Phosphatidic acid binding inhibits RGS1 activity to affect specific signaling pathways in Arabidopsis.
Modulation of the active versus inactive forms of the Gα protein is critical for the signaling processes mediated by the heterotrimeric G-protein complex. We have recently established that in Arabidopsis, the regulator of G-protein signaling (RGS1) protein and a lipid-hydrolyzing enzyme, phospholipase Dα1 (PLDα1), both act as GTPase-activity accelerating proteins (GAPs) for the Gα protein to attenuate its activity. RGS1 and PLDα1 interact with each other, and RGS1 inhibits the activity of PLDα1 during regulation of a subset of responses. In this study, we present evidence that this regulation is bidirectional. Phosphatidic acid (PA), a second messenger typically derived from the lipid-hydrolyzing activity of PLDα1, is a molecular target of RGS1. PA binds and inhibits the GAP activity of RGS1. A conserved lysine residue in RGS1 (Lys259) is directly involved in RGS1-PA binding. Introduction of this RGS1 protein variant in the rgs1 mutant background makes plants hypersensitive to a subset of abscisic acid-mediated responses. Our data point to the existence of negative feedback loops between these two regulatory proteins that precisely modulate the level of active Gα, consequently generating a highly controlled signal-response output.
Donald Danforth Plant Science Center, 975 N. Warson Road, St Louis, MO, 63132, USA.
Swarup
S
Roy Choudhury
Donald Danforth Plant Science Center, 975 N. Warson Road, St Louis, MO, 63132, USA.
Sona
S
Pandey
D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism* / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism; D011485:Protein Binding; D020710:RGS Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
D029681:Arabidopsis Proteins; D044385:GTP-Binding Protein alpha Subunits; D010712:Phosphatidic Acids; D020710:RGS Proteins; C477755:RGS1 protein, Arabidopsis; D000040:Abscisic Acid; D010739:Phospholipase D

Arabidopsis thaliana
; G-protein cycle regulation; GTPase activity accelerating proteins; abscisic acid; heterotrimeric G-proteins; phosphatidic acid; phosphatidic acid binding; phospholipase Dα1; regulator of G-protein signaling