C4.4A, a structural homologue of the urokinase-type plasminogen activator receptor (uPAR), was originally identified as a metastasis-associated membrane protein, but little is known about its structural and functional properties. Therefore, we expressed, purified and characterized a soluble truncated form of human C4.4A, and used this protein to produce specific polyclonal anti-C4.4A antibodies. By immunohistochemistry we observed a pronounced surface staining for C4.4A in suprabasal keratinocytes of chronic human wounds and found C4.4A expression markedly upregulated in migrating keratinocytes during re-epithelisation of incisional skin wounds. Phorbol-ester-induced hyperplasia of mouse skin is also accompanied by a significant induction of C4.4A expression in the multilayered, suprabasal keratinocytes. C4.4A contains two Ly-6 (leucocyte antigen 6)/uPAR/α-neurotoxin modules. Our recombinant human C4.4A is extensively modified by post-translational glycosylation, which include 5–6 N-linked carbohydrates primarily located in or close to its second Ly-6/uPAR/α-neurotoxin module and approximately 15 O-linked carbohydrates clustered in a Ser/Thr/Pro-rich region at the C-terminus. A highly protease-sensitive region (Tyr200–Arg204) is located between these two clusters of N- and O-linked carbohydrates. The natural, glycolipid-anchored C4.4A from amnion membranes of human term placenta exhibits similar properties. Using recombinant, soluble C4.4A or MCF 7 cells, which express significant amounts of GPI-anchored C4.4A, we find no evidence for an interaction between C4.4A and uPA, a property suggested previously for rat C4.4A. Collectively these data indicate that C4.4A, although being a structural homologue of uPAR, is unlikely to have a functional overlap with uPAR.
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Research Article|
June 15 2004
Structural analysis and tissue localization of human C4.4A: a protein homologue of the urokinase receptor
Line V. HANSEN;
Line V. HANSEN
*Finsen Laboratory, Rigshospitalet, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
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Henrik GÅRDSVOLL;
Henrik GÅRDSVOLL
*Finsen Laboratory, Rigshospitalet, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
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Boye S. NIELSEN;
Boye S. NIELSEN
*Finsen Laboratory, Rigshospitalet, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
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Leif R. LUND;
Leif R. LUND
*Finsen Laboratory, Rigshospitalet, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
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Keld DANØ;
Keld DANØ
*Finsen Laboratory, Rigshospitalet, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
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Ole N. JENSEN;
Ole N. JENSEN
†Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
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Michael PLOUG
Michael PLOUG
1
*Finsen Laboratory, Rigshospitalet, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
1To whom correspondence should be addressed (e-mail m-ploug@finsenlab.dk).
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Publisher: Portland Press Ltd
Received:
September 26 2003
Revision Received:
February 24 2004
Accepted:
March 10 2004
Accepted Manuscript online:
March 10 2004
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2004
2004
Biochem J (2004) 380 (3): 845–857.
Article history
Received:
September 26 2003
Revision Received:
February 24 2004
Accepted:
March 10 2004
Accepted Manuscript online:
March 10 2004
Citation
Line V. HANSEN, Henrik GÅRDSVOLL, Boye S. NIELSEN, Leif R. LUND, Keld DANØ, Ole N. JENSEN, Michael PLOUG; Structural analysis and tissue localization of human C4.4A: a protein homologue of the urokinase receptor. Biochem J 15 June 2004; 380 (3): 845–857. doi: https://doi.org/10.1042/bj20031478
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