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Glucan receptor and zymosan-induced lysosomal enzyme secretion in macrophages
Abstract:
A receptor for beta-glucan was in the present study shown to mediate binding of zymosan particles to resident mouse peritoneal macrophages. Lysosomal enzyme secretion in response to zymosan was maximal at a low particle/cell ratio, continuous for at least 3 h after particle/cell contact and inhibitable by soluble glucan. Latex particles of various size caused no selective secretory response, but at high particle/cell ratios were toxic. By use of a fluorescent ligand, the macrophage beta-glucan receptor was shown to be trypsin-sensitive, Ca2+/Mg(2+)-independent, recirculating and also present in an intracellular mobilizable pool. Binding of ligand to the beta-glucan receptor and inhibition of the lysosomal secretory response to zymosan were both more efficient with glucans of larger size, indicating that clustering of glucan receptors at the cell surface occurs. Such clustering could stabilize ligand binding by multiple interactions and possibly trigger intracellular signaling events on binding of zymosan particles.
Insights
Researchers identified a beta-glucan receptor on mouse macrophages that binds zymosan particles, triggering enzyme secretion. Receptor clustering enhances binding and may initiate signaling pathways for immune responses.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophages play a crucial role in innate immunity.
- Beta-glucans are fungal polysaccharides that can activate immune cells.
Purpose of the Study:
- To investigate the role of a beta-glucan receptor in macrophage activation.
- To characterize the properties and behavior of this receptor.
Main Methods:
- Utilized zymosan particles and latex beads to stimulate mouse peritoneal macrophages.
- Employed fluorescent ligands to track beta-glucan receptor dynamics.
- Measured lysosomal enzyme secretion in response to particle binding.
Main Results:
- A specific beta-glucan receptor mediates zymosan binding to macrophages.
- Lysosomal enzyme secretion is dependent on particle-to-cell ratio and glucan size.
- The receptor is trypsin-sensitive, Ca2+/Mg2+-independent, and recirculates.
- Evidence suggests receptor clustering enhances ligand binding and may trigger signaling.
Conclusions:
- The beta-glucan receptor is key for zymosan recognition and subsequent macrophage activation.
- Receptor clustering is important for efficient binding and potential downstream signaling.
- Understanding this receptor offers insights into fungal-macrophage interactions and immune modulation.