Inerolysin, a cholesterol-dependent cytolysin produced by Lactobacillus iners.

Area of Science:

• Microbiology
• Molecular Biology
• Toxicology

Background:

• Lactobacillus iners is a prevalent species in the human vaginal microbiota.
• Its role in bacterial vaginosis pathogenesis is hypothesized but not fully understood.
• Fastidious growth requirements have historically limited the characterization of L. iners.

Purpose of the Study:

• To identify and characterize a protein toxin produced by Lactobacillus iners.
• To investigate the molecular mechanisms and activity spectrum of this novel toxin.
• To establish a new target for research into L. iners' role in vaginal health and disease.

Main Methods:

• Bioinformatic analysis of the L. iners genome for toxin-encoding genes.
• Western blot analysis to confirm in vitro protein production by clinical isolates.
• Biochemical assays to determine toxin activity, pH optimum, and inhibition by cholesterol.
• Cell-based assays to assess toxin effects on epithelial cells, including MAPK activation and phalloidin uptake.

Main Results:

• Identification and characterization of inerolysin (INY), a novel pore-forming protein toxin from L. iners.
• INY shares sequence similarity with known cholesterol-dependent cytolysins (CDCs) like vaginolysin and intermedilysin.
• The toxin is activated by reducing agents, inhibited by cholesterol, and active at acidic pH (4.5-6.0).
• Sublytic INY concentrations activate p38 MAPK and facilitate cytoplasmic entry of molecules into epithelial cells.
• Unlike VLY and ILY, INY exhibits activity against a broad range of species, not limited to human cells.

Conclusions:

• Lactobacillus iners produces a functional pore-forming toxin, inerolysin (INY).
• INY's broad species activity and cellular effects suggest a significant role in the vaginal environment.
• INY presents a novel molecular target for investigating the contribution of L. iners to vaginal health and disease states.