A single-cell atlas of Plasmodium falciparum transmission through the mosquito

Malaria parasites have a complex life cycle featuring diverse developmental strategies, each uniquely adapted to navigate specific host environments. Here we use single-cell transcriptomics to illuminate gene usage across the transmission cycle of the most virulent agent of human malaria - Plasmodium falciparum. We reveal developmental trajectories associated with the colonization of the mosquito midgut and salivary glands and elucidate the transcriptional signatures of each transmissible stage. Additionally, we identify both conserved and non-conserved gene usage between human and rodent parasites, which point to both essential mechanisms in malaria transmission and species-specific adaptations potentially linked to host tropism. Together, the data presented here, which are made freely available via an interactive website, provide a fine-grained atlas that enables intensive investigation of the P. falciparum transcriptional journey. As well as providing insights into gene function across the transmission cycle, the atlas opens the door for identification of drug and vaccine targets to stop malaria transmission and thereby prevent disease

Diversity in protein post-translational modifications and their critical impacts on the lytic cycle of Toxoplasma gondii

Apicomplexan phylum comprises obligate intracellular parasites, infecting a wide range of hosts from vertebrates to invertebrates. My thesis covers two main aspects of their biology. Firstly, I delineated the establishment of intracellular parasitism in Apicomplexans over the course of evolution by studying the phylogeny, morphology, metabolic and invasive capabilities of a fish coccidian parasite, Goussia janae. In the second section of the thesis, I dealt with the investigation of the role of two post-translational modifications, proteolytic processing and palmitoylation, of proteins. We identified and characterized the essentiality of an aspartyl protease 3 (TgASP3) for the lytic cycle of the parasite by highlighting its role as a maturase for integral secretory organelle proteins. Furthermore, we identified a potential drug candidate 49c, a peptidomimetic inhibitor that targets. We characterized the essential nature of 2 inner membrane complex (IMC)-resident palmitoyl acyl transferases, TgDHHC2 and TgDHHC14, and a Golgi-resident TgDHHC5

Biology of rhomboid proteases in infectious diseases

Rhomboids are a well-conserved class of intramembrane serine proteases found in all kingdoms of life, sharing a conserved core structure of at least six transmembrane (TM) domains that contain the catalytic serine-histidine dyad. The rhomboid proteases, which cleave membrane embedded substrates within their TM domains, are emerging as an important group of enzymes controlling a myriad of biological processes. These enzymes are found in a wide variety of pathogens manifesting important roles in their pathological processes. Accordingly, they have received considerable attention as potential targets for pharmacological intervention over the past few years. This review provides a general update on rhomboid proteases and their roles in pathogenesis of human infectious agents

Toxoplasma gondii TFP1 is an essential transporter family protein critical for microneme maturation and exocytosis

Invasion and egress are two key steps in the lytic cycle of Apicomplexa that are governed by the sequential discharge of proteins from two apical secretory organelles called micronemes and rhoptries. In Toxoplasma gondii, the biogenesis of these specialized organelles depends on the post Golgi trafficking machinery, forming an endosomal-like compartment (ELC) resembling endomembrane systems found in eukaryotes. In this study, we have characterized four phylogenetically related Transporter Facilitator Proteins (TFPs) conserved among the apicomplexans. TFP1 localises to the micronemes and ELC, TFP2 and TFP3 to the rhoptries and TFP4 to the Golgi. TFP1 crucially contributes to parasite fitness and survival while the other members of this family are dispensable. Conditional depletion of TFP1 impairs microneme biogenesis and leads to a complete block in exocytosis, which hampers gliding motility, attachment, invasion and egress. Morphological investigations revealed that TFP1 participates in the condensation of the microneme content, suggesting the transport of a relevant molecule for maintaining the intraluminal microenvironment necessary for organelle maturation and exocytosis. In absence of TFP2, rhoptries adopt a considerable elongated shape, but the abundance, processing or secretion of the rhoptry content are not affected. These findings establish the relevance of TFPs in organelle maturation of T. gondii. This article is protected by copyright. All rights reserved

A druggable secretory protein maturase of Toxoplasma essential for invasion and egress

Micronemes and rhoptries are specialized secretory organelles that deploy their contents at the apical tip of apicomplexan parasites in a regulated manner. The secretory proteins participate in motility, invasion, and egress and are subjected to proteolytic maturation prior to organellar storage and discharge. Here we establish that Toxoplasma gondii aspartyl protease 3 (ASP3) resides in the endosomal-like compartment and is crucially associated to rhoptry discharge during invasion and to host cell plasma membrane lysis during egress. A comparison of the N-terminome, by terminal amine isotopic labelling of substrates between wild type and ASP3 depleted parasites identified microneme and rhoptry proteins as repertoire of ASP3 substrates. The role of ASP3 as a maturase for previously described and newly identified secretory proteins is confirmed in vivo and in vitro. An antimalarial compound based on a hydroxyethylamine scaffold interrupts the lytic cycle of T. gondii at submicromolar concentration by targeting ASP3

Neuroinflammation-Associated Aspecific Manipulation of Mouse Predator Fear by <i>Toxoplasma gondii</i>

In rodents, the decrease of felid aversion induced by Toxoplasma gondii, a phenomenon termed fatal attraction, is interpreted as an adaptive manipulation by the neurotropic protozoan parasite. With the aim of understanding how the parasite induces such specific behavioral modifications, we performed a multiparametric analysis of T. gondii-induced changes on host behavior, physiology, and brain transcriptome as well as parasite cyst load and distribution. Using a set of complementary behavioral tests, we provide strong evidence that T. gondii lowers general anxiety in infected mice, increases explorative behaviors, and surprisingly alters predator aversion without selectivity toward felids. Furthermore, we show a positive correlation between the severity of the behavioral alterations and the cyst load, which indirectly reflects the level of inflammation during brain colonization. Taken together, these findings refute the myth of a selective loss of cat fear in T. gondii-infected mice and point toward widespread immune-related alterations of behaviors