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CD44 is not an adhesive receptor for osteopontin
L L Smith1, B W Greenfield, A Aruffo
1Department of Pathology, University of Washington, Seattle 98195, USA.
Journal of Cellular Biochemistry
|March 24, 1999
Summary
This study investigated osteopontin binding to CD44 variants. Researchers found no interaction between standard or variant CD44 proteins and osteopontin, suggesting limited in vivo binding.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Osteopontin is a glycoprotein involved in cell adhesion and migration.
- Cellular interactions with osteopontin are typically mediated by integrin receptors recognizing its RGD domain.
- CD44, a non-integrin adhesion molecule, was recently identified as a potential osteopontin receptor.
Purpose of the Study:
- To determine which CD44 isoforms mediate binding to osteopontin.
- To investigate the interaction between various CD44 variants and different forms of osteopontin.
Main Methods:
- Enzyme-linked immunosorbent assays (ELISAs) were employed.
- Standard CD44 and several splice variants were tested using CD44-human immunoglobulin fusion proteins.
- Multiple osteopontin preparations were used, including native, urinary, and recombinant forms.
Main Results:
- CD44-human immunoglobulin fusion proteins successfully interacted with hyaluronic acid.
- No interaction was observed between CD44H, CD44E, CD44v3, v8-v10, or CD44v3 and osteopontin.
- These findings indicate a lack of binding across tested CD44 isoforms to osteopontin.
Conclusions:
- CD44-osteopontin interactions may not be prevalent in vivo.
- Potential interactions might be restricted to specific, yet unidentified, CD44 isoforms.
- Alternatively, particular modified forms of osteopontin may be required for CD44 binding.