Mechanisms and functions of host organelle usurpation by intravacuolar Toxoplasma

液泡内弓形虫侵占宿主细胞器的机制和功能

• 批准号: 10649407
• 负责人: Isabelle Coppens
• 金额: $ 69.69万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-20 至 2027-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10649407
• 关键词: Abbreviations; Address; Affect; Binding; Biochemical; Biochemical Pathway; Biological Assay; Cell membrane; Cell physiology; Cells; Cellular biology; Cholesterol; Clustered Regularly Interspaced Short Palindromic Repeats; Complex; Cytoplasm; Cytoplasmic Granules; Development; Docking; Encephalitis; Endosomes; Filament; Future; Genes; Genetic Screening; Genetic Techniques; Genome; Goals; Golgi Apparatus; HIV/AIDS; Immunocompromised Host; Immunofluorescence Immunologic; Individual; Infection; Intercept; Intervention; Lipids; Mammalian Cell; Mediating; Membrane; Membrane Proteins; Microscopic; Modeling; Molecular; Nature; Nutrient; Organelles; Parasites; Pathway interactions; Patients; Penetration; Phosphatidylcholine-Sterol O-Acyltransferase; Phospholipase; Plasma Cells; Play; Process; Protein Secretion; Proteins; Proteome; Recycling; Resources; Role; Route; Site; Sorting; Sphingolipids; System; Toxoplasma; Toxoplasma gondii; Toxoplasmosis; Transmembrane Transport; Vacuole; Vesicle; Work; chemotherapy; design; differential expression; genetic manipulation; insight; lipid transfer protein; lipid transport; microorganism; model organism; mutant; novel; obligate intracellular parasite; opportunistic pathogen; pathogen; protein complex; rab GTP-Binding Proteins; recruit; response; trafficking; vesicle-associated membrane protein

SUMMARY Lipids are transferred between membranes by vesicular and non-vesicular routes. Many microorganisms that infect mammalian cells subvert the function of these host cellular lipid trafficking pathways to acquire lipids. Toxoplasma gondii is an obligate intracellular parasite that multiplies in the cytoplasm of mammalian cells within a self-made membrane-bound compartment – the parasitophorous vacuole (PV). The PV of T. gondii does not fuse with host organelles. However, we showed that the parasite’s intracellular survival relies on lipids retrieved from various mammalian organelles. For example, T. gondii scavenges cholesterol and sphingolipids from host endocytic organelles and Golgi vesicles, respectively, which raises the perplexing question of how T. gondii can access the lipid content of these organelles without fusion. To address this issue, our first strategy was to analyze vesicular trafficking pathways in infected mammalian cells. We showed that Toxoplasma intercepts mammalian Rab vesicles associated with recycling, endocytic and secretory pathways, and sequesters these vesicles into a network of membranous tubules appended to the PV membrane. Our second approach was to analyze non- vesicular routes of lipid transfer, specifically Membrane Contact Sites (MCS). By examining the physical connectivity of mammalian host organelles with the PV membrane, we showed that Toxoplasma attracts host ER tubules and lipid droplets to the PV, where they are closely apposed to the PV membrane at distances reminiscent of inter-organelle contacts. Mammalian ER-resident Vesicle-Associated Membrane Proteins (VAP), components of MCS, are associated with the PV membrane, suggesting the potential exploitation of Lipid Transfer Proteins by Toxoplasma for lipid acquisition. Based on these preliminary observations, we propose two models for lipid scavenging by Toxoplasma either mammalian vesicular or non-vesicular lipid transport pathways. We will assess the steps of these models by defining the molecular machineries and mechanisms involved in the interception of host vesicular pathways by T. gondii (Aim 1), the formation of a network of membranous tubules in the PV and its role in mammalian organelle sequestration (Aim 2) and the acquisition of lipids via non-vesicular transfer from mammalian organelles closely associated with the PVM, possibly through MCS (Aim 3). Completing these aims would unravel the complexity of lipid salvage processes mediated by Toxoplasma, providing mechanistic details and identifying future targets for intervention. Indeed, T. gondii can cause fatal encephalitis in immunocompromised individuals, and current treatment options for toxoplasmosis are limited. Furthermore, studying the mechanisms used by Toxoplasma to usurp Rab-mediated vesicle trafficking may yield valuable insights into how Rab GTPases coordinate membrane transport in mammalian cells. Examining the potential strategies developed by Toxoplasma to exploit MCS may also provide important information on how the loss of MCS affect mammalian cellular physiology and organismal function.

总结