부산대학교 도서관

Slow and persistent synaptic inhibition is mediated by metabotropic [GABA.sub.B] receptors ([GABA.sub.B]RS). [GABA.sub.B]Rs are responsible for the modulation of neurotransmitter release from presynaptic terminals and for hyperpolarization at postsynaptic sites. Postsynaptic [GABA.sub.B]RS are predominantly found on dendritic spines, adjacent to excitatory synapses, but the control of their plasma membrane availability is still controversial. Here, we explore the role of glutamate receptor activation in regulating the function and surface availability of [GABA.sub.B]Rs in central neurons. We demonstrate that prolonged activation of NMDA receptors (NMDA-Rs) leads to endocytosis, a diversion from a recycling route, and subsequent lysosomal degradation of [GABA.sub.B]Rs. These sorting events are paralleled by a reduction in [GABA.sub.B]R-dependent activation of inwardly rectifying [K.sup.+] channel currents. Postendocytic sorting is critically dependent on phosphorylation of serine 783 (S783) within the [GABA.sub.B]R2 subunit, an established substrate of AMP-dependent protein kinase (AMPK). NMDA-R activation leads to a rapid increase in phosphorylation of S783, followed by a slower dephosphorylation, which results from the activity of AMPK and protein phosphatase 2A, respectively. Agonist activation of [GABA.sub.B]Rs counters the effects of NMDA. Thus, NMDA-R activation alters the phosphorylation state of S783 and acts as a molecular switch to decrease the abundance of [GABA.sub.B]RS at the neuronal plasma membrane. Such a mechanism may be of significance during synaptic plasticity or pathological conditions, such as ischemia or epilepsy, which lead to prolonged activation of glutamate receptors. endocytic | recycling | excitation-inhibition | glutamate doi/ 10.1073/pnas.1000853107