Molecular dissection of DHHC protein targeting and its importance for post-synaptic palmitoylation dynamics

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Genes present within the DNA of living organisms encode for the production of specific proteins. The thousands of proteins that are produced within a single cell interact to drive a multitude of pathways, such as cell growth and division. Protein modifications can enhance protein diversity beyond that encoded at the DNA level. For example, many proteins are modified by the attachment of the fatty acid palmitate, a process termed palmitoylation.Communication between neurons, specialised cells in the brain, underlies every movement, thought and sensation; this neuronal communication occurs at specialised sites termed synapses. Palmitoylation of several proteins that are essential for neuronal communication mediates their targeting to synapses; modulating the extent of this targeting affects synaptic communication. It is well established that changes in synaptic communication are important for events such as learning and memory. Despite the importance of palmitoylation for normal synaptic function, there is very little known about how the enzymes that mediate palmitoylation reactions are regulated in neurons. Recent work identified a family of 24 'DHHC' proteins that are responsible for essentially all cellular palmitoylation activity. The importance of DHHC proteins for normal brain function is highlighted by work linking genetic mutations in these proteins with schizophrenia and mental retardation.This research project will focus on DHHC2, which is one of the most highly expressed DHHC proteins in brain. Furthermore, DHHC2 is targeted to synaptic regions, where it has been shown to palmitoylate a protein called PSD95; this protein plays an important role in stabilising neurotransmitter receptors and is therefore essential for synaptic communication. Palmitoylation of PSD95 by DHHC2 leads to an increase in synaptic targeting of PSD95, which in turn affects synaptic dynamics of neurotransmitter receptors. In this project, we will investigate the mechanisms that regulate DHHC2 movement to synapses where it palmitoylates PSD95. Furthermore, we will examine how interfering with the mobility of DHHC2 at synapses impacts neuronal communication. This work will play a major role in delineating how palmitoylation dynamics are regulated at synapses and the downstream effects of this regulation on neurotransmitter receptor dynamics.There is currently much interest in DHHC proteins as potential drug targets for the treatment of diverse human disorders, thus delineating the mechanisms whereby specific DHHC proteins regulate cellular dynamics is of major importance.