Prof Mark Evans

Personal profile

• 2009 - present: Chair of Cellular Pharmacology, University of Edinburgh
• 2008 - present: Senior Academic Fellow, University of Edinburgh
• 2007 - 2008: Professor, Personal Chair in Cell Biology, University of East Anglia
• 2005 - 2007: Reader, University of St Andrews
• 2002 - 2005: University Lectureship, University of St Andrews
• 2001 - 2002: Wellcome Trust Non-Clinical Lectureship, University of St Andrews
• 1996 - 2001: Wellcome Trust Career Development Research Fellow, University Department of Pharmacology, University of Oxford
• 1994 - 1996: Visiting Research Fellow, Department of Pharmacology, United Medical and Dental Schools, St. Thomas's Hospital, University of London
• 1993 - 1994: Postdoctoral Research Fellow, Department of Pharmacology, St George's Hospital Medical School, University of London
• 1992 - 1993: Postdoctoral Research Fellow, Department of Pharmacology, United Medical and Dental Schools, St Thomas's Hospital, University of London
• 1990 - 1992: Postdoctoral Research Fellow, Department of Preclinical Veterinary Sciences, University of Edinburgh

Research Theme

• Synapses, Circuits and Behaviour 
• Signalling, Homeostasis and Energy Balance  

Research

The work of my laboratory

Investigations of my laboratory are focused on developing our understanding of cellular calcium signalling and respiratory control mechanisms, with particular reference to hypoxia response-coupling in oxygen-sensing cells. My broad experimental interests and expertise range from fundamental cellular mechanisms to lung and respiratory disease, with a keen eye on evolution and the natural history of respiratory disorders.

Career milestones:

1. Discovered, characterised and mathematically model multi-ion channel block.
2. Discovered and characterized K_V7 potassium channel currents in arterial smooth muscles;
3. Demonstrated that Rho-associated kinase inhibitors block hypoxic pulmonary vasoconstriction, and proposed their use against pulmonary hypertension;
4. Synthesised and confirmed the hypothesis that AMP-activated protein kinase (AMPK) mediates hypoxic pulmonary vasoconstriction and thus acute hypoxic pulmonary hypertension;
5. Synthesised and confirmed the hypothesis that AMPK supports the hypoxic ventilatory response, and thus opposes hypoventilation and apnoea during hypoxia;
6. Co-discovered and characterized Two Pore Channel 2 (TPC2), and identified TPC1-3 as a family endolysosome targeted ion channels.
7. Predicted the existence of and discovered the cell‑wide web, a network of cytoplasmic nanocourses that direct intracellular calcium signals in differentiated cells.

Current hypotheses that we are addressing:

1. In multicellular eukaryotes the function of AMPK has been extended through natural selection, to coordinate of not only cell‑autonomous metabolic homeostasis but also respiratory control mechanisms that regulate oxygen and thus energy supply to the whole body (Evans 2006; Evans and Hardie 2020).

2. Intracellular calcium signals are directed by the cell-wide web, a network of cytoplasmic nanocourses delineated by membrane-membrane nanojunctions of the sarcoplasmic reticulum (SR), which provide discrete lines of communication that span the entire cell, from the nucleus to the periphery of all cells. The full panoply of cellular processes, from muscle contraction to gene expression, may thus be directed by calcium flux across stimulus-specified nanojunctions, through the differential modulation of their designate calcium release channels and their juxtaposed signalling complexes (van Breemen et al 2013; Evans 2017; Duan et al 2019).

Regulation of breathing and oxygen supply by AMPK

In 2006 I hypothesised that the function of AMPK in multicellular eukaryotes might have become extended, through natural selection, to encompass not only cell‑autonomous metabolic homeostasis but also system-level control of oxygen and energy supply, through its coordination of two key cardiorespiratory reflexes that are governed by “oxygen-sensing” cells, incorporating mitochondria that are exquisitely sensitive to changing PO₂ within the physiological range:

• Hypoxic pulmonary vasoconstriction (HPV), aiding ventilation-perfusion matching at the lungs by diverting blood from oxygen-deprived to oxygen-rich areas;
• Hypoxic ventilatory responses (HVR), increasing breathing and hence oxygen delivery to the body.

