title: Heterodimerization is required for the formation of a functional GABA(B) receptor.
abstract: GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the mammalian central nervous system, where it exerts its effects through ionotropic (GABA(A/C)) receptors to produce fast synaptic inhibition and metabotropic (GABA(B)) receptors to produce slow, prolonged inhibitory signals. The gene encoding a GABA(B) receptor (GABA(B)R1) has been cloned; however, when expressed in mammalian cells this receptor is retained as an immature glycoprotein on intracellular membranes and exhibits low affinity for agonists compared with the endogenous receptor on brain membranes. Here we report the cloning of a complementary DNA encoding a new subtype of the GABAB receptor (GABA(B)R2), which we identified by mining expressed-sequence-tag databases. Yeast two-hybrid screening showed that this new GABA(B)R2-receptor subtype forms heterodimers with GABA(B)R1 through an interaction at their intracellular carboxy-terminal tails. Upon expression with GABA(B)R2 in HEK293T cells, GABA(B)R1 is terminally glycosylated and expressed at the cell surface. Co-expression of the two receptors produces a fully functional GABA(B) receptor at the cell surface; this receptor binds GABA with a high affinity equivalent to that of the endogenous brain receptor. These results indicate that, in vivo, functional brain GABA(B) receptors may be heterodimers composed of GABA(B)R1 and GABA(B)R2.
authors.affiliation: Receptor Systems, Molecular Pharmacology Unit, GlaxoWellcome, Medicines Research Centre, Stevenage, Hertfordshire, UK.
authors.forename: J H
authors.initials: JH
authors.lastname: White
authors.forename: A
authors.initials: A
authors.lastname: Wise
authors.forename: M J
authors.initials: MJ
authors.lastname: Main
authors.forename: A
authors.initials: A
authors.lastname: Green
authors.forename: N J
authors.initials: NJ
authors.lastname: Fraser
authors.forename: G H
authors.initials: GH
authors.lastname: Disney
authors.forename: A A
authors.initials: AA
authors.lastname: Barnes
authors.forename: P
authors.initials: P
authors.lastname: Emson
authors.forename: S M
authors.initials: SM
authors.lastname: Foord
authors.forename: F H
authors.initials: FH
authors.lastname: Marshall
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002531:Cerebellum / Q000378:metabolism; D003001:Cloning, Molecular; D019281:Dimerization; D004926:Escherichia coli; D006031:Glycosylation; D006801:Humans; D008969:Molecular Sequence Data; D051381:Rats; D018079:Receptors, GABA; D011963:Receptors, GABA-A / Q000737:chemistry / Q000235:genetics*; D018080:Receptors, GABA-B; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D014162:Transfection
chemical_list: C485503:GABBR2 protein, human; C116566:Gabbr2 protein, rat; D018079:Receptors, GABA; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B