Dynamics of the LINC complex

Abstract

The LINC complex is composed of SUN and KASH domain proteins spanning the nuclear envelope (NE), allowing communication between the cytoskeleton and the nucleoskeleton. Mutations in these proteins can result in diseases known as nuclear envelopathies. Early Onset Torsion Dystonia (EOTD) is caused by a mutation in a protein called TorsinA and is associated with disruption of the NE similar to some nuclear envelopathies. TorsinA is an AAA ATPase located in the endoplasmic reticulum (ER) and the NE. Although the function of TorsinA is unknown, a potential target for TorsinA is the LINC complex. This study aimed to examine the role of TorsinA in regulating LINC complex assembly/disassembly in mitosis and interphase. Localisation and levels of the relevant proteins were studied using microscopy experiments and biochemical assays. As an alternative approach to study TorsinA function, biotin ligase proximity labelling (BioID) was used to biotinylate near neighbours of TorsinA and its cofactors LAP1 and LULL1, with the aim of identifying TorsinA interacting proteins. The results suggest that LINC components do not always interact throughout the cell cycle, and a population of SUN1 and the KASH domain protein nesprin-2 remain trapped in ER clusters after the NE reseals at the end of mitosis. Nesprin-2 trapped in the ER is likely targeted for degradation, as evidenced by the effect of displacing nesprin-2 to the ER on levels of exogenously expressed nesprin-2. Finally, TorsinA was suggested to affect the LINC complex by strengthening the interaction between LINC components as TorsinA depletion increased mobility and degradation rate of nesprin-2. BioID provided a few candidate proteins that may be interesting TorsinA interactors, including Lamin-B1 and emerin.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Eileithyia Swanton (Supervisor)