Elucidation of the molecular basis for the activation of trypanosomal receptor adenylate cyclases by stimulus-induced ectodomain conformational change.

Neglected tropical diseases (NTDs) comprise a wide variety of communicable diseases that are prevalent in (sub)tropical regions and affect more than 1 billion people worldwide. NTDs are hallmarked by a significant mortality and a high morbidity, thereby severely impacting the quality of life and socio-economic status of those affected. The WHO has listed 20 NTDs that should be tackled in the interest of global health and well-being. Three of these are caused by kinetoplastids, a group of flagellated, single-celled eukaryotic organisms comprising parasites of the Trypanosoma and Leishmania genera. Trypanosomes are the causative agents of animal and human trypanosomiasis (AT and HT, respectively) and are of the most cunning pathogens to have burdened humankind in past and present times. While anthroponotic HT (T. brucei gambiense) is perceived as a minor threat, zoonotic HT (T. b. rhodesiense) remains a worrisome health problem. Likewise, AT (T. b. brucei, T. congolense, T. vivax, T. evansi) still has a devastating socio-economic impact (annual losses of ~$5 billion). The battle against trypanosomes requires a concerted approach involving vaccination and drug treatment. However, the development of an effective vaccine against trypanosomes is thwarted by sophisticated immune-evasion strategies and the current drug treatment schemes are largely unsatisfactory. Hence, there is a dire need for alternative control strategies, which advocates the need for active research into trypanosome (immuno)biology. The life cycle of salivarian trypanosomes requires passages through two host organisms: the tsetse fly and mammals. As part of their obligate bipartite life cycle, these parasites have evolved to adapt, mediate immune evasion, and undergo developmental transitions within changing host environments. While trypanosomes are notorious for their ability to masterfully manipulate host-parasite interactions, many of the underlying molecular mechanisms remain poorly characterised. Trypanosomal receptor-like adenylate cyclases (TrypRACs) have been identified as important operators in these processes. The TrypRACs represent a large polymorphic family displaying a conserved architecture in which a single transmembrane helix separates an N-terminal extracellular receptor domain from a cytosolic enzymatic domain with cyclase activity. Specific TrypRACs are expressed in insect vector and mammalian host stages. In the mammalian host, it has been shown that the activation of the bloodstream-specific TrypRAC ESAG4 via mild acid stress results in massive cAMP production, thereby inhibiting TNF-α synthesis by host myeloid cells and contributing to innate immune evasion at the onset of infection. In the tsetse fly, several insect-specific TrypRACs coordinate so-called "social motility (SoMo)" of the parasite population, which is crucial for vector infection. SoMo is regulated by a cAMP signaling complex containing specific TrypRAC isoforms (especially the TrypRAC ACP5 is essential) and other trypanosome factors. While our preliminary data indicate that the TrypRAC ectodomain is pivotal for the control of cyclase activity, the molecular mechanisms that underlie ectodomain-mediated TrypRAC activation are poorly understood. Especially the effect of putative natural ligands on the TrypRAC structure-function relationship remains unknown. Therefore, this project aims to study the molecular aspects of TrypRAC ectodomain-ligand interactions using a combination of functional, biophysical, and structural methods (the research stay at UAntwerp will be critical to support the structural work). We propose that the TrypRAC extracellular sensor domains are promising targets for the development of novel anti-trypanosomal therapies and that a thorough characterisation of their structure-function relationship will yield highly valuable insights.

Keywords:PROTEINS, STRUCTURAL BIOLOGY, TRYPANOSOMA

Disciplines:Proteins, Parasitology, Structural biology, Molecular biophysics

Project type:Collaboration project