title: KCTD Hetero-oligomers Confer Unique Kinetic Properties on Hippocampal GABAB Receptor-Induced K+ Currents.
abstract: GABABreceptors are the G-protein coupled receptors for the main inhibitory neurotransmitter in the brain, GABA. GABABreceptors were shown to associate with homo-oligomers of auxiliary KCTD8, KCTD12, KCTD12b, and KCTD16 subunits (named after their T1 K+-channel tetramerization domain) that regulate G-protein signaling of the receptor. Here we provide evidence that GABABreceptors also associate with hetero-oligomers of KCTD subunits. Coimmunoprecipitation experiments indicate that two-thirds of the KCTD16 proteins in the hippocampus of adult mice associate with KCTD12. We show that the KCTD proteins hetero-oligomerize through self-interacting T1 and H1 homology domains. Bioluminescence resonance energy transfer measurements in live cells reveal that KCTD12/KCTD16 hetero-oligomers associate with both the receptor and the G-protein. Electrophysiological experiments demonstrate that KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties on G-protein-activated Kir3 currents. During prolonged receptor activation (one min) KCTD12/KCTD16 hetero-oligomers produce moderately desensitizing fast deactivating K+currents, whereas KCTD12 and KCTD16 homo-oligomers produce strongly desensitizing fast deactivating currents and nondesensitizing slowly deactivating currents, respectively. During short activation (2 s) KCTD12/KCTD16 hetero-oligomers produce nondesensitizing slowly deactivating currents. Electrophysiological recordings from hippocampal neurons of KCTD knock-out mice are consistent with these findings and indicate that KCTD12/KCTD16 hetero-oligomers increase the duration of slow IPSCs. In summary, our data demonstrate that simultaneous assembly of distinct KCTDs at the receptor increases the molecular and functional repertoire of native GABABreceptors and modulates physiologically induced K+current responses in the hippocampus.
  
  
  
  The KCTD proteins 8, 12, and 16 are auxiliary subunits of GABABreceptors that differentially regulate G-protein signaling of the receptor. The KCTD proteins are generally assumed to function as homo-oligomers. Here we show that the KCTD proteins also assemble hetero-oligomers in all possible dual combinations. Experiments in live cells demonstrate that KCTD hetero-oligomers form at least tetramers and that these tetramers directly interact with the receptor and the G-protein. KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties to GABABreceptor-induced Kir3 currents in heterologous cells. KCTD12/KCTD16 hetero-oligomers are abundant in the hippocampus, where they prolong the duration of slow IPSCs in pyramidal cells. Our data therefore support that KCTD hetero-oligomers modulate physiologically induced K+current responses in the brain.
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Fritzius
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.|Institute of Experimental Medicine, ASCR, 14220 Prague 4-Krc, Czech Republic, and.
authors.forename: Rostislav
authors.identifier: 0000-0003-4978-7556
authors.initials: R
authors.lastname: Turecek
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
authors.forename: Riad
authors.initials: R
authors.lastname: Seddik
authors.affiliation: Department of Biochemistry, Institute for Research in Immunology and Cancer, Université de Montréal, Montreal, Quebec H3C 3J7, Canada.
authors.forename: Hiroyuki
authors.identifier: 0000-0003-4965-0883
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
authors.forename: Jim
authors.initials: J
authors.lastname: Tiao
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
authors.forename: Pascal D
authors.initials: PD
authors.lastname: Rem
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
authors.forename: Michaela
authors.identifier: 0000-0001-6319-1527
authors.initials: M
authors.lastname: Metz
authors.affiliation: Institute of Experimental Medicine, ASCR, 14220 Prague 4-Krc, Czech Republic, and.
authors.forename: Michaela
authors.initials: M
authors.lastname: Kralikova
authors.affiliation: Department of Biochemistry, Institute for Research in Immunology and Cancer, Université de Montréal, Montreal, Quebec H3C 3J7, Canada.
authors.forename: Michel
authors.identifier: 0000-0003-1128-0100
authors.initials: M
authors.lastname: Bouvier
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Gassmann
authors.affiliation: Department of Biomedicine, Institute of Physiology, University of Basel, 4056 Basel, Switzerland, bernhard.bettler@unibas.ch.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Bettler
mesh_terms: D000818:Animals; D001923:Brain Chemistry / Q000235:genetics; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D055724:Electrophysiological Phenomena / Q000235:genetics; D019706:Excitatory Postsynaptic Potentials / Q000235:genetics; D005260:Female; D007700:Kinetics; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D018080:Receptors, GABA-B / Q000235:genetics* / Q000378:metabolism*; D054340:Receptors, KIR / Q000378:metabolism
chemical_list: D015221:Potassium Channels; D043562:Receptors, G-Protein-Coupled; D018080:Receptors, GABA-B; D054340:Receptors, KIR
keywords: G-protein coupled receptor; GABA-B; GPCR; KCTD12; KCTD16; Kir3