Extrusion of actin-positive strands from HEp-2 and Int 407 cells caused by outer membrane preparations of enteropathogenicEscherichia coliand specific attachment of wild type bacteria to the strands

Enteropathogenic Escherichia coli (EPEC) causes persistent infantile diarrhoea. This nontoxigenic E. coli exhibits a complicated pathogenic mechanism in which its outer membrane proteins and type III secretory proteins damage intestinal epithelium and cause diarrhoea. In accordance with this, our previous study using HEp-2 cells demonstrated cytopathic effects caused by cell-free outer membrane preparations of EPEC. In this study, we report the extrusion of actin-positive strands from HEp-2 and Int 407 cells when treated with outer membrane preparations. An interesting observation of this work, perhaps relevant to the characteristic localized three-dimensional colony formation of EPEC, is the attachment of a wild type EPEC strain to these actin-positive strands.Key words: enteropathogenic Escherichia coli, actin, outer membrane proteins, cytoskeletal elements.

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Outer membrane proteins of wild-type and intimin-deficient enteropathogenic Escherichia coli induce Hep-2 cell death through intrinsic and extrinsic pathways of apoptosis

International Journal of Medical Microbiology ◽

10.1016/j.ijmm.2008.07.005 ◽

2009 ◽

Vol 299 (2) ◽

pp. 121-132 ◽

Cited By ~ 5

Author(s):

B SHANKAR ◽

S KRISHNAN ◽

V MALLADI ◽

A BALAKRISHNAN ◽

P WILLIAMS

Keyword(s):

Escherichia Coli ◽

Cell Death ◽

Membrane Proteins ◽

Outer Membrane ◽

Outer Membrane Proteins ◽

Enteropathogenic Escherichia Coli ◽

Wild Type

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Localized adherence by enteropathogenic Escherichia coli is an inducible phenotype associated with the expression of new outer membrane proteins.

Journal of Experimental Medicine ◽

10.1084/jem.174.5.1167 ◽

1991 ◽

Vol 174 (5) ◽

pp. 1167-1177 ◽

Cited By ~ 64

Author(s):

J Vuopio-Varkila ◽

G K Schoolnik

Keyword(s):

Escherichia Coli ◽

Membrane Proteins ◽

Outer Membrane ◽

De Novo ◽

Outer Membrane Proteins ◽

Temporal Correlation ◽

Enteropathogenic Escherichia Coli ◽

E Coli

Enteropathogenic Escherichia coli grow as discrete colonies on the mucous membranes of the small intestine. A similar pattern can be demonstrated in vitro; termed localized adherence (LA), it is characterized by the presence of circumscribed clusters of bacteria attached to the surfaces of cultured epithelial cells. The LA phenotype was studied using B171, an O111:NM enteropathogenic E. coli (EPEC) strain, and HEp-2 cell monolayers. LA could be detected 30-60 min after exposure of HEp-2 cells to B171. However, bacteria transferred from infected HEp-2 cells to fresh monolayers exhibited LA within 15 min, indicating that LA is an inducible phenotype. Induction of the LA phenotype was found to be associated with de novo protein synthesis and changes in the outer membrane proteins, including the production of a new 18.5-kD polypeptide. A partial NH2-terminal amino acid sequence of this polypeptide was obtained and showed it to be identical through residue 12 to the recently described bundle-forming pilus subunit of EPEC. Expression of the 18.5-kD polypeptide required the 57-megadalton enteropathogenic E. coli adherence plasmid previously shown to be required for the LA phenotype in vitro and full virulence in vivo. This observation, the correspondence of the 18.5-kD polypeptide to an EPEC-specific pilus protein, and the temporal correlation of its expression with the development of the LA phenotype suggest that it may contribute to the EPEC colonial mode of growth.

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Effects of SecE Depletion on the Inner and Outer Membrane Proteomes of Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.01631-07 ◽

2008 ◽

Vol 190 (10) ◽

pp. 3505-3525 ◽

Cited By ~ 36

Author(s):

Louise Baars ◽

Samuel Wagner ◽

David Wickström ◽

Mirjam Klepsch ◽

A. Jimmy Ytterberg ◽

...

Keyword(s):

Escherichia Coli ◽

Membrane Proteins ◽

Outer Membrane ◽

Protein Identification ◽

Protein Translocation ◽

Outer Membrane Proteins ◽

Specific Model ◽

Secretory Proteins ◽

Inner Membrane ◽

Sec Translocon

ABSTRACT The Sec translocon is a protein-conducting channel that allows polypeptides to be transferred across or integrated into a membrane. Although protein translocation and insertion in Escherichia coli have been studied using only a small set of specific model substrates, it is generally assumed that most secretory proteins and inner membrane proteins use the Sec translocon. Therefore, we have studied the role of the Sec translocon using subproteome analysis of cells depleted of the essential translocon component SecE. The steady-state proteomes and the proteome dynamics were evaluated using one- and two-dimensional gel analysis, followed by mass spectrometry-based protein identification and extensive immunoblotting. The analysis showed that upon SecE depletion (i) secretory proteins aggregated in the cytoplasm and the cytoplasmic σ32 stress response was induced, (ii) the accumulation of outer membrane proteins was reduced, with the exception of OmpA, Pal, and FadL, and (iii) the accumulation of a surprisingly large number of inner membrane proteins appeared to be unaffected or increased. These proteins lacked large translocated domains and/or consisted of only one or two transmembrane segments. Our study suggests that several secretory and inner membrane proteins can use Sec translocon-independent pathways or have superior access to the remaining Sec translocons present in SecE-depleted cells.

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