Spatial Organisation of Signalling
Dynamic GPCR signalling localised to the nucleus (left) or plasma membrane (right) of single live cells.
Cells endogenously express a variety of different receptors that can activate the same second messenger but with remarkably diverse physiological outcomes. This suggests a high degree of organisation and regulation of intracellular signalling, which is achieved by the spatiotemporal compartmentalisation of signals – the restriction of second messengers in space and time. Spatial and temporal compartmentalisation of signalling provides a mechanism whereby G protein-coupled receptors (GPCRs) can affect numerous aspects of cell function in a controlled manner. In this way, GPCRs can direct the assembly of focused "platforms" for specific signalling. These signalling platforms facilitate second messenger production, the organisation and scaffolding of effectors, and co-ordination of regulatory elements.
My research focuses on two interrelated themes: GPCR signalosomes as high resolution signalling platforms, and compartmentalisation of GPCR signalling. Using pharmacological, biochemical and single cell approaches, we can study the assembly of GPCR signalling platforms in order to identify novel ways with which to pharmacologically manipulate GPCR function for therapeutic benefit.
Cartoon depicting the experimentally determined spatial organisation of the constitutively active RXFP1 signalosome
GPCRs can act as membrane-bound scaffolds within higher order protein complexes, to direct remarkably specialised and functionally specific signalling. This is exemplified by the receptor for relaxin, RXFP1; RXFP1 expression induces the formation of a constitutively active and tightly regulated protein complex termed a signalosome that specifically responds to attomolar-picomolar concentrations of relaxin. Importantly, this mechanism is absolutely distinct from the cAMP signalling activated by higher concentrations of the hormone: the signalosome dissociates following receptor activation with nanomolar relaxin. Thus the specific assembly of an RXFP1 signalosome facilitates a substantially increased sensitivity of the receptor to ligand. We are currently exploring the ability of other GPCRs to form highly sensitive signalosomes.
Compartmentalisation of GPCR signalling
Live cell imaging of compartmentalised signalling showing increasing responses (dark blue is no response, pink/white is a large response) specifically localised to defined regions of the plasma membrane (top panels), cytosol (middle panels) or nucleus (lower panels) of single cells.
Compartmentalisation of signalling is required for the efficient organisation and regulation of cellular responses.
By using targeted FRET biosensors, we can resolve sub-cellular spatial and temporal dynamics of GPCR signalling at a single cell level.
This reveals intricate detail about the role of receptor trafficking and regulation in the transmission of signalling, and how this is disrupted in various disease states.
There are a number of ongoing collaborative projects within this area (see collaborations for further information).
* denotes joint first author, ^ denotes co-corresponding author
Patil R, Mohanty B, Liu B, Chandrashekaran IR, Headey SJ, Williams ML, Clements CS, Ilyichova O, Doak BC, Genissel P, Weaver RJ, Vuillard L, Halls ML^, Porter CJH^ & Scanlon MJ^ (2019) A ligand-induced structural change in fatty acid-binding protein 1 is associated with potentiation of peroxisome proliferator-activated receptor alpha agonists. J. Biol. Chem., 294(10), 3720-3734.
Civciristov S, Ellisdon AM, Suderman R, Pon CK, Evans BA, Kleifeld O, Charlton SJ, Hlavacek WS, Canals M & Halls ML (2018) Preassembled GPCR signalling complexes mediate distinct cellular responses to ultralow ligand concentrations. Sci. Signal., 11(551), eaan1188.
Jensen DD*, Lieu T*, Halls ML*, Veldhuis NA, Imlach WL, Mai QN, Poole DP, Quach T, Aurelio L, Conner J, Herebrink CK, Barlow N, Simpson JS, Scanlon MJ, Graham B, McClusky A, Robinson PJ, Escriou V, Nassini R, Materazzi S, Geppetti P, Hicks GA, Christie MJ, Porter CJH, Canals M & Bunnett NWB (2017) Neurokinin 1 receptor signalling in endosomes mediates sustained nociception and is a viable therapeutic target for prolonged pain relief. Sci. Trans. Med.,9(392), eaal3447.
Furness SG, Liang YL, Nowell CJ, Halls ML, Wookey PJ, Dal Maso E, Inoue A, Christopoulos A, Wootten D & Sexton PM (2016) Ligand-dependent modulation of G protein conformation alters drug efficacy. Cell,167(3), 739-749.
