Investigating the role of TLDc proteins in neuroprotection and disease-associated comorbidities

Thesis

The TLDc family of proteins is characterized by a conserved Tre2/Bub2/Cdc16 (TBC), lysin motif (LysM), domain catalytic (TLDc) domain. While the domain has been shown to protect against oxidative stress (OS), the mechanism of its protection and the distinct molecular functions of the TLDc family members are yet to be fully ascertained. In this thesis, the function and dysfunction of Tbc1d24 and Oxr1, two clinically important members of the TLDc family, are investigated.

Mutations in TBC1D24 are associated with a broad spectrum of neurological disorders, including epilepsy and the gene is implicated in synaptic transmission and neuronal development. Using knock-in mouse models, this thesis has studied the functional and physiological consequences of disruption in Tbc1d24, determining that loss-of-function mutations within Tbc1d24 result in a significant knock down of protein expression, ultimately resulting in seizures. Furthermore, a key interaction between Tbc1d24 and the V-ATPase has been confirmed, supporting a role for Tbc1d24 in the endolysosomal pathway. Unexpectedly, data from the new mouse models implicated Tbc1d24 in anaemia, revealing a novel role for the gene in the haematological system.

Oxr1 has been demonstrated to effectively protect against OS-induced cell death in neuronal cells, while overexpression of Oxr1 in vivo is able to delay neurodegeneration and neuroinflammation in mouse models of ALS. These findings support the promise of Oxr1 as a safe therapeutic target against OS-related neurodegeneration. This thesis has investigated the pharmacological induction of Oxr1 as a viable protective strategy, through generation of a stable cell line based on the highly conserved Oxr1 promoter element. Compound screening using this line has produced some early leads for exogenous upregulation of Oxr1. Furthermore, the in vivo genetic over-expression system was used to determine whether Oxr1 could functionally compensate for a loss-of-function Tbc1d24 mutation, shedding light on the lack of functional redundancy between TLDc family members.

This thesis addresses both the deleterious consequences of disruption, and the protective potential of overexpression of the TLDc family, combining new mouse genetic models with a range of molecular and cellular techniques. These studies have furthered understanding of the TLDc family and elucidated its therapeutic potential in protecting against OS and neurodegeneration.

Authors: Parsons, ALM

• DOI: 10.5287/ora-eo4mj1m7v
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: anaemia; mammalian genetics; epilepsy; neuroprotection; endolysosomal pathway; neurotransmission; compound screening; molecular biology; oxidative stress; mouse genetics; neurodegeneration
• Subjects: Genetics; Neurosciences; Anemia; Epilepsy