Wednesday, April 08, 2015

Distinct contribution of Toxoplasma gondii rhomboid proteases 4 and 5 to micronemal protein protease 1 activity during invasion

2015 Apr 2. doi: 10.1111/mmi.13021. [Epub ahead of print]
 
 
Host cell entry by the Apicomplexa is associated with the sequential secretion of invasion factors from specialized apical organelles. Secretion of micronemal proteins (MICs) complexes by Toxoplasma gondii facilitates parasite gliding motility, host cell attachment and entry, as well as egress from infected cells. The shedding of MICs during these steps is mediated by micronemal protein proteases MPP1, MPP2, and MPP3. The constitutive activity of MPP1 leads to the cleavage of transmembrane MICs and is linked to the surface rhomboid protease 4 (ROM4) and possibly to rhomboid protease 5 (ROM5). To determine their importance and respective contribution to MPP1 activity, in this study ROM4 and ROM5 genes were abrogated using Cre-recombinase and CRISPR-Cas9 nuclease, respectively, and shown to be dispensable for parasite survival. Parasites lacking ROM4 predominantly engage in twirling motility and exhibit enhanced attachment and impaired invasion, whereas intracellular growth and egress are not affected. The substrates MIC2 and MIC6 are not cleaved and accumulate on the rom4-ko parasite surface. In contrast, intramembrane cleavage of AMA1 is reduced but not completely abolished. Shedding of MICs and invasion are not altered in the absence of ROM5 however this protease responsible for the residual cleavage of AMA1, is able to cleave other AMA family members and exhibits a detectable contribution to invasion in the absence of ROM4.
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KEYWORDS:

Toxoplasma gondii; invasion; microneme secretion; motility; proteolytic cleavage; rhomboid protease; shedding
PMID:
25846828
[PubMed - as supplied by publisher]

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