Investigating the molecular mechanism underlying CMT1c disease

Abstract

Endocytosis involves the incorporation of surface proteins into intracellular vesicles and downstream compartments from where they are sorted to different destinations. This highly regulated process is essential for information exchange between the extracellular environment and the cell, and is required for uptake of nutrients, regulation of signalling and transport of proteins within the cell. Dysregulated endocytic trafficking is implicated in a wide range of diseases including cancer, infectious disease and neurological disorders. Charcot-Marie-Tooth (CMT) disease is the most common inherited peripheral neuropathy, estimated to affect 1:2500 people, with at least 80 genes identified as causative. Missense mutations in lipopolysaccharide-induced tumour necrosis factor α factor (LITAF) result in CMT type 1c, which is an autosomal dominant demyelinating disease. It is likely that LITAF functions in endocytic trafficking. However, its precise mechanism of action is still not clear and hence the molecular cause of CMT1c is not well understood. Here, we show that CMT1c mutations in LITAF impaired localisation to recycling endosomes. These mutations rendered LITAF unable to regulate the tubular recycling compartment, and disrupted trafficking of an endocytic recycling cargo, CD98. We performed a proximity labelling BioID screen to identify potential interactors of LITAF and LITAF containing two CMT1c mutations. A large number of potential interacting partners were identified, and novel protein associations with LITAF have begun to be uncovered. Links with integrin trafficking were revealed as well as other adhesion proteins which are likely to have relevance to the disease. Additionally, we generated transgenic zebrafish lacking LITAF or a similar protein, cell death inducing p53-target protein 1 (CDIP1) and double LITAF and CDIP1 knock-out zebrafish. The zebrafish are viable and have no overt phenotype, and they may provide a useful model in which to further explore the function of these proteins in a physiological context. Overall this study indicates that CMT1c disease may result from dysregulation of the endocytic recycling pathway and provides additional insights into the possible links between LITAF and demyelination. Further understanding of the function of LITAF and the molecular cause of this disease is required to develop therapeutic targets for this group of demyelinating disorders.

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Philip Woodman (Supervisor) & Martin Lowe (Supervisor)