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Infection and Immunity, September 2000, p. 5154-5166, Vol. 68, No. 9
Division of Infectious Diseases, Department
of Medicine, UCLA School of Medicine, Center for Health Sciences,
Los Angeles, California 90095
Received 17 March 2000/Returned for modification 5 May
2000/Accepted 19 June 2000
Rab7 is a small GTPase that regulates vesicular traffic from early
to late endosomal stages of the endocytic pathway. Phagosomes containing inert particles have also been shown to transiently acquire
Rab7 as they mature. Disruption in the pathway prior to the acquisition
of Rab7 has been suggested as playing a role in the altered maturation
of Mycobacterium bovis BCG phagosomes. As a first step to
determine whether disruption in the delivery or function of Rab7 could
play a role in the altered maturation of Legionella
pneumophila and M. tuberculosis phagosomes, we have examined the distribution of wild-type Rab7 and the GTPase-deficient, constitutively active mutant form of Rab7 in HeLa cells infected with
L. pneumophila or M. tuberculosis. We have
found that the majority of L. pneumophila and M. tuberculosis phagosomes acquire relatively abundant staining for
Rab7 and for the constitutively active mutant Rab7 in HeLa cells that
overexpress these proteins. Nevertheless, despite acquisition of
wild-type or constitutively active Rab7, both the L. pneumophila and the M. tuberculosis phagosomes continue to exhibit altered maturation as manifested by a failure to
acquire lysosome-associated membrane glycoprotein 1. These results
demonstrate that L. pneumophila and M. tuberculosis phagosomes have receptors for Rab7 and that the
altered maturation of these phagosomes is not due to a failure to
acquire Rab7.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Mycobacterium tuberculosis and Legionella
pneumophila Phagosomes Exhibit Arrested Maturation despite
Acquisition of Rab7
*
Corresponding author. Mailing address: Division of
Infectious Diseases, Department of Medicine, UCLA School of Medicine,
CHS 37-121, Los Angeles, CA 90095. Phone: (310) 825-9324. Fax: (310) 794-7156. E-mail: dclemens{at}mednet.ucla.edu.
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