Protein that helps parasite survive in host cells identified

WASHINGTON - Researchers at the Washington University School of Medicine in St. Louis have identified a protein that helps parasite survive in host cells.

Toxoplasma gondii and other related parasites surround themselves with a membrane to protect against factors in host cells that would otherwise kill them.

And the researchers have now identified a parasite protein that protects this membrane from host proteins that can rupture it.

They believe that disabling the parasite’s defensive protein could help give hosts an advantage in the battle against infection.

In the study, scientists showed that the ROP18 protein disables host cell proteins that would otherwise pop a protective bubble the parasite makes for itself.

The parasite puts the bubble on like a spacesuit by forming a membrane around itself when it enters host cells. This protects it from the hostile environment inside the cell, which would otherwise kill it.

“If we can find therapies that block ROP18 and other parasite proteins like it, that could give the host the upper hand in the battle against infection,” said first author Sarah Fentress, a graduate student in the laboratory of L. David Sibley, professor of molecular microbiology.

“The exact role of ROP18 and related proteins in human disease remains to be studied. But mice are natural hosts of Toxoplasma, so studies in laboratory mice are relevant to the spread of infection,” said Sibley.

In the new study, Fentress showed that the ROP18 protein binds to a class of host proteins known as immunity-related GTPases. Tests in cell cultures and animal models showed that this binding leads to a reaction that disables the GTPases, which normally would rupture the parasite’s protective membrane.

The findings were published in the journal Cell Host and Microbe. (ANI)