Sristi Raj Rai, Amity University Kolkata
Wanderers outside our body are in search of nutrients and host to persist and multiply to survive on the planet. Obligate endoparasite of Apicomplexa phylum invades human – intermediate/secondary hosts. These single-celled eukaryotes are of high medical and agricultural importance. Members such as Toxoplasma gondii and Plasmodium falciparum can glide without changing its structure along the surface of human skin cells surprisingly, entering into the blood vessels. Plasmodium species results in 414,000 deaths per year due to malaria infection. Toxoplasma is solely responsible for toxoplasmosis infection of 30% of the population across the world with compromised immunity and in pregnant women.
Gliding motility efficiently utilizes actin-myosin motor present in vertebrates for cell invasion leading to proliferation, migration, and transmission. The parasitic anchor for the motor is located in the intermembrane space between the plasma membrane and inner membrane complex (IMC) – an extra layer unique to these intracellular organisms. Myosin protein interacts with several proteins from the parasitic system forming dynamic macromolecular machinery known as glideosome. Incomplete information about glideosome functioning and molecular mechanisms due to lack of structural data hindered the understanding of the apicomplexan gliding and invasion complexes. Scientists from Germany took the pain of analyzing the molecular structure of a glideosome member-protein – essential light chains (ELCs) found in T. gondii (TgELC1 and TgELC2) and P. falciparum (PfELC) by using X-ray crystallography and nuclear magnetic resonance (NMR).
Studies revealed IMC with the help of three glideosome-associated proteins (GAPs) gets linked to small unconventional myosin protein (MyoA) to which myosin light chain (MLC1) and ELC binding takes place and stabilizes it. After the completion of Ca-independent assembly, ELCs undergo compression forming α helix thereby, stiffening the MyoA to act as lever arms enabling it to take longer leaps and doubling its speed, ready to empower parasitic motility. Preventing the assembly of the glideosome by mutating the phosphorylation sites can decrease the binding affinity of ELCs and thus can stop the progression of diseases with the help of drugs.
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SOURCE – Pazicky, S., Dhamotharan, K., Kaszuba, K., Mertens, H., Gilberger, T., Svergun, D., Kosinski, J., Weininger, U. and Löw, C., 2020. Structural role of essential light chains in the apicomplexan glideosome. Communications Biology, 3(1).https://doi.org/10.1038/s42003-020-01283-8
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