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Apical organelles and host-cell invasion by Apicomplexa
J F Dubremetz1, N Garcia-Réguet, V Conseil
1Unité 42 INSERM, Villeneuve d'Ascq, France. JFDubremetz@compuserve.com
International Journal for Parasitology
|September 2, 1998
Summary
Apicomplexan parasites invade host cells using three organelles: micronemes, rhoptries, and dense granules. These organelles share conserved functions across species, aiding in host cell recognition, vacuole formation, and metabolic remodeling during invasion.
Area of Science:
- Parasitology
- Cell Biology
- Molecular Biology
Background:
- Apicomplexan parasites employ sequential exocytosis of micronemes, rhoptries, and dense granules for host-cell invasion.
- Recent studies reveal structural homologies and shared functions among these organelles across apicomplexan species.
- Conserved protein domains, particularly thrombospondin-like domains in microneme proteins, are implicated in host-cell binding and parasite motility.
Purpose of the Study:
- To elucidate the conserved roles of micronemes, rhoptries, and dense granules in apicomplexan host-cell invasion.
- To highlight the functional significance of conserved protein domains in parasite invasion mechanisms.
- To review the application of gene transfection in studying the fate and function of exocytosed proteins.
Main Methods:
- Comparative analysis of organelle structures and functions across apicomplexan species.
- Gene cloning and sequencing to identify conserved protein domains.
- Review of studies examining protein localization and function during invasion, particularly in Plasmodium and Toxoplasma.
- Utilizing parasite transformation via gene transfection to study protein fate and function.
Main Results:
- Micronemes facilitate host-cell recognition, binding, and motility; rhoptries are crucial for parasitophorous vacuole formation; dense granules remodel the vacuole for metabolic activity.
- Thrombospondin-like domains in microneme proteins are involved in binding to sulphated glycoconjugates and are essential for Plasmodium sporozoite motility.
- Exocytosed proteins from rhoptries and dense granules associate with the parasitophorous vacuole membrane, mediating host-parasite metabolic interactions.
Conclusions:
- The three secretory organelles (micronemes, rhoptries, dense granules) play distinct yet coordinated roles in apicomplexan invasion.
- Conserved protein domains underscore shared molecular mechanisms underlying invasion across the phylum.
- Gene transfection technologies offer powerful avenues for dissecting the precise functions of these invasion-associated proteins.