OC 29.2 - Surface exposure of cellular factor XIII on activated platelets and platelet microparticles is unrelated to the elevation of cytoplasmic Ca2+ concentration

Sunday, July 10, 2022

3:00 PM – 3:15 PM

Location: ExCel Center, ICC Capital Suite Room 1

Presentation Format: In-Person

Presenting Author(s)

Laura Somodi

PhD student
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary

Co-Author(s)

IB

Ildikó Beke Debreceni

Research Fellow
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary
GK

Gréta Kis

Research Fellow
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary
MC

Marco Cozzolino

PhD student
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary
JK

János Kappelmayer

professor
Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
Debrecen, Hajdu-Bihar, Hungary
MA

Miklós Antal

Professor
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary
GP

György Panyi

Professor
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary
HB

Helga Bárdos

Associate Professor
University of Debrecen
Debrecen, Hajdu-Bihar, Hungary
Nicola J. J. Mutch, PhD

Professor
Aberdeen Cardiovascular & Diabetes Centre, School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen
Aberdeen, Scotland, United Kingdom
LM

László Muszbek

Professor
University of Debrecen, Medical Faculty, Department of Laboratory Medicine, Division of Clinical Laboratory Science,
Debrecen, Hajdu-Bihar, Hungary

Background: Platelets contain a high amount of potentially active A subunit dimer of coagulation factor XIII (cellular FXIII; cFXIII). It is of cytoplasmic localization, not secreted, but becomes translocated to the surface of platelets activated by convulxin and thrombin (CVX+Thr) (Mitchell et al. Blood 2014;124:3982-90).

Aims: To explore the difference in cFXIII translocation on platelets and platelet microparticles between receptor mediated and non-receptor mediated platelet activation and how the translocation is related to cytoplasmic Ca2+ concentration. A further aim was to shed some light on the mechanism of cFXIII translocation.

Methods: Gel-filtered platelets were activated by CVX+Thr or Ca2+-ionophore (calcimycin). The translocation of cFXIII and phosphatidylserine (PS) to the surface of activated platelets and platelet-derived microparticles was investigated by flow cytometry, immunofluorescence and immune electron microscopy. Fluo-4-AM fluorescence was used for the measurement of intracellular Ca2+ concentration. The role of RhoA and the activation of cFXIII were tested by studying the effect of their inhibitors.

Results: Receptor mediated activation by CVX+Thr exposed cFXIII and PS to the surface of over 60% and 30% of platelets, respectively. Electron microscopy revealed microparticles with preserved membrane structure and also microparticles devoid of labeling for membrane glycoprotein CD41a. cFXIII was observed on both types of microparticles but was more abundant in the absence of CD41a. cFXIII translocation was eliminated by Rhosin, a RhoA inhibitor, while only partial decrease could be achieved by T101, a transglutaminase inhibitor. Non-receptor mediated activation of platelets by calcimycin highly elevated cytoplasmic Ca2+ concentration, it induced the translocation of PS to the surface of platelets and microparticles, but failed to expose cFXIII.

Conclusion(s): The elevation of intracellular Ca2+ concentration is sufficient for the translocation of PS from the internal layer of the membrane, while the translocation of cFXIII from the platelet cytoplasm requires additional receptor mediated mechanism(s).