Interplay between host cell cycle and Legionella pneumophila intracellular replication.
de Jesus-Diaz, Dennise.
pneumophila is a Gram-negative, intracellular pathogen that targets amoebal species in
aquatic environments and alveolar macrophages during human infections. To sustain
intracellular replication L. pneumophila uses a type IV secretion system (T4SS) that
translocates bacterial proteins into the host to form the Legionella containing vacuole
(LCV), the site of bacterial ... read morereplication. Most of the knowledge about host factors that
restrict L. pneumophila intracellularly has been acquired by studies of host networks
known to be involved in pathogen clearance. However, the role of host proteins outside
of these pathways remained unclear. We developed a dsRNA interference screen strategy
against more that 50% of the D. melanogaster annotated Orfs to identify host factors
that restrict L. pneumophila intracellular growth. This strategy allowed us to identify
a role for proteins involved in host cell cycle control in restricting L. pneumophila
growth. Studies to determine the cell cycle phase that facilitates L. pneumophila
intracellular replication demonstrated that the bacterium is capable of arresting the
host cell cycle at any stage and prevent cell proliferation of amoebal hosts in a
T4SS-dependent manner. Furthermore, five effector proteins that target the host protein
synthesis machinery restrict cell cycle progression through mitosis. The levels of
bacterial replication in either proliferating or arrested host cells varied depending on
the cell cycle stage the host was at the time of infection. Host cells present in G1 and
G2 were exploited by the bacterium for replication. In contrast, bacterial replication
was depressed in cells present in S-phase, as the integrity of the LCV was compromised,
resulting in L. pneumophila detection from the cytosol and eventual degradation.
Together, our results are consistent with the model that L. pneumophila inhibits entry
into S-phase by causing perturbations in the host protein synthesis machinery, because
this phase in the cell cycle is detrimental for bacterial
Thesis (Ph.D.)--Tufts University, 2014.
Submitted to the Dept. of Molecular Microbiology.
Advisor: Ralph Isberg.
Committee: Ekaterina Heldwein, Joan Mecsas, and Andrew Camilli.
Keyword: Microbiology.read less