Increased Expression of Rab5a Correlates Directly with Accelerated Maturation of Listeria monocytogenesPhagosomes*
Abstract
Previous studies have shown that Listeria monocytogenes (LM) modulates phagocytic membrane traffic. Here we explore whether Rab5a, a GTPase associated with phagosome-endosome fusion, is related to phagosome maturation and to the intracellular survival of LM. Stable transfection of Rab5a cDNA into macrophages accelerates intracellular degradation of LM. Morphological studies confirmed that phagosome maturation and phagosome-lysosome fusion is enhanced by overexpression of Rab5a.
Down-regulation experiments using antisense oligonucleotides targeted to the Rab5a mRNA efficiently reduced Rab5a synthesis, reduced phagosome-endosome traffic, blocked phagosome-lysosome fusion, and extended intraphagosomal survival of LM. Down-regulation of Rab5a had no effect on LM internalization. Down-regulation of Rab5c had no effect on phagosome maturation and phagosome-lysosome fusion. The results indicate that Rab5a controls early phagosome-endosome interactions and governs the maturation of the early phagosome leading to phagosome-lysosome fusion.
Footnotes
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↵* This work was supported by National Institutes of Health grants (to P. D. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Recipient of a Postdoctoral Fellowship from the Formación de Personal Investigador, Ministerio de Educación y Ciencia, Madrid, Spain.
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↵§ To whom correspondence and reprint requests should be addressed. Tel.: 314-362-6950; Fax: 314-362-1490; E-mail:pstahl{at}cellbio.wustl.edu.
- LM
- Listeria monocytogenes
- PT
- phosphothioate
- cfu
- colony forming units
- BSA
- bovine serum albumin
- Received January 29, 1999.
- Revision received February 19, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
