Open Access
CC-BY 4.0 · Thromb Haemost 2018; 118(06): 1009-1020
DOI: 10.1055/s-0038-1646924
Cellular Haemostasis and Platelets
Schattauer GmbH Stuttgart

Significant Hypo-Responsiveness to GPVI and CLEC-2 Agonists in Pre-Term and Full-Term Neonatal Platelets and following Immune Thrombocytopenia

Alexander T. Hardy*
1   Institute of Cardiovascular Science, IBR Building, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
,
Verónica Palma-Barqueros*
2   Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, U765-CIBERER, Murcia, Spain
,
Stephanie K. Watson
1   Institute of Cardiovascular Science, IBR Building, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
,
Jean-Daniel Malcor
3   Department of Biochemistry, University of Cambridge, Downing Site, Cambridge, United Kingdom
,
Johannes A. Eble
4   Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany
,
Elizabeth E. Gardiner
5   ACRF Department of Cancer Biology and Therapeutics, John Curtin School of Medical Research, Australian National University, Canberra, Australia
,
José E. Blanco
6   Departamento de Ginecología y Obstetricia, Hospital Clínico Universitario Virgen de la Arrixaca. IMIB-Arrixaca, Murcia, Spain
,
Rafael Guijarro-Campillo
6   Departamento de Ginecología y Obstetricia, Hospital Clínico Universitario Virgen de la Arrixaca. IMIB-Arrixaca, Murcia, Spain
,
Juan L. Delgado
6   Departamento de Ginecología y Obstetricia, Hospital Clínico Universitario Virgen de la Arrixaca. IMIB-Arrixaca, Murcia, Spain
,
María L. Lozano
2   Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, U765-CIBERER, Murcia, Spain
,
Raúl Teruel-Montoya
2   Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, U765-CIBERER, Murcia, Spain
,
Vicente Vicente
2   Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, U765-CIBERER, Murcia, Spain
,
Steve P. Watson
1   Institute of Cardiovascular Science, IBR Building, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
7   Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands, United Kingdom
,
José Rivera
2   Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, U765-CIBERER, Murcia, Spain
,
Francisca Ferrer-Marín
2   Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Arrixaca, U765-CIBERER, Murcia, Spain
8   Grado de Medicina, Universidad Católica San Antonio de Murcia, Murcia, Spain
› Author Affiliations

Funding Research by the group of F.F.-M. and J.R. is supported by grants from Instituto de Salud Carlos III and Feder (PI14/01956) and Fundación Séneca (19873/GERM/15). V.P.-B. holds a research fellowship from CIBERER (CB15/00055). Research by the group of S.P.W. is supported by the British Heart Foundation (RG/ PG/13/36/30275; RG/09/007).
Further Information

Publication History

16 January 2018

01 April 2018

Publication Date:
25 April 2018 (online)

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Abstract

Neonatal platelets are hypo-reactive to the tyrosine kinase-linked receptor agonist collagen. Here, we have investigated whether the hypo-responsiveness is related to altered levels of glycoprotein VI (GPVI) and integrin α2β1, or to defects in downstream signalling events by comparison to platelet activation by C-type lectin-like receptor 2 (CLEC-2). GPVI and CLEC-2 activate a Src- and Syk-dependent signalling pathway upstream of phospholipase C (PLC) γ2. Phosphorylation of a conserved YxxL sequence known as a (hemi) immunotyrosine-based-activation-motif (ITAM) in both receptors is critical for Syk activation. Platelets from human pre-term and full-term neonates display mildly reduced expression of GPVI and CLEC-2, as well as integrin αIIbβ3, accounted for at the transcriptional level. They are also hypo-responsive to the two ITAM receptors, as shown by measurement of integrin αIIbβ3 activation, P-selectin expression and Syk and PLCγ2 phosphorylation. Mouse platelets are also hypo-responsive to GPVI and CLEC-2 from late gestation to 2 weeks of age, as determined by measurement of integrin αIIbβ3 activation. In contrast, the response to G protein-coupled receptor agonists was only mildly reduced and in some cases not altered in neonatal platelets of both species. A reduction in response to GPVI and CLEC-2, but not protease-activated receptor 4 (PAR-4) peptide, was also observed in adult mouse platelets following immune thrombocytopenia, whereas receptor expression was not impaired. Our results demonstrate developmental differences in platelet responsiveness to GPVI and CLEC-2, and also following immune platelet depletion leading to reduced Syk activation. The rapid generation of platelets during development or following platelet depletion is achieved at the expense of signalling by ITAM-coupled receptors.

Supplementary Material