A cleavable propeptide influences Toxoplasma infection by facilitating the trafficking and secretion of the TgMIC2-M2AP invasion complex

被引:90
作者
Harper, Jill M.
Huynh, My-Hang
Coppens, Isabelle
Parussini, Fabiola
Moreno, Silvia
Carruthers, Vern B.
机构
[1] Johns Hopkins Bloomberg Sch Publ Hlth, W Harry Feinstone Dept Mol Microbiol & Immunol, Baltimore, MD 21205 USA
[2] Univ Georgia, Ctr Trop & Emerging Global Dis, Athens, GA 30602 USA
关键词
D O I
10.1091/mbc.E06-01-0064
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Propeptides regulate protein function and trafficking in many eukaryotic systems and have emerged as important features of regulated secretory proteins in parasites of the phylum Apicomplexa. Regulated protein secretion from micronemes and host cell invasion are inextricably linked and essential processes for the apicomplexan parasite Toxoplasma gondii. TgM2AP is a propeptide-containing microneme protein found in a heterohexameric complex with the microneme protein TgMIC2, a protein that has a demonstrated fundamental role in gliding motility and invasion. TgM2AP function is also central to these processes, because disruption of TgM2AP (m2apKO) results in secretory retention of TgMIC2, leading to reduced TgMIC2 secretion from the micronemes and impaired invasion. Because the TgM2AP propeptide is predicted to be processed in an intracellular site near where TgMIC2 is retained in m2apKO parasites, we hypothesized that the propeptide and its proteolytic removal influence trafficking and secretion of the complex. We found that proTgM2AP traffics through endosomal compartments and that deletion of the propeptide leads to defective trafficking of the complex within or near this site, resulting in aberrant processing and decreased secretion of TgMIC2, impaired invasion, and reduced virulence in vivo, mirroring the phenotypes observed in m2apKO parasites. In contrast, mutation of several cleavage site residues resulted in normal localization, but it affected the stability and secretion of the complex from the micronemes. Therefore, the propeptide and its cleavage site influence distinct aspects of TgMIC2-M2AP function, with both impacting the outcome of infection.
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页码:4551 / 4563
页数:13
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