Critically, from its two α and β and three g subunits, 12 heterotrimeric AMPK complexes could be formed, each with different sensitivities to AMP/ADP and capacities to phosphorylate different targets, including some, such as ion channels, outside the canonical pathways by which AMPK regulates cell-autonomous energy homeostasis.

Until recently, the mechanism(s) of mitochondria-to-reflex coupling in oxygen-sensing cells was equivocal. However, using gene deletion strategies my lab has shown that:

• HPV and thus acute hypoxic pulmonary hypertension is triggered by LKB1 and AMPK‑α1 in pulmonary arterial myocytes (Moral-Sanz et al 2018).
• HVR is mediated by AMPK‑α1 activation in catecholaminergic cells that lie downstream of the carotid bodies, the primary arterial chemoreceptors, within brainstem respiratory networks (Mahmoud et al 2017);
• system-specific functions are mediated by cell-specific expression of AMPK subunit isoforms and target proteins, including ion channels (Ikematsu et al 2011; Ross et al 2011; Moral-Sanz et al 2018).

 

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New investigations have, however, revealed important paradoxes:

• dual AMPK‑α1/α2 deletion in cardiac and smooth muscles precipitates pulmonary hypertension and premature death (unpublished);
• AMPK‑α1/α2 deletion in catecholaminergic cells confers neonate-like HVR with delayed hypoventilation and apnoea, and preservation of hypoxic‑hypercapnic ventilatory responses (Mahmoud et al 2017).  

I have therefore extended my initial hypothesis, to encompass the proposal that changes in AMPK expression patterns coordinate ventilatory adaptation to extrauterine life, and throughout adulthood by modifying hypoxia-responsive cardiorespiratory systems and their aforementioned reflex responses.

Calcium signalling across the cell-wide web

Cells select for one or a combination of distinct functions through calcium signalling. Therefore, stimuli must induce different calcium signals to engage specific cellular responses, such as, for example, contraction or relaxation of smooth muscles as well as their switch from a contractile to migratory-proliferative phenotypes, which additionally requires changes in gene expression. However, despite the extraordinarily detailed mapping of the temporal characteristics of both unitary and macroscopic calcium signals across a wide variety of cell types, how cells deliver the diverse range of site- and function-specific calcium signals necessary to coordinate the full panoply of cellular processes remains enigmatic.

The current consensus is that highly localized calcium signals from single release sites (e.g. calcium sparks) direct local responses, while propagating global calcium waves select for primary cell function, with adjustments to gene expression presumed to be governed by the spatiotemporal patterns of global calcium transients that gain unrestricted entry to the nucleoplasm across the nuclear envelope and its invaginations.

I developed and addressed an alternative proposal, that different calcium signals may arise in distinct cytoplasmic spaces demarcated by junctions between the SR and its target organelles. In doing so, we identified a cell-wide network of distinct cytoplasmic “nanocourses”, demarcated both by the SR and by different types of SR resident calcium transporters and release channels. This extends from the plasma membrane to nuclear envelope invaginations, delivering highly localised, “quantum calcium flux”, with path lengths on the nanoscale at all points. Cells may thus support unforeseen levels of network activity, across discrete lines of intracellular communication. Intriguingly, this cell-wide web reconfigures for different outputs during, for example, cell proliferation.

Our further aims are to determine how: (1) Stimulus-specific Ca²⁺ flux within nuclear invaginations regulates gene expression; (2) Nanocourse networks reconfigure in response to “environmental cues”; (3) Nuclear invagination formation and loss delivers expression regulation during cell specification and proliferation.

