Deciphering the Gating Mechanism of Intraflagellar Transport in Trypanosoma brucei

About This Grant

Project Summary Trypanosoma brucei (T. brucei) is a eukaryotic protozoan parasite responsible for African trypanosomiasis in humans and livestock, a debilitating illness that can lead to death if left untreated. This disease is not only a significant human health threat but also has extensive economic repercussions, impacting agriculture and reducing productivity. Current treatments are challenging to administer, often use potentially toxic drugs, and drug resistance is a growing challenge. A promising path toward novel therapeutic strategies is to target essential biological processes, such as flagellum (or cilia) biogenesis. It drives motility, enables environmental sensing, and facilitates transmission between mammalian hosts by the tsetse fly throughout its complex life cycle. Recent findings have revealed that the flagellum exhibits spatial compartmentalization of signaling proteins, such as cAMP effectors, especially at the flagellar tip, suggesting tightly regulated trafficking mechanisms. A key process governing flagellar assembly and maintenance is intraflagellar transport (IFT), which relies on a gating mechanism at the flagellar base, known as the transition zone (TZ). While significant progress has been made in characterizing IFT complex composition and associated motors, the molecular mechanisms by which these complexes dock at and transit through the TZ gate remain poorly understood, particularly in divergent organisms like T. brucei. Addressing this knowledge gap is essential to understanding how flagellar protein trafficking is regulated in kinetoplastids. To fill this knowledge gap, we will utilize genetically engineered miniaturized T. brucei cells and employ advanced techniques including cryogenic electron microscopy and Magnify expansion microscopy, coupled with mutation phenotype analysis to structurally and functionally characterize the TZ components and their interaction with the TZ as well as their role in IFT regulation. Our goal is to construct a three-dimensional molecular and structural model of the TZ and reveal the path by which IFT complexes pass through this gate at the flagellar base. While our primary focus is on T. brucei, the TZ gating mechanisms we investigate are conserved across flagellated pathogens and ciliated eukaryotic cells. At the same time, T. brucei displays unique architectural and regulatory features that are different from classical models of ciliopathies. By studying this divergent organism, we aim to uncover both parasite-specific adaptations and fundamental principles of IFT and TZ function. In summary, our long-term goal is to elucidate how flagellum biogenesis is driven by the coordination between IFT machinery and the TZ gate, advancing our understanding of both protozoan pathogenesis and conserved mechanisms of ciliary assembly in eukaryotic cells.