Résumé
Host cell entry by the A picomplexa is associated with the sequential secretion of invasion factors from specialized apical organelles. Secretion of micronemal proteins ( MIC s) complexes by T oxoplasma gondii facilitates parasite gliding motility, host cell attachment and entry, as well as egress from infected cells. The shedding of MIC s during these steps is mediated by micronemal protein proteases MPP 1, MPP 2 and MPP 3. The constitutive activity of MPP 1 leads to the cleavage of transmembrane MIC s and is linked to the surface rhomboid protease 4 ( ROM 4) and possibly to rhomboid protease 5 ( ROM 5). To determine their importance and respective contribution to MPP 1 activity, in this study ROM 4 and ROM 5 genes were abrogated using C re‐recombinase and CRISPR ‐ C as9 nuclease, respectively, and shown to be dispensable for parasite survival. Parasites lacking ROM 4 predominantly engage in twirling motility and exhibit enhanced attachment and impaired invasion, whereas intracellular growth and egress is not affected. The substrates MIC 2 and MIC 6 are not cleaved in rom4‐ko parasites, in contrast, intramembrane cleavage of AMA 1 is reduced but not completely abolished. Shedding of MIC s and invasion are not altered in the absence of ROM 5; however, this protease responsible for the residual cleavage of AMA 1 is able to cleave other AMA family members and exhibits a detectable contribution to invasion in the absence of ROM 4.