Application of cryo-EM to understanding of channels and receptors involved in neurological process

Research at the Wollongong Node will revolve around the investigation and development of cryo-EM techniques to enable structural resolution of the interactions. Knowledge obtained by the structural work will be used iteratively to computationally model and design novel compounds.

This work will be completed with the University of Wollongong Node.

The Adams group at the University of Wollongong has identified a group of analgesic peptides (α-conotoxins), from marine cone snails, that target the γ- aminobutyric acid B receptor (GABABR). This modulates voltage-gated calcium channels and, through G protein signalling, G protein inwardly rectifying potassium (GIRK) channels, both known analgesia producing targets. Although several GPCR structures have been determined, the heterodimeric nature of the GABABR has hindered efforts for its structural elucidation. Cryo-EM is ideally suited to circumvent hurdles associated with recombinant protein production and heteromeric arrangement. The apo- and holo- states of GABABR in the absence and presence of the analgesic α-conotoxin Vc1.1 would provide the first atomistic picture of GABABR and will provide details on the molecular mechanism of its action and modulation by Vc1.1. Prof Adams has already shown that Vc1.1 binds to a site distinct from the classic GABABR agonists, GABA and Baclofen. Novel compounds will be functionally screened in the high throughput (HT) patch clamp instrument SynchroPatch384PE housed at Illawarra Health and Medical Research Institute (IHMRI).

Investigating ion channels that control neuronal excitability in health and disease

A/Prof Lezanne Ooi and Dr Gokhan Tolun

Neurons communicate with one another via the flow of ions across membranes, mediated by ion channel activity that coordinates action potential firing. The likelihood and rate of firing is underpinned by neuronal excitability, which can become dysregulated in diseases, such as epilepsy, pain and motor neuron disease. This research will investigate the structures of ion channels that are central to the control of neuronal excitability in health and disease.

This project will use a combination of innovative molecular, cell biological and electrophysiological techniques. The knowledge gathered from this study will be crucial in improving current drugs and designing novel ones for treating neurological disorders.

Determining the 3D structure of Salmonella typhimurium voltage-gated potassium channel

 

Dr Rocio Finol Urdaneta and Dr Gokhan Tolun

 

The interplay between bioelectrical and biochemical signals at the intra- and intercellular levels determines physiological function. These signals are shaped by the movement of sodium (Na+), potassium (K+) and calcium (Ca2+) ions into and out of cells. Selective ionic passage through cell membranes occurs via channels formed by membrane proteins. Channels that open and close in response to changes in the transmembrane voltage are called voltage gated ion channels (VGICs). VGICs are typically associated with fast electrical signalling in multicellular organisms, whilst VGICs are abundantly found in bacteria. Despite their abundance in mesophilic bacteria, the only available prokaryotic Kv channel structure comes from a hyperthermophilic archaea Aeropyrum pernix (KvAP), which may not be representative of mesophilic bacterial Kv channels.

 

Salmonella typhimurium (STM) is a mesophilic bacterium, a pathogen that causes gastroenteritis and typhoid fever. Relatively little is known about STM’s signalling or specific metabolic requirements yet transport and maintenance of K+ homoeostasis are important for Salmonella’s extracellular and invasive strategies. We propose to determine the molecular 3D structure of Salmonella’s KvSTM channel by cryo-EM, providing the first mesophilic bacterial Kv channel structure. This structural insight will complement functional and physiological research to elucidate features underlying STM’s fitness. Furthermore, comparing KvSTM to its eukaryotic counterparts may enable the development of species-specific Kv modulators thereby improving the therapeutic window of currently used drugs.