Two Pore Channels in health and disease

In 2004 we discovered lysosome‑SR nanojunctions in pulmonary arterial myocytes (Boittin et al., 2002; Kinnear et al., 2004), which are critical to the amplification of calcium signals from lysosomes triggered by the calcium mobilising pyridine nucleotide nicotinic acid adenine dinucleotide phosphate (NAADP). We later demonstrated that lysosome‑SR nanojunctions are primarily formed by the interaction of lysosomes with perinuclear regions of the SR that are rich in RyR3 (Kinnear et al., 2008), and thus constitute a trigger zone, or intracellular synapse for amplification and further propagation of calcium signals from lysosomes (Kinnear et al., 2004; Kinnear et al., 2008).

The nature of the calcium release channel on the lysosome was enigmatic. However, in 2005 I struck up a collaboration with Mike Zhu, who had cloned Two Pore Channel 2 (TPC2) and demonstrated that it was targeted to lysosomes. Thereafter, my lab was the first to demonstrate that NAADP gated lysosomal calcium release through TPC2 (Calcraft et al., 2008; Calcraft et al., 2009). We have since established that mTORC1 also regulates lysosomal calcium flux through TPC2, and that TPC2 plays a role in autophagy termination.

Our ongoing studies aim to determine how TPC1 and TPC2 coordinate edolysosome trafficking through the cell-wide web, and further explore the role of TPCs in health and disease.

Lab members

Esmahan Durmaz (MSc student)

Esraa Said (PhD student)

Nanjun Chen (PhD student)

Nie Jiahui (PhD student)

Previous lab members

Michelle Dipp, Francois Boittin; Nicholas Kinnear; Christopher Wyatt; Jill Clark; Oluseye Ogunbayo; Nicole Rafferty; Amira Mahmoud; Ejaife Agbani; Ryan Lewis; Jorge Navarro-Dorado; Sophronia Lewis; Javier Moral-Sanz, Jingxian Duan; Sandy MacMillan.

Collaborators

• D. Grahame Hardie, University of Dundee.
• Eric Schirmer, University of Edinburgh
• Michael Zhu, University of Texas Medical School at Houston, USA. 
• Casey van Breemen, & Nicola Fameli University of British Columbia 
• Sutherland McIver, University of Edinburgh
• Thomas Theil, University of Edinburgh

