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Biochemistry

Vital protection

Pocket with calcium allows the causer of malaria to live in the inside of blood cells

For years, people have been intrigued by the capacity of the parasite that causes malaria, the Plasmodium falciparum protozoon, for living in an inhospitable environment: the inside of the red blood cells, where there is 10,000 times less calcium than what is needed for their survival. The team led by Célia Garcia, from the Biosciences Institute of the University of São Paulo (USP), has revealed how this feat comes about: at the moment the parasite penetrates into the red blood cells, part of the membrane of the blood cell is folded and, like a glove that covers the hand, forms a pocket around the protozoon.

That is the secret of Plasmodium’s survival. The team from USP discovered that the parasite creates a calcium-rich environment around it, inside the pocket that involves it, called a parasitophorous vacuole. This is how it manages to survive inside the red cell and use the calcium in its favor, to reproduce itself. A protein from the wall of this pocket, the Ca++ ATPase enzyme, plays an essential role in this process, by capturing calcium from the inside of the red cells. “Little by little, we are revealing the strategies for survival that allow the parasite to do so well in the cells where it shelters”, Célia explains.

Commented on in the editorial of the same issue of the Journal of Cell Biology in which it was published, the discovery reveals possible targets for combating malaria, a disease transmitted by mosquitoes of the Anopheles genus, which in Brazil alone brings about some 600,000 new cases a year. It is believed that it may be possible to develop medicines that block the supply of calcium and thus hinder Plasmodium’s reproduction.

In a study published in Nature Cell Biology in 2000, Célia showed another peculiarity of this protozoon’s procreation. In the red blood cells, the parasites reproduce themselves in 24-hour cycles until exploding the red cells and tumbling by the billion into the bloodstream – that is when a fever of up to 40º Celsius breaks out. This is how they escape the defenses of the organism and infect other red cells. The Plasmodium synchronizes its reproduction using one of the main hormones that regulate the biological rhythm of mammals, melatonin, released every 24 hours. Now, for having detailed these connections, the work of the team from USP was described in the news section of Nature’s May 1st issue.

The project
Cellular and Molecular Biology of Plasmodium (nº 98/00410-2); Modality Thematic project; Coordinator Célia Regina da Silva Garcia – IB/USP; Investment R$ 440,152.46

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