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Regulation of C-type lectin-like receptors dectin-1 and CLEC-2 by tetraspanins

Tomlinson, Neil David (2010)
Ph.D. thesis, University of Birmingham.

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Abstract

Tetraspanins are a superfamily of glycoproteins that function as ‘organisers’ of membranes by clustering with each other to form tetraspanin-enriched microdomains, into which certain other receptors and signalling proteins are recruited and regulated. Tetraspanin microdomains have been implicated in a range of biological processes including cell signalling, adhesion, intracellular trafficking, cell-cell fusion and viral entry. The tetraspanin CD37 was recently shown to negatively regulate the C-type lectin-like receptor dectin-1, which is essential for innate immune responses to fungal pathogens. The aim of this thesis was to firstly develop a cell line model system to investigate the mechanism by which tetraspanins inhibit dectin-1, and to secondly extend this work to the dectin-1-related CLEC-2, which is essential for platelet thrombus formation and stability. Using a nuclear factor of activated T-cells (NFAT) transcriptional reporter assay in the Jurkat T-cell line, transient over-expression of CD37 was found to powerfully inhibit dectin-1 signalling following stimulation with its ligand, β-glucan. Over-expression of other tetraspanins also inhibited dectin-1 signalling, but did not globally inhibit receptor signalling because the platelet collagen receptor, GPVI, was unaffected. Similar to dectin-1, CLEC-2 signalling in response to its ligand, the snake venom toxin rhodocytin, was also abrogated following tetraspanin over-expression. However, stable tetraspanin over-expression only partially reduced signalling. Moreover, knockdown of the major Jurkat cell tetraspanin, CD81, and deletion of the major platelet tetraspanin, CD9, did not affect dectin-1 and CLEC-2 signalling, respectively. In summary, the importance of transient tetraspanin over-expression for dectin-1 and CLEC-2 inhibition, and the fact that any tetraspanin can inhibit, suggests that tetraspanin microdomains are disrupted by the presence of one over-expressed tetraspanin. This leads to a failure of dectin-1 and CLEC-2 signalling by a mechanism that is not clear, but suggests that tetraspanin microdomains are important for signalling by these C-type lectin-like receptors.

Type of Work:Ph.D. thesis.
Supervisor(s):Tomlinson, Mike and Watson, Steve P.
School/Faculty:Colleges (2008 onwards) > College of Medical & Dental Sciences
Department:Institute for Biomedical Research, Centre for Cardiovascular Sciences
Subjects:QR180 Immunology
RC Internal medicine
Institution:University of Birmingham
ID Code:826
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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