Membrane proteins located at the surface of viruses and bacteria are excellent targets to cure and prevent infection. The research project at The University of Melbourne will focus on the areas outlined below:
Characterising the conformation of the HIV envelope susceptible to immune responses:
The HIV-1 envelope glycoprotein (Env or (gp120/gp41)3) is expressed on the surface of human immunodeficiency virus (HIV) and at the surface of HIV-infected cells. By default, Env adopts a compact, closed conformation that is not recognized by antibodies inducing the antibody-dependent cellular cytotoxicity (ADCC) response. We have shown that binding of Env to a CD4 mimetic and a specific combination of non-neutralizing antibodies stabilize Env in an intermediate conformation (called State 2A) and that cells expressing Env in this conformation are susceptible to ADCC (Alsahafi et al., Cell Host & Microbe, 2019). We aim to characterise the state 2A conformation. We will use single particle cryo-EM and electron-tomography combined with subtomogram averaging to determine the high-resolution 3-dimentional structures of the HIV-1 envelope glycoprotein Env in conformations that are the vulnerable to ADCC. It is anticipated that the cryo-EM structures will inform the development of new strategies in the treatment and prevention of HIV infections.
Targeting nutrient scavengers to fight bacterial infections:
The membrane of bacteria is an important barrier to both keep nutrients, proteins and other essential components inside the cell and toxic compounds outside the cell. We will determine the structure of zinc transporter AdcCB alone and in complex with two substrate-binding proteins (SBPs), AdcA and AdcAII, using single particle cryo-EM. These studies will inform on the molecular mechanism responsible for selective transport of zinc across the membrane of Streptococcus pneumonia and the role of SBPs in the delivery of the substrate to the transporter. A better understanding of these mechanisms will allow the development of antimicrobial strategies to combat S. pneumoniae infection.
Defining the role of TACAN in pain sensitivity:
Mechanosensitive ion channels (MSC) are the sensors for a number of systems including the senses of touch, hearing and balance. They function as mechanotransducers by generating both electrical and ion flux signal as a response to mechanical stimuli. TACAN, is a membrane protein important for detection of painful mechanical stimuli. In this project, you will determine the structures using single particle cryo-EM of TACAN in various lipidic environments. These structures will inform on the molecular mechanism of TACAN in pain sensitivity. Advances will make significant contributions to the fundamental understanding of pain sensing and signal sensing by cells in our body. This knowledge will allow the development of novel drugs to treat chronic pain.
Stopping pore-forming proteins punching holes in membranes:
One of the largest and most sequence diverse Pore-forming proteins (PFP) superfamilies identified to date are the CDC superfamily of pore-forming toxins which play a key role in bacterial pathogenesis. The detailed mechanism by which these molecules form pores remains an enigma. We will determine the atomic resolution structures of prepores, pores and intermediate conformations using cryo-EM and biophysical data that is representative of the transition from the prepore to the pore state. The structures will shed light on one of the most fundamental biological events (namely, protein insertion into cell membranes), and provide the basis for designing pan CDC inhibitors that might be developed into antibiotics for diverse diseases including gas gangrene, listeria and bacterial pneumonia.
Manipulating signalling in cytokine receptors:
Glycoprotein 130 (gp130) is the common signal transducing receptor used by the interleukin (IL)-6 family of cytokines. The IL-11/IL-6 sub-class signals through a gp130 dimer; while leukemia inhibitory factor (LIF) and oncostatin M (OSM) use gp130 in complex with a co-receptor. We have determined the structure of the complete extracellular domains of the IL11 signalling complex by cryo-electron microscopy. We aim to determine the structures of IL-6 family cytokines in complex with their intact receptors, including intracellular regions bound to JAK kinases, in order to elucidate the molecular mechanisms of signal transduction. This knowledge will identify new approaches to investigate cytokine biology in general, and provide a structural platform that will enable researchers to understand dysregulated cytokine signalling in disease. Inhibitors of IL-6 family cytokine signalling may provide potential therapeutics for a range of cancers and other conditions such as cardiovascular fibrosis.
Understanding key drug targets in Alzheimer’s disease:
We aim is to determine the structures of key proteins in Alzheimer’s disease as a basis for understanding their normal physiological function and to guide structure-based drug discovery. In the late nineties we embarked on an ambitious project to determine the complete structure of amyloid precursor protein (APP), a membrane-bound receptor that plays a central role in Alzheimer’s disease (AD). APP contains the Abeta peptide thought to cause the disease. We have determined the structures of a number of components by crystallography and now aim to visualise the complete intact structure of APP by cryo-EM. Anti-Abeta monoclonal antibodies are the leading therapeutics being tested in human clinical trials. My lab has visualised how three such clinical antibodies recognise the Abeta peptide. We now aim to visualise how some of these antibodies bind the Abeta fibrils, one of the principal pathologies in AD.
This project is part of the Australian Research Council (ARC) Training Centre for cryo-electron Microscopy of Membrane Proteins (CCeMMP) are looking for highly motivated, passionate and competitive PhD candidates to join the Doctoral Training Program. Successful candidates will be offered a four-year fully funded PhD position with a strong industry focus, and will work within the Centre at The University of Melbourne located in Australia. The Centre is a collaboration between Nodes led by the Institute of Pharmaceutical Sciences at Monash University, and in partnership with The University of Melbourne (Bio21 Institute), University of Wollongong (Molecular Horizons) and the Walter and Eliza Hall Institute (WEHI).
For more information on the PhD program and the research project, please register to attend our PhD Information Night at 5:30pm AEDT 28th of September 2021. To register: https://www.eventbrite.com.au/e/ccemmp-hdr-night-2021-tickets-168521509371