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Infection and Immunity, June 1999, p. 3073-3081, Vol. 67, No. 6
Department of Immunology and Infectious
Diseases1 and BioMedical Imaging
Institute,2 Harvard School of Public Health,
Boston, Massachusetts 02115
Received 8 October 1998/Returned for modification 10 November
1998/Accepted 23 February 1999
Entamoeba histolytica, the protozoan parasite that
phagocytoses bacteria and host cells, has a vesicle/vacuole-filled
cytosol like that of macrophages. In contrast, the infectious cyst form has four nuclei and a chitin wall. Here, anti-chitinase antibodies identified hundreds of small secretory vesicles in encysting E. invadens parasites and in E. histolytica trophozoites
overexpressing chitinase under an actin gene promoter.
Abundant small secretory vesicles were also identified with antibodies
to the surface antigen Ariel and with a fluorescent substrate of
cysteine proteinases. Removal of an N-terminal signal sequence directed
chitinase to the cytosol. Addition of a C-terminal KDEL peptide,
identified on amebic BiP, retained chitinase in a putative endoplasmic
reticulum, which was composed of a few vesicles of mixed sizes. A
putative Golgi apparatus, which was Brefeldin A sensitive and
composed of a few large, perinuclear vesicles, was identified with
antibodies to ADP-ribosylating factor and to
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Chitinase Secretion by Encysting Entamoeba invadens
and Transfected Entamoeba histolytica Trophozoites:
Localization of Secretory Vesicles, Endoplasmic Reticulum, and
Golgi Apparatus
-COP. We conclude that
the amebic secretory pathway is similar to those of other eukaryotic cells, even if its appearance is somewhat different.
*
Corresponding author. Mailing address: Department of
Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115. Phone: (617) 432-4670. Fax:
(617) 738-4914. E-mail: jsamuels{at}hsph.harvard.edu.
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