Here, we uncover a mechanism for regulating the number of active presynaptic GABAB receptors (GABABRs) at nerve terminals, an important determinant of neurotransmitter release. We find that GABABRs gain access to axon terminals by lateral diffusion in the membrane. Their relative accumulation is dependent upon agonist activation and the presence of the two distinct sushi domains that are found only in alternatively spliced GABABR1a subunits. Following brief activation of NMDA receptors (NMDARs) using glutamate, GABABR diffusion is reduced, causing accumulation at presynaptic terminals in a Ca(2+)-dependent manner that involves phosphorylation of GABABR2 subunits at Ser783. This signaling cascade indicates how synaptically released glutamate can initiate, via a feedback mechanism, increased levels of presynaptic GABABRs that limit further glutamate release and excitotoxicity.
Keywords: AMPK; Ca(2+) signaling; GABA receptors; GABA(B) receptors; NMDA receptors; bungarotoxin binding site; excitotoxicity; glutamate receptors; hippocampus; homeostatic signaling; lateral diffusion; phosphorylation; presynaptic terminal; quantum dots; receptor mobility; single-particle tracking; sushi domains.
Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.