Imperial College London
Portrait Picture

Dr Josefin Ahnström

Faculty of Medicine, Department of Immunology and Inflammation

Senior Lecturer in Haematology
 
 
 
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Contact

 

+44 (0)20 3313 4236j.ahnstrom

 
 
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Location

 

5S5Commonwealth BuildingHammersmith Campus

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Summary

 

Publications

Citation

BibTex format

@article{Somajo:2015:10.1160/TH14-09-0803,
author = {Somajo, S and Ahnstroem, J and Gierula, M and Fernandez-Recio, J and Villoutreix, BO and Dahlbaeck, B},
doi = {10.1160/TH14-09-0803},
journal = {Journal of Thrombosis and Haemostasis},
pages = {976--987},
title = {Amino acid residues in the laminin G domains of protein S involved in tissue factor pathway inhibitor interaction},
url = {http://dx.doi.org/10.1160/TH14-09-0803},
volume = {113},
year = {2015}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Protein S functions as a cofactor for tissue factor pathway inhibitor (TFPI) and activated protein C (APC). The sex hormone binding globulin (SHBG)-like region of protein S, consisting of two laminin G-like domains (LG1 and LG2), contains the binding site for C4b-binding protein (C4BP) and TFPI. Furthermore, the LG-domains are essential for the TFPI-cofactor function and for expression of full APC-cofactor function. The aim of the current study was to localise functionally important interaction sites in the protein S LG-domains using amino acid substitutions. Four protein S variants were created in which clusters of surface-exposed amino acid residues within the LG-domains were substituted. All variants bound normally to C4BP and were fully functional as cofactors for APC in plasma and in pure component assays. Two variants, SHBG2 (E612A, I614A, F265A, V393A, H453A), involving residues from both LG-domains, and SHBG3 (K317A, I330A, V336A, D365A) where residues in LG1 were substituted, showed 50-60 % reduction in enhancement of TFPI in FXa inhibition assays. For SHBG3 the decreased TFPI cofactor function was confirmed in plasma based thrombin generation assays. Both SHBG variants bound to TFPI with decreased affinity in surface plasmon resonance experiments. The TFPI Kunitz 3 domain is known to contain the interaction site for protein S. Using in silico analysis and protein docking exercises, preliminary models of the protein S SHBG/TFPI Kunitz domain 3 complex were created. Based on a combination of experimental and in silico data we propose a binding site for TFPI on protein S, involving both LG-domains.
AU  - Somajo,S
AU  - Ahnstroem,J
AU  - Gierula,M
AU  - Fernandez-Recio,J
AU  - Villoutreix,BO
AU  - Dahlbaeck,B
DO  - 10.1160/TH14-09-0803
EP  - 987
PY  - 2015///
SN  - 1538-7933
SP  - 976
TI  - Amino acid residues in the laminin G domains of protein S involved in tissue factor pathway inhibitor interaction
T2  - Journal of Thrombosis and Haemostasis
UR  - http://dx.doi.org/10.1160/TH14-09-0803
UR  - http://hdl.handle.net/10044/1/49735
VL  - 113
ER  -
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