The SH3 domain of cortactin is important for <i>C. burnetii</i> internalization.

<p>(A) HeLa cells were transfected with pGFP-cortactin WT, GFP-cortactin W22A, a mutant that does not interact with Arp 2/3, or GFP-W525K, a mutant unable to bind and activate targets such as N-WASP. Transfected cells were infected for 4 h with <i>C. burnetii</i>. Cells were fixed and processed for immunofluorescence with a specific anti-<i>C. burnetii</i> antibody (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039348#s2" target="_blank">Methods</a>). Cells were analyzed by confocal microscopy. In the merged images (panels d, h, l and p), extracellular <i>C. burnetii</i> are shown in green and red pseudocolors while intracellular <i>C. burnetii</i> are shown in red pseudocolor. Bars, 10 µm. (B) Quantification of <i>C. burnetii</i> internalized by transfected HeLa cells. Results are expressed as means ± SE of at least three independent experiments. *, P<0.05. (%), percentage of total number of bacteria.