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The role of erythrocyte cytoskeleton proteins during invasion by Francisella tularensis
Rebecca Barnes, James W. M. Birch, Aleksandr Florjanczyk, Adam Kenney, Deanna Schmitt,
and Joseph Horzempa
Department of Natural Sciences and Mathematics, West Liberty, WV USA
Abstract
Background and Objective
Francisella tularensis is classified as a Category A bioterrorism agent by the Centers for
Disease Control and Prevention. Inhaling as few as ten of these bacteria can develop into an
acute, lethal pneumonia if untreated. Studies using mouse models of tularemia have shown
that F. tularensis invades erythrocytes during infection. However, the mechanism by which this
bacterium enters red blood cells is unknown. Cytoskeletal rearrangements of other host cells
are required for entry of F. tularensis. Therefore, in this study, we evaluated the role of the major
erythrocyte cytoskeletal components, actin and spectrin, in erythrocyte invasion.
Methods
Human erythrocytes were treated with various compounds to disrupt standard cytoskeleton
structure and then co-cultured with F. tularensis bacteria. Cells were then subjected to a
gentamicin protection assay to measure bacterial invasion.
Results
Our findings indicated that actin had no involvement during erythrocyte invasion by F. tularensis.
However, venom from the Blue-bellied black snake (Pseudechis guttatus), which aggregates the
spectrin in the cytoskeleton, significantly reduced the number of intra-erythrocytic bacteria. This
suggests that spectrin is involved in erythrocyte invasion.
Discussion and Conclusions
This is the first study showing the involvement of an erythrocyte protein during invasion by F.
tularensis. Our results reveal that F. tularensis may exploit unique cytoskeletal rearrangements
to invade erythrocytes.
This work was funded by a grant through the NASA WV Space Grant Consortium
(NNX10AK62H), an Institutional Development Award (IDeA) from the National Institute of
General Medical Sciences of the National Institutes of Health (P20GM103434), a grant from the
National Institutes of Health, National Institute of Allergy and Infectious Diseases
(5K22AI087703), and funding from the WV Research Challenge Fund [HEPC.dsr.14.13].