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Figure 15.2 HGF-induced cell motility in villin expressing MDCK cells. Phase contrast
images of villin or villin +MDCK cells before (panel a) and after 9 h of HGF (10 IU/ml)
stimulation (panel b). Panel c illustrates cell tracking after 9 h of treatment
dynamics in response to specific physiological stimuli. We have developed
several approaches to evaluate the role of villin in cellular events that require
actin cytoskeleton plasticity and remodelling, such as cell motility, cell
morphogenesis and bacterial infections. These studies were performed using
primary cultures of enterocytes derived from vil +/+ and vil / mice and Tet
Off MDCK cells expressing the villin transgene in a doxycycline-controlled
manner. We show that villin plays a role as a potentiator of the actin
cytoskeleton dynamics elicited by extracellular signals. Indeed, we have found
that villin is an enhancer of HGF-induced cell motilty and morphogenesis
(Figure 15.2 and Table 15.1). Moreover, its role as a potentiator of actin
dynamics upon growth factor stimulation takes place through the PLCg
signalling pathway (Athman et al., in press).
The actin cytoskeleton remodelling is also required in other cellular
processes such as bacterial infection. Shigella flexneri is the causative agent of
bacillary dysentery. This gram-negative pathogen induces the reorganization
of the host actin cytoskeleton during the infection process. The main target of
this bacterium being the enterocyte, we took advantage of our villin KO
model to study the infectious process in intestinal primary cultures from
vil +/+ and vil / . This work in progress has been performed in collaboration
with Dana Philpott and Philippe Sansonetti (Institut Pasteur, Paris). Briefly,
we have shown, using primary cultures of enterocytes, that villin is involved in
bacterial entry and cell-to-cell dissemination. Villin is present in the actin
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