A Functional Yeast-Based Screen Identifies the Host Microtubule Cytoskeleton as a Target of Numerous Proteins.

Bacterial pathogens have evolved intricate ways to manipulate the host to support infection. Here, we systematically assessed the importance of the microtubule cytoskeleton for infection by , which are obligate intracellular bacteria that are of great importance for human health. The elimination of microtubules in human HEp-2 cells prior to infection profoundly attenuated the infection efficiency, demonstrating the need for microtubules for the early infection processes. To identify microtubule-modulating proteins, a screen in the model yeast was performed. Unexpectedly, among 116 selected chlamydial proteins, more than 10%, namely, 13 proteins, massively altered the yeast interphase microtubule cytoskeleton. With two exceptions, these proteins were predicted to be inclusion membrane proteins. As proof of principle, we selected the conserved CPn0443 protein, which caused massive microtubule instability in yeast, for further analysis. CPn0443 bound and bundled microtubules in vitro and co-localized partially with microtubules in vivo in yeast and human cells. Furthermore, CPn0443-transfected U2OS cells had a significantly reduced infection rate by EBs. Thus, our yeast screen identified numerous proteins encoded using the highly reduced genome that modulated microtubule dynamics. Hijacking of the host microtubule cytoskeleton must be a vital part of chlamydial infection.