Glial Expression of the Caenorhabditis elegans Gene swip-10 Supports Glutamate Dependent Control of Extrasynaptic Dopamine Signaling

Abstract

Glial cells play a critical role in shaping neuronal development, structure, and function. In a screen for Caenorhabditis elegans mutants that display dopamine (DA)-dependent, Swimming-Induced Paralysis (Swip), we identified a novel gene, swip-10, the expression of which in glia is required to support normal swimming behavior. swip-10 mutants display reduced locomotion rates on plates, consistent with our findings of elevated rates of presynaptic DA vesicle fusion using fluorescence recovery after photobleaching. In addition, swip-10 mutants exhibit elevated DA neuron excitability upon contact with food, as detected by in vivo Ca 2ϩ monitoring, that can be rescued by glial expression of swip-10. Mammalian glia exert powerful control of neuronal excitability via transporter-dependent buffering of extracellular glutamate (Glu). Consistent with this idea, swip-10 paralysis was blunted in mutants deficient in either vesicular Glu release or Glu receptor expression and could be phenocopied by mutations that disrupt the function of plasma membrane Glu transporters, most noticeably glt-1, the ortholog of mammalian astrocytic GLT1 (EAAT2). swip-10 encodes a protein containing a highly conserved metallo-␤-lactamase domain, within which our swip-10 mutations are located and where engineered mutations disrupt Swip rescue. Sequence alignments identify the CNS-expressed gene MBLAC1 as a putative mammalian ortholog. Together, our studies provide evidence of a novel pathway in glial cells regulated by swip-10 that limits DA neuron excitability, DA secretion, and DA-dependent behaviors through modulation of Glu signaling.

Acute blockade of the Caenorhabditis elegans dopamine transporter DAT-1 by the mammalian norepinephrine transporter inhibitor nisoxetine reveals the influence of genetic modifications of dopamine signaling in vivo

“…Experimenters were blind to genotype and/or drug. Automated analyses were performed using 10 min videos of individual worms captured from at least 25 worms per genotype/treatment using Tracker software and analyzed using SwimR software as previously described (Hardaway et al, 2015; Hardaway et al, 2014). Latency to paralysis was measured as the time until the thrashing frequency for each animal dropped below 20% of the maximum thrashing value for at least 20 seconds.…”

The THO Complex Coordinates Transcripts for Synapse Development and Dopamine Neuron Survival

“…Animals expressing the calcium sensor Gcamp6 in DA neurons were imaged during the basal slowing response (Hardaway et al, 2015; Piggott et al, 2011). Upon entry into the bacterial food, wt PDE neurons were activated (Figure S3C) and this activation was the same in thoc-5 mutant animals.…”

VTA dopamine neuron plasticity – the unusual suspects

“…A similar adaptation in the VTA could greatly impact signalling onto DA neurons. In support of this hypothesis, pharmacological blockade of GLT‐1 and GLAST increases activation of extrasynaptic NMDARs in DA neurons (Wild et al ., ), and disrupting the orthologue of GLT‐1 ( glt‐1‐6 ) in C. elegans produces DA neuron hyperexcitability (Hardaway et al ., ). It is conceivable, then, that certain stimulus‐triggered adaptations within the VTA may be resulting from, or at least enhanced by, a reduction in astrocyte uptake of glutamate.…”