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Dectin-1 Reactivity to Paramylon Derived from Euglena gracilis EOD-1
Ken-Ichi Ishibashi1,2, Nobuteru Onaka3, Norihisa Nishida3
1Laboratory of Host Defense and Responses, Faculty of Nutrition, Kagawa Nutrition University.
Abstract:
Euglena gracilis is a microalga that has recently attracted attention because of its bioactivities. Paramylon (PM), a major β-1,3-glucan, constitutes 70-80% of the cells of the E. gracilis EOD-1 strain. Dectin-1 is a pattern recognition receptor that recognizes β-glucan. However, it is unclear whether PM binds to dectin-1. In this study, we investigated the reactivity of EOD1PM with dectin-1 by analyzing the binding of soluble murine and human dectin-1-Fc fusion protein (m dectin-1 Fc, h dectin-1 Fc) to EOD1PM using flow cytometry and enzyme-linked immunosorbent assay (ELISA). m Dectin-1 Fc bound to EOD1PM particles when m dectin-1-Fc is added. Furthermore, the binding specificity was examined in a competitive reaction following addition of a soluble antigen. It was found that the binding of m dectin-1-Fc to EOD1PM was not inhibited by the addition of dextran or ovalbumin but by the addition of solubilized EOD1PM or Candida cell wall- solubilized β-glucan. In addition, the h dectin-1-Fc fusion protein was found to specifically bind to EOD1PM. These results suggest that dectin-1 recognizes and binds to the β-glucan structure of EOD1PM. Dectin-1 is expressed in leukocytes as a β-glucan receptor and is involved in the expression of various biological activities; therefore, the dectin-1 pathway may be involved in the biological activity of EOD1PM.
Insights
This study shows that dectin-1, a key immune receptor, binds to paramylon (PM) from Euglena gracilis. This interaction suggests a role for the dectin-1 pathway in the microalga
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Euglena gracilis microalgae possess bioactivities.
- Paramylon (PM), a β-1,3-glucan, comprises 70-80% of E. gracilis EOD-1 cells.
- Dectin-1 is a pattern recognition receptor that recognizes β-glucans.
Purpose of the Study:
- To investigate the binding of paramylon (PM) from E. gracilis EOD-1 strain to dectin-1.
- To determine if dectin-1 recognizes the β-glucan structure of EOD1PM.
- To explore the potential involvement of the dectin-1 pathway in the biological activity of EOD1PM.
Main Methods:
- Flow cytometry and ELISA were used to analyze the binding of murine and human dectin-1-Fc fusion proteins to EOD1PM.
- Competitive binding assays with soluble antigens (dextran, ovalbumin, solubilized EOD1PM, Candida β-glucan) were performed.
- Specificity of binding was assessed using both murine and human dectin-1-Fc fusion proteins.
Main Results:
- Murine dectin-1-Fc fusion protein demonstrated binding to EOD1PM particles.
- Binding was specific, as it was inhibited by solubilized EOD1PM and Candida β-glucan, but not by dextran or ovalbumin.
- Human dectin-1-Fc fusion protein also specifically bound to EOD1PM.
Conclusions:
- Dectin-1 recognizes and binds to the β-glucan structure present in EOD1PM from Euglena gracilis.
- The dectin-1 pathway, known to be involved in leukocyte functions, may mediate the biological activities of EOD1PM.
- This finding opens avenues for understanding the immunomodulatory potential of microalgal β-glucans.
