Tuesday May 17th, 2016 at 3 pm, Location TBD
Karen Lo, PhD Candidate, Dept. of Biological Sciences, Simon Fraser University
Title: Identification and Characterization of Francisella tularensis Virulence Factors Associated with Invasion of Liver Tissue Cells.
The potential bioterrorism agent, Francisella tularensis (F. tularensis), causes the fatal disease tularemia with as few as 10 bacteria. Tularemia develops by bacteria invading, replicating, and spreading continuously within cells of the host. Host cell invasion is the first requirement for disease. We tested the hypothesis thatFrancisella has proteins on the bacterial membrane surface responsible for host cell invasion and disease. To identify F. tularensis proteins involved with host cell invasion, we screened a mutant library of a commonly used surrogate microbe, F. tularensis subspecies novicida (F. novicida), and found that mutants for each of 201 genes were deficient in invasion and intracellular replication in cultured hepatocytes. To screen for proteins critical for tularemia development, we infected mice with a subset of mutants in 32 genes. We discovered disease was dramatically attenuated in mice infected with bacteria mutant for gene Francisellavirulence factor A (FvfA). We demonstrate FvfA protein contributes to bacterial invasion by comparing host cell uptake of FvfA-coated latex beads with a control protein. We found FvfA-coated beads are internalized two times more readily than the control and identified clathrin-mediated endocytosis as the host cell mechanism for uptake. We further characterized FvfA by examining the protein localization within the bacteria and crystallizing the protein structure. Our findings suggest that the protein FvfA is involved in bacterial invasion and is ultimately important for disease.
© Herbert H. Tsang, http://www.herberttsang.org