Presence and primary sequence of a high-affinity IgG receptor on canine mastocytoma (CM-MC) cells
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Published on: June 29, 2016
Ryosuke Nakamura1, Yoshitaka Sato, Kayoko Takagi
1Division of Biochemistry and Immunochemistry, National Institute of Health Sciences, Tokyo, Japan.
Insights
Canine mastocytoma cells express high-affinity IgG receptors (FcgammaRI), crucial for studying allergic responses. This finding reveals FcgammaRI
Area of Science:
- Immunology
- Cell Biology
- Veterinary Medicine
Background:
- Mast cells mediate IgE-dependent allergic reactions.
- Previous understanding suggested mast cells lack high-affinity IgG receptors (FcgammaRI).
- Canine mastocytoma cells (CM-MC) showed activation by monomeric canine IgG, implying FcgammaRI presence.
Purpose of the Study:
- To quantify canine IgG binding affinity to CM-MC cells.
- To confirm the expression and sequence of FcgammaRI on CM-MC cells.
- To establish CM-MC cells as a model for FcgammaRI research.
Main Methods:
- Affinity measurements of canine IgG binding to CM-MC cells.
- Immunoprecipitation using canine IgG-conjugated beads to detect FcgammaRI protein.
- Reverse transcriptase polymerase chain reaction (RT-PCR) for FcgammaRI mRNA detection.
- cDNA sequencing of the FcgammaRI alpha subunit.
Main Results:
- CM-MC cells express (7.5+/-3.1)x10^4 FcgammaRI molecules per cell with a binding affinity (Ka) of (9.1+/-1.6)x10^7 M(-1) for monomeric canine IgG.
- A ~72-kDa surface protein, consistent with FcgammaRI alpha subunit, was identified.
- FcgammaRI mRNA expression was confirmed via RT-PCR.
- Canine FcgammaRI alpha subunit cDNA showed 84% and 78% similarity to human and mouse sequences, respectively.
Conclusions:
- Canine mastocytoma CM-MC cells express functional high-affinity IgG receptors (FcgammaRI).
- These cells possess FcgammaRI protein and mRNA, with sequence homology to human and mouse counterparts.
- CM-MC cells provide a valuable model for investigating FcgammaRI-mediated signal transduction in mast cells.
Abstract:
Mast cells play a central role in IgE-dependent allergic responses. Although they have been reported to express only low-affinity IgG receptors and no high-affinity receptors (FcgammaRI), our recent study showed that canine mastocytoma CM-MC cells are activated by monomeric canine IgG, suggesting the presence of FcgammaRI on CM-MC cells. In the present study, we measured the affinity of canine IgG with CM-MC cells, determined the presence of the FcgammaRI protein and mRNA, and identified the cDNA sequence of it. The results showed that (7.5+/-3.1)x10(4) receptor molecules are expressed on a CM-MC cell with a Ka of (9.1+/-1.6)x10(7)M(-1) for binding to monomeric canine IgG. Canine IgG-conjugated beads precipitated an approximately 72-kDa surface protein, whose size is consistent with that of the FcgammaRI alpha subunit of humans and mouse. The expression of FcgammaRI mRNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR), and the cDNA encoding the FcgammaRI alpha subunit was found to be 84% and 78% similar to that of humans and the mouse, respectively. The predicted amino acid sequence was 72% and 63% identical, respectively. Canine mastocytoma CM-MC cells are therefore very useful for studying FcgammaRI-mediated signal transduction in mast cells.
