Dual role of the Toxoplasma gondii clathrin adaptor AP1 in the sorting of rhoptry and microneme proteins and in parasite division

Toxoplasma gondii possesses a highly polarized secretory system,which efficiently assembles de novo micronemes and rhoptries during parasite replication. these apical secretory organelles release their contents into host cells promoting parasite invasion and survival. using a crelox-based inducible knock-out strategy and the ddfkbp over-expression system,we unraveled novel functions of the clathrin adaptor complex tgap1. first,our data indicate that ap1 in t. gondii likely functions as a conserved heterotetrameric complex composed of the four subunits γ,β,μ1,σ1 and interacts with known regulators of clathrin-mediated vesicular budding such as the unique enth-domain containing protein,which we named epsin-like protein (tgepsl). disruption of the μ1 subunit resulted in the mis-sorting of microneme proteins at the level of the trans-golgi-network (tgn). furthermore,we demonstrated that tgap1 regulates rhoptry biogenesis by activating rhoptry protein exit from the tgn,but also participates in the post-golgi maturation process of prerop compartments into apically anchored club-shaped mature organelles. for this latter activity,our data indicate a specific functional relationship between tgap1 and the rab5a-positive endosome-like compartment. in addition,we unraveled an original role for tgap1 in the regulation of parasite division. apμ1-depleted parasites undergo normal daughter cell budding and basal complex assembly but fail to segregate at the end of cytokinesis. © 2017 venugopal et al.