Thromb Haemost 2000; 84(06): 1087-1094
DOI: 10.1055/s-0037-1614175
Review Article
Schattauer GmbH

Occurrence of Amphoterin (HMG1) as an Endogenous Protein of Human Platelets that Is Exported to the Cell Surface upon Platelet Activation

Ari Rouhiainen
1   From Finnish Red Cross Blood Transfusion Service, Helsinki, Finland
2   Laboratory of Molecular Neurobiology, Institute of Biotechnology, Department of Biosciences, Division of Biochemistry, University of Helsinki, Finland
,
Shinji Imai
2   Laboratory of Molecular Neurobiology, Institute of Biotechnology, Department of Biosciences, Division of Biochemistry, University of Helsinki, Finland
3   Department of Anatomy, Shiga University of Medical Science, Shiga-ken, Japan
,
Heikki Rauvala
2   Laboratory of Molecular Neurobiology, Institute of Biotechnology, Department of Biosciences, Division of Biochemistry, University of Helsinki, Finland
,
Jaakko Parkkinen
1   From Finnish Red Cross Blood Transfusion Service, Helsinki, Finland
› Author Affiliations

The authors thank Dr. Riitta Kekomäki for help in platelet binding studies. The excellent technical assistance of Anne Remes is gratefully acknowledged. This work was supported by the Sigrid Jusélius Foundation and the Academy of Finland.
Further Information

Publication History

Received 14 February 2000

Accepted after resubmission 14 July 2000

Publication Date:
13 December 2017 (online)

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Summary

Amphoterin (HMG1) is a 30-kD heparin-binding protein which is functionally associated with the outgrowth of cytoplasmic processes in developing neurones. Amphoterin has been shown to mediate adhesive and proteolytic interactions at the leading edge of motile cells. Recently it was shown that inhibition of amphoterin interactions with its cell surface receptor (RAGE) suppresses tumour growth and metastasis. In this work we have identified amphoterin polypeptide and its mRNA in human platelets. Amphoterin had a cytoplasmic localisation in resting platelets according to subcellular fractionation studies and immunogold electronmicroscopy. After platelet activation, part of amphoterin was associated with the external surface of plasma membrane. Externalisation of amphoterin during platelet activation was also detected in immunofluorescence studies. Amphoterin was detectable in human serum (0.2 ng/ml) but not in plasma. Resting platelets treated with PGI2 and forskolin bound to immobilised recombinant amphoterin independently of divalent cations. The binding induced a spicular morphology in platelets, and was effectively inhibited by heparin. Amphoterinbinding protein components on the platelet surface were not identified, but amphoterin bound to phosphatidylserine and sulfatide in lipid binding assays. Our results suggest that amphoterin is an endogenous protein in human platelets, which is exported to the cell surface during platelet activation. Interaction of amphoterin with the platelet surface may be mediated by sulfoglycolipids and phospholipids.