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The influence of tissue transglutaminase on the function of Fc receptors
Abstract:
In contrast to FcRII the soluble Fc receptor (FcRI) of human peripheral mononuclear blood cells (PMBC) is shed from PMBC following a 4-37 degrees C temperature shift and inhibits rosette formation of nonshed PMBC with antibody-coated erythrocytes (EA). Purified FcR, could be polymerized by tissue transglutaminase as was revealed by SDS-polyacrylamide gel electrophoresis. Comparing the Sephadex G-150 elution profile of the EA rosette inhibitory capacity of FcRI vs FcRI incubated in the presence of transglutaminase, the latter was found in a higher mol. wt region and could inhibit rosette formation by both FcRI and FcRII. Furthermore, the shedding of FcRI could be prevented by the addition of transglutaminase or Ca2+-ionophore A23187 (which leads to the activation of PMBC transglutaminase) to the cell suspension. The function of FcRII was not affected by either the addition of transglutaminase or Ca2+-ionophore to the cells. The results point to the involvement of transglutaminase in the determination of the functional state of the Fc receptor on the cell surface.
Insights
Soluble Fc receptor (FcRI) shedding from peripheral mononuclear blood cells (PMBC) is temperature-dependent and inhibited by transglutaminase. This enzyme also polymerizes FcRI, enhancing its inhibitory capacity on Fc receptor function.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Fc receptors (FcR) mediate immune responses by binding antibodies.
- Fc receptor II (FcRII) and Fc receptor I (FcRI) are expressed on peripheral mononuclear blood cells (PMBC).
- FcRI shedding from PMBC is a known phenomenon affecting immune cell function.
Purpose of the Study:
- To investigate the role of transglutaminase in FcRI shedding and function.
- To explore the effect of transglutaminase on FcRI polymerization and inhibitory capacity.
- To determine if transglutaminase influences FcRII function.
Main Methods:
- Temperature shift experiments on PMBC to induce FcRI shedding.
- Purification of FcRI and polymerization using tissue transglutaminase.
- SDS-polyacrylamide gel electrophoresis to analyze FcRI polymerization.
- Sephadex G-150 gel filtration to assess molecular weight and inhibitory capacity.
- Treatment of PMBC with transglutaminase or Ca2+-ionophore A23187.
Main Results:
- FcRI sheds from PMBC after a temperature shift (4-37°C) and inhibits rosette formation.
- Purified FcRI can be polymerized by transglutaminase, forming higher molecular weight complexes.
- Transglutaminase-treated FcRI exhibits enhanced rosette inhibitory capacity, affecting both FcRI and FcRII.
- Transglutaminase or Ca2+-ionophore prevents FcRI shedding, while FcRII function remains unaffected.
Conclusions:
- Transglutaminase plays a critical role in regulating FcRI shedding and function.
- FcRI polymerization by transglutaminase alters its inhibitory properties.
- The findings suggest transglutaminase involvement in controlling the functional state of Fc receptors on cell surfaces.