Immobilized collagen prevents shedding and induces sustained GPVI clustering and signaling in platelets

Abstract

Collagen, the most thrombogenic constituent of blood vessel walls, activates platelets through glycoprotein VI (GPVI). In suspension, following platelet activation by collagen, GPVI is cleaved by A Disintegrin And Metalloproteinase (ADAM)10 and ADAM17. In this study, we use single-molecule localization microscopy and a 2-level DBSCAN-based clustering tool to show that GPVI remains clustered along immobilized collagen fibers for at least 3 hours in the absence of significant shedding. Tyrosine phosphorylation of spleen tyrosine kinase (Syk) and Linker of Activated T cells (LAT), and elevation of intracellular Ca²⁺, are sustained over this period. Syk, but not Src kinase-dependent signaling is required to maintain clustering of the collagen integrin α2β1, whilst neither is required for GPVI. We propose that clustering of GPVI on immobilized collagen protects GPVI from shedding in order to maintain sustained Src and Syk-kinases dependent signaling, activation of integrin α2β1, and continued adhesion.

KEYWORDS:

• Glycoprotein (GP) VI
• platelets
• receptor shedding
• signaling
• super resolution microscopy

Acknowledgements

This work was funded by the British Heart Foundation, through the Chair award [CH0/03/003)] to Steve P. Watson, and the Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands, UK. We thank Deirdre Kavanagh, the COMPARE microscope officer, for support with imaging and Mark Probert for preliminary imaging data. We also thank Steve Thomas, Abdullah Khan, Julie Rayes and Christopher Smith for helpful discussions.

Author Contributions

C.P. did experimental work, analyzed the data, prepared figures and wrote the manuscript. J.A.P. implemented the cluster analysis and platelet spreading workflows. C.O’S. created the calcium analysis code and analyzed the data. R.K.A. and E.E.G. provided key reagents and expertise. S.P.W. provided supervision, devised experiments and interpreted the data. N.S.P. conceived the project, devised experiments, interpreted the data, prepared figures, and wrote the manuscript. All authors reviewed the manuscript.

Competing Interests

The authors declare no competing interests.

Supplementary Material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the British Heart Foundation [CH0/03/003].