The Ebolavirus genus includes several viruses that are highly pathogenic in humans and cause periodic episodes of lethal disease, including a currently persisting outbreak in the Democratic Republic of the Congo. Lassa virus, an arenavirus, is endemic in West Africa and causes up to 300,00 infections annually with disease similar to that of the ebolaviruses. Both Lassa and the Ebolaviruses display a single trimeric glycoprotein, which is the primary target for protective antibody responses. Structural analyses of the glycoprotein in complex with protective antibodies from human survivors illuminates how an immune response ca be successful against these viruses and provides a roadmap for therapeutic interventions. A multidisciplinary, global collaboration bridging X-ray crystallography and cryoEM to field work in endemic sites in Africa led to the identification of unusual molecules of broader specificity and activity and the development of several therapeutic strategies where none existed before.

In metazoans, tissues experiencing proteotoxic stress induce “transcellular chaperone signalling” (TCS) that activates molecular chaperones, such as hsp-90, in distal tissues. How this form of inter-tissue communication is mediated to upregulate systemic chaperone expression and whether it can be utilized to protect against protein misfolding diseases remain open questions. Using C. elegans, we have now identified key components of a transcellular chaperone signalling pathway that promotes protective hsp-90 expression from one tissue to another. This inter-cellular activation of hsp-90 is mediated via glutamatergic neuronal signalling and requires the zinc finger transcription factor PQM-1 and membrane-associated channel protein
CLEC-41 to induce hsp-90 in muscle cells. We show that the TCS-induced expression of hsp-90 suppresses amyloid beta associated toxicity in different C. elegans Alzheimer’s Disease models, expressing Aβ(3-42) in muscle or neurons. Importantly, the increased hsp-90 expression substantially reduces the formation and accumulation of high molecular weight amyloid oligomers, suggesting the involvement of hsp-90 in Aβ oligomer assembly. Thus, our data may have implications for the treatment of protein misfolding diseases via TCS-mediated hsp-90 induction.

Abstract to followA predominant form of eukaryotic regulation involves the dynamic linkage and removal of ubiquitin (and structurally-related ubiquitin-like proteins, UBLs) to control the half-lives, subcellular location, conformation, and other properties of most intracellular proteins. The specificity of ubiquitylation depends on a vast collection of E3 ligase enzymes that modify particular protein substrates at the right time and place in a cell. With more than 200 different family members in humans, and even more in plants and other organisms, the largest E3 ligase family comprises the modular, multisubunit Cullin-RING ligases (CRLs). CRLs regulate virtually every facet of cell biology, including the cell cycle, DNA repair, stress responses, signaling, immunity, circadian rhythms, and a plethora of other pathways. Meanwhile defects in specific CRL subunits underlie numerous diseases including hypertension, neurodegenerative disorders, developmental defects, many cancers, and immune system dysfunction. Moreover, many bacterial and viral pathogens subvert and/or hijack CRL pathways to promote infection and evade host defense systems. To understand this immense regulation, a major focus of our lab is to identify pathways and determine molecular mechanisms underlying CRL activities.

Numerous facets of CRL activation – from E3 ligase assembly to catalysis of ubiquitylation to subsequent processing of ubiquitylated substrates – depend on the dynamic linkage and removal of the distinctive UBL NEDD8. NEDD8 is nearly 60% identical to ubiquitin, yet it predominantly regulates CRLs. In my talk, I will describe our findings that reveal the marvellous ways NEDD8 uniquely brings CRLs – and 20% of all ubiquitylation - to life.

The talk will describe the evolutionary loss of a de novo cytosine DNA methyltransferse and its subsequent propagation for millions of years by a exquisitely specific maintenance methyltransferase in the lineage that gave rise to the human fungal pathogen Cryptococcus neoformans.