Mucor circinelloides induces platelet aggregation through integrin αIIbβ3 and FcγRIIA

Abstract

Thrombosis is a hallmark of the fatal fungal infection mucormycosis. Yet, the platelet activation pathway in response to mucormycetes is unknown. In this study we determined the platelet aggregation potential of Mucor circinelloides (M. circinelloides) NRRL3631, characterized the signaling pathway facilitating aggregation in response to fungal spores, and identified the influence of the spore developmental stage upon platelet aggregation potential. Using impedance and light-transmission aggregometry, we showed that M. circinelloides induced platelet aggregation in whole blood and in platelet-rich plasma, respectively. The formation of large spore-platelet aggregates was confirmed by light-sheet microscopy, which showed spores dispersed throughout the aggregate. Aggregation potential was dependent on the spore’s developmental stage, with the strongest platelet aggregation by spores in mid-germination. Inhibitor studies revealed platelet aggregation was mediated by the low affinity IgG receptor FcγRIIA and integrin αIIbβ3; Src and Syk tyrosine kinase signaling; and the secondary mediators TxA₂ and ADP. Flow cytometry of antibody stained platelets showed that interaction with spores increased expression of platelet surface integrin αIIbβ3 and the platelet activation marker CD62P. Together, this is the first elucidation of the signaling pathways underlying thrombosis formation during a fungal infection, highlighting targets for therapeutic intervention.

Keywords:

• FcγRIIA
• Mucor circinelloides
• mucormycetes
• mucormycosis
• platelets
• thrombosis

Acknowledgments

We would like to thank Soo Chan Lee for providing the mucormycete strain NRRL3631 used in this study.

Declaration of Interests

The authors report no declarations of interest.

Supplemental data

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

Additional information

Funding

This work was supported by Wellcome ISSF grant [175ISSFPP to KV] and the British Heart Foundation [CH03/03 to SPW]. HG is supported by MRC doctoral training partnership: Integrated Midlands Partnership for Biomedical Training (MR/N013913/1).

Notes on contributors

Harlene Ghuman

Conceived and designed the experiments: KV, SPW, HG, MZ. Performed the experiments: HG, AS-R, MZ. Analyzed the data: HG, SW, KV. Wrote the paper: HG, KV. Critically reviewed the manuscript: KV, SPW.