Dr Kathryn Taylor - PhD
Member of the School's Pharmacology & Physiology Research Discipline
I am especially interested in investigating the mechanism of action of cellular zinc transporters, especially the ZIP family (also known as SLC39A). The intention is to substantiate a model for integrated zinc signalling in cells, confirming the key role of zinc transporters, especially ZIP7, and relating the findings to the fundamental biological effects of cellular zinc. These zinc signalling events are thought to be primarily controlled by specific zinc transporters and my recent novel finding that their zinc transport ability can be controlled by phosphorylation, a mechanism previously unprecedented for zinc transporters, will be examined for a direct structural and/or functional relationship with cellular signalling pathways. These events lead to diverse cellular effects on normal processes such as growth, development and migration or, when aberrantly regulated, diseases such as cancer, diabetes and neurodegeneration ensuring that this project has widespread application for normal and disease states.
Zinc handling in cells
Two families of zinc transporters enable zinc to traverse biological membranes: The ZnT family of zinc efflux transporters (termed SLC30A) and the ZIP family of zinc influx transporters (termed SLC39A). The ZIP family of zinc transporters generate labile cytosolic zinc and as such have been demonstrated to have wide ranging biological roles both in normal and disease states. Zinc transporter ZIP7, uniquely among ZIP transporters, is located on the ER membrane and we have recently proposed a controlling role for ZIP7 in zinc release from intracellular stores (Hogstrand et al 2009) resulting in activation of multiple tyrosine kinases through zinc-mediated inactivation of protein phosphatases. We propose that, uniquely, ZIP7 is a hub in the new pathway of zinc-mediated growth factor signalling.
The mechanism of action of the LIV-1 family of zinc transporters
Using computer software to compare protein sequences, I was able to demonstrate that LIV-1 belongs to a new family of zinc influx transporters which totals nine human family members (Taylor and Nicholson, 2003). Computer searches of secondary structure predicted that these molecules contain 8 transmembrane domains, a long extracellular N-terminus, a short extracellular C-terminus, a consensus sequence for the ZIP family of zinc transporters and a consensus sequence for the catalytic zinc-binding site of metalloproteases, (HEXXH, where H = histidine, E = glutamic acid and X = any amino acid). This latter motif was unusual in that it also contained two novel residues (HEXPHE), proline (P) and glutamic acid (E), previously unprecedented in these positions in any other metalloprotease motifs. Searching the non-redundant NCBI database using BLAST and the unique HEXPHEXGD motif of LIV-1, we have identified over 39 sequences from 12 species, including human, mouse, C.elegans, Drosophila, yeast and bacteria, that contain this unique and highly conserved motif. This family has now been termed SLC39A. The members of the LIV-1 subfamily are similar to ZIP superfamily transporters in secondary structure and ability to transport metal ions across the plasma membrane or intracellular membranes. The localisation of some family members to lamellipodiae mirrors cellular location of the membrane-type matrix metalloproteases. These differences to other zinc transporters may be consistent with an alternative role for them in cells, particularly in diseases such as cancer.
The role of zinc transporters in health and disease
The 9 human members of the LIV-1 family of zinc transporters are increasingly being implicated in a variety of disease states, notably neurodegeneration, asthma, prostate cancer and breast cancer. Investigation of how the cellular localisation and tissue specificity of these zinc transporters can alter zinc homeostasis is paramount to understanding the exact role of these transporters in these different disease states.
The role of zinc transporters in cell migration
LIV-1 is an oestrogen-regulated gene that has been implicated in metastatic breast cancer. Its detection has been associated with oestrogen receptor positive breast cancer and with the metastatic spread of these cancers to the regional lymph nodes. We are investigating the mechanism of action of LIV-1 in promoting cell migration and hope to use this research to further our understanding of this important cellular end point.
The role of zinc and zinc transporters in breast cancer
We have observed an increased level of intracellular zinc in our ‘in house’ model of tamoxifen resistant breast cancer. This has initiated an investigation of a potential role for zinc in the activation of signalling pathways observed in these cells as well as in the increase in aggressive behaviour observed in these cells.
Cardiff University collaborators
- Prof. Robert Nicholson, School of Pharmacy and Pharmaceutical Sciences, Cardiff University
- Dr. Julia Gee, School of Pharmacy and Pharmaceutical Sciences, Cardiff University
- Dr Stephen Hiscox, School of Pharmacy and Pharmaceutical Sciences, Cardiff University
- Dr. Peter Kille, School of Biosciences, Cardiff University,
- Prof Christer Hogstrand, Kings College, London
- Prof. Iain Ellis, Molecular Medical Sciences, City Hospital, Nottingham: collaboration on clinical breast cancer series
- Prof John Robertson, City Hospital, Nottingham: collaboration on clinical breast cancer series
- Prof. Glen Andrews, Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas, USA
- Prof Leigh Ackland, Deakin University, Australia
- Dr. Peter Zalewski, Queen Elizabeth Hospital, Woodville, Australia
- Engineering constructs for expression of recombinant proteins in mammalian cells using TOPO-TA cloning and PCR.
- Knockdown of protein expression using siRNA
- Generation of mutants using site-directed mutagenesis to enable investigation of key residues in functional activity of different molecules
- Use of tags for monitoring expression of recombinant proteins in cells
- Fluorescent and confocal microscopy of multiple probes in live and fixed cells
- Real-time monitoring of Zn2+ concentrations in cells using different zinc specific indicators such as Newport Green, Fluozin-3 and Zinquin.
- Design and generation of novel antibodies to zinc transporter proteins
- SDS-PAGE, Western Blotting, FACS analysis, immunocytochemistry.
Recent Research Funding
- Taylor KM Wellcome Trust University Research Award entitled ‘The role of zinc transporters in cellular zinc signalling’ from 13/9/1010-12/9/1015 for £307,291
- Taylor KM, Wellcome summer studentships, 2004, 2005, 2007, 2009
- Taylor KM, Biochemical Society Vacation Scholarship and Eisenthal prize, 2009
- Taylor KM, CUROP grant for summer student projects, 2007, 2009
- Taylor KM Pilot grant from Breast Cancer Campaign to investigate the role of zinc transporter HKE4 in tamoxifen resistant breast cancer 1/10/2007
- Taylor KM, Gee JM and Nicholson RI, The role of LIV-1 family proteins in breast cancer funded by Tenovus the cancer charity 1/12/2003-31/8/2007 for £232,890