Structural analysis and tissue localization of human C4.4A: a protein homologue of the urokinase receptor.

Abstract

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/alpha-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/alpha-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.

• Authors: Line V Hansen, Henrik Gårdsvoll, Boye S Nielsen, Leif R Lund, Keld Danø, Ole N Jensen, Michael Ploug
• Journal: The Biochemical journal (Biochem J) Vol. 380 Issue Pt 3 Pg. 845-57 (Jun 15 2004) ISSN: 1470-8728 [Electronic] England
• PMID: 15012588 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cell Adhesion Molecules
• GPI-Linked Proteins
• LYPD3 protein, human
• PLAUR protein, human
• Peptide Fragments
• Plaur protein, mouse
• Plaur protein, rat
• Receptors, Cell Surface
• Receptors, Urokinase Plasminogen Activator
• Recombinant Fusion Proteins
• phorbolol myristate acetate
• Tetradecanoylphorbol Acetate

Topics

• Amino Acid Sequence
• Animals
• Breast Neoplasms (pathology)
• Cell Adhesion Molecules (biosynthesis, chemistry, genetics, metabolism)
• Dermatologic Surgical Procedures
• GPI-Linked Proteins
• Humans
• Hyperplasia (chemically induced, metabolism)
• Immunohistochemistry
• Mice
• Mice, Inbred C57BL
• Molecular Sequence Data
• Peptide Fragments (chemistry)
• Peptide Mapping (methods)
• Placenta (chemistry)
• Protein Interaction Mapping (methods)
• Protein Processing, Post-Translational (genetics)
• Receptors, Cell Surface (biosynthesis, chemistry, genetics, metabolism)
• Receptors, Urokinase Plasminogen Activator
• Recombinant Fusion Proteins (biosynthesis, genetics)
• Sequence Homology, Amino Acid
• Skin (chemistry, pathology)
• Tetradecanoylphorbol Acetate (adverse effects, analogs & derivatives)
• Wound Healing