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The N-terminal half of membrane CD14 is a functional cellular lipopolysaccharide receptor
1Department of Pathology, Department of Veterans Affairs Medical Center, San Diego, California 92161, USA.
Abstract:
CD14, a glycosylphosphatidylinositol-anchored protein on the surface of monocytes, macrophages, and polymorphonuclear leukocytes, is a receptor for lipopolysaccharide (LPS). It was recently reported that an N-terminal 152-amino-acid fragment of soluble CD14 was an active soluble lipopolysaccharide receptor (T. S. -C. Juan, M. J. Kelley, D. A. Johnson, L. A. Busse, E. Hailman, S. D. Wright, and H. S. Lichenstein, J. Biol. Chem. 270:1382-1387, 1995). To determine whether the N-terminal half of the membrane CD14 was a functional LPS receptor on the cell membrane, we engineered a chimeric gene coding for amino acids 1 to 151 of CD14 fused to the C-terminal region of decay-accelerating factor and expressed it in Chinese hamster ovary cells and 70Z/3 cells. We found that the chimeric, truncated CD14 is a fully functional LPS receptor in both cell lines.
Insights
The N-terminal half of CD14 functions as a lipopolysaccharide (LPS) receptor. This truncated CD14, when expressed on cell surfaces, effectively binds and responds to LPS, confirming its role in innate immunity.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- CD14 is a cell surface protein on immune cells that acts as a receptor for lipopolysaccharide (LPS).
- A soluble N-terminal fragment of CD14 has been identified as an active soluble LPS receptor.
Purpose of the Study:
- To investigate if the N-terminal half of membrane-bound CD14 can function as a lipopolysaccharide (LPS) receptor.
- To engineer and express a truncated CD14 molecule to assess its LPS-binding capabilities.
Main Methods:
- Engineered a chimeric gene encoding amino acids 1-151 of CD14 fused to decay-accelerating factor.
- Expressed the chimeric gene in Chinese hamster ovary (CHO) cells and 70Z/3 cells.
- Assessed the functionality of the truncated CD14 as an LPS receptor in these cell lines.
Main Results:
- The chimeric, truncated CD14 molecule was successfully expressed on the cell surface.
- The truncated CD14 demonstrated full functionality as a lipopolysaccharide (LPS) receptor in both Chinese hamster ovary and 70Z/3 cells.
- This indicates that the N-terminal portion of CD14 is sufficient for LPS recognition.
Conclusions:
- The N-terminal half of CD14 is sufficient for its function as a lipopolysaccharide (LPS) receptor.
- These findings contribute to understanding the molecular mechanisms of innate immune recognition of bacterial components.
- The truncated CD14 can serve as a functional LPS receptor on the cell membrane.