http://hdl.handle.net/10027/7421 Sun, 26 May 2013 03:10:35 GMT 2013-05-26T03:10:35Z http://hdl.handle.net/10027/7730 Enterohemorrhagic E. coli Requires N-WASP for Efficient Type III Translocation but Not for EspFU-Mediated Actin Pedestal Formation Vingadassalom, Didier; Campellone, Kenneth G.; Brady, Michael J.; Skehan, Brian; Battle, Scott E.; Robbins, Douglas; Kapoor, Archana; Hecht, Gail; Snapper, Scott B.; Leong, John M. Upon infection of mammalian cells, enterohemorrhagic E. coli (EHEC) O157:H7 utilizes a type III secretion system to translocate the effectors Tir and EspFU (aka TccP) that trigger the formation of F-actin-rich ‘pedestals’ beneath bound bacteria. EspFU is localized to the plasma membrane by Tir and binds the nucleation-promoting factor N-WASP, which in turn activates the Arp2/3 actin assembly complex. Although N-WASP has been shown to be required for EHEC pedestal formation, the precise steps in the process that it influences have not been determined. We found that N-WASP and actin assembly promote EHEC-mediated translocation of Tir and EspFU into mammalian host cells. When we utilized the related pathogen enteropathogenic E. coli to enhance type III translocation of EHEC Tir and EspFU, we found surprisingly that actin pedestals were generated on N-WASP-deficient cells. Similar to pedestal formation on wild type cells, Tir and EspFU were the only bacterial effectors required for pedestal formation, and the EspFU sequences required to interact with N-WASP were found to also be essential to stimulate this alternate actin assembly pathway. In the absence of N-WASP, the Arp2/3 complex was both recruited to sites of bacterial attachment and required for actin assembly. Our results indicate that actin assembly facilitates type III translocation, and reveal that EspFU, presumably by recruiting an alternate host factor that can signal to the Arp2/3 complex, exhibits remarkable versatility in its strategies for stimulating actin polymerization. © 2010 Vingadassalom et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The original publication is available through the Public Library of Science at DOI: 10.1371/journal.ppat.1001056. Thu, 19 Aug 2010 05:00:00 GMT http://hdl.handle.net/10027/7730 2010-08-19T05:00:00Z http://hdl.handle.net/10027/7602 Single Nucleotide Polymorphisms in the Wnt and BMP Pathways and Colorectal Cancer Risk in a Spanish Cohort Fernandez-Rozadilla, Ceres; de Castro, Luisa; Clofent, Juan; Brea-Fernandez, Alejandro; Bessa, Xavier; Abuli, Anna; Andreu, Montserrat; Jover, Rodrigo; Xicola, Rosa; Llor, Xavier; Castells, Antoni; Castellvi-Bel, Sergi; Carracedo, Angel; Ruiz-Ponte, Clara Background: Colorectal cancer (CRC) is considered a complex disease, and thus the majority of the genetic susceptibility is thought to lie in the form of low-penetrance variants following a polygenic model of inheritance. Candidate-gene studies have so far been one of the basic approaches taken to identify these susceptibility variants. The consistent involvement of some signaling routes in carcinogenesis provided support for pathway-based studies as a natural strategy to select genes that could potentially harbour new susceptibility loci. Methodology/Principal Findings: We selected two main carcinogenesis-related pathways: Wnt and BMP, in order to screen the implicated genes for new risk variants. We then conducted a case-control association study in 933 CRC cases and 969 controls based on coding and regulatory SNPs. We also included rs4444235 and rs9929218, which did not fulfill our selection criteria but belonged to two genes in the BMP pathway and had consistently been linked to CRC in previous studies. Neither allelic, nor genotypic or haplotypic analyses showed any signs of association between the 37 screened variants and CRC risk. Adjustments for sex and age, and stratified analysis between sporadic and control groups did not yield any positive results either. Conclusions/Significance: Despite the relevance of both pathways in the pathogenesis of the disease, and the fact that this is indeed the first study that considers these pathways as a candidate-gene selection approach, our study does not present any evidence of the presence of low-penetrance variants for the selected markers in any of the considered genes in our cohort. The original source for this publication is at Public Library of Science; DOI: 10.1371/journal.pone.0012673 Thu, 09 Sep 2010 05:00:00 GMT http://hdl.handle.net/10027/7602 2010-09-09T05:00:00Z