Halls ML^, Yeatman HR, Nowell CJ, Thompson GL, Gondin AB, Civciristov S, Bunnett NW, Lambert NA, Poole DP & Canals M^ (2016) Plasma membrane localisation of the mu-opioid receptor controls spatiotemporal signalling. Sci. Signal., 9(414), ra16.
Ercole F, Mansfeld FM, Kavallaris M, Whittaker MR, Quinn JF^, Halls ML^ & Davis TP^ (2016) Macromolecular hydrogen sulphide donors trigger spatiotemporally confined changes in cell signalling. Biomacromolecules, 17(1), 371-383.
Pon CK, Lane JR, Sloan EK & Halls ML (2016) The beta2-adrenoceptor activates a positive cAMP-calcium feedforward loop to drive breast cancer cell invasion. FASEB J., 30(3), 1144-1154.
Halls ML^, Poole DP, Ellisdon AM, Nowell CJ & Canals M^ (2015) Detection and quantification of intracellular signalling using FRET-based biosensors and high content imaging. Meth. Mol. Biol., 1335, 131-161.
Halls ML & Cooper DMF (2010). Sub-picomolar relaxin signalling by a pre-assembled RXFP1, AKAP79, AC2, beta-arrestin 2, PDE4D3 complex. EMBO J., 29(16), 2772-87. IF, 10.1; CI, 52; contributed 90% to design, execution, interpretation and writing. Recommended by The Faculty of 1000.
Halls ML, Bathgate RAD & Summers RJ (2006). Relaxin family peptide receptors, RXFP1 and RXFP2, modulate cAMP signalling by distinct mechanisms. Mol. Pharmacol., 70(1), 214-26. Recommended by The Faculty of 1000.
* denotes joint first author, ^ denotes co-corresponding author
Civciristov S and Halls ML (2019) Signalling in response to sub-picomolar concentrations of active compounds: pushing the boundaries of G protein-coupled receptor sensitivity. Br. J. Pharmacol., in press
Halls ML (2019) Localised GPCR signalling as revealed by FRET biosensors. Curr. Opin. Cell Biol., 57, 48-56.
Halls ML^ and Canals M^ (2018) Genetically encoded FRET biosensors to illuminate compartmentalised GPCR signalling. Trends Pharmacol. Sci., 39(2), 148-157.
Halls ML and Cooper DMF (2017) Adenylyl cyclase signalling complexes – pharmacological challenges and opportunities. Pharmcol. Ther., 172, 171-180.
Ellisdon AM and Halls ML (2016) Compartmentalisation of GPCR signalling controls unique cellular responses. Biochem. Soc. Trans., 44(2), 562-567.
Dr Srgjan Civciristov
Mr Bonan Liu
- Ms Maxine Roberts (University of Nottingham)
- Mr Andrew Zhang
- Ms Thuy (Vivian) Lam
- Mr Christopher Leung
Compartmentalised signalling in cancer
- Dr Erica K Sloan, Drug Discovery Biology, MIPS
- Dr Andrew M Ellisdon, Biomedicine Discovery Institute, Monash University
- Professor Stephen J Hill, University of Nottingham, UK
Signalling of nuclear hormone receptors
- Professor Chris JH Porter, Drug Delivery, Disposition and Dynamics, MIPS
- Professor Martin J Scanlon, Medicinal Chemistry and Drug Action, MIPS
Targeted sub-cellular delivery using nanotechnology
- Dr John Quinn, Drug Delivery, Disposition and Dynamics, MIPS
- Professor Thomas P Davis, Drug Delivery, Disposition and Dynamics, MIPS
GPCR compartmentalised signalling
- Professor Meritxell Canals, University of Nottingham, UK
- Associate Professor Harald Janovjak, Australian Regenerative Medicine Institute, Monash
- Dr Ralf Schittenhelm, Monash Biomedical Proteomics Platform
- Dr William S Hlavacek, Los Alamos National Laboratories, USA
- Professor Steven Charlton, University of Nottingham, UK
- Dr Stephen Briddon, University of Nottingham, UK
- Dr Daniel P Poole, Drug Discovery Biology, MIPS
- Professor Nigel W Bunnett, Columbia University, USA
- Professor Patrick M Sexton, Drug Discovery Biology, MIPS
- A/Prof Denise Wootten, Drug Discovery Biology, MIPS
- Professor Roger J Summers, Drug Discovery Biology, MIPS
- Dr Dana S Hutchinson, Drug Discovery Biology, MIPS