Depolymerization of Cytokeratin Intermediate Filaments Facilitates Intracellular Infection of

Bartonella henselae is capable of invading epithelial and endothelial cells by modulating the function of actin-dependent cytoskeleton proteins. Although understanding of the pathogenesis has been increased by the development of an in vitro infection model involving endothelial cells, little is known about the mecha-nism of interaction between B. henselae and epithelial cells. This study aims to identify the binding candi-dates of B. henselae in epithelial cells and explores their effect on B. henselae infection. Pull-down assays and mass spectrometry analysis confirmed that some of the binding proteins (keratin 14, keratin 6, and F-actin) are cytoskeleton associated. B. henselae infection significantly induces the expression of the cytokeratin genes. Chemical disruption of the keratin network by using ethylene glycol tetraacetic acid promotes the intracellu-lar persistence of B. henselae in HeLa cells. However, cytochalasin B and phalloidin treatment inhibits B. henselae invasion. Immunofluorescent staining demonstrates that B. henselae infection induces an F-actin– dependent rearrangement of the cytoskeleton. However, we demonstrated via immunofluorescent staining and whole-mount cell electron microscopy that keratin intermediate filaments are depolymerized by B. hense-lae. The results indicate that B. henselae achieves an intracellular persistence in epithelial cells through the depolymerization of cytokeratin intermediate filaments that are protective against B. henselae invasion. Keywords. Bartonella henselae; keratin intermediate filament; intracellular infection