Cyclin-dependent kinase-5 regulates the polarized trafficking of dense-core vesicles in C. elegans motor neurons.
Cyclin-dependent kinase-5 (CDK-5) is a serine/threonine kinase with many important
functions in neurons, including regulation of development, protein transport, synaptic
transmission and plasticity, and neurodegeneration. Aberrant activation of CDK-5 can
cause neuronal death, and inhibition of CDK-5 is protective in animal models of
Alzheimer's disease, prion protein disease, and ... read moreHuntington's disease. In this thesis, I
use C. elegans to investigate the role of CDK-5 in regulation of neuropeptide
trafficking and synaptic transmission. In Chapter 2, I identify a novel role for CDK-5
in the regulation of polarized trafficking of dense-core vesicles. Dense-core vesicles
(DCVs) release neuropeptides, which are key regulators of synaptic strength and
plasticity, but little is known about the regulation of DCV transport. I utilize a
fluorescently-tagged neuropeptide (INS-22::Venus) to visualize DCVs in DA and DB
cholinergic neurons, which have a well-defined axon and dendrite. In wild-type animals
INS-22::Venus localizes primarily to axons, but cdk-5 mutants have reduced axonal DCVs
and increased dendritic DCVs, indicating that CDK-5 promotes the polarized distribution
of DCVs to the axon. I find that CDK-5 is not required to establish axon/dendrite
polarity, but instead acts at the cell body to inhibit the trafficking of DCVs into the
dendrite. Mutations in cytoplasmic dynein (dhc-1) completely block the increase in
dendritic DCVs observed in cdk-5 mutants, suggesting that CDK-5 inhibits dynein-mediated
trafficking of DCVs into dendrites. In Chapter 3, I identify cell-type specific
differences between DA and DB motor neurons. In DA neurons, cdk-5 mutants have increased
dendritic DCV markers without a corresponding change in axonal DCVs, suggesting CDK-5
has independent functions in the axon and dendrite. DB motor neurons, in contrast, have
decreased axonal DCVs in cdk-5 mutants. Similarly, time-lapse imaging shows that DCV
trafficking to the axon is altered in DB neurons, but not DA neurons, in cdk-5 mutants.
Finally, I investigate the role of CDK-5 in synaptic transmission at the neuromuscular
junction (NMJ) using a paralysis assay based on an inhibitor of acetylcholinesterase,
aldicarb. These studies reveal that CDK-5 promotes acetylcholine release at the NMJ and
lay the groundwork for future studies to identify novel CDK-5 substrates and regulators
that promote synaptic transmission.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Neuroscience.
Advisor: Peter Juo.
Committee: Michele Jacob, F Jackson, Larry Feig, and Anne Hart.
Keyword: Neurosciences.read less