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NIDA Proteomics Center
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Investigators
> Maria Morabito
Pilot Project: Cdk5-dependent
posttranslational modifications of PSD-95
Maria Morabito, Department of Cell Biology,
The University of Massachusetts Medical School
The kinase Cdk5 regulates dopamine neurotransmission, plays a key role in
synaptic plasticity associated with learning and memory, and is an important
player in the cellular and physiological responses to drugs of abuse by
integrating a number of intracellular pathways that are targeted by
psychostimulant drugs. Thus, understanding the molecular mechanisms by which
Cdk5 regulates glutamatergic synaptic function is critical for understanding how
drugs of abuse alter glutamatergic transmission and induce various forms of
synaptic plasticity within the reward circuitry of the brain.
We have shown that Cdk5 phosphorylates PSD-95, a major postsynaptic scaffolding
protein of glutamatergic synapses that interacts with NMDA and AMPA receptors
and has been implicated in addiction and the regulation of synaptic strength and
plasticity. The N-terminus of PSD-95 binds to the tyrosine kinase Src and
contains a PEST motif implicated in the ubiquitination of PSD-95 and critical in
regulating AMPA receptor surface expression, while the C-terminus of PSD-95
contains a tyrosine-based motif implicated in the trafficking of PSD-95. We have
previously shown that Cdk5 phosphorylates PSD-95 within the PEST motif and this
phosphorylation regulates the binding of Src to PSD-95. Furthermore, our
preliminary studies indicate that Cdk5 regulates both tyrosine phosphorylation
and ubiquitination of PSD-95, implicating Cdk5 in the regulation of the
trafficking and stability of PSD-95.
We propose to identify the residues of PSD-95 that are phosphorylated and
ubiquitinated in a Cdk5-dependent manner by Mass Spectrometry analysis. The
proposed study will provide fundamental insights into the mechanisms by which
Cdk5 regulates PSD-95 and will improve our understanding of the functions of
both Cdk5 and PSD-95. Given the importance of PSD-95 in synaptic plasticity and
drug addiction, the identification of the sites of phosphorylation and
ubiquitination of PSD-95 is an essential step toward the characterization of the
post-synaptic proteomic changes underlying synaptic plasticity and drug
addition. |
