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Nanoscale study of perforin pore formation and lipid specificity

Hodel, Adrian; (2019) Nanoscale study of perforin pore formation and lipid specificity. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Perforin is a key effector protein of the vertebrate immune system. Secreted as soluble monomers by cytotoxic T lymphocytes and natural killer cells, perforin selectively forms oligomeric transmembrane pore assemblies on the surface of virus infected and cancerous cells. These 10-20 nm wide pores allow diffusion of co-secreted granzymes into the target cells, which next trigger apoptotic cell killing. To understand the pathway of perforin pore assembly on/in target membranes, we have visualised different stages of this process by atomic force and electron microscopy. Initially, perforin forms intermediate, prepore oligomers of up to 8 subunits on the membrane surface. These short oligomers can subsequently convert to membrane pores with a tighter subunit packing. These pore assemblies next recruit further prepore oligomers from the membrane surface to grow the pore size. Most of the resulting arc- and ring-shaped perforin pores contain between 10 - 30 subunits. To identify mechanisms by which immune cells are protected from self-harm by perforin, we have investigated how perforin pore assembly depends on the lipid composition of the target membrane. Perforin binding is affected by the packing density of lipid molecules in the membrane: It does not or hardly binds to raft-like, liquid ordered lipid domains. Furthermore, negatively charged membrane surfaces, i.e., rich in phosphatidylserine, allow perforin binding and oligomerization of short intermediate assemblies, but subsequently trap these assemblies in a non-porating, dysfunctional state. These findings coincide with reports of increased lipid packing and phosphatidylserine exposure on the surface of activated cytotoxic T lymphocytes.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Nanoscale study of perforin pore formation and lipid specificity
Event: UCL
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
URI: https://discovery.ucl.ac.uk/id/eprint/10069689
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