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Integrin-associated protein: a 50-kD plasma membrane antigen physically and functionally associated with integrins
The Journal of Cell Biology
|December 1, 1990
Summary
A novel 50-kD Integrin-associated Protein (IAP) enhances phagocytosis by mediating Arg-Gly-Asp ligand binding to leukocytes. This protein is crucial for immune cell signaling and function.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Phagocytosis enhancement in monocytes and neutrophils is mediated by Arg-Gly-Asp (RGD) containing proteins.
- Previous research identified an mAb, B6H12, that inhibits RGD-mediated enhancement of neutrophil phagocytosis by blocking RGD binding to leukocyte integrins.
Purpose of the Study:
- To purify and characterize the antigen recognized by the B6H12 mAb.
- To investigate the role of this antigen in RGD-mediated phagocytosis enhancement and its association with integrins.
Main Methods:
- Purification of the B6H12 antigen to homogeneity.
- Expression analysis of the purified antigen on various hematopoietic cells.
- Co-immunoprecipitation studies to assess association with integrins.
- Functional assays using anti-beta 3 and anti-50-kD protein mAbs to inhibit RGD-stimulated phagocytosis.
Main Results:
- A 50-kD molecule, designated Integrin-associated Protein (IAP), was purified.
- IAP is expressed on all hematopoietic cells, including erythrocytes, platelets, and placenta.
- IAP is associated with a beta 3 integrin on platelets and placenta, but not erythrocytes.
- Both anti-beta 3 and anti-IAP antibodies inhibit RGD-stimulated phagocytosis.
Conclusions:
- The 50-kD IAP is associated with beta 3 integrins on certain cell types.
- IAP plays a significant role in mediating RGD ligand-stimulated phagocytosis.
- IAP is hypothesized to be involved in signal transduction pathways for enhanced phagocytosis.