authors.initials: AM
authors.lastname: Jones
authors.forename: Francis S
authors.initials: FS
authors.lastname: Willard
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; C429765:GPA1 protein, Arabidopsis; D044385:GTP-Binding Protein alpha Subunits; D020690:GTPase-Activating Proteins; D021122:Protein Subunits; D020710:RGS Proteins; C477755:RGS1 protein, Arabidopsis; D020962:Heterotrimeric GTP-Binding Proteins; D005947:Glucose