The Snail Transcription Factor CES-1 Regulates Trafficking of the C. elegans AMPA Receptor GLR-1
Park, Lidia.
2018
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Regulation of glutamate receptor (GluR) levels at synapses controls
synaptic strength and plasticity. Although many proteins and mechanisms have been
identified that regulate GluR trafficking, less is known about whether those
mechanisms are controlled at the transcriptional level to regulate glutamatergic
signaling. We created an RNAi, optogenetic screen to look for conserved
transcription ... read morefactors (TFs) that are required for a simple, glutamatergic,
mechanosensory reflex behavior in the worm called the nose-touch response. We
identified several TFs from this screen, including ceh-20 and ces-1, which
regulate glutamatergic behavior. I found that ceh-20 mutants have defects in two
different glutamatergic behaviors, response to nose touch and frequency of
spontaneous locomotion reversals. CEH-20 is a homolog of the PBX family of TFs. I
also found that ceh-20 mutants have a reduced number of GLR-1-expressing cells,
suggesting that CEH-20 may regulate development or survival of GLR-1-expressing
neurons. Our results suggest that several novel TFs regulate glutamatergic
behavior. I also identified the Snail family-related TF CES-1 as a novel regulator
of GLR-1 AMPA receptor trafficking in C. elegans. CES-1 is known to have a
selective role in inhibiting the programmed cell death of two pairs of sister
cells, those of the serotonergic NSM neurons and the pharyngeal I2 interneurons. I
found that ces-1 loss-of-function mutants also have defects in the nose-touch
response, validating our RNAi results. ces-1 mutants have wild type cholinergic
neuromuscular junction function, suggesting that they do not have a general defect
in synaptic transmission or muscle function. However, ces-1 appears to globally
affect glutamatergic signaling, as ces-1 loss-of-function mutants also exhibit
decreased spontaneous locomotion reversal frequency, a behavior dependent on the
level of glutamatergic signaling. Conversely, ces-1 gain-of-function mutants
exhibit increased reversal frequency in a manner that was dependent on glr-1.
Additionally, ces-1 loss-of-function mutants suppress the increased reversal
frequencies stimulated by a constitutively active form of GLR-1, GLR-1(A/T).
Together, these data suggest that ces-1 acts in the same genetic pathway as glr-1
to regulate glutamatergic behavior. The number of GLR-1-expressing neurons appears
normal in ces-1 mutants, suggesting that ces-1 does not affect cell death of these
cells. We found that the total number and levels of GFP-tagged GLR-1 puncta are
normal in the ventral nerve cord of ces-1 loss-of-function mutants, suggesting
that ces-1 does not regulate total GLR-1 expression or the number of
GLR-1-containing synapses. In contrast, we found that cell surface levels of
GLR-1, measured using pH-sensitive superecliptic-pHluorin (SEP)-tagged receptors,
are decreased in the ventral nerve cord of ces-1 loss-of-function mutants,
suggesting that CES-1 promotes surface levels of GLR-1. Finally we have
preliminary data suggesting that CES-1 may regulate cell surface levels of GLR-1
by controlling transcription of the WD40-repeat protein WDR-20. Our lab previously
has shown that the deubiquitinating enzyme USP-46 promotes cell surface levels of
GLR-1. WDR-20 is a positive regulator of the deubiquitinating enzyme USP-46. The
wdr-20 promoter contains potential binding sites for CES-1, and we found that
expression of a wdr-20 transcriptional reporter decreases in ces-1 mutants,
suggesting that CES-1 may promote WDR-20 expression to control GLR-1 surface
levels and glutamatergic behavior. These data identify the TF CES-1 as a novel
regulator of GluR surface levels that impacts glutamatergic
behavior.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Cell, Molecular & Developmental Biology.
Advisor: Peter Juo.
Committee: Victor Hatini, Jim Schwob, Larry Feig, and Jeremy Dittman.
Keywords: Neurosciences, Biology, and Genetics.read less - ID:
- mp48sr82h
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