Liz Fitzgerald, BSc, PhD, DIC

Despite substantial roles in undergraduate teaching and postgraduate research management, Dr Fitzgerald maintains research interests in the molecular and cellular physiology of ion channels. More specifically, her work has focused on 2 main areas: 1. Structure-function studies of voltage-gated calcium channels and 2) Ion channels and cancer.  She has extensive expertise in a broad range of techniques in physiology, biochemistry, molecular biology and cell biology.

Qualifications:

1988: BSc in Zoology, University of Newcastle, UK

1992: PhD and DIC in Neurobiology, Imperial College, London, UK

Employment History:

1993-1995: Postdoctoral Research Associate, Royal Free Hospital School of Medicine, UK

1996-1997: Postdoctoral Research Associate, University College London, UK

1998-2003: Wellcome Trust Career Development Fellow, University College London, UK

2003-2004: Lecturer in Pharmacology, School of Biological Sciences, University of Manchester, UK

2004-2016: Lecturer in Pharmacology, Faculty of Life Sciences, University of Manchester, UK

2016-present: Lecturer in Pharmacology, School of Biological Sciences, Faculty of Biology, Medicine and Health (FBMH), University of Manchester, UK

Faculty Positions:

2014-2016: Academic Lead for International Postgraduate Research, Faculty of Life Sciences.

2016-present: Doctoral Academy Lead for International Postgraduate Research, FBMH.

Internal Committees:

2014-2016: Postgraduate Research Committee, Faculty of Life Sciences.

2016-present: Doctoral Academy Management Group, FBMH.

2016-present: Doctoral Academy Research Degrees Panel, FBMH.

2016-present: International PGR Strategy and Implementation Group (Chair), FBMH.

2017 - present: Faculty Internationalisation Group, FBMH.

Patents:

2012: Patent 1210983, Modulators of Calcium Signalling. Drs Owen Jones & Liz Fitzgerald.

Molecular and Cellular Physiology of Ion Channels

1. Functional mapping of the voltage-gated calcium channel α₂δ subunit: Voltage-gated calcium channels (Ca_v) represent the primary means by which changes in cell membrane potential are coupled to the influx of second messenger calcium ions. As such, these channels play a pivotal role in orchestrating diverse excitable cell functions, including muscle contraction, neurotransmitter release and gene expression. Moreover, Ca_v are targets for some of the most widely used drugs world-wide, including anti-arrhythmics, anti-hypertensives and anti-nociceptives.

Ca_v exist as multi-protein complexes comprising a pore-forming α₁ subunit with regulatory β and α₂δ subunits, in a 1:1:1 stoichiometry. The β and α₂δ subunits serve two main functions: 1. to modify channel biophysical properties and thus how much calcium enters a cell, 2. to enhance channel expression (trafficking and distribution) at the cell surface. Each subunit is encoded by multiple genes (10 α₁, 4 β, 4 α₂δ), many with alternative RNA splice variants that exhibit specific, often overlapping spatio-temporal patterns of cell expression. It is this molecular heterogeneity which allows Ca_v to tailor Ca²⁺ influx to discrete cellular demands.

Clinically, α₂δ subunits are implicated in a growing number of pathological conditions and are primary targets of the anti-convulsant and anti-nociceptive gabapentinoid drugs. However, the precise mechanisms of gabapentinoid function remain unclear, not least because detailed functional mapping of the α₂δ has been lacking. Moreover, in order to exploit further the therapeutic potential of these key regulators of cellular excitability, a detailed understanding of α₂δ structure and function is essential. To this end, we have used molecular biology, electrophysiology, biochemistry and live-cell imaging, to conduct the most detailed mapping of α₂δ structure and function to date [1-5].

Role of α₂δ in targeting Ca_v to membrane signalling domains: Using functionally active HA-epitope tagged Ca_v and α₂δ subunits, we have shown that α₂δ-1 and likely other α₂δ subunits are necessary and sufficient for targeting N-type Ca_v2.2 channels into signalling complexes termed lipid rafts. However, formation of Ca_v2.2 clusters at the cell surface, supporting “hotspots” of Ca_v signalling, requires aggregation of macromolecular complexes containing raft components, stabilised by interactions with the cytoskeleton (Fig. 1) [1]. Exactly how α₂δ mediates raft targeting remains controversial. However, work from this lab suggests that α₂δ subunits are Type 1 transmembrane glycoproteins and that raft localisation of α₂δ depends upon exofacial sequences upstream and independent of a putative GPI-anchoring motif [2]. More recent work has focused on defining the precise region of α₂δ that is responsible for raft localisation [3]. Identification of the mechanisms that regulate cell surface distribution of Ca_v is not only critical for understanding the functional roles of these channels but is also essential for development of a more rational pharmacology of Ca_v.

