The antimicrobial peptide LL-37 triggers release of apoptosis-inducing factor and shows direct effects on...

Area of Science:

• Cell Biology
• Biochemistry
• Mitochondrial Research

Background:

• The human antimicrobial peptide LL-37 is known to permeabilize host cell plasma membranes.
• Direct effects of LL-37 on mitochondrial membrane permeability and function remain largely uncharacterized.

Purpose of the Study:

• To investigate the impact of LL-37 on mitochondrial membrane permeability and function in human cells.
• To determine if LL-37 accumulates in mitochondria and affects the release of key mitochondrial proteins.

Main Methods:

• LL-37 internalization and co-localization with mitochondria were assessed in MG63 cells using MitoTracker.
• Subcellular fractionation and Western blot analysis were employed to detect the release of mitochondrial proteins (AIF, cytochrome C oxidase subunit IV).
• Dot blot assays and lipid vesicle experiments were used to evaluate AIF and cytochrome C release from isolated mitochondria and LL-37's effect on membrane permeabilization.

Main Results:

• LL-37 was rapidly internalized by MG63 cells and accumulated in mitochondria within 20 minutes.
• LL-37 triggered the release of apoptosis-inducing factor (AIF) into the cytosol but not cytochrome C oxidase subunit IV.
• Isolated mitochondria treated with LL-37 showed increased release of both AIF and cytochrome C, and LL-37 permeabilized lipid vesicles mimicking mitochondrial membranes.

Conclusions:

• LL-37 is rapidly internalized by human osteoblast-like cells and accumulates within mitochondria.
• LL-37 directly affects mitochondrial membrane permeability, leading to the release of pro-apoptotic factor AIF and cytochrome C.
• The peptide's interaction with mitochondrial membranes suggests a novel mechanism of LL-37-induced cellular effects.