TY - JOUR

T1 - GABAB receptor phosphorylation regulates KCTD12-induced K+ current desensitization

AU - Adelfinger, L

AU - Turecek, R

AU - Ivankova, K

AU - Jensen, Anders A.

AU - Moss, S.J.

AU - Gassmann, M

AU - Bettler, B

PY - 2014

Y1 - 2014

N2 - 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.

AB - 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.

U2 - 10.1016/j.bcp.2014.07.013

DO - 10.1016/j.bcp.2014.07.013

M3 - Journal article

C2 - 25065880

VL - 91

SP - 369

EP - 379

JO - Biochemical Pharmacology

JF - Biochemical Pharmacology

SN - 0006-2952

IS - 3

ER -