Identification of factors that modulate Yop translocation during animal and tissue culture infection of Yersinia pseudotuberculosis.
gram-negative pathogen, Yersinia pseudotuberculosis evades the host immune system by
injecting effector proteins (Yops) into host cells through its type III secretion
system. These effector proteins disarm host defenses and allow the bacteria to establish
infection. Both host and bacterial factors modulate Yop translocation. Bacterial growth
during animal infection is controlled... read moreby neutrophils, iMo, and iDC. These cells are
selectively targeted for Yop translocation and are essential for controlling Yersinia
infection. Translocation of Yops into host cells is largely abolished in the absence of
neutrophils, iMo and iDC. Here we show that in the absence of neutrophils alone, Yop
translocation levels are higher than expected. By microscopic analysis of infected
spleens, we found that small microcolonies are formed in the absence of neutrophils,
while very large microcolonies are formed in the absence of iMo and iDCs. We propose
that since smaller microcolonies allow for more contact of the bacteria with host cells,
the smaller colonies formed in the absence of neutrophils result in higher numbers of
Yop-intoxicated host cells. We also report that the adhesin YadA is required for the
formation of large microcolonies. Calcium flux may be required to prime host cells to be
translocated with Yops. Neutrophils undergo calcium flux when responding to infection,
and when exposed to Yersinia byproducts. In neutropenic and monocytic cell lines,
chemically inducing a calcium flux increased Yop translocation. In contrast, blocking
calcium flux with chemical inhibitors decreased Yop translocation into these cell lines.
Combined, these results suggest that calcium flux enhances translocation of Yops, and
that signals that trigger recognition of pathogens may prime cells for Yop delivery.
Additionally, we further characterized dynamics of translocation and Rho-GAP activity of
YopE, an effector protein that regulates effector translocation into host
Thesis (Ph.D.)--Tufts University, 2015.
Submitted to the Dept. of Molecular Microbiology.
Advisor: Joan Mecsas.
Committee: Linden Hu, Abraham Sonenshein, and Ralph Isberg.
Keywords: Microbiology, and Immunology.read less