# Interrogating the molecular architecture of the Cryptosporidium host-parasite interface > **NIH NIH F32** · UNIVERSITY OF PENNSYLVANIA · 2024 · $73,828 ## Abstract ABSTRACT Cryptosporidium infections are a leading cause of diarrheal disease in young children for which no vaccine or universally effective treatment is available. Apicomplexan parasites such as Cryptosporidium, Toxoplasma, and Plasmodium actively invade their host cells and reside within a specialized membrane-bound compartment, or parasitophorous vacuole (PV). To survive and replicate, intracellular parasites must evade immune detection and extract nutrients from the host cytosol. Toxoplasma and Plasmodium secrete the contents of specialized secretory organelles, such as dense granules, to the PV where they orchestrate vacuole remodeling and immune evasion, while solute transporters at the parasite plasma membrane import small molecules such as amino acids and sugars. In addition, a conserved Kelch13-containing complex in these parasites is responsible for the formation of specialized membrane invaginations in the parasite plasma membrane that facilitate nutrient extraction from the host by bulk endocytosis. Cryptosporidium resides in a unique intracellular but extra-cytoplasmic niche. Transmission electron microscopy of intracellular Cryptosporidium revealed intricate ultrastructural features at the host-parasite interface, including electron dense bands, tight junction-like rings, and a highly invaginated membrane termed the feeder organelle. The three-dimensional architecture, composition, and function of these features are poorly understood. Recent studies and preliminary data have identified a handful of proteins that localize to the C. parvum host-parasite interface, including secreted effectors and solute transporters. The relationship between these components to each other, to the host cytosol, and to the ultrastructural features observed at the interface are unknown. In addition, the machinery responsible for shaping the membrane invaginations at the feeder organelle has not been identified. I hypothesize that transporters and secreted effectors occupy separate compartments at the interface, with transporters assembled in the parasite plasma membrane and effectors delivered to the PV membrane or lumen. I will uncover the three-dimensional ultrastructure, molecular architecture, and composition of the host- parasite interface at unprecedented resolution using cryogenic electron-microscopy-based volume imaging techniques. I will also use high-resolution optical microscopy and fluorescence complementation to determine whether transporters and dense granule effectors are trafficked to the same compartment. I also propose that the feeder organelle is shaped by K13 complex-mediated endocytosis, and I will determine the localization of these candidates in intracellular C. parvum parasites using light and electron microscopy. These studies will leverage innovative structural and molecular parasitology approaches to reveal mechanisms of membrane remodeling and nutrient acquisition fundamental to the biology of intracellular parasitism, yiel... ## Key facts - **NIH application ID:** 10900977 - **Project number:** 1F32AI183654-01 - **Recipient organization:** UNIVERSITY OF PENNSYLVANIA - **Principal Investigator:** Allison Cohen - **Activity code:** F32 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2024 - **Award amount:** $73,828 - **Award type:** 1 - **Project period:** 2024-08-01 → 2027-07-31 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10900977 ## Citation > US National Institutes of Health, RePORTER application 10900977, Interrogating the molecular architecture of the Cryptosporidium host-parasite interface (1F32AI183654-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10900977. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*