Thromb Haemost 2000; 84(03): 413-419
DOI: 10.1055/s-0037-1614037
Commentary
Schattauer GmbH

Protein S Thr103Asn Mutation Associated with Type II Deficiency Reproduced In Vitro and Functionally Characterised

Tusar Kanti Giri
1   From the Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, University Hospital Malmö, Malmö, Sweden
,
Pablo García de Frutos
1   From the Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, University Hospital Malmö, Malmö, Sweden
,
Björn Dahlbäck
1   From the Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, University Hospital Malmö, Malmö, Sweden
› Author Affiliations

This work was supported by the Swedish Medical Research Council (grants 07143, 12561 and 13000), a Senior Investigators Award from the Swedish Foundation for Strategic Research, research funds from the University Hospital in Malmö, the Fondation Louis-Jeantet de Médecine, the Alfred Österlund Trust, and the Albert Påhlsson Trust.
Further Information

Publication History

Received 14 February 2000

Accepted after resubmission 10 April 2000

Publication Date:
14 December 2017 (online)

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Summary

Protein S functions as a cofactor to activated protein C (APC) in the degradation of FVa and FVIIIa. In protein S, the thrombin sensitive region (TSR) and the first EGF-like domain are important for expression of the APC cofactor activity. A naturally occurring Thr103Asn (T103N) mutation in the first EGF-like domain of protein S has been associated with functional (type II) protein S deficiency. To elucidate the functional consequences of the T103N mutation, recombinant protein S mutant was expressed in mammalian cells and functionally characterised. The expression level of protein S T103N from transiently transfected COS 1 cells was equal to that of wild type protein S. The mutant protein S and wild type protein S were also expressed in 293 cells after stable transfection, and the recombinant proteins purified. In APTT-and PT-based coagulation assays, the mutant protein demonstrated approximately 50% lower anticoagulant activity as compared to wild type protein S. The functional defect was further investigated in FVa-and FVIIIa-degradation assays. The functional defect of mutant protein S was attenuated at increasing concentrations of APC. The results demonstrate the region around residue 103 of protein S to be of functional importance, possibly through a direct interaction with APC.