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Dynamic Regulation of a GPCR-Tetraspanin-G Protein Complex on Intact Cells: Central Role of CD81 in Facilitating GPR56-Gαq/11 Association
Journal article   Open access   Peer reviewed

Dynamic Regulation of a GPCR-Tetraspanin-G Protein Complex on Intact Cells: Central Role of CD81 in Facilitating GPR56-Gαq/11 Association

Kevin D Little, Martin E Hemler and Christopher S Stipp
Molecular biology of the cell, Vol.15(5), pp.2375-2387
2004
DOI: 10.1091/mbc.E03-12-0886
PMCID: PMC404030
PMID: 15004227
url
https://doi.org/10.1091/mbc.E03-12-0886View
Published (Version of record) Open Access

Abstract

By means of a variety of intracellular scaffolding proteins, a vast number of heterotrimeric G protein-coupled receptors (GPCRs) may achieve specificity in signaling through a much smaller number of heterotrimeric G proteins. Members of the tetraspanin family organize extensive complexes of cell surface proteins and thus have the potential to act as GPCR scaffolds; however, tetraspanin-GPCR complexes had not previously been described. We now show that a GPCR, GPR56/TM7XN1, and heterotrimeric G protein subunits, Galpha(q), Galpha(11), and Gbeta, associate specifically with tetraspanins and CD81, but not with other tetraspanins. CD9 Complexes of GPR56 with CD9 and CD81 remained intact when fully solubilized and were resistant to cholesterol depletion. Hence they do not depend on detergent-insoluble, raft-like membrane microdomains for stability. A central role for CD81 in promoting or stabilizing a GPR56-CD81-Galpha(q/11) complex was revealed by CD81 immunodepletion and reexpression experiments. Finally, antibody engagement of cell surface CD81 or cell activation with phorbol ester revealed two distinct mechanisms by which GPR56-CD81-Galpha(q/11) complexes can be dynamically regulated. These data reveal a potential role for tetraspanins CD9 and CD81 as GPCR scaffolding proteins.

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