From the plasma membrane to the plasma membrane, following recycling and flow of Toxoplasma gondii membrane proteins.

The plasma membrane (PM) plays a critical role in numerous functions, from motility to cell communication, and serves as a gateway between intracellular content and the extracellular environment^1,2. This is particularly true for intracellular parasites, which switch between drastically different environments during their life cycles³. Endocytosis is an important mechanism involved in the regulation of plasma membrane surface proteins and uptake of environmental molecules. We recently demonstrated endocytosis in Toxoplasma gondii (T. gondii) by labelling endogenous Halo-tagged SAG1 with a non-permeable dye⁴. This uptake occurring at the micropore is important for intracellular development, as knockdown of the protein composing the micropore impairs endocytosis and disturbs plasma membrane dynamics, leading to membrane accumulation and death of the parasite^5,6. However, little is known about the normal behaviour of PM in T. gondii. Here, using SAG1-Halo as a proxy, we followed the dynamics of the PM using a dual (spatial and/or temporal) labelling strategy, allowing the differentiation between internal and surface proteins, but also between the mother and de novo synthesized material during replication. Using this strategy, we showed the presence of a complete cycle of endo-exocytosis in Toxoplasma gondii, regulating PM dynamics during the parasite lytic cycle.

Thottacherry, J. J., Sathe, M., Prabhakara, C. & Mayor, S. Spoiled for Choice: Diverse Endocytic Pathways Function at the Cell Surface. Annu Rev Cell Dev Biol 35, 55–84 (2019). Redpath, G. M. I., Betzler, V. M., Rossatti, P. & Rossy, J. Membrane Heterogeneity Controls Cellular Endocytic Trafficking. Frontiers in Cell and Developmental Biology 8, (2020). Attias, M. et al. The life-cycle of Toxoplasma gondii reviewed using animations. Parasit Vectors 13, 588 (2020). Gras, S. et al. An endocytic-secretory cycle participates in Toxoplasma gondii in motility. PLoS Biol 17, e3000060 (2019). Koreny, L. et al. Stable and ancient endocytic structures navigate the complex pellicle of apicomplexan parasites. bioRxiv 2022.06.02.494549 (2022) doi:10.1101/2022.06.02.494549. Wan, W. et al. The Toxoplasma micropore mediates endocytosis for selective nutrient salvage from host cell compartments. Nat Commun 14, 977 (2023).