ANALYSIS OF ZDHHC17 INTERACTION NETWORKS AND PROTEIN INTERACTIONS LINKED TO NEURODEGENERATION

The cells in our body contain a diverse array of different proteins that coordinate and drive specific pathways, such as neuronal communication in the brain. These proteins are often tightly regulated to ensure that they perform their specific functions in the required spatial and temporal manner. A major way of regulating protein function is by specific chemical modifications that are made to the amino acid backbone, and a variety of different chemical groups are added to proteins that affect their activity. One important but poorly understood modification is "S-acylation", the attachment of fatty acids onto proteins. S-acylation of cellular proteins is catalysed by a family of twenty-four "zDHHC" enzymes. The importance of these enzymes for normal brain function is underscored by reported links between zDHHC enzyme dysfunction and conditions such as neurodegeneration, schizophrenia, and intellectual disability.

Despite the importance of zDHHC enzymes, we lack fundamental knowledge about this protein family, including the substrate interaction networks of individual enzyme isoforms, how changes in these interactions contribute to disease pathology, and how these interactions can be targeted as a therapeutic strategy. Recent work from our group has provided an important breakthrough in this area by identifying a specific protein sequence that is recognised by the enzyme zDHHC17; this enzyme is essential for brain function and is associated with specific neurodegenerative disorders. In this project, we will exploit our new findings about the zDHHC17 recognition sequence to identify the substrate interaction network of this enzyme in neurons, providing a major advance in our understanding of the physiological functions of zDHHC17. In addition, we will investigate how the interaction of zDHHC17 with one of its key substrates, huntingtin, is affected in Huntington's disease to provide new insight into the pathogenesis of this neurodegenerative disorder. Finally, we will employ the novel information on the zDHHC17 recognition sequence to develop compounds that may have potential for the treatment of the neurodegenerative disease, neuronal ceroid lipofuscinosis. Collectively, these studies focused on the zDHHC17 recognition sequence will provide new information on the physiological functions of zDHHC17, its links with Huntington's disease, and the potential of this enzyme to serve as a novel therapeutic target for neuronal ceroid lipofuscinosis.

The zDHHC enzyme family, which is encoded by twenty-four distinct genes in humans, mediates the S-acylation of a diverse array of neuronal proteins. The importance of this enzyme family is highlighted by links between enzyme dysfunction and disorders including neurodegeneration, intellectual disability and schizophrenia. zDHHC17 is essential for neuronal function and has been linked with Huntington's disease due to its interactions with huntingtin. We have also identified this enzyme as a potential therapeutic target for the neurodegenerative disorder neuronal ceroid lipofuscinosis. However, our understanding of the physiological functions and pathophysiological effects of zDHHC17 is severely hindered by a lack of knowledge about the substrate targets of this enzyme.

We have identified a novel zDHHC17 recognition motif (termed zDABM), which mediates the interaction of known substrates with this enzyme. Furthermore, we have recently defined the sequence rules of the zDABM and used this novel information to predict new substrates of zDHHC17. In this project, we will capitalise on these important breakthroughs to identify the substrate interaction network of zDHHC17 in neurons. The role of the zDABM sequence in controlling the S-acylation and localisation of the zDHHC17 substrate network will also be determined. To investigate the potential importance of the zDABM sequence in Huntington's disease, we will explore how the zDABM of huntingtin is impacted by polyglutamine tract expansion and how it contributes to the regulation of zDHHC17 S-acylation activity. Finally, we develop novel peptide inhibitors based on the zDABM sequence and test their therapeutic potential for the treatment of neuronal ceroid lipofuscinosis. Overall, this study will provide a major advance in our understanding of the physiological functions of zDHHC17 and its role and therapeutic potential in neurodegenerative diseases.

The results of this project grant will not only benefit academics but will also impact the commercial and healthcare sectors, charities and the general public. As zDHHC17 activity has been suggested to be reduced in Huntington's disease, identification of the substrate interaction network of this enzyme will provide new insight into cellular changes that may take place in this neurodegenerative disease. Indeed, we will also generate new data on the effects of polyglutamine tract expansion on interaction of huntingtin with zDHHC17 and changes that occur in S-acylation of these proteins in Huntington's disease. The results of these analyses are likely to attract interest and potentially investment from pharmaceutical companies searching for new therapies for this disease, and will also be of interest to clinicians working on this condition. In addition, our work on peptide inhibitors of zDHHC17 and their potential use in the treatment of neuronal ceroid lipofuscinosis has the potential to lead to very rapid impact and interest from relevant industrial and healthcare partners. The time-scale for these impacts is short-term (within the time-frame of the grant or shortly thereafter).

Other short-term beneficiaries of the research will be Huntington's disease and neuronal ceroid lipofuscinosis charities and the general public. A longer-term impact (5-15 years) may be on patients suffering from neuronal ceroid lipofuscinosis and Huntington's disease and their families through the development of new treatments for these disorders. A shorter-term impact (during the grant) will be on local schoolchildren; we play a prominent role interacting with schoolchildren by accepting pupils on work experience placements and participating in university open days, science fairs and school visits. This will hopefully allow us to inspire a future generation of biomedical scientists by highlighting the importance of both fundamental research and research into the causes of neurodegeneration and their treatment. Another societal impact of the research will be the high-quality training that the post-doctoral research assistant will receive, enhancing the skills base of the UK and our global competitiveness.