Selected publications

1. Duan J., Navarro-Dorado J., Clark J.H., Kinnear N.P., Meinke P., Schirmer E.C., Evans A.M. (2019). The‑cell wide web coordinates cellular processes by directing site-specific Ca²⁺ flux through cytoplasmic nanocourses. Nature Communications, 10, Article number: 2299. 10.1038/s41467-019-10055-w. 
2. Moral-Sanz, J., Lewis, S.A., MacMillan, S., Ross, F.A., Thomson, A., Foretz, M., Viollet, B., Moran, C., Hardie D.G., Evans, A.M. (2018). The LKB1-AMPK-a1 signaling pathway triggers hypoxic pulmonary vasoconstrction downstream of mitochondria. Science Signaling, 11, pii: eaau0296. doi: 10.1126/scisignal.aau0296.
3. MacMillan S, Evans AM (2018). AMPK-α1 or AMPK-α2 Deletion in Smooth Muscles Does Not Affect the hypoxic ventilatory response or systemic arterial blood pressure regulation during hypoxia. Frontiers in Physiology, 9, doi: 10.3389/fphys.2018.00655.
4. Ogunbayo OA, Duan J, Xiong J, Wang Q, Feng X, Ma J, Zhu MX and Evans AM. (2018). mTORC1 controls lysosomal Ca²⁺ release through the two-pore channel TPC2. Science Signaling, 11, doi: 10.1126/scisignal.aao5775.
5. Vara-Ciruelos, D., Dandapani, M., Gray, A., Agbani, E.O., Evans, A.M., Hardie, D.G. (2017). DNA damage by etoposide activates the α-1 isoform of AMP-activated protein kinase in the nucleus via the Ca²⁺ /CaMKK2 pathway, enhancing human tumor cell survival. Molecular Cancer Research, 16, 345-357.
6. Moral-Sanz, J., Mahmoud, A.D., Ross, F.A., Eldstom, J., Fedida, D., Hardie D.G., Evans, A.M. (2016). AMP-activated protein kinase inhibits Kv1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation. J. Physiol., 594, 4901-4915.
7. Tarailo-Graovac M., Shyr C., Ross C.J., et al. (2016). Exome Sequencing and the Management of Neurometabolic Disorders. N. Engl. J. Med., 374, 2246-2255.
8. Mahmoud, A.D., Lewis, S., Juricic, L., Udoh, U.A., Hartmann, S., Jansen, M.A., Ogunbayo, O.A., Puggioni, P., Holmes, A.P., Kumar, P., Navarro-Dorado, J., Foretz, M., Viollet, B., Dutia, M.B., Marshall, I., Evans, A.M. (2015). AMP-activated protein kinase deficiency blocks the hypoxic ventilatory response and thus precipitates hypoventilation and apnea.  AJRCCM, 193, 1032-1043.
9. Ogunbayo, O.A., Zhu, Y., Shen, B., Agbani, E., Li, J., Ma, J., Zhu, M.X., Evans, A.M. (2015). Organelle-specific Subunit Interactions of the Vertebrate Two-pore Channel Family. J. Biol. Chem., 290, 1086-1095.
10. Ikematsu, N., Dallas, M. L., Ross, F.A., Lewis, R.W., Rafferty, J.N., David, J.A., Suman, R., Peers, C., Hardie, D.G., Evans, A.M. (2011). Phosphorylation of the voltage-gated potassium channel Kv2.1 by AMP-activated protein kinase regulates membrane excitability. PNAS, 108, 18132-18137. Citations = 102. Current Journal IF = 10.
11. Ross F.A., Rafferty J.N., Dallas M.L., Ogunbayo O., Ikematsu N., McClafferty H., Tian L., Widmer H., Rowe I.C., Wyatt C.N., Shipston M.J., Peers C., Hardie D.G., Evans A.M. (2011). Selective Expression in Carotid Body Type I Cells of a Single Splice Variant of the Large Conductance Calcium- and Voltage-activated Potassium Channel Confers Regulation by AMP-activated Protein Kinase. J. Biol. Chem., 286, 11929-11936.
12. Ogunbayo O.A., Zhu Y., Rossi D., Sorrentino V., Ma J., Zhu M.X., Evans A.M. (2011). Cyclic adenosine diphosphate ribose activates ryanodine receptors, whereas NAADP activates two-pore domain channels. J. Biol. Chem., 286, 9136-9140.
13. Clark, J.H., Kinnear, N.P., Kalujnaiab, S., Cramb, G., Fleischer, S., Jeyakumar, L.H., Wuytack, F., Evans, A.M. (2010). Identification of Functionally Segregated Sarcoplasmic Reticulum Calcium Stores in Pulmonary Arterial Smooth Muscle. J. Biol. Chem., 285, 13542-13549.
14. Hawley S.A., Ross F.A., Chevtzoff C., Green K.A., Evans A., Fogarty S., Towler M.C., Brown L.J., Ogunbayo O.A., Evans A.M., Hardie D.G. (2010). Use of cells expressing gamma subunit variants to identify diverse mechanisms of AMPK activation. Cell Metab., 11, 554-565.
15. Calcraft, P.J., Arredouani, A., Ruas, M., Pan, Z., Cheng, X., Hao, X., Tang, J., Reindorf, K., Teboul, L., Chuang, K-T, Lin, P., Rui Xiao, R., Wang, C., Lin, Y., Wyatt, C.N., Parrington, J., Ma, J, Evans, A.M., Galione, A., Zhu, M.X. (2009). NAADP targets TPC2 to release Ca²⁺ from lysosomal stores in mammalian cells. Nature, 459, 596-600.

Information for students:

Willingness to discuss research projects with undergraduate and postgraduate students: YES - please click here