Lack of Dynamin Protein Prevents Cell Division in Toxoplasma Gondii

A team of molecular biologists and parasitologists working with the protozoan parasite Toxoplasma gondii has identified a protein critically involved in the process of cell division that may represent a promising drug target.

Toxoplasma belongs to a group of parasites, including the malaria parasites, which contain apicoplasts, relict nonphotosynthetic plastids found in all protozoan parasites belonging to the phylum Apicocomplexa. Apicoplasts are essential for parasite growth and must correctly divide and segregate into daughter cells upon cytokinesis. Apicoplast division depends on association with the mitotic spindle, although little is known about the molecular machinery involved in this process.

To study the T. gondii apocopate, investigators from the University of Georgia (Athens, USA) genetically engineered a strain of the parasite to lack the gene for the dynamin protein DrpA. Dynamins are GTP (guanine triphosphate)ase enzymes responsible for endocytosis in eukaryotic cells. They are principally involved in the separation of newly formed vesicles from the membrane of one cellular compartment and their targeting to, and fusion with, another compartment, both at the cell surface as well as at the Golgi apparatus. Dynamins also play a role in many processes including division of organelles, cytokinesis, and microbial pathogen resistance.

Results published in the February 12, 2009, online edition of the journal Current Biology revealed that apicoplast replication was disrupted in the parasites lacking DrpA protein. Their apicoplasts could not pinch into daughter organelles, and the failure to reproduce the apicoplast caused the death of the parasite.

"The apicoplast is essential for parasitic growth and must correctly divide for the organism to stay alive,” said senior author Dr. Boris Striepen, professor of cell biology at the University of Georgia. "Understanding more of how it works is crucial to progress in understanding how these disease processes evolve.”

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