Cln3 function in the model organism Dictyostelium discoideum

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Background CLN3 (ceroid lipofuscinosis neuronal 3) belongs to the NCL family of proteins. Current knowledge suggests that NCL proteins participate in pathways that engulf and process extracellular material to provide the cell with nutrients and digest unwanted material. However their specific functions in these pathways remain to be clarified. Previous research has linked CLN3 to a diversity of cellular processes. However its precise function in the cell is still unclear, in large part due to previous work being unable to determine the precise localization of the protein. Dictyostelium discoideum has long served as a model system for cell and developmental biology. The life cycle of this soil microbe is comprised of both single-cell and multicellular phases, which allows for a variety of cellular processes to be examined in great detail. Our previous work showed that loss of CLN3 in Dictyostelium (denoted Cln3) causes abnormal growth and multicellular development. We also revealed that Cln3 localizes to the contractile vacuole (CV) system, which is an intracellular compartment that helps the cell respond and adapt to different environmental conditions (e.g., maintain water and ion balance), as well as move material between compartments within the cell. However, the importance of the CV system is not just limited to Dictyostelium. It is also essential to the survival of a diversity of ecologically important organisms in freshwater environments and has been investigated as a potential target for novel plant protection strategies. Objectives We are using the defined localization of Cln3 in Dictyostelium to fuel research into determining its precise function in the cell. We will use a diversity of cellular, molecular, and biochemical approaches to reveal the function of Cln3 in Dictyostelium, the proteins it interacts with, and the signalling pathways that regulate its function. This will involve assessing the effect of Cln3-deficiency on processes linked to the CV system (e.g., water and ion balance) and studying the interaction of Cln3 with proteins involved in CV system function (e.g., Rab proteins, calmodulin). Our long-term objective is to use Dictyostelium as a model system for studying the functions of all NCL proteins. Significance This research will significantly advance our understanding of Cln3 function in Dictyostelium. The efficient trafficking of material within a cell is critical to its overall health and function. In humans, mutations in NCL proteins cause Batten disease, the most common form of childhood neurodegeneration. In the long-term, this work will have a significant impact on our understanding of the roles these important, but poorly characterized proteins play in the cell. Finally, personnel participating in this research will acquire knowledge and develop technical and transferrable skills that will help support the creation of highly-skilled Canadian workforce.