Chemistry Defense: Michael Chirgwin: Exploring trafficking mechanisms during the Plasmodium Liver stage

Exploring trafficking mechanisms during the Plasmodium Liver stage

Malaria is a devastating disease caused by parasites from the genus Plasmodium. Once an infected female Anopheles mosquito takes a blood meal, the parasite is deposited into the skin of the mammalian host and migrates to the liver for the first stage of infection. Once in the liver, parasites asexually replicate and form blood-infective merozoites. During the asymptomatic liver stage, the parasite develops within a parasitophorous vacuole (PV), surrounded by the PV membrane (PVM) that separates the parasite from the host cytosol. The PVM is the site for host-parasite interactions and is highly dynamic throughout the liver stage. Interestingly, some host proteins localize to the PVM and have been shown to be essential for parasite development, yet the mechanisms for host protein recruitment remain unresolved. Here, we found that the parasite relies on host endocytosis and exocytosis processes, specifically the host SNARE protein VAMP3, for protein recruitment and development. Using ultrastructure expansion microscopy and chemical inhibition of VAMP3 vesicle recycling, we show that VAMP3 vesicles fuse to the PVM. Moreover, the PV of liver stage P. berghei parasites rapidly expands between 24 and 48 hours post infection, which must require a dynamic proteome. Using the proximity labeling technique called biotinylation by antibody recognition, we labeled and enriched parasite proteins every 12 hours throughout liver stage infection identified the proteome by mass spectrometry. Interestingly, when we compared our data with RNA-seq, we observed that liver stage parasites use translational repression programs to orchestrate their rapid expansion. Collectively, these studies investigate liver stage Plasmodium biology and its interactions with the host cell, which could be exploited for future malaria treatment.