scholarly journals Role of the Lipopolysaccharide-CD14 Complex for the Activity of Hemolysin from Uropathogenic Escherichia coli

2006 ◽  
Vol 75 (2) ◽  
pp. 997-1004 ◽  
Author(s):  
Lisa E. Månsson ◽  
Peter Kjäll ◽  
Shahaireen Pellett ◽  
Gábor Nagy ◽  
Rodney A. Welch ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Membrane ◽  
Signal Transduction Pathway ◽  
Recognition System ◽  
Small Gtpase ◽  
Host Cell Membrane ◽  
Common View ◽  
Experimental Artifact ◽  
Intracellular Ca

ABSTRACT Bacterial pathogens produce a variety of exotoxins, which often become associated with the bacterial outer membrane component lipopolysaccharide (LPS) during their secretion. LPS is a potent proinflammatory mediator; however, it is not known whether LPS contributes to cell signaling induced by those microbial components to which it is attached. This is partly due to the common view that LPS present in bacterial component preparations is an experimental artifact. The Escherichia coli exotoxin hemolysin (Hly) is a known inducer of proinflammatory signaling in epithelial cells, and the signal transduction pathway involves fluctuation of the intracellular-Ca2+ concentration. Since LPS is known to interact with Hly, we investigated whether it is required as a cofactor for the activity of Hly. We found that the LPS/Hly complex exploits the CD14/LPS-binding protein recognition system to bring Hly to the cell membrane, where intracellular-Ca2+ signaling is initiated via specific activation of the small GTPase RhoA. Hly-induced Ca2+ signaling was found to occur independently of the LPS receptor TLR4, suggesting that the role of LPS/CD14 is to deliver Hly to the cell membrane. In contrast, the cytolytic effect triggered by exposure of cells to high Hly concentrations occurs independently of LPS/CD14. Collectively, our data reveal a novel molecular mechanism for toxin delivery in bacterial pathogenesis, where LPS-associated microbial compounds are targeted to the host cell membrane as a consequence of their association with LPS.

Über die Zellmembran von Escherichia Coli B

1954 ◽  
Vol 9 (6) ◽  
pp. 398-406 ◽  
Author(s):  
Wolfhard Weidel ◽  
Gebhard Koch ◽  
Friedrich Lohss
Keyword(s):  
Escherichia Coli ◽  
Chemical Analysis ◽  
Cell Membrane ◽  
B Cell ◽  
Dry Weight ◽  
Shigella Sonnei ◽  
Receptor Activity ◽  
Escherichia Coli B

Dissociation in 90% phenol uncovers a layer of the Coli B-cell membrane showing the typical antiviral specificity of the receptor for phages T3, T4 and T7. Chemical analysis proved glucose, glucosamine and a yet unknown carbohydrate, probably a heptose, to be components of the receptor material, which amounts to about 13% of the dry weight of the whole membrane.Analogous material obtained from the membrane of B/3,4,7, a B-mutant resistant against phages T3, T4 and T7, has no activity against these phages and contains glucosamine and small amounts of glucose, but no heptose.In view of similar findings of Jesaitis and Goebel with T3,4,7 - receptor material from Shigella Sonnei, the rôle of the heptose as a characteristic and functionally indispensable component of lipocarbohydrates with receptor activity against T3, T4 and T7 is discussed.

Tauroursodeoxycholate inhibits human cholangiocarcinoma growth via Ca2+-, PKC-, and MAPK-dependent pathways

2004 ◽  
Vol 286 (6) ◽  
pp. G973-G982 ◽  
Author(s):  
Gianfranco Alpini ◽  
Noriatsu Kanno ◽  
Jo Lynne Phinizy ◽  
Shannon Glaser ◽  
Heather Francis ◽  
...  
Keyword(s):  
Sclerosing Cholangitis ◽  
Signal Transduction Pathway ◽  
Inhibitory Effect ◽  
Time Dependent ◽  
Transduction Pathway ◽  
Cholangiocarcinoma Cell ◽  
Intracellular Ca ◽  
Regulation Of Growth ◽  
Primary Risk Factor

