How Deadly Parasites “Glide” Along and Into Human Cells

In biological terms, gliding refers to the type of movement during which a cell moves along a surface without changing its shape. This form of movement is unique to parasites from the phylum Apicomplexa, such as Plasmodium and Toxoplasma. Both parasites, which are transmitted by mosquitoes and cats, have an enormous impact on global heath. Plasmodium causes 228 million malaria infections and approximately 400,000 deaths per year. Toxoplasma, which infects an estimated one third of the human population, can cause severe symptoms in some people, and is particularly dangerous during pregnancy. Gliding enables the Apicomplexa parasites to enter and move between host cells. For example, upon entering the human body through a mosquito bite, Plasmodium glides through human skin before crossing into human blood vessels. This type of motion relies on actin and myosin, which are the same proteins that enable muscle movement in humans and other vertebrates. Myosin has a form of molecular 'legs' that 'march' along actin filaments and thereby create movement. In Apicomplexa, myosin interacts with several other proteins, which together form a complex called the “glideosome.” The exact mechanism by which the glideosome works is not well understood, among other reasons because the molecular structure of most glideosome proteins are unknown. Yet understanding this mechanism could aid the development of drugs that prevent the assembly of the glideosome and thereby stop the progression of diseases such as malaria and toxoplasmosis. Scientists at European Molecular Biology Laboratory (EMBL) Hamburg analyzed the molecular structure of essential light chains (ELCs), which are glideosome proteins that bind directly to myosin.
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