Identification of the α₂δ R-domain: a novel locus for therapeutic intervention?: In this project we generated a series of cDNA constructs encoding chimera in which the extracellular head of a similar Type-1 reporter protein – PIN-G [6], was fused to successive polypeptides and amino acids of the rat α₂δ-1 sequence. Using this approach, we have identified the minimal region of α₂δ – the R domain (Rd) – that is both necessary and sufficient to impart the primary functional effects of α₂δ on Ca_v2.2, the N-type channel. Since the Rd is highly conserved in all known α₂δ subtypes, we suggest that this region represents the primary locus for all electrophysiological and trafficking functions of α₂δ subunits (Fig. 1).

Fig. 1. Comparison of predicted R domain tertiary structures. A) Subdivisions of the R domain used to develop corresponding PIN-α₂δ-1 chimera into regions A, B and C, based on inspection of predicted secondary structure. Further sub-divisions (A1-A4, B1-B2, C1-C2 and A3a-d) were guided by experimentation. B) Structures inferred for the human R domains, Rd-1, Rd-2, -3 and -4 are shown. All structures are shown in side-on orientation with the major A1-2 and A3-4 helices at left. Colours as follows: Rd-A: Light turquoise; Rd-B: lavender; Rd-C1: yellow; Rd-C2: light orange. The region shown in C2 as dark orange corresponds to core C2 residues while the residue shown in red (asterisked) indicates a highly conserved tryptophan whose mutation to alanine in Rat Rd-1 abrogates function.

This finding not only helps to rationalise the pharmacology of gabapentinoid drugs but also provides avenues for the development of novel therapeutics targeting Ca_v [4]. More recent work has focused on dissecting the cellular functions of Rd [5].

2. Ion Channels and Cancer: Various ion channels are expressed in human cancers where they are intimately involved in proliferation, angiogenesis, invasion and metastasis. In particular, the functional expression of voltage-gated sodium channels (Na_v) is implicated in the metastatic potential of breast, prostate, lung and colon cancer cells. However, the cellular mechanisms that regulate Na_v expression in cancers are not well understood. Growth factors not only play crucial roles in cancer progression but are also key regulators of ion channel expression and activity in non-cancerous cells. This lab has a longstanding interest in growth factor-mediated regulation of ion channels and in this project we have examined the role of epidermal growth factor receptor (EGFR) signalling and Na_v in non-small cell lung carcinoma (NSCLC).

NSCLC is one of the most prevalent cancers world-wide; it has a low average survival rate (14%) and development of metastases results in extremely poor prognosis. Small molecule EGFR inhibitors (gefitinib and erlotinib) show significant therapeutic benefit in patients with advanced NSCLC but drug resistance (inherent or acquired) remains a cause of chemotherapy failure. Consequently, there is a need for improved treatments based upon a better understanding of the effector pathways downstream of EGFR signalling.

Fig. 2. Expression of Nav1.7 is higher in cancerous versus normal-matched human lung tissue. Images are representative from sections of the following formalin-fixed, paraffin-embedded specimens: (A) Normal and cancerous lung tissue from three patients (P1-P3). (B) Controls: un-transfected HEK-293 cells, -ve CTL; HEK-293 cells stably expressing Nav1.7, +ve CTL; weakly invasive A549 cells; strongly invasive H460 cells; low- and high-grade prostate tumour tissue microarray preparations. DAB+ stained areas, representing areas of primary antibody immunoreactivity with Nav1.7, are shown as brown on the images.

Briefly, we have shown that the Na_v1.7 isoform is functionally expressed in strongly metastatic NSCLC cells where it promotes up to 50% of their invasive capability. EGF/EGFR signalling enhances proliferation, migration and invasion but specifically, EGFR-mediated up-regulation of Na_v 1.7 expression via the ERK1/2 pathway is required for invasive behaviour. Examination of patient biopsies has confirmed the clinical relevance of Na_v1.7 expression in NSCLC and defines its potential as a new target for therapeutic intervention and/or as a diagnostic or prognostic marker in NSCLC (Fig. 3) [7,8].

References:

1. Robinson et al. (2010) Cell Calcium, 48, 183-194

2. Robinson et al. (2011) PLoS One, 6, e19802

3. Robinson POD (2012) PhD Thesis, University of Manchester

4. Song et al. (2015) Curr Mol Pharmacol, 8, 169-179

5. Espinoza-Fuenzalida IA (2016) PhD Thesis, University of Manchester

6. McKeown et al (2006) BMC Biotechnol, 6, 15.

7. Campbell TM et al. (2013) J Cell Sci, 126, 4939-4949.

8. Campbell TM (2012) PhD Thesis, University of Manchester.