PB0846 - Membrane Procoagulation and N‑Terminomics/TAILS Profiling in Montreal Platelet Syndrome Kindred with VWF p.V1316M mutation

Monday, June 26, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

Ejaife O. Agbani, BPharm, MSc, PhD

Assistant Professor
University of Calgary
Calgary, Alberta, Canada

Co-Author(s)

DY

Daniel Young

Research Manager
University of Calgary
Calgary, Alberta, Canada
SC

Si An Chen

Research Assistant
University of Calgary
Calgary, Alberta, Canada
SS

Sophie Smith

Research Assistant
University of Calgary
Calgary, Alberta, Canada
AL

Adrienne Lee

Physician
Division of Hematology & Hematological Malignancies, Department of Medicine, Cumming School of Medicine, University of Calgary, Alberta, Canada.
Calgary, Alberta, Canada
AP

Alastair W. Poole

Principal Investigator
School of Physiology, Pharmacology and Neuroscience/University of Bristol
Bristol, England, United Kingdom
AD

Antoine Dufour

Assistant Professor
University of Calgary
Calgary, Alberta, Canada
MP

Man-Chiu Poon

Clinical Professor; Professor Emeritus of Medicine - Paediatrics and Oncology
Division of Hematology and Hematological Malignancies, Department of Medicine, University of Calgary, Calgary, AB, Canada
Calgary, Alberta, Canada

Background: The Montreal Platelet Syndrome Kindred (MPS) with VWF p.V1316M mutation (2B-VWDMPS) has been associated with macrothrombocytopenia, spontaneous platelet clumping, mucocutaneous and other bleeding which can be largely prevented by von Willebrand factor concentrate infusion. However, supplemental platelet transfusion has been required on occasions, particularly for severe gastro-intestinal bleeds.

Aims: We addressed the question of whether a previously uncharacterized platelet dysfunction contributes to bleeding diathesis in 2B-VWDMPS patients.

Methods: We studied the 2 members (mother and daughter) of the MPS kindred with severe bleeding phenotype and addressed this question by coupling quantitative platelet shotgun proteomics and validating biochemical assays, with the systematic analysis of platelet procoagulant membrane dynamics (PMD).

Results: Previously, we showed that membrane ballooning, a principal part of the platelet PMD after collagen stimulation, is driven by the influx of Na+ and Cl-, followed by the entry of water. Here, we report in 2B-VWDMPS platelets, loss of the transmembrane chloride channel-1 (CLIC1), and reduced chloride ion influx after collagen stimulation. This was associated with diminished membrane ballooning, phosphatidylserine externalisation and membrane thrombin formation, as well as a distinct phenotypic composition of platelets over fibrillar collagen. Using N-terminomics/TAILS (terminal amine isotopic labeling of substrates), we compared changes in proteolysis between healthy and 2B-VWDMPS platelets and identified processing differences of von Willebrand factor (VWF), fibronectin (FN1) and Crk-like protein (CRKL).

Conclusion(s): 2B-VWDMPS platelets are basally activated, partially degranulated, and have marked loss of regulatory, cytoskeletal, and contractile proteins that may account for structural disorganization, giant platelet formation and the reduction in the haemostatic response.