‘The glideosome’: a dynamic complex powering gliding motion and host cell invasion by Toxoplasma gondii

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Abstract
Motion is an intrinsic property of all living organisms, and each cell displays a variety of shapes and modes of locomotion. How structural proteins support cellular movement and how cytoskeletal dynamics and motor proteins are harnessed to generate order and movement are among the fundamental and not fully resolved questions in biology today. Protozoan parasites belonging to the Apicomplexa are of enormous medical and veterinary significance, being responsible for a wide variety of diseases in human and animals, including malaria, toxoplasmosis, coccidiosis and cryptosporidiosis. These obligate intracellular parasites exhibit a unique form of actin-based gliding motility, which is essential for host cell invasion and spreading of parasites throughout the infected hosts. A motor complex composed of a small myosin of class XIV associated with a myosin light chain and a plasma membrane-docking protein is present beneath the parasite's plasma membrane. According to the capping model, this complex is connected directly or indirectly to transmembrane adhesin complexes, which are delivered to the parasite surface upon microneme secretion. Together with F-actin and as yet unknown bridging molecules and proteases, these complexes are among the structural and functional components of the 'glideosome'.