In contrast to healthy controls, the heterotrimeric G protein, Gsalpha (Gsα) is ensconced predominantly in lipid rafts in subjects with major depressive disorder (MDD) resulting in impaired stimulation of adenylyl cyclase. In this small proof-of-concept study, we examined the hypothesis that translocation of Gsα from lipid rafts toward a more facile activation of adenylyl cyclase is a biomarker for clinical response to antidepressants. There were 49 subjects with MDD (HamD score ≥15) and 59 healthy controls at the screen visit.
View Article and Find Full Text PDFSignals that activate the G protein Gαs and promote neuronal differentiation evoke Gαs internalization in rat pheochromocytoma (PC12) cells. These agents also significantly increase Gαs association with microtubules, resulting in an increase in microtubule dynamics because of the activation of tubulin GTPase by Gαs. To determine the function of Gαs/microtubule association in neuronal development, we used real-time trafficking of a GFP-Gαs fusion protein.
View Article and Find Full Text PDFEnteropathogenic Escherichia coli (EPEC) is an enteric pathogen able to cause severe diarrhea. Once adhered to the small intestine, EPEC disrupts tight junctions that are important for intestinal barrier function. This disruption is dependent on the bacterial type III secretion system, as well as the translocated effectors EspF and Map.
View Article and Find Full Text PDFEnteric bacterial pathogens have evolved sophisticated strategies to evade host immune defences. Some pathogens deliver anti-inflammatory effector molecules into the host cell cytoplasm via a type III secretion system (T3SS). Enteropathogenic Escherichia coli (EPEC) inhibits inflammation by an undefined, T3SS-dependent mechanism.
View Article and Find Full Text PDFShiga toxin (Stx) is implicated in the development of hemorrhagic colitis and hemolytic-uremic syndrome, but early symptoms of enterohemorrhagic Escherichia coli (EHEC) infection such as nonbloody diarrhea may be Stx independent. In this study, we defined the effects of EHEC, in the absence of Stx, on the intestinal epithelium using a murine model. EHEC colonization of intestines from two groups of antibiotic-free and streptomycin-treated C57Bl/6J mice were characterized and compared.
View Article and Find Full Text PDFEnteropathogenic Escherichia coli (EPEC) is a diarrhoeal pathogen that adheres to epithelial cells of the small intestine and uses a type III secretion system to inject effector proteins into host cells. EPEC infection leads to disruption of host intestinal tight junctions that are important for maintaining intestinal barrier function. This disruption is dependent on the bacterial type III secretion system, as well as the translocated effectors EspF and Map.
View Article and Find Full Text PDFAm J Physiol Gastrointest Liver Physiol
September 2009
Infection with the enteric pathogen enterohemorrhagic Escherichia coli (EHEC) causes a variety of symptoms ranging from nonbloody diarrhea to more severe sequelae including hemorrhagic colitis, altered sensorium and seizures, and even life-threatening complications, such as hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. The more severe consequences of EHEC infection are attributable to the production of Shiga toxin (Stx) and its subsequent effects on the vasculature, which expresses high levels of the Stx receptor, Gb3. Interestingly, the intestinal epithelium does not express Gb3.
View Article and Find Full Text PDFProbiotics are viable nonpathogenic microorganisms that are considered to confer health benefits to the host. Recent studies indicated that some Lactobacillus species function as probiotics and have been used as alternative treatments for diarrhea, which occurs due to increased secretion, decreased absorption, or both. However, the direct effects of probiotics on intestinal electrolyte absorption are not known.
View Article and Find Full Text PDFAm J Physiol Gastrointest Liver Physiol
May 2008
Enteropathogenic Escherichia coli (EPEC) is a diarrheagenic pathogen that perturbs intestinal epithelial function. Many of the alterations in the host cells are mediated by effector molecules that are secreted directly into epithelial cells by the EPEC type III secretion system. The secreted effector molecule EspF plays a key role in redistributing tight junction proteins and altering epithelial barrier function.
View Article and Find Full Text PDFThe diarrheagenic pathogen enteropathogenic Escherichia coli (EPEC) is responsible for significant infant mortality and morbidity, particularly in developing countries. EPEC pathogenesis relies on a type III secretion system-mediated transfer of virulence effectors into host cells. EPEC modulates host cell survival and inflammation, although the proximal signaling pathways have not been well defined.
View Article and Find Full Text PDFEnteropathogenic Escherichia coli (EPEC) infection disrupts tight junctions (TJs) and perturbs intestinal barrier function in vitro. E. coli secreted protein F (EspF) is, in large part, responsible for these physiological and morphological alterations.
View Article and Find Full Text PDFBackground & Aims: Enteropathogenic Escherichia coli and enterohemorrhagic E. coli harbor highly homologous pathogenicity islands yet show key differences in their mechanisms of action. Both disrupt host intestinal epithelial tight junctions, but the effects of enteropathogenic E.
View Article and Find Full Text PDFEnteropathogenic Escherichia coli (EPEC) pathogenesis requires the delivery of effector proteins into host cytosol by a type III secretion system. The effector protein EspF, while critical for disruption of epithelial barrier function through alteration of tight junctions, is not required for bacterial viability or attachment. Yeast two-hybrid analyses revealed host intermediate filament (IF) protein cytokeratin 18 (CK18) as an interacting partner of EspF.
View Article and Find Full Text PDFEnteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) are related intestinal pathogens that harbor highly similar pathogenicity islands known as the locus of enterocyte effacement (LEE). Despite their genetic similarity, these two pathogens disrupt epithelial tight junction barrier function with distinct kinetics.
View Article and Find Full Text PDFEnteropathogenic Escherichia coli (EPEC) disrupts the structure and barrier function of host intestinal epithelial tight junctions (TJs). The impact of EPEC on TJ "fence function," i.e.
View Article and Find Full Text PDFAm J Physiol Cell Physiol
September 2003
We showed previously that enteropathogenic Escherichia coli (EPEC) infection of intestinal epithelial cells induces inflammation by activating NF-kappa B and upregulating IL-8 expression. We also reported that extracellular signal-regulated kinases (ERKs) participate in EPEC-induced NF-kappa B activation but that other signaling molecules such as PKC zeta may be involved. The aim of this study was to determine whether PKC zeta is activated by EPEC and to investigate whether it also plays a role in EPEC-associated inflammation.
View Article and Find Full Text PDFBackground & Aims: Maintenance of the mucosal barrier is a critical function of intestinal epithelia. Myosin regulatory light chain (MLC) phosphorylation is a common intermediate in the pathophysiologic regulation of this barrier. The aim of this study was to determine whether a membrane permeant inhibitor of MLC kinase (PIK) could inhibit intracellular MLC kinase and regulate paracellular permeability.
View Article and Find Full Text PDFDisruption of the barrier properties of the enterocyte tight junction is believed to be important in the pathogenesis of diarrhea caused by enteropathogenic Escherichia coli (EPEC). This phenotype can be measured in vitro as the ability of EPEC to reduce transepithelial resistance (TER) across enterocyte monolayers and requires the products of the locus of enterocyte effacement (LEE) and, in particular, the type III secreted effector protein EspF. We report a second LEE-encoded gene that is also necessary for EPEC to fully reduce TER.
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