Molecular Mechanisms and Evolution of the Rhoptry Secretion System

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

PROJECT SUMMARY This research program focuses on understanding the rhoptry secretion system in unicellular eukaryotes within the Alveolata superphylum, including apicomplexan parasites and non-pathogenic ciliates. Apicomplexans, such as Toxoplasma and Plasmodium, utilize rhoptry secretion for host invasion, a process with poorly understood mechanisms. Recent progress, utilizing cryo-electron tomography, uncovered a novel Rhoptry Secretory Apparatus crucial for apicomplexan rhoptry secretion and host invasion. Similar machineries were found in ciliates, lacking the apical vesicle, suggesting evolutionary adaptations. The research program is structured around three main questions: A) What is the conserved basic architecture of these secretion machineries? Using cryo-electron tomography, the team will systematically image species across the Alveolata superphylum, comparing apicomplexans and ciliates to understand architectural variations. B) How are these machineries built? Focusing on one model apicomplexan, Toxoplasma gondii, and one model ciliate, Tetrahymena thermophila, the team will dissect and compare the detailed assembly of these secretion machineries using a combination of genetics, structural biology, and proteomics approaches. C) What is the mechanism for organelle content secretion? The team will study structural changes of these machineries during active secretion events in both apicomplexans and ciliates, utilizing innovative cryo-correlative microscopy and time-resolved sample freezing methods to capture these spatially and temporally transient activities. Capitalizing on the unique opportunity provided by the recent discovery of the Rhoptry Secretory Apparatus, this comprehensive strategy integrates cutting-edge technologies and multidisciplinary approaches to unravel the molecular structures, mechanisms, and evolutionary aspects of the rhoptry secretion system. The findings will provide unprecedented and fundamental insights into molecular secretions in this prominent branch of eukaryotic organisms for crucial biological functions.