Tauroursodeoxychate (TUDCA) is used for the treatment of cholangiopathies including primary sclerosing cholangitis, which is considered the primary risk factor for cholangiocarcinoma. The effect of TUDCA on cholangiocarcinoma growth is unknown. We evaluated the role of TUDCA in the regulation of growth of the cholangiocarcinoma cell line Mz-ChA-1. TUDCA inhibited the growth of Mz-ChA-1 cells in concentration- and time-dependent manners. TUDCA inhibition of cholangiocarcinoma growth was blocked by BAPTA-AM, an intracellular Ca2+ concentration ([Ca2+]i) chelator, and H7, a PKC-α inhibitor. TUDCA increased [Ca2+]i and membrane translocation of the Ca2+-dependent PKC-α in Mz-ChA-1 cells. TUDCA inhibited the activity of MAPK, and this inhibitory effect of TUDCA was abrogated by BAPTA-AM and H7. TUDCA did not alter the activity of Raf-1 and B-Raf and the phosphorylation of MAPK p38 and JNK/stress-activated protein kinase. TUDCA inhibits Mz-ChA-1 growth through a signal-transduction pathway involving MAPK p42/44 and PKC-α but independent from Raf proteins and MAPK p38 and JNK/stress-activated protein kinases. TUDCA may be important for the treatment of cholangiocarcinoma.

scholarly journals Membrane Curvature and the Tol-Pal Complex Determine Polar Localization of the Chemoreceptor Tar in Escherichia coli

2018 ◽  
Vol 200 (9) ◽  
Author(s):  
Terrens N. V. Saaki ◽  
Henrik Strahl ◽  
Leendert W. Hamoen
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Cell Membrane ◽  
Cellular Localization ◽  
Signal Transduction Pathway ◽  
Membrane Curvature ◽  
Deletion Mutants ◽  
Content Type ◽  
E Coli ◽  
Polar Localization

ABSTRACT Chemoreceptors are localized at the cell poles of Escherichia coli and other rod-shaped bacteria. Over the years, different mechanisms have been put forward to explain this polar localization, including stochastic clustering, membrane curvature-driven localization, interactions with the Tol-Pal complex, and nucleoid exclusion. To evaluate these mechanisms, we monitored the cellular localization of the aspartate chemoreceptor Tar in different deletion mutants. We did not find any indication for either stochastic cluster formation or nucleoid exclusion. However, the presence of a functional Tol-Pal complex appeared to be essential to retain Tar at the cell poles. Interestingly, Tar still accumulated at midcell in tol and in pal deletion mutants. In these mutants, the protein appears to gather at the base of division septa, a region characterized by strong membrane curvature. Chemoreceptors, like Tar, form trimers of dimers that bend the cell membrane due to a rigid tripod structure. The curvature approaches the curvature of the cell membrane generated during cell division, and localization of chemoreceptor tripods at curved membrane areas is therefore energetically favorable, as it lowers membrane tension. Indeed, when we introduced mutations in Tar that abolish the rigid tripod structure, the protein was no longer able to accumulate at midcell or the cell poles. These findings favor a model where chemoreceptor localization in E. coli is driven by strong membrane curvature and association with the Tol-Pal complex. IMPORTANCE Bacteria have exquisite mechanisms to sense and adapt to the environment they live in. One such mechanism involves the chemotaxis signal transduction pathway, in which chemoreceptors specifically bind certain attracting or repelling molecules and transduce the signals to the cell. In different rod-shaped bacteria, these chemoreceptors localize specifically to cell poles. Here, we examined the polar localization of the aspartate chemoreceptor Tar in E. coli and found that membrane curvature at cell division sites and the Tol-Pal protein complex localize Tar at cell division sites, the future cell poles. This study shows how membrane curvature can guide localization of proteins in a cell.

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