Editorial on the Research Topic The Cell Biology of Protist Parasite-Host Interfaces Molecular exchange at the parasite-host interface is key to parasite survival since these eukaryotic species feed off of host-acquired nutrients and often complete key stages of their life-cycles within them. The focus of this special issue is on our level of mechanistic understanding of the complex communication established between a parasite and a host, with a focus on protist parasites which cause

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... morbidity and disability worldwide in both medical and veterinary contexts. Protist parasites have evolved an incredibly diverse range of strategies to invade their hosts and ensure survival and the cell biology underlying interactions and protein/metabolite trafficking at protist parasite-host interfaces, whether extra-or intra-cellular, is a field of intense investigation. In this special issue, contributions from experts in Plasmodium, Toxoplasma, Theileria, Giardia, Leishmania, Trypanosoma and Entamoeba cell biology provide critical reviews and experimental data on essential topics such as parasite nutrition, parasite surface remodeling, protein trafficking and parasite biology in terms of invasion and niche establishment. Focusing on parasite cell biology, Zeeshan et al. report on the essentiality of parasite kinesin 5 for the production of infectious Plasmodium berghei sporozoites. They are joined by Thomas et al. in their investigation of the role for GlRac in defining progression and maturation of organelles essential for infectious cyst formation in Giardia lamblia. A more "omics"-based approach enables Sun et al. to investigate global proteomics changes in both host and parasite cells during Toxoplasma gondii infection while König et al. compare and contrast the predicted proteome of Entamoeba histolytica and its sister species to discern lineage-specific genes which may help explain virulence patterns in otherwise closely-related species. With a focus on Leishmania pathogenesis, Salloum et al. discuss insight from RNA-Seq based analyses and present an exciting outlook for investigation which includes the host's/vector's microbiota in the equation for a parasite's pathobiology. Critical reviews on parasite-dependent hijacking of host cell-specific pathways include an indepth discussion and appreciation for the role of autophagy in Toxoplasma gondii infection and establishment in nervous tissue by Subauste, joined by Woods et al. for a discussion of strategies Theileria parasites to invade and immortalize leukocytes. For a stronger focus on parasite nutrition, Counihan et al. discuss recent advances in our understanding of how Plasmodium parasites take up nutrients from the host cell milieu, including the role for endocytosis in ferrying hemoglobin to the parasitophorous vacuole. Endocytosis and protein trafficking routes involved in parasite virulence are discussed in three manuscripts. Link et al. discuss secretory and endosomal pathways in trypanosomes with a focus on VSG proteins, antigenic variation and its important role in immune evasion. They are joined by Borges et al. for a targeted appraisal of the GPI anchor as