Transporter Biology Group

Lab head: Robert Vandenberg, Renae Ryan
Location: Blackburn Building, Camperdown

This group investigates the pharmacology and biochemistry of neurotransmitter transporters in the central nervous system and amino acid transporters. This involves the use of a combination of recombinant DNA, electrophysiological techniques and structural biology to investigate the molecular basis for the actions of endogenous modulators as well as novel agents on membrane transporters.

Lab members: Rob Vandenberg (head), Renae Ryan (head), Cheryl Handford (Lab Manager), Jane Carland (Postdoctoral Scientist), Josep Font(Postdoctoral Scientist), Rosemary Cater(PhD student), Shannon Mostyn (PhD student), Chris Sirote (MPhil), Ben McIlwain (PhD student), Ben Gallagher (Honours student)
Funding: NHMRC Project Grant
Research approach equipment: Molecular biology, computer modelling, electrophysiology, protein chemistry

Ryan RM, Kortt NC, Sirivanta T, Vandenberg RJ (2010)

The position of an arginine residue influences substrate affinity and K(+) coupling in the human glutamate transporter, EAAT1. Journal of Neurochemistry 114, 565-75.

 Ryan RM, Compton EL, Mindell JA (2009)

Functional characterization of a Na+-dependent aspartate transporter from Pyrococcus horikoshii. The Journal of Biological Chemistry 284,17540-17548.

 Huang S, Ryan RM, Vandenberg RJ (2009)

The role of cation binding in determining substrate selectivity of glutamate transporters. The Journal of Biological Chemistry 284, 4510-4515.

 Boudker O, Ryan RM, Yernool D, Shimamoto, K and Gouaux E (2007)

Coupling substrate and ion binding to extracellular gate of a sodium-dependent aspartate transporter. Nature 445, 387-393.

Understanding the mechanism of transport by the glutamate transporter family using chimeras and site-directed mutagenesis

Primary supervisor: Renae Ryan

Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system and activates a wide range of receptors to mediate a complex array of functions.  Extracellular glutamate concentrations are tightly controlled by a family of glutamate transporters expressed in both neurons and glia. The aim of our research is to develop a structural model for how glutamate transporters work, and in this way lay the foundations for a more rational approach to the development of drugs that are both transporter-specific and subtype selective.  Such compounds will help to delineate the roles of different transporter subtypes in normal brain functions and also in various neuropathological conditions, such as ischemia following a stroke, Alzheimer’s disease, motor neurone disease and obsessive compulsive disorder. 

Several crystal structures of a prokaryotic homologue of the glutamate transporters (GltPh) have recently been determined. We use these snapshots to direct our research on the human EAATs to try and understand the conformational changes associated with glutamate transport.

Understanding the mechanism of transport by the glutamate transporter family using chimeras and site-directed mutagenesis

The glutamate transporter family is made up of proteins from several species and includes the human glutamate transporters (EAATs) and neutral amino acid transporters (ASCTs), and a prokaryotic aspartate transporter GltPh. All of these transporters share significant amino acid homology and share some functional properties but also exhibit some differences. For example, the EAATs are secondary active transporters of acidic amino acids while the ASCTs are electroneutral exchangers of neutral amino acids.

The aim of this project is to exploit the similarities and differences between these 3 transporters by making chimeric transporters and performing site-directed mutagenesis to identify the molecular determinants for substrate selectivity and ion-coupling in the glutamate transporter family.

Glutamate transporter dysfunction has been implicated in disease states such as ischemia following a stroke, Alzheimer’s disease and obsessive compulsive disorder. The expression of the neutral amino acid transporter ASCT2 is known to be upregulated in some prostate, breast and skin cancers. Through a better understanding of the mechanism of these transporters we can develop compounds that may have therapeutic benefits in these disease states.

Discipline: Pharmacology
Co-supervisors: Robert Vandenberg
Keywords: Neuropharmacology, Molecular biology, protein structure/function