Calmodulin Distribution and the Actomyosin Cytoskeleton in Toxoplasma gondii

• Published in: The journal of histochemistry and cytochemistry Vol. 49; no. 4; pp. 445 - 453
• Main Authors: Pezzella-D'Alessandro, Nathalie, Le Moal, Herve, Bonhomme, Annie, Valere, Audrey, Klein, Christophe, Gomez-Marin, Jorge, Pinon, Jean-Michel
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA Histochemical Soc 01.04.2001; SAGE Publications
• Subjects: Actins - metabolism; Actomyosin - ultrastructure; Animals; Calmodulin - metabolism; Cytoskeleton - ultrastructure; Humans; Image Processing, Computer-Assisted; KB Cells; Microscopy, Confocal; Myosin-Light-Chain Kinase - metabolism; Myosins - metabolism; Toxoplasma - metabolism; Toxoplasma - ultrastructure; T. gondii; MLCK; 3D reconstruction; calmodulin; actomyosin complex; confocal microscopy
• ISSN: 0022-1554; 1551-5044
• DOI: 10.1177/002215540104900404

The gliding motility of the protozoan parasite Toxoplasma gondii and its invasion of cells are powered by an actin–myosin motor. We have studied the spatial distribution and relationship between these two cytoskeleton proteins and calmodulin (CaM), the Ca2+-dependent protein involved in invasion by T. gondii. A 3D reconstruction using labeling and tomographic studies showed that actin was present as a V-like structure in the conoidal part of the parasite. The myosin distribution overlapped that of actin, and CaM was concentrated at the center of the apical pole. We demonstrated that the actomyosin network, CaM, and myosin light-chain kinases are confined to the apical pole of the T. gondii tachyzoite. MLCK could act as an intermediate molecule between CaM and the cytoskeleton proteins. We have developed a model of the organization of the actomyosin-CaM complex and the steps of a signaling pathway for parasite motility.