During infection, Chlamydia trachomatis exploits the cytoskeleton of the host for efficient internalisation and inclusion formation, as well as for eventual extrusion. In particular, microtubules (MTs) are recruited to the vicinity of the inclusion and used for sequestering secretory vesicles at the inclusion; however, how the MT network is subjugated by bacterial proteins remains unknown. In this issue (p. ), Richard Hayward and colleagues elucidate a new mechanism of how C. trachomatis hijacks host MTs. They report here that the C-terminal domain (CTD) of bacterial CT233 bears a high sequence similarity to MT-interacting proteins and thus renamed it ‘inclusion protein acting on MTs’ (IPAM). In non-infected cells, the IPAM CTD associated with the pericentriolar matrix, and its overexpression caused the formation of ectopic MT-nucleation foci, indicating that the IPAM CTD is able to take control of the MT-organising activity of the cell. The authors then showed that IPAM interacted and colocalised with centrosomal protein 170 (CEP170) at the inclusion during infection, where together they promoted MT assembly from the inclusion. Importantly, knockdown of CEP170 interfered with the re-organisation of MT network, as well as affecting the inclusion shape and decreasing the infectivity of the bacterial progeny. Thus, these results not only identify IPAM as a new effector of chlamydial infection, but also demonstrate that the interaction with CEP170 is the main mechanism that underlies the hijacking and reorganisation of the host MT network.
