Spatial regulation of Galphai protein signaling in clathrin-coated membrane microdomains containing GAIP

Mol Pharmacol. 2003 Jul;64(1):11-20. doi: 10.1124/mol.64.1.11.

Abstract

Regulators of G-protein signaling (RGS) proteins are GTPase-activating proteins (GAPs) that bind to Galpha subunits and attenuate G protein signaling, but where these events occur in the cell is not yet established. Here we investigated, by immunofluorescence labeling and deconvolution analysis, the site at which endogenous Galpha-interacting protein (GAIP) (RGS19) binds to Galphai3-YFP and its fate after activation of delta-opioid receptor (DOR). In the absence of agonist, GAIP is spatially segregated from Galphai3 and DOR in clathrin-coated domains (CCPs) of the cell membrane (PM), whereas Galphai3-YPF and DOR are located in non-clathrin-coated microdomains of the PM. Upon addition of agonist, Galphai3 partially colocalizes with GAIP in CCPs at the PM. When endocytosis is blocked by expression of a dynamin mutant [dyn(K44A)], there is a striking overlap in the distribution of DOR and Galphai3-YFP with GAIP in CCPs. Moreover, Galphai3-YFP and GAIP form a coprecipitable complex. Our results support a model whereby, after agonist addition, DOR and Galphai3 move together into CCPs where Galphai3 and GAIP meet and turn off G protein signaling. Subsequently, Galphai3 returns to non-clathrin-coated microdomains of the PM, GAIP remains stably associated with CCPs, and DOR is internalized via clathrin-coated vesicles. This constitutes a novel mechanism for regulation of Galpha signaling through spatial segregation of a GAP in clathrin-coated pits.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Protein Complex 2 / metabolism
  • Bacterial Proteins / chemistry
  • Cells, Cultured
  • Clathrin / metabolism*
  • Coated Vesicles / metabolism
  • Dynamins / metabolism
  • Endosomes / metabolism
  • GTP-Binding Protein alpha Subunits, Gi-Go*
  • GTP-Binding Proteins / metabolism
  • GTPase-Activating Proteins / metabolism
  • Heterotrimeric GTP-Binding Proteins / metabolism*
  • Humans
  • Luminescent Proteins / chemistry
  • Membrane Microdomains / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • RGS Proteins
  • Receptors, Opioid, delta / metabolism
  • Signal Transduction / physiology*

Substances

  • Adaptor Protein Complex 2
  • Bacterial Proteins
  • Clathrin
  • GTPase-Activating Proteins
  • Luminescent Proteins
  • Phosphoproteins
  • RGS Proteins
  • Receptors, Opioid, delta
  • regulator of G-protein signalling 19
  • yellow fluorescent protein, Bacteria
  • GTP-Binding Proteins
  • GNAI3 protein, human
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • Heterotrimeric GTP-Binding Proteins
  • Dynamins