Klebsiella pneumoniaedisassembles host microtubules in lung epithelial cells

Abstract

Klebsiella pneumoniae raises significant concerns to the health care industry as these microbes are the source of widespread contamination of medical equipment, cause pneumonia as well as other multiorgan metastatic infections and have gained multidrug resistance. Despite soaring mortality rates, the host cell alterations occurring during these infections remain poorly understood. Here, we show that during in vitro and in vivo K. pneumoniae infections of lung epithelia, microtubules are severed and then eliminated. This destruction does not require direct association of K. pneumoniae with the host cells, as microtubules are disassembled in cells that are distant from the infecting bacteria. This microtubule dismantling is dependent on the K. pneumoniae (Kp) gene ytfL as non‐pathogenic Escherichia coli expressing Kp ytfL disassemble microtubules in the absence of K. pneumoniae itself. Our data points to the host katanin catalytic subunit A like 1 protein (KATNAL1) and the katanin regulatory subunit B1 protein (KATNB1) as the gatekeepers to the microtubule severing event as both proteins localise specifically to microtubule cut sites. Infected cells that had either of these proteins knocked out maintained intact microtubules. Taken together, we have identified a novel mechanism that a bacterial pathogen has exploited to cause microtubule destruction within the host epithelia.

Klebsiella pneumoniae Redistributes Katanin Severing Proteins and Alters Astral Microtubules during Mitosis

“…On the other hand, the catalytic subunit KATNAL1 and the regulatory subunit KATNB1 were both redistributed throughout the cytoplasm, which could sever the remaining microtubules. Interestingly, the coincidental pairing of KATNAL1 and KATNB1 further supports our previous report that KATNAL1 and KATNB1 were the gatekeepers in K. pneumoniae ‐induced microtubule disassembly (Chua et al, ). Thus, these observations point to the notion that K. pneumoniae exploits the katanins to control its host cells whether the host cells are in interphase or mitosis.…”

“…Microtubule polymerization was enhanced by tilivalline in vitro , and more multipolar spindles were observed in mitotic cells exposed to tilivalline (Unterhauser et al, ). In contrast, K. pneumoniae disassembled microtubule networks of A549 cells (Chua et al, ), and in this study, we did not observe any multipolar spindles. Additionally, the astral microtubules were not elongated in tilivalline‐treated mitotic cells (Unterhauser et al, ), suggesting that different mechanisms are employed by K. oxytoca and K. pneumoniae to cause cell cycle arrest.…”

“…There are relatively few mitotic cells in an epithelium as compared to interphase cells. Because direct attachment of K. pneumoniae on the host cells is not necessary for microtubule alterations (Chua et al, ), this poses a potential obstacle for the progression of the infections as cells that are not targeted by the bacteria can propagate new uninfected cells for the recovery of the tissue. Instead of devising a separate strategy to target and act on mitotic cells, K. pneumoniae has found a single group of proteins (the katanins) that can be exploited regardless of whether the host cell has started dividing.…”

“…Ultimately, bacterial colonization of the epithelial tissues leads to bacteria‐induced host cell death (Cano et al, ). Recently, we have shown that prior to the death of lung cells, K. pneumoniae disassembles the microtubule network (Chua et al, ). The destruction of the microtubule network is triggered through the activation of microtubule severing enzymes from the katanin family.…”

“…We have previously shown that K. pneumoniae targets specific katanins to disassemble the microtubule network of its host (Chua et al, ). As katanins are crucial proteins for effective mitotic events, we examined whether K. pneumoniae also altered the robust microtubule networks of mitotic cells.…”