Sallee, N. A. et al. The pathogen protein EspF(U) hijacks actin polymerization using mimicry and multivalency. Nature 454, 1005-1008

Graduate Program in Chemistry and Chemical Biology, University of California, San Francisco, 600 16th Street, San Francisco, California 94158, USA.
Nature (Impact Factor: 41.46). 07/2008; 454(7207):1005-1008. DOI: 10.1038/nature07170


Enterohaemorrhagic Escherichia coli attaches to the intestine through actin pedestals that are formed when the bacterium injects its protein EspFU ( also known as TccP) into host cells(1). EspFU potently activates the host WASP ( Wiskott - Aldrich syndrome protein) family of actin- nucleating factors, which are normally activated by the GTPase CDC42, among other signalling molecules. Apart from its amino- terminal type III secretion signal, EspFU consists of five- and- a- half 47- amino- acid repeats. Here we show that a 17- residue motif within this EspFU repeat is sufficient for interaction with N- WASP ( also known as WASL). Unlike most pathogen proteins that interface with the cytoskeletal machinery, this motif does not mimic natural upstream activators: instead of mimicking an activated state of CDC42, EspFU mimics an auto-nhibitory element found within N- WASP. Thus, EspFU activates N- WASP by competitively disrupting the autoinhibited state. By mimicking an internal regulatory element and not the natural activator, EspFU selectively activates only a precise subset of CDC42- activated processes. Although one repeat is able to stimulate actin polymerization, we show that multiple- repeat fragments have notably increased potency. The activities of these EspFU fragments correlate with their ability to coordinate activation of at least two N- WASP proteins. Thus, this pathogen has used a simple autoinhibitory fragment as a component to build a highly effective actin polymerization machine.

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    • "helical-and proline-rich-containing) domains, suggesting that multiple repeats confer a selective advantage to EHEC (Garmendia et al., 2005). Multiple EspFU/TccP repeats synergistically enhance activation of Arp2/3 in vitro (Campellone et al., 2008; Sallee et al., 2008). In addition, we speculated above that the dimerization domains of intimin and Tir might promote a higher-order structure conducive to efficient actin signalling. "
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    • "Consistent with this hypothesis, previous observations have shown that the density of artificially clustered Nck or its SH3 domains impacts on its ability to induce actin polymerization (Blasutig et al., 2008; Campellone et al., 2004; Rivera et al., 2004, 2009). A similar synergistic activation of actin polymerization is also induced by clustering increasing numbers of EspFu repeats, which bind N-WASP to stimulate its ability to activate the Arp2/3 complex (Campellone et al., 2008; Cheng et al., 2008; Sallee et al., 2008). In the absence of clathrin recruitment, fewer viruses reach the threshold of A36 clustering required to efficiently nucleate actin polymerization. "
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    • "In this way, IcsA would appear analogous to other bacterial and host proteins that either interact with or functionally mimic WASP family members. Most of these have been shown to either directly self-associate (enterohaemorrhagic E. coli intimin-tir), to spatially cluster (Listeria monocytogenes ActA) or they are inherently multivalent with internal repeats (enterohaemorrhagic E. coli EspF, EspF U and Tccp) (Alto et al., 2007; Campellone et al., 2008; Footer et al., 2008; Sallee et al., 2008; Touzé et al., 2004). Significantly, our data demonstrate self-association of yet another protein known to activate a WASP family protein, which has emerged as an important feature in the regulation of the host actin cytoskeleton. "
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