Revisiting the role of Toxoplasma gondii ERK7 in the maintenance and stability of the apical complex
Toxoplasma gondii ERK7 is known to contribute to the integrity of the apical complex and to be involved only in the final step of the conoid biogenesis. In the absence of ERK7, mature parasites lose their conoid complex and are unable to glide, invade or egress from host cells. In contrast to a previous report, we show here that depletion of ERK7 phenocopies the depletion of the apical cap proteins AC9 or AC10. The absence of ERK7 leads to the loss of the apical polar ring, the disorganization of the basket of subpellicular microtubules and an impairment in micronemes secretion. Ultra-expansion microscopy (U-ExM) coupled to NHS-Ester staining on intracellular parasites offers an unprecedented level of resolution and highlights the disorganization of the rhoptries as well as the dilated plasma membrane at the apical pole in the absence of ERK7. Comparative proteomics analysis of wild-type and ERK7 or AC9 depleted parasites led to the disappearance of known, predicted, as well as putative novel components of the apical complex. In contrast, the absence of ERK7 led to an accumulation of microneme proteins, resulting from the defect in exocytosis of the organelles.