Title:
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Mechanisms underlying the
trafficking and distribution of
cannabinoid receptor type 1 in
primary hippocampal neurons
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coupled receptors (GPCRs) in the central nervous system, where it is
concentrated at the axonal plasma membrane of specific neurons. Whilst the
, therapeutic and psychotropic effects of cannabinoid receptor stimulation have
been recognised for over 4000 years, through recreational and medicinal
Cannabis use, ,it is only in the last few decades that our scientific understanding
of both exogenous and endogenous cannabinoid system regulation has
significantly advanced. At the presynaptic terminal, CB1R activation mediates
neurotransmission through retrograde messengers, which are released from
the post-synaptic terminal in response to activity-dependent signal
transduction. Consequently the CB1R can be considered as a master regulator
of synaptic transmission.
However, compared to other GPCRs, the field of CB1R trafficking is in its infancy
and the pathways and mechanisms of CB1R regulation are at best, incomplete.
Using N-terminal fluorescent-tagged CB1R constructs, I have investigated the
trafficking and diffusional mobility of CB1Rs in cultured hippocampal neurons.
My work has revealed a crucial role for the C-terminal tail of the CB1R (ctCB1R)
in regulating both its plasma membrane dynamics and surface
localization. Specifically, using truncation and deletion mutagenesis I identified
a 21 amino acid stretch in the ct-CB1R, which is critical for maintaining its
axonal polarized surface distribution in hippocampal neurons. This region
corresponds to a putative helical motif, H9, for which no known functional role
has previously been identified. Moreover, I have demonstrated that the ct-CB1R .
is sufficient to promote an axonal fate, presumably through interactions with
specific scaffolding and adaptor proteins. Accordingly, I have performed an
unbiased proteomics analysis using affinity purification mass spectrometry and
have identified several candidate interactors, including a cluster of proteins
associated with clathrin-mediated 'endocytosis, which , provide additional
mechanistic insight into the underlying biochemical machinery regulating CB1R
distribution in neurons .
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