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Cell Host Microbe. 2014 Feb 12;15(2):177-89. doi: 10.1016/j.chom.2014.01.005.

A fluorescent reporter reveals on/off regulation of the Shigella type III secretion apparatus during entry and cell-to-cell spread.

Author information

1
Institut Pasteur, Unité de Pathogénie Microbienne Moléculaire, 75724 Paris, France; INSERM, U786, 75015, Paris, France. Electronic address: fxcamval@pasteur.fr.
2
Institut Pasteur, Unité de Pathogénie Microbienne Moléculaire, 75724 Paris, France; INSERM, U786, 75015, Paris, France.
3
Institut Pasteur, Plateforme de Microscopie Ultrastructurale, 75724 Paris, France.
4
Institut Pasteur, Unité de Pathogénie Microbienne Moléculaire, 75724 Paris, France; INSERM, U786, 75015, Paris, France; Collège de France, Chaire de Microbiologie et Maladies infectieuses, 75005 Paris, France.

Abstract

Numerous pathogenic Gram-negative bacteria use a type three secretion apparatus (T3SA) to translocate effector proteins into host cells. Detecting and monitoring the T3SA of intracellular bacteria within intact host cells has been challenging. Taking advantage of the tight coupling between T3S effector-gene transcription and T3SA activity in Shigella flexneri, together with a fast-maturing green fluorescent protein, we developed reporters to monitor T3SA activity in real time. These reporters reveal a dynamic temporal regulation of the T3SA during the course of infection. T3SA is activated initially during bacterial entry and downregulated subsequently when bacteria gain access to the host cell cytoplasm, allowing replenishment of the bacterial stores of T3S substrates necessary for invading neighboring cells. Reactivation of the T3SA was strictly dependent on actin-based motility and formation of plasma membrane protrusions during cell-to-cell spread. Thus, the T3SA is subject to a tight on/off regulation within the bacterial intracellular niche.

PMID:
24528864
DOI:
10.1016/j.chom.2014.01.005
[Indexed for MEDLINE]
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