Figure 2.

Hypothetical models for Toxoplasma gondii endocytosis and trafficking of ingested protein. Ingested proteins are proposed to traverse the PVM in internally budding vesicles and enter the parasite at a discrete site. Mechanisms could resemble model systems and depend on coat proteins, dynamin, and actin. Examples of (A) clathrin-mediated or (B) clathrin-independent processes, represented by CLIC-GEEC, are depicted. (C) Scission of endocytic vesicles may also require host proteins for pinching of the PVM as depicted by possible recruitment of host Endosomal Sorting Complex Required for Transport (ESCRT) machinery and garroting at the parasite plasma membrane by a dynamin-related protein. (D) After scission from the PVM (step 1) and entering the parasite (step 2), guided by a putative ingestion receptor, the ingested material is proposed to traverse the TGN (step 3) before trafficking through the ELCs (step 4) en route to the VAC for degradation by proteases including CPL. Mn, microneme; Rop, rhoptry.