Related Experiment Videos
CR1-receptor recycling in phorbol ester-activated polymorphonuclear leucocytes
A Malbran1, S Siwik, M M Frank
1Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892.
Immunology
|February 1, 1988
Summary
Neutrophils internalize complement receptor 1 (CR1) bound to C3b or antibodies. This internalized CR1 recycles intact ligand-receptor complexes via a prelysosomal compartment, suggesting a novel pathway for immune cell signaling.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Complement receptor 1 (CR1) on phagocytic cells recognizes C3b.
- CR1 requires activation for internalization, with phorbol esters increasing its expression.
- The fate of internalized CR1-ligand complexes was previously unclear.
Purpose of the Study:
- To investigate the fate of internalized CR1-ligand complexes in neutrophils.
- To determine if internalized CR1 and its ligand are degraded or recycled.
- To explore the mechanism and compartment involved in CR1 recycling.
Main Methods:
- Human neutrophils were activated with phorbol dibutyrate (PDBu).
- Internalization of CR1-C3b or CR1-antibody complexes was tracked using radiolabeled ligands.
- Ligand release and structural integrity were assessed after internalization.
Main Results:
- Rapid internalization of CR1-C3b and CR1-antibody complexes was observed.
- Internalized C3b ligand was externalized intact in a time- and temperature-dependent manner.
- Chloroquine treatment did not inhibit the recycling process, suggesting a prelysosomal compartment.
Conclusions:
- Neutrophils recycle intact CR1-ligand complexes.
- Recycling occurs through a prelysosomal, predegradative compartment.
- This finding suggests a novel mechanism for CR1 function and immune regulation.