title: Phospho-dependent binding of the clathrin AP2 adaptor complex to GABAA receptors regulates the efficacy of inhibitory synaptic transmission.
abstract: The efficacy of synaptic inhibition depends on the number of gamma-aminobutyric acid type A receptors (GABA(A)Rs) expressed on the cell surface of neurons. The clathrin adaptor protein 2 (AP2) complex is a critical regulator of GABA(A)R endocytosis and, hence, surface receptor number. Here, we identify a previously uncharacterized atypical AP2 binding motif conserved within the intracellular domains of all GABA(A)R beta subunit isoforms. This AP2 binding motif (KTHLRRRSSQLK in the beta3 subunit) incorporates the major sites of serine phosphorylation within receptor beta subunits, and phosphorylation within this site inhibits AP2 binding. Furthermore, by using surface plasmon resonance, we establish that a peptide (pepbeta3) corresponding to the AP2 binding motif in the GABA(A)R beta3 subunit binds to AP2 with high affinity only when dephosphorylated. Moreover, the pepbeta3 peptide, but not its phosphorylated equivalent (pepbeta3-phos), enhanced the amplitude of miniature inhibitory synaptic current and whole cell GABA(A)R current. These effects of pepbeta3 on GABA(A)R current were occluded by inhibitors of dynamin-dependent endocytosis supporting an action of pepbeta3 on GABA(A)R endocytosis. Therefore phospho-dependent regulation of AP2 binding to GABA(A)Rs provides a mechanism to specify receptor cell surface number and the efficacy of inhibitory synaptic transmission.
authors.affiliation: Department of Physiology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Josef T
authors.initials: JT
authors.lastname: Kittler
authors.forename: Guojun
authors.initials: G
authors.lastname: Chen
authors.forename: Stephan
authors.initials: S
authors.lastname: Honing
authors.forename: Yury
authors.initials: Y
authors.lastname: Bogdanov
authors.forename: Kristina
authors.initials: K
authors.lastname: McAinsh
authors.forename: I Lorena
authors.initials: IL
authors.lastname: Arancibia-Carcamo
authors.forename: Jasmina N
authors.initials: JN
authors.lastname: Jovanovic
authors.forename: Menelas N
authors.initials: MN
authors.lastname: Pangalos
authors.forename: Volker
authors.initials: V
authors.lastname: Haucke
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yan
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Moss
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000235:genetics* / Q000502:physiology; D000818:Animals; D004705:Endocytosis / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D018079:Receptors, GABA / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D033962:Adaptor Protein Complex 2; D018079:Receptors, GABA