TheCaenorhabditis elegans snf-11Gene Encodes a Sodium-dependent GABA Transporter Required for Clearance of Synaptic GABA

Abstract

Sodium-dependent neurotransmitter transporters participate in the clearance and/or recycling of neurotransmitters from synaptic clefts. The snf-11 gene in Caenorhabditis elegans encodes a protein of high similarity to mammalian GABA transporters (GATs). We show here that snf-11 encodes a functional GABA transporter; SNF-11-mediated GABA transport is Na ؉ and Cl ؊ dependent, has an EC 50 value of 168 M, and is blocked by the GAT1 inhibitor SKF89976A. The SNF-11 protein is expressed in seven GABAergic neurons, several additional neurons in the head and retrovesicular ganglion, and three groups of muscle cells. Therefore, all GABAergic synapses are associated with either presynaptic or postsynaptic (or both) expression of SNF-11. Although a snf-11 null mutation has no obvious effects on GABAergic behaviors, it leads to resistance to inhibitors of acetylcholinesterase. In vivo, a snf-11 null mutation blocks GABA uptake in at least a subset of GABAergic cells; in a cell culture system, all GABA uptake is abolished by the snf-11 mutation. We conclude that GABA transport activity is not essential for normal GABAergic function in C. elegans and that the localization of SNF-11 is consistent with a GABA clearance function rather than recycling.

Optogenetic analysis of GABABreceptor signaling inCaenorhabditis elegansmotor neurons

“…When the SNF-11 high-affinity GABA transporter was absent, ACh-evoked contractions were stronger, and they were even further enhanced when the GBB-1/2 receptor was missing. This could be in line with a function of SNF-11 as a reuptake transporter or with a possible function of SNF-11 in GABAergic neurons, providing/recycling some of the GABA produced and released by these cells, as suggested by two conflicting previous reports (Jiang et al 2005;Mullen et al 2006). However, both continuously elevated and reduced levels of GABA in the cleft may affect compensatory mechanisms in GABA receptors, making it difficult to interpret our findings conclusively.…”

“…A high-affinity GABA transporter, SNF-11, has been described, which according to one study is expressed in muscles, as well as some neurons, excluding most of the inhibitory, GABAergic MNs (Mullen et al 2006). This receptor is likely to act as a reuptake transporter, and not a transporter required in GABAergic MNs to provide GABA for release.…”

Choline Transport and de novo Choline Synthesis Support Acetylcholine Biosynthesis in Caenorhabditis elegans Cholinergic Neurons

“…Secondary antibodies were obtained from Jackson ImmunoResearch (West Grove, PA). Nematodes were stained using a modified freeze-fracture procedure as previously described (Duerr et al 1999;Mullen et al 2006).…”

Genetic Interactions Between UNC-17/VAChT and a Novel Transmembrane Protein in Caenorhabditis elegans

“…Nematodes were stained using a modified freeze-fracture procedure as previously described (Duerr et al 1999;Mullen et al 2006). Antibodies used in this study include chicken polyclonal (C96) and mouse monoclonal (mAb1403) a-UNC-17 antibodies (Duerr et al 2008).…”