Potent diarrheagenic mechanism mediated by the cooperative action of three enteropathogenic Escherichia coli -injected effector proteins

doi:10.1073/pnas.0509451103

Potent diarrheagenic mechanism mediated by the cooperative action of three enteropathogenic Escherichia coli-injected effector proteins

*Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle, Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom; and
^‡Centre for Paediatric Gastroenterology, Royal Free Hospital and University College Medical School, London NW3 2PF, United Kingdom

Edited by Stanley Falkow, Stanford University, Stanford, CA, and approved December 2, 2005 (received for review October 31, 2005)

Abstract

Enteropathogenic Escherichia coli (EPEC) induces a severe watery diarrhea responsible for several hundred thousand infant deaths each year by a process correlated with the loss (effacement) of absorptive microvilli. Effacement is linked to the locus of enterocyte effacement pathogenicity island that encodes an “injection system,” “effector” proteins, and the Intimin outer membrane protein. Here, we reveal that effacement (i) is a two-step process, (ii) requires the cooperative action of three injected effectors (Map, EspF, and Tir) as well as Intimin, and (iii) leads to the retention, not release (into the extracellular milieu), of the detached microvillar material. We also discover that EPEC rapidly inactivates the sodium-d-glucose cotransporter (SGLT-1) by multiple mechanisms. Indeed, the finding that one mechanism occurs more rapidly than microvilli effacement provides a plausible explanation for the rapid onset of severe watery diarrhea, given the crucial role of SGLT-1 in the daily uptake of ≈6 liters of fluids from the normal intestine. The importance of SGLT-1 in the disease process is supported by severe EPEC diarrheal cases being refractory to oral rehydration therapy (dependent on SGLT-1 function). Moreover, the identification of effector activities that alter microvilli structure and SGLT-1 function provides new tools for studying the underlying regulatory processes.

Footnotes

^§To whom correspondence should be addressed. E-mail: brendan.kenny{at}ncl.ac.uk
↵ ^†Present address: Departement Agroressources et Procedes Biologiques, Universite Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.
Author contributions: P.D., M.M., and B.K. designed research; P.D. and S.S. performed research; M.M., A.D.P., and B.K. contributed new reagents/analytic tools; and B.K. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

AMG,

α-methyl-d-glucopyranoside;

AP,

alkaline phosphatase;

EPEC,

enteropathogenic Escherichia coli;

LEE,

locus of enterocyte effacement;

moi,

multiplicity of infection;

SEM,

scanning electron microscopy;

SGLT-1,

sodium-d-glucose cotransporter;

T3SS,

type three secretion system.