PB0389 - The C-Type Lectin CD93 Regulates Platelet Activation Induced by PAR4 Stimulation

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Silvia Maria Grazia Trivigno

PhD student
University School for Advanced Studies IUSS, Pavia
Pavia, Lombardia, Italy

Co-Author(s)

Mauro Vismara

PhD
University of Pavia, Pavia
Pavia, Lombardia, Italy
MZ

Marta Zarà

PhD
Centro Cardiologico Monzino IRCCS, Milano
Milano, Lombardia, Italy
LG

Luca Galgano

PhD student
University School for Advanced Studies IUSS, Pavia
Pavia, Lombardia, Italy
SC

Sara Carnevali Carlino

Master's degree student
University of Pavia, Pavia
Pavia, Lombardia, Italy
Ilaria Canobbio, PhD

Associate Professor
University of Pavia, Pavia
Pavia, Lombardia, Italy
FG

Federico Galvagni

Associate Professor
University of Siena, Siena
Siena, Toscana, Italy
MO

Maurizio Orlandini

Associate Professor
University of Siena, Siena
Siena, Toscana, Italy
MT

Mauro Torti

Full Professor
University of Pavia
Pavia, Lombardia, Italy
GG

Gianni Francesco Guidetti

Associate Professor
University of Pavia, Pavia
Pavia, Lombardia, Italy

Background: CD93 is a member of group XIV in the C-type lectin superfamily and plays a prominent role in inflammation, vascular diseases and cancer. In endothelial cells, CD93 is an adhesion molecule regulating angiogenesis through the interaction with the extracellular matrix protein Multimerin-2. CD93 also regulates leukocyte recruitment and migration, as well as efferocytosis. The extracellular domain of CD93 can be released as a soluble factor by proteolytic shedding and its plasma levels are increased in different disorders. Despite its emerging importance in several vascular contexts, the contribution of CD93 to platelet biology is still unknown.

Aims: In this study we investigated the role of CD93 in platelet activation induced by physiological platelet agonists.

Methods: Platelet aggregation, secretion, protein phosphorylation and platelet-neutrophil aggregate formation induced by several agonists were investigated in whole blood and purified human and murine platelets by lumiaggregometry, immunoblotting, and flow cytometry.

Results: CD93 is expressed in human and murine platelets, as demonstrated by immunoblotting and immunofluorescence microscopy analyses. Stimulation of human platelets with thrombin or collagen induced CD93 tyrosine phosphorylation and shedding, promoting its release as a soluble extracellular domain. Platelets from CD93-knockout (KO) mice aggregated normally when stimulated with convulxin, thrombin or U46619, but displayed a defective aggregation upon selective stimulation of PAR4. Moreover, activation of integrin αIIbβ3 and α-granule release induced by PAR4-activating peptide were significantly reduced in CD93KO platelets, and formation of platelet-neutrophil aggregates was also impaired. These functional defects were mirrored by a reduction of protein tyrosine phosphorylation and protein kinase C activation. Interestingly, analysis of platelet response upon multiple stimulations over time with low doses of PAR4-activating peptide revealed a more pronounced desensitisation of CD93-deficient platelets compared to wild type cells.

Conclusion(s): This study reveals a novel role for CD93 in platelet function as a selective regulator of PAR4-mediated signaling.