Regulation of the major platelet collagen and fibrin receptor GPVI by ADAM10 and Tspanc8 tetraspanins

Matthews, Alexandra (2019). Regulation of the major platelet collagen and fibrin receptor GPVI by ADAM10 and Tspanc8 tetraspanins. University of Birmingham. Ph.D.

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Abstract

The platelet collagen/fibrin receptor GPVI is a critical mediator of arterial thrombosis, but plays a minor role in haemostasis. ADAM10 is a ubiquitously expressed molecular scissor that proteolytically cleaves GPVI. ADAM10 associates with six tetraspanins (Tspan5, Tspan10, Tspan14, Tspan15, Tspan17 and Tspan33) termed the TspanC8 subgroup. TspanC8s regulate ADAM10 enzymatic maturation, intracellular trafficking and substrate specificity. Human platelets express three TspanC8s - Tspan14, Tspan15 and Tspan33. It was hypothesised that ADAM10 exists as three different molecular scissors with distinct capacities to cleave GPVI, depending on the associated TspanC8. The aim of this thesis was to identify the GPVI molecular scissor(s) using CRISPR/Cas9 genome editing and cleavage assays in cell line models.

Tspan15/ADAM10 and Tspan33/ADAM10, but not Tspan14/ADAM10, complexes were identified as the GPVI molecular scissors. Confocal microscopy revealed that Tspan15 and Tspan33 localised predominantly at the cell periphery, similar to GPVI, but Tspan14 was mainly localised intracellularly. Therefore, Tspan15 and Tspan33 most likely promote GPVI cleavage by trafficking ADAM10 into proximity with this substrate. These findings are important because they identify Tspan15/ADAM10 and Tspan33/ADAM10 as potential anti-platelet therapeutic targets, whereby their activation would induce GPVI cleavage and protect a patient from heart attack or stroke, without the toxic side effects of global ADAM10 activation.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):