Article

Regulation of the Legionella mip-promotor during infection of human monocytes.

Abteilung Transfusionsmedizin, AG Infektionsbiologie, Zentrum für Medizinische Forschung, Universitätsklinikum Tübingen, Waldhörnlestrasse 22, 72076 Tübingen, Germany.
FEMS Microbiology Letters (impact factor: 2.04). 07/2002; 212(1):127-32. pp.127-32
Source: PubMed

ABSTRACT The opportunistic pathogen Legionella pneumophila, the etiologic agent of Legionnaires disease, is able to invade and multiply intracellularly in human macrophages. This process is controlled by several bacterial virulence factors. As recently demonstrated, one of these virulence factors, the macrophage infectivity potentiator (Mip) protein, is important for invasion and proper intracellular establishment of L. pneumophila in macrophages and protozoa. Knockout mutants devoid of a functional mip-gene enter host cells much less effectively but intracellular replication is not affected. Using a P(mip)-green fluorescent protein reporter construct in L. pneumophila substrain Corby, P(mip) was recently shown to be constitutively active in replicating bacteria. A stringent regulation during the infection process could not be observed, neither in intracellular nor in BYE broth-grown bacteria. For enhanced temporal and quantitative resolution, we examined the activity of mip on RNA level in order to detect short transient regulatory events. Our results show that P(mip) of L. pneumophila is temporarily repressed directly after invasion of the monocytic human cell line MonoMac 6 and regains activity after 24 h of intracellular replication.

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Keywords

bacteria
 
bacterial virulence factors
 
functional mip-gene
 
human macrophages
 
intracellular
 
intracellular replication
 
intracellularly
 
Knockout mutants devoid
 
L. pneumophila
 
L. pneumophila substrain Corby
 
Legionnaires disease
 
macrophage infectivity potentiator
 
macrophages
 
monocytic human cell line MonoMac 6
 
opportunistic pathogen Legionella pneumophila
 
P(mip)-green fluorescent protein reporter
 
proper intracellular establishment
 
regains activity
 
RNA level
 
short transient regulatory events
 

Hagen Wieland