Invasion of Toxoplasma gondii occurs by active penetration of the host cell

J. H. Morisaki, J. E. Heuser, L. D. Sibley

Research output: Contribution to journalArticle

245 Scopus citations

Abstract

Toxoplasma gondii is an obligate intracellular parasite that infects a wide variety of vertebrate cells including macrophages. We have used a combination of video microscopy and fluorescence localization to examine the entry of Toxoplasma into macrophages and nonphagocytic host cells. Toxoplasma actively invaded host cells without inducing host cell membrane ruffling, actin microfilament reorganization, or tyrosine phosphorylation of host proteins. Invasion occurred rapidly and within 25-40 seconds the parasite penetrated into a tight-fitting vacuole formed by invagination of the plasma membrane. In contrast, during phagocytosis of Toxoplasma, extensive membrane ruffling captured the parasite in a loose-fitting phagosome that formed over a period of 2-4 minutes. Phagocytosis involved both reorganization of the host cytoskeleton and tyrosine phosphorylation of host proteins. In some cases, parasites that were first internalized by phagocytosis, were able to escape from the phagosome by a process analogous to invasion. These studies reveal that active penetration of the host cell by Toxoplasma is fundamentally different from phagocytosis or induced endocytic uptake. The novel ability to penetrate the host cell likely contributes to the capability of Toxoplasma-containing vacuoles to avoid endocytic processing.

Original languageEnglish
Pages (from-to)2457-2464
Number of pages8
JournalJournal of cell science
Volume108
Issue number6
StatePublished - 1995

Keywords

  • Endocytosis
  • Invasion
  • Parasite
  • Phagocytosis

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