Distinct phosphorylation requirements regulate cortactin activation by Tir EPEC and its binding to N-WASP
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BioMed Central
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Distinct phosphorylation requirements regulate cortactin activation by TirEPEC and its binding to N-WASP Elvira Nieto-Pelegrin and Narcisa Martinez-Quiles*
Address: Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain Email: Elvira Nieto-Pelegrin - [email protected]; Narcisa Martinez-Quiles* - [email protected] * Corresponding author
Published: 6 May 2009 Cell Communication and Signaling 2009, 7:11
doi:10.1186/1478-811X-7-11
Received: 10 February 2009 Accepted: 6 May 2009
This article is available from: http://www.biosignaling.com/content/7/1/11 © 2009 Nieto-Pelegrin and Martinez-Quiles; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: Cortactin activates the actin-related 2/3 (Arp2/3) complex promoting actin polymerization to remodel cell architecture in multiple processes (e.g. cell migration, membrane trafficking, invadopodia formation etc.). Moreover, it was called the Achilles' heel of the actin cytoskeleton because many pathogens hijack signals that converge on this oncogenic scaffolding protein. Cortactin is able to modulate N-WASP activation in vitro in a phosphorylation-dependent fashion. Thus Erk-phosphorylated cortactin is efficient in activating N-WASP through its SH3 domain, while Src-phosphorylated cortactin is not. This could represent a switch on/off mechanism controlling the coordinated action of both nucleator promoting factors (NPFs). Pedestal formation by enteropathogenic Escherichia coli (EPEC) requires N-WASP activation. N-WASP is recruited by the cell adapter Nck which binds a major tyrosine-phosphorylated site of a bacterial injected effector, Tir (translocated intimin receptor). Tir-Nck-N-WASP axis defines the current major pathway to actin polymerization on pedestals. In addition, it was recently reported that EPEC induces tyrosine phosphorylation of cortactin. Results: Here we demonstrate that cortactin phosphorylation is absent on N-WASP deficient cells, but is recovered by re-expression of N-WASP. We used purified recombinant cortactin and Tir proteins to demonstrate a direct interaction of both that promoted Arp2/3 complex-mediated actin polymerization in vitro, independently of cortactin phosphorylation. Conclusion: We propose that cortactin binds Tir through its N-terminal part in a tyrosine and serine phosphorylation independent manner while SH3 domain binding and activation of N-WASP is regulated by tyrosine and serine mediated phosphorylation of cortactin. Therefore cortactin could act on Tir-Nck-N-WASP pathway and control a possible cycling activity of N-WASP underlying pedestal formation.
Background Enteropathogenic Escherichia coli (EPEC) are an important cause of infantile diarrhea, especially in developing countries.
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