title: Membrane glycoprotein M6a interacts with the micro-opioid receptor and facilitates receptor endocytosis and recycling.
abstract: Using a yeast two-hybrid screen, the neuronal membrane glycoprotein M6a, a member of the proteolipid protein family, was identified to be associated with the mu-opioid receptor (MOPr). Bioluminescence resonance energy transfer and co-immunoprecipitation experiments confirmed that M6a interacts agonist-independently with MOPr in human embryonic kidney 293 cells co-expressing MOPr and M6a. Co-expression of MOPr with M6a, but not with M6b or DM20, exists in many brain regions, further supporting a specific interaction between MOPr and M6a. After opioid treatment M6a co-internalizes and then co-recycles with MOPr to cell surface in transfected human embryonic kidney 293 cells. Moreover, the interaction of M6a and MOPr augments constitutive and agonist-dependent internalization as well as the recycling rate of mu-opioid receptors. On the other hand, overexpression of a M6a-negative mutant prevents mu-opioid receptor endocytosis, demonstrating an essential role of M6a in receptor internalization. In addition, we demonstrated the interaction of M6a with a number of other G protein-coupled receptors (GPCRs) such as the delta-opioid receptor, cannabinoid receptor CB1, and somatostatin receptor sst2A, suggesting that M6a might play a general role in the regulation of certain GPCRs. Taken together, these data provide evidence that M6a may act as a scaffolding molecule in the regulation of GPCR endocytosis and intracellular trafficking.
authors.affiliation: Department of Pharmacology and Toxicology, Otto von Guericke University, Magdeburg, Germany.
authors.forename: Dai-Fei
authors.initials: DF
authors.lastname: Wu
authors.forename: Thomas
authors.initials: T
authors.lastname: Koch
authors.forename: Ying-Jian
authors.initials: YJ
authors.lastname: Liang
authors.forename: Ralf
authors.initials: R
authors.lastname: Stumm
authors.forename: Stefan
authors.initials: S
authors.lastname: Schulz
authors.forename: Helmut
authors.initials: H
authors.lastname: Schröder
authors.forename: Volker
authors.initials: V
authors.lastname: Höllt
mesh_terms: D000818:Animals; D002460:Cell Line; D004705:Endocytosis; D031541:Fluorescence Resonance Energy Transfer; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D051381:Rats; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: C484159:Gpm6a protein, rat; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D017450:Receptors, Opioid, mu; D011994:Recombinant Proteins