title: GABAB receptor phosphorylation regulates KCTD12-induced K⁺ current desensitization.
abstract: GABAB receptors assemble from GABAB1 and GABAB2 subunits. GABAB2 additionally associates with auxiliary KCTD subunits (named after their K(+) channel tetramerization-domain). GABAB receptors couple to heterotrimeric G-proteins and activate inwardly-rectifying K(+) channels through the βγ subunits released from the G-protein. Receptor-activated K(+) currents desensitize in the sustained presence of agonist to avoid excessive effects on neuronal activity. Desensitization of K(+) currents integrates distinct mechanistic underpinnings. GABAB receptor activity reduces protein kinase-A activity, which reduces phosphorylation of serine-892 in GABAB2 and promotes receptor degradation. This form of desensitization operates on the time scale of several minutes to hours. A faster form of desensitization is induced by the auxiliary subunit KCTD12, which interferes with channel activation by binding to the G-protein βγ subunits. Here we show that the two mechanisms of desensitization influence each other. Serine-892 phosphorylation in heterologous cells rearranges KCTD12 at the receptor and slows KCTD12-induced desensitization. Likewise, protein kinase-A activation in hippocampal neurons slows fast desensitization of GABAB receptor-activated K(+) currents while protein kinase-A inhibition accelerates fast desensitization. Protein kinase-A fails to regulate fast desensitization in KCTD12 knock-out mice or knock-in mice with a serine-892 to alanine mutation, thus demonstrating that serine-892 phosphorylation regulates KCTD12-induced desensitization in vivo. Fast current desensitization is accelerated in hippocampal neurons carrying the serine-892 to alanine mutation, showing that tonic serine-892 phosphorylation normally limits KCTD12-induced desensitization. Tonic serine-892 phosphorylation is in turn promoted by assembly of receptors with KCTD12. This cross-regulation of serine-892 phosphorylation and KCTD12 activity sharpens the response during repeated receptor activation.
authors: Department of Biomedicine, University of Basel, 4056 Basel, Switzerland.
authors: Lisa
authors: L
authors: Adelfinger
authors: Department of Biomedicine, University of Basel, 4056 Basel, Switzerland; Institute of Experimental Medicine, ASCR, Videnska 1083, 14220 Prague 4-Krc, Czech Republic.
authors: Rostislav
authors: R
authors: Turecek
authors: Department of Biomedicine, University of Basel, 4056 Basel, Switzerland.
authors: Klara
authors: K
authors: Ivankova
authors: Department of Biomedicine, University of Basel, 4056 Basel, Switzerland.
authors: Anders A
authors: AA
authors: Jensen
authors: Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, United States.
authors: Stephen J
authors: SJ
authors: Moss
authors: Department of Biomedicine, University of Basel, 4056 Basel, Switzerland.
authors: Martin
authors: M
authors: Gassmann
authors: Department of Biomedicine, University of Basel, 4056 Basel, Switzerland. Electronic address: bernhard.bettler@unibas.ch.
authors: Bernhard
authors: B
authors: Bettler
mesh_terms: D000409:Alanine / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D003412:Cricetulus; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D018079:Receptors, GABA / Q000235:genetics / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000235:genetics / Q000378:metabolism
chemical_list: D018079:Receptors, GABA; D018080:Receptors, GABA-B; C493176:pfetin protein, mouse; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D000409:Alanine; D011188:Potassium
keywords: G-protein coupled receptor; GABA-B; GPCR; Kir3; PKA