This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Clemens, D. L.
Right arrow Articles by Horwitz, M. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Clemens, D. L.
Right arrow Articles by Horwitz, M. A.
Right arrowPubmed/NCBI databases
*Substance via MeSH

 Previous Article  |  Next Article 

Infection and Immunity, May 2009, p. 1757-1773, Vol. 77, No. 5
0019-9567/09/$08.00+0     doi:10.1128/IAI.01485-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Francisella tularensis Phagosomal Escape Does Not Require Acidification of the Phagosome{triangledown}

Daniel L. Clemens,* Bai-Yu Lee, and Marcus A. Horwitz

Division of Infectious Diseases, Department of Medicine, University of California-Los Angeles School of Medicine, Center for Health Sciences, Los Angeles, California 90095-1688

Received 4 December 2008/ Returned for modification 11 January 2009/ Accepted 9 February 2009

Following uptake, Francisella tularensis enters a phagosome that acquires limited amounts of lysosome-associated membrane glycoproteins and does not acquire cathepsin D or markers of secondary lysosomes. With additional time after uptake, F. tularensis disrupts its phagosomal membrane and escapes into the cytoplasm. To assess the role of phagosome acidification in phagosome escape, we followed acidification using the vital stain LysoTracker red and acquisition of the proton vacuolar ATPase (vATPase) using immunofluorescence within the first 3 h after uptake of live or killed F. tularensis subsp. holarctica live vaccine strain (LVS) by human macrophages. Whereas 90% of the phagosomes containing killed LVS stained intensely for the vATPase and were acidified, only 20 to 30% of phagosomes containing live LVS stained intensely for the vATPase and were acidified. To determine whether transient acidification might be required for phagosome escape, we assessed the impact on phagosome permeabilization of the proton pump inhibitor bafilomycin A. Using electron microscopy and an adenylate cyclase reporter system, we found that bafilomycin A did not prevent phagosomal permeabilization by F. tularensis LVS or virulent type A strains (F. tularensis subsp. tularensis strain Schu S4 and a recent clinical isolate) or by "F. tularensis subsp. novicida," indicating that F. tularensis disrupts its phagosomal membrane by a mechanism that does not require acidification.

* Corresponding author. Mailing address: Division of Infectious Diseases, Department of Medicine, UCLA School of Medicine, CHS 37-121, 10833 LeConte Avenue, Los Angeles, CA 90095-1688. Phone: (310) 825-9324. Fax: (310) 794-7156. E-mail: dclemens{at}mednet.ucla.edu

{triangledown} Published ahead of print on 23 February 2009.

Editor: W. A. Petri, Jr.

Infection and Immunity, May 2009, p. 1757-1773, Vol. 77, No. 5
0019-9567/09/$08.00+0     doi:10.1128/IAI.01485-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»