Acidification Activates Toxoplasma gondii Motility and Egress by Enhancing Protein Secretion and Cytolytic Activity

PLoS Pathogens

Marijo S. Roiko¹  Nadezhda Svezhova¹  Vern B. Carruthers¹ 

[1] Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America

关键词: Secretion;    Parasitic diseases;    Host cells;    Parasite replication;    Pathogen motility;    Cell membranes;    Cell motility;    Malarial parasites;   

DOI  :  10.1371/journal.ppat.1004488

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Pathogenic microbes rely on environmental cues to initiate key events during infection such as differentiation, motility, egress and invasion of cells or tissues. Earlier investigations showed that an acidic environment activates motility of the protozoan parasite T. gondii. Conversely, potassium ions, which are abundant in the intracellular milieu that bathes immotile replicating parasites, suppress motility. Since motility is required for efficient parasite cell invasion and egress we sought to better understand its regulation by environmental cues. We found that low pH stimulates motility by triggering Ca2+-dependent secretion of apical micronemes, and that this cue is sufficient to overcome suppression by potassium ions and drive parasite motility, cell invasion and egress. We also discovered that acidification promotes membrane binding and cytolytic activity of perforin-like protein 1 (PLP1), a pore-forming protein required for efficient egress. Agents that neutralize pH reduce the efficiency of PLP1-dependent perforation of host membranes and compromise egress. Finally, although low pH stimulation of microneme secretion promotes cell invasion, it also causes PLP1-dependent damage to host cells, suggesting a mechanism by which neutral extracellular pH subdues PLP1 activity to allow cell invasion without overt damage to the target cell. These findings implicate acidification as a signal to activate microneme secretion and confine cytolytic activity to egress without compromising the viability of the next cell infected.

【 授权许可】

CC BY