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Applied and Environmental Microbiology, September 1998, p. 3134-3139, Vol. 64, No. 9
Department of Microbiology and Immunology,
University of Kentucky Chandler Medical Center, Lexington, Kentucky
40536-0084
Received 28 April 1998/Accepted 5 June 1998
The intracellular pathogens Legionella micdadei and
Legionella pneumophila are the two most common
Legionella species that cause Legionnaires' disease.
Intracellular replication within pulmonary cells is the hallmark of
Legionnaires' disease. In the environment, legionellae are parasites
of protozoans, and intracellular bacterial replication within
protozoans plays a major role in the transmission of Legionnaires'
disease. In this study, we characterized the initial host signal
transduction mechanisms involved during attachment to and invasion of
the protozoan host Hartmannella vermiformis by L. micdadei. Bacterial attachment prior to invasion of H. vermiformis by L. micdadei is associated with
tyrosine dephosphorylation of multiple host cell proteins, including a
170-kDa protein. We have previously shown that this 170-kDa protein is
the galactose N-acetylgalactosamine
(Gal/GalNAc)-inhibitable lectin receptor that mediates attachment to
and invasion of H. vermiformis by L. pneumophila. Subsequent bacterial entry targets L. micdadei into a phagosome that is not surrounded by the rough
endoplasmic reticulum (RER). In contrast, uptake of L. pneumophila mediated by attachment to the Gal/GalNAc lectin is
followed by targeting of the bacterium into an RER-surrounded
phagosome. These results indicate that despite similarities in the
L. micdadei and L. pneumophila attachment-mediated signal transduction mechanisms in H. vermiformis, the two bacterial species are targeted into
morphologically distinct phagosomes in their natural protozoan host.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Signal Transduction in the Protozoan Host
Hartmannella vermiformis upon Attachment and Invasion by
Legionella micdadei
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, University of Kentucky Chandler Medical Center, Lexington, KY 40536-0084. Phone: (606) 323-3873. Fax: (606)
257-8994. E-mail: yabukw{at}pop.uky.edu.
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