A Homolog of Eukaryotic Flotillin Is Involved in Cholesterol Accumulation, Epithelial Cell Responses and Host Colonization.

The human pathogen acquires cholesterol from membrane raft domains in eukaryotic cells, commonly known as "lipid rafts." Incorporation of this cholesterol into the cell membrane allows the bacterium to avoid clearance by the host immune system and to resist the effects of antibiotics and antimicrobial peptides. The presence of cholesterol in bacteria suggested that this pathogen may have cholesterol-enriched domains within its membrane. Consistent with this suggestion, we identified a hypothetical protein (HP0248) with homology to the flotillin proteins normally found in the cholesterol-enriched domains of eukaryotic cells. As shown for eukaryotic flotillin proteins, HP0248 was detected in detergent-resistant membrane fractions of . Importantly, mutants contained lower levels of cholesterol than wild-type bacteria ( < 0.01). mutant bacteria also exhibited defects in type IV secretion functions, as indicated by reduced IL-8 responses and CagA translocation in epithelial cells ( < 0.05), and were less able to establish a chronic infection in mice than wild-type bacteria ( < 0.05). Thus, we have identified an flotillin protein and shown its importance for bacterial virulence. Taken together, the data demonstrate important roles for flotillin in host-pathogen interactions. We propose that flotillin may be required for the organization of virulence proteins into membrane raft-like structures in this pathogen.