title: A crucial role of the RGS domain in trans-Golgi network export of AtRGS1 in the protein secretory pathway.
abstract: The secretory pathway is responsible for the transport of newly synthesized transmembrane proteins from the endoplasmic reticulum to their destinations via the Golgi/trans-Golgi network (TGN). Cargo proteins at each station are actively sorted by specific sorting signals on the cargo and the corresponding coat complexes. Here, we used the Arabidopsis regulator of G-protein signaling (AtRGS1), which contains an N-terminal potentially sensing glucose seven-transmembrane domain and a C-terminal RGS domain, as a model to uncover sorting motifs required for its cell surface expression. Expression of wild-type and truncated or mutated AtRGS1 fluorescent fusion proteins identified two cysteine residues in the extracellular N-terminus that are essential for endoplasmic reticulum exit and/or correct folding of AtRGS1. The linker between the seven-transmembrane and RGS domains contains an endoplasmic reticulum export signal, whereas the C-terminus is dispensable for the plasma membrane expression of AtRGS1. Interestingly, deletion of the RGS domain results in Golgi/TGN localization of the truncated AtRGS1. Further analysis using site-directed mutagenesis showed that a tyrosine-based motif embedded in the RGS domain is essential for Golgi/TGN export of AtRGS1. These results reveal a new role for the RGS domain in regulating AtRGS1 trafficking from the Golgi/TGN to the plasma membrane and explain the interaction between the seven-transmembrane and RGS domains.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Feng Lin Road, Shanghai 200032, China.
authors.forename: Guangzhen
authors.initials: G
authors.lastname: Hu
authors.forename: Yiping
authors.initials: Y
authors.lastname: Suo
authors.forename: Jirong
authors.initials: J
authors.lastname: Huang
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D003545:Cysteine / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D049790:Nuclear Export Signals; D020710:RGS Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D055571:Secretory Pathway; D021601:trans-Golgi Network / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D049790:Nuclear Export Signals; D020710:RGS Proteins; C477755:RGS1 protein, Arabidopsis; D003545:Cysteine
keywords: Arabidopsis.; AtRGS1; G-proteins; RGS domain; TGN sorting signal