P2X7 Receptor Regulates Internalization of Antimicrobial Peptide LL-37 by Human Macrophages That Promotes...

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• The cathelicidin family member LL-37 (hCAP18) is a crucial human antimicrobial peptide involved in pathogen defense and immune regulation.
• Understanding the cellular mechanisms of LL-37 uptake by immune cells is vital for developing novel therapeutic strategies.

Purpose of the Study:

• To elucidate the endocytotic pathways and molecular players involved in human macrophage uptake of LL-37.
• To investigate the role of the P2X7 receptor (P2X7R) in LL-37 internalization and subsequent intracellular pathogen clearance.

Main Methods:

• Investigated LL-37 internalization in human macrophages using time-, dose-, temperature-, and peptide sequence-dependent assays.
• Utilized clathrin and caveolae/lipid raft inhibitors, P2X7R antagonists, and gene silencing (P2X7R) in THP-1 cells.
• Tracked internalized LL-37 localization and measured reactive oxygen species and lysosome formation.

Main Results:

• LL-37 is internalized by human macrophages through a regulated endocytotic process involving both clathrin- and caveolae/lipid raft-mediated pathways.
• The P2X7 receptor significantly mediates LL-37 internalization, particularly via the clathrin pathway.
• Internalized LL-37 localizes to endosomes/lysosomes, enhances intracellular bacterial clearance, and increases reactive oxygen species and lysosome formation.
• Macrophages can import LL-37 released from activated neutrophils.

Conclusions:

• Human macrophages internalize antimicrobial peptide LL-37 via a P2X7R-dependent, clathrin-mediated endocytotic mechanism.
• This process enhances the macrophages' capacity for intracellular pathogen clearance, highlighting a novel immune defense pathway.