title: Toxoplasma gondii protease TgSUB1 is required for cell surface processing of micronemal adhesive complexes and efficient adhesion of tachyzoites.
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.
authors.affiliation: Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Lagal
authors.forename: Emily M
authors.initials: EM
authors.lastname: Binder
authors.forename: My-Hang
authors.initials: MH
authors.lastname: Huynh
authors.forename: Bjorn F C
authors.initials: BF
authors.lastname: Kafsack
authors.forename: Philippa K
authors.initials: PK
authors.lastname: Harris
authors.forename: Roberto
authors.initials: R
authors.lastname: Diez
authors.forename: Dawn
authors.initials: D
authors.lastname: Chen
authors.forename: Robert N
authors.initials: RN
authors.lastname: Cole
authors.forename: Vern B
authors.initials: VB
authors.lastname: Carruthers
authors.forename: Kami
authors.initials: K
authors.lastname: Kim
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D004195:Disease Models, Animal; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006801:Humans; D008124:Locomotion; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D013381:Subtilisins / Q000235:genetics / Q000378:metabolism*; D014122:Toxoplasma / Q000201:enzymology* / Q000378:metabolism* / Q000472:pathogenicity / Q000502:physiology; D014124:Toxoplasmosis, Animal / Q000469:parasitology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D015815:Cell Adhesion Molecules; C408878:MIC2 protein, Toxoplasma gondii; C428323:MIC4 protein, Toxoplasma gondii; D008565:Membrane Proteins; D015800:Protozoan Proteins; C450759:TgM2AP protein, Toxoplasma gondii; D037521:Virulence Factors; C443133:SUB1 protein, Toxoplasma gondii; D013381:Subtilisins