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Infection and Immunity, November 2009, p. 4724-4739, Vol. 77, No. 11
0019-9567/09/$08.00+0     doi:10.1128/IAI.00150-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

The Purified and Recombinant Legionella pneumophila Chaperonin Alters Mitochondrial Trafficking and Microfilament Organization{triangledown}

Audrey Chong,1,{dagger} Celia A. Lima,1 David S. Allan,1 Gheyath K. Nasrallah,1 and Rafael A. Garduño1,2*

Department of Microbiology and Immunology,1 Department of Medicine-Division of Infectious Diseases, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada2

Received 8 February 2009/ Returned for modification 21 March 2009/ Accepted 5 August 2009

A portion of the total cellular pool of the Legionella pneumophila chaperonin, HtpB, is found on the bacterial cell surface, where it can mediate invasion of nonphagocytic cells. HtpB continues to be abundantly produced and released by internalized L. pneumophila and may thus have postinvasion functions. We used here two functional models (protein-coated beads and expression of recombinant proteins in CHO cells) to investigate the competence of HtpB in mimicking early intracellular trafficking events of L. pneumophila, including the recruitment of mitochondria, cytoskeletal alterations, the inhibition of phagosome-lysosome fusion, and association with the endoplasmic reticulum. Microscopy and flow cytometry studies indicated that HtpB-coated beads recruited mitochondria in CHO cells and U937-derived macrophages and induced transient changes in the organization of actin microfilaments in CHO cells. Ectopic expression of HtpB in the cytoplasm of transfected CHO cells also led to modifications in actin microfilaments similar to those produced by HtpB-coated beads but did not change the distribution of mitochondria. Association of phagosomes containing HtpB-coated beads with the endoplasmic reticulum was not consistently detected by either fluorescence or electron microscopy studies, and only a modest delay in the fusion of TrOv-labeled lysosomes with phagosomes containing HtpB-coated beads was observed. HtpB is the first Legionella protein and the first chaperonin shown to, by means of our functional models, induce mitochondrial recruitment and microfilament rearrangements, two postinternalization events that typify the early trafficking of virulent L. pneumophila.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, 5850 College Street, Sir Charles Tupper Medical Building, 7th Floor, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada. Phone: (902) 494-6575. Fax: (902) 494-5125. E-mail: rafael.garduno{at}dal.ca

{triangledown} Published ahead of print on 17 August 2009.

Editor: J. B. Bliska

{dagger} Present address: Laboratory of Intracellular Parasites, NIAID, National Institutes of Health, Rocky Mountain Laboratories, 903 South 4th St., Hamilton, MT 59840.

Infection and Immunity, November 2009, p. 4724-4739, Vol. 77, No. 11
0019-9567/09/$08.00+0     doi:10.1128/IAI.00150-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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