Phosphorylation dynamics in a flg22-induced, G-protein dependent network reveals the RGS1 phosphatase

Mol Cell Proteomics. 2023 Dec 20:100705. doi: 10.1016/j.mcpro.2023.100705. Online ahead of print.ABSTRACTThe Microbe Associated Molecular Pattern flg22 is recognized in a FLAGELLIN-SENSITVE 2-dependent manner in root tip cells. Here, we show a rapid and massive change in protein abundance and phosphorylation state of the Arabidopsis root cell proteome in wildtype and a mutant deficient in heterotrimeric G-protein-coupled signaling. flg22-induced changes fall on proteins comprising a subset of this proteome, the heterotrimeric G protein interactome, and on highly populated hubs of the immunity network. Approximately 95% of the phosphorylation changes in the heterotrimeric G-protein interactome depend, at least partially, on a functional G protein complex. One member of this interactome is ATBα, a substrate subunit of a protein phosphatase 2A complex and an interactor to REGULATOR OF G SIGNALING 1 protein (AtRGS1), a flg22-phosphorylated, 7-transmembrane spanning modulator of the nucleotide-binding state of the core G-protein complex. A null mutation of ATBα strongly increases basal endocytosis of AtRGS1. AtRGS1 steady-state protein level is lower in the atbα mutant in a proteasome-dependent manner. We propose that phosphorylation-dependent endocytosis of AtRGS1 is part of the mechanism to degrade AtRGS1 thus sustaining activation of the heterotrimeric G protein complex required for regulation of system dynamics in innate immunity. The PP2A(ATBα) complex is a critical regul...
Source: Molecular and Cellular Proteomics : MCP - Category: Molecular Biology Authors: Source Type: research