CDw149 antibodies recognize a clustered subset of CD47 molecules associated with cytoplasmic signaling molecules
K Drbal1, J Cerný, P Angelisová
1Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague.
Insights
Researchers identified CDw149, a leukocyte antigen, as a clustered form of CD47 (integrin-associated protein). This finding clarifies CDw149
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- CDw149 is a broadly expressed human leukocyte antigen.
- Its molecular identity and function remained uncharacterized.
- Previous studies suggested CD47 has signaling capabilities.
Purpose of the Study:
- To determine the molecular basis of the CDw149 antigen.
- To investigate the relationship between CDw149 and CD47.
- To understand the signaling mechanisms of CD47.
Main Methods:
- Utilized monoclonal antibodies (mAbs) against CDw149.
- Performed molecular characterization of the antigen.
- Analyzed CD47 expression and clustering on leukocytes and erythrocytes.
- Investigated mAb binding affinities to monomeric and clustered CD47.
- Examined CD47 association with signaling complexes.
Main Results:
- Anti-CDw149 mAbs recognize a clustered subset of CD47 (integrin-associated protein).
- This clustered CD47 subset is present on leukocytes but not erythrocytes.
- Low-affinity binding of mAbs to monomeric CD47 contrasts with high avidity to clustered CD47.
- A fraction of CD47 associates with signaling molecules within microdomains, explaining its signaling capacity.
Conclusions:
- CDw149 represents a specific clustered form of CD47 on leukocytes.
- Low-affinity anti-CD47 mAbs can target specific receptor complexes involved in cell activation.
- This reactivity explains previously described activation forms of cell surface molecules.
Abstract:
One of the recently described antigens broadly expressed on human leukocytes is CDw149, which was defined at the 6th Human Leukocyte Differentiation Antigen (HLDA) Workshop by means of 2 monoclonal antibodies (mAbs). Molecular characterization of this antigen has been lacking. In the present study we demonstrate that these anti-CDw149 mAbs actually recognize a clustered subset of a well-defined membrane protein, CD47, also known as integrin-associated protein (IAP). This clustered subset is present on leukocytes but not erythrocytes. The anti-CDw149 mAbs bind with only low affinity to a monomeric (unclustered) subset of CD47 but with high avidity to the CD47 clusters. A fraction of CD47 is associated with large complexes containing cytoplasmic signaling molecules (Src family kinases and heterotrimeric G-proteins) similar to glycosphingolipid-enriched microdomains (GEMs), which may explain the previously described signaling capacity of CD47. The low-affinity anti-CD47 mAbs may be useful tools targeting specific receptor complexes involved in cell activation. Specific reactivity of low-affinity mAbs with clustered subsets of cell surface antigens may more generally explain the nature of poorly defined "activation forms" or activation neoepitopes described previously for several cell surface molecules.
