Thromb Haemost 2003; 89(04): 687-695
DOI: 10.1055/s-0037-1613576
Platelet and Blood Cells
Schattauer GmbH

Store-mediated calcium entry in the regulation of phosphatidylserine exposure in blood cells from Scott patients

Imke C.A. Munnix
1   Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, The Netherlands
,
Marjan Harmsma
1   Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, The Netherlands
,
John C. Giddings
2   Department of Haematology, Welsh National School of Medicine, Heath Park, Cardiff, United Kingdom
,
Peter W. Collins
2   Department of Haematology, Welsh National School of Medicine, Heath Park, Cardiff, United Kingdom
,
Marion A.H. Feijge
1   Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, The Netherlands
,
Paul Comfurius
1   Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, The Netherlands
,
Johan W. M. Heemskerk
1   Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, The Netherlands
,
Edouard M. Bevers
1   Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, The Netherlands
› Institutsangaben

Financial support: Part of this work was supported by the Netherlands Foundation for Scientific Research, NWO 902-68-241.
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Publikationsverlauf

Received 17. Oktober 2002

Accepted after revision 27. Januar 2003

Publikationsdatum:
07. Dezember 2017 (online)

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Summary

Scott syndrome is a bleeding disorder, characterized by impaired surface exposure of procoagulant phosphatidylserine (PS) on platelets and other blood cells, following activation with Ca2+-elevating agents. Since store-mediated Ca2+ entry (SMCE) forms an important part of the Ca2+ response in various blood cells, it has been proposed that deficiencies in Ca2+ entry may relate to the impaired PS exposure in the Scott syndrome. Here, we have tested this hypothesis by investigating the relationship between Ca2+ fluxes and PS exposure in platelets as well as B-lymphoblasts derived from the original Scott patient (M.S.), a newly identified Welsh patient (V.W.) with similar bleeding symptoms, and two control subjects. Procoagulant activity of V.W. platelets in suspension, measured after stimulation with collagen/thrombin or Ca2+-ionophore, ionomycin, resulted in 52% or 17%, respectively, compared to that of correspondingly activated control platelets. Procoagulant activity of V.W. erythrocytes treated with Ca2+-ionophore resulted in less than 6% of the activity of control erythrocytes. Single-cell Ca2+ responses of M.S. and V.W. platelets, adhering to collagen, were similar to those of platelets from control subjects, while PS exposure was reduced to 7% and 15%, respectively, compared to controls. Stimulation of non-apoptotic B-lymphoblasts derived from both patients and controls with Ca2+-ionophore or agents causing Ca2+ mobilization and SMCE, resulted in similar Ca2+ responses. However, in lymphoblasts from M.S. and V.W. Ca2+-induced PS exposure was reduced to 7% and 13% of the control lymphoblasts, respectively. We conclude that i. patient V.W. is a new case of Scott syndrome, ii. Ca2+ entry in the platelets and lymphoblasts from both Scott patients is normal, and iii. elevated [Ca2+]i as caused by SMCE is not sufficient to trigger PS exposure.