Toxoplasma gondii protease TgSUB1 is required for cell surface processing of micronemal adhesive complexes and efficient adhesion of tachyzoites

Cell Microbiol. 2010 Dec;12(12):1792-808. doi: 10.1111/j.1462-5822.2010.01509.x.

Abstract

Host cell invasion by Toxoplasma gondii is critically dependent upon adhesive proteins secreted from the micronemes. Proteolytic trimming of microneme contents occurs rapidly after their secretion onto the parasite surface and is proposed to regulate adhesive complex activation to enhance binding to host cell receptors. However, the proteases responsible and their exact function are still unknown. In this report, we show that T. gondii tachyzoites lacking the microneme subtilisin protease TgSUB1 have a profound defect in surface processing of secreted microneme proteins. Notably parasites lack protease activity responsible for proteolytic trimming of MIC2, MIC4 and M2AP after release onto the parasite surface. Although complementation with full-length TgSUB1 restores processing, complementation of Δsub1 parasites with TgSUB1 lacking the GPI anchor (Δsub1::ΔGPISUB1) only partially restores microneme protein processing. Loss of TgSUB1 decreases cell attachment and in vitro gliding efficiency leading to lower initial rates of invasion. Δsub1 and Δsub1::ΔGPISUB1 parasites are also less virulent in mice. Thus TgSUB1 is involved in micronemal protein processing and regulation of adhesive properties of macromolecular adhesive complexes involved in host cell invasion.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Adhesion Molecules / metabolism
  • Cell Adhesion*
  • Cells, Cultured
  • Disease Models, Animal
  • Gene Deletion
  • Genetic Complementation Test
  • Humans
  • Locomotion
  • Membrane Proteins / metabolism
  • Mice
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • Subtilisins / genetics
  • Subtilisins / metabolism*
  • Toxoplasma / enzymology*
  • Toxoplasma / metabolism*
  • Toxoplasma / pathogenicity
  • Toxoplasma / physiology
  • Toxoplasmosis, Animal / parasitology
  • Virulence
  • Virulence Factors / genetics
  • Virulence Factors / metabolism*

Substances

  • Cell Adhesion Molecules
  • MIC2 protein, Toxoplasma gondii
  • MIC4 protein, Toxoplasma gondii
  • Membrane Proteins
  • Protozoan Proteins
  • TgM2AP protein, Toxoplasma gondii
  • Virulence Factors
  • SUB1 protein, Toxoplasma gondii
  • Subtilisins