Trafficking of lipid-modified proteins to specialised membrane domains

ElMaghloob, Yasmin (2020) Trafficking of lipid-modified proteins to specialised membrane domains. PhD thesis, University of Glasgow.

Abstract

Protein localisation is an important determinant of its function; trafficking mechanisms which bring about this localisation regulate signalling. These are crucial in functional membrane domains which remain continuous with the rest of the bilayer yet retain a distinct composition. This thesis presents my work as part of our investigation into the trafficking of lipid-modified proteins to two of these domains. These are the immune synapse, which is formed at the interface of immune cells with their targets, and the primary cilium, which is a cell surface microtubule-based sensory organelle. Using biochemical, structural, and imaging approaches, we study the trafficking of lipid-modified proteins to these domains. First, we attempt to answer the question of how the lymphocyte-specific kinase (LCK) is targeted to the CD4+ T cell synapse and then retained in the domain, a process which remains not fully understood. In the second part of the thesis, we demonstrate the clinical relevance of ciliary lipid-associated cargo trafficking and the underlying biochemical pathology due to a novel Joubert syndrome patient mutation.

Although synapse-forming lymphocytes do not have primary cilia, the two membrane domains have been shown to share structural and functional similarities. We show that the LCK trafficking to the immune synapse involves GDI-like solubilising factor (GSF)-mediated transport, which has been previously described in the primary cilium. The GSF UNC119A facilitates LCK extraction from the membranes into the cytoplasm. LCK release occurs specifically at the synapse under the action of the G protein ARL3 and the regulation of the synapse-localised ARL13B. Retention is mediated by phosphoregulation of the LCK-UNC119A interaction. A very similar system operates in the cilium, and therefore it is another shared feature between cilia and synapses. Furthermore, we show that a novel ARL3 mutation identified by our collaborators interferes with GSF-mediated trafficking and disrupts maintenance of ciliary composition. Finally, I present my preliminary investigations into using GSF-mediated trafficking to manipulate ciliary signalling.

The flexibility of GSF-mediated trafficking results in efficient cellular transportation, as well as far-reaching consequences in case of its impairment. Our work provides insights into potential avenues of manipulating signalling pathways through affecting the underlying transport.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QR Microbiology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Supervisor's Name: Ismail, Dr. Shehab and Norman, Prof. James
• Date of Award: 2020
• Embargo Date: 15 January 2023
• Depositing User: Mrs Marie Cairney
• Unique ID: glathesis:2020-77892
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 15 Jan 2020 15:07
• Last Modified: 18 Jan 2023 13:50
• Thesis DOI: 10.5525/gla.thesis.77892
• URI: https://theses.gla.ac.uk/id/eprint/77892