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CDB Seminars
All welcome

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All Seminars are held in the Gavin De Beer Lecture Theatre, Anatomy Building, Thursday 1-2pm

5 Feb: Dr Andrew Macaskill, UCL NPP
Title: Reorganisation of Striatal Connectivity After Cocaine Exposure
Host: Prof Steve Hunt

12 Feb: Ana Faro (Wilson lab)/ Irene Marta Almeida (Stern lab)

26 Feb: Prof Hannes E. Buelow, Albert Einstein College of Medicine, NY.
Title: To Branch or not to branch - Shaping Sensory Dendrites
Host: Dr Richard Poole

5 March: András Szabó (Mayor lab) / Pedro Pereira (Henriques’ lab)

12 March: Jose Gomez (Jessen lab)/Sara Maffioletti (Tedesco lab)

26 March: Lizzie Yates (Patel lab) / Melissa Barber (Parnavelas lab)

9 April: Zeki lab –TBC/ Francis Carpenter (Caswell Barry lab)

23 April: Florent Peglion (Nate Guring lab)/Michele Sammut (Barrios lab, now in Poole lab) 

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Prof Sandip Patel

Prof Sandip Patel

Professor of Cell Signalling

patel.s@ucl.ac.uk

Telephone:
Office: 020 7679 4437
(Int: 34437)

The Patel lab: Ca2+ signalling through acidic organelles

Our lab focuses on the role of acidic organelles, such as lysosomes, in Ca2+ signalling in both health and disease. See the outreach section for a plain English summary.

  Figure 1  
rfig1
 


Background

Changes in cytosolic Ca2+ form the basis of a ubiquitous, evolutionary conserved signalling pathway. These Ca2+ signals drive many, if not all cellular processes from the very start of life (fertilisation), during vital processes such as neurotransmission, through to death (apoptosis). It is now clear that so-called “acidic Ca2+ stores” dynamically regulate cytosolic Ca2+ levels, both in isolation and in conjunction with the better-characterised Ca2+ stores of the endoplasmic reticulum. Acidic Ca2+ stores is an umbrella term that describes a cross-kingdom collection of morphologically distinct-yet-functionally related organelles united by their acid and Ca2+-rich interior. Lysosomes and lysosome-related organelles are key acidic Ca2+ stores that are considered functionally related to acidocalcisomes, vacuoles, endosomes, secretory granules and the Golgi complex. The Ca2+ mobilising messenger NAADP plays a critical role in controlling acidic Ca2+ store signalling.

Vision

We are i) defining the Ca2+ signalling “toolkit” (channels, transporters) of acidic Ca2+ stores at the molecular level and their evolutionary origins (form), ii) probing their physiological roles in processes such as membrane trafficking and cell migration (function) and iii) investigating how deviant signalling through these organelles can precipitate disorders such as Parkinson disease (failure).

Approach

Our work is interdisciplinary, encompassing both “wet” (molecular, cell and structural biology) and “dry” (bioinformatics, phylogenetics and computational modelling) approaches in a highly collaborative and international context.

NAADP: An unusual Ca2+ mobilizing messenger

NAADP is a potent Ca2+ mobilising messenger, discovered in the 1990s by Hon Cheung Lee and colleagues. Over the last 15 years or so, we have played a central role in defining its mechanism of action using many model systems spanning from sea urchin eggs to primary human fibroblasts. In early work, we: i) identified and characterised the binding properties of NAADP receptors; ii) showed that NAADP is highly unusual in activating Ca2+-permeable channels located on non-canonical, acidic Ca2+ stores such as lysosomes and lysosome-like organelles; iii) quantified cellular NAADP levels and identified NAADP generating signals, such as the hormones and neurotransmitters; iv) identified and characterised NAADP synthesizing enzymes – the ADP-ribosyl cyclases - from both invertebrate and vertebrate systems and v) extended the actions of NAADP to the nervous system. Researchfig1


Patel, S., G.C.Churchill, T.Sharp, and A.Galione. 2000. Widespread distribution of binding sites for the novel Ca2+-mobilizing messenger, nicotinic acid adenine dinucleotide phosphate, in the brain. J. Biol. Chem. 275:36495-36497.

Berridge, G., G.Dickinson, J.Parrington, A.Galione, and S.Patel. 2002. Solubilization of receptors for the novel Ca2+-mobilizing messenger, nicotinic acid adenine dinucleotide phosphate. J. Biol. Chem. 277:43717-43723.

Churchill, G.C., Y.Okada, J.M.Thomas, A.A.Genazzani, S.Patel, and A.Galione. 2002. NAADP mobilizes Ca2+ from reserve granules, lysosome-related organelles, in sea urchin eggs. Cell 111:703-708.

Churamani, D., E.A.Carrey, G.D.Dickinson, and S.Patel. 2004. Determination of cellular nicotinic acid-adenine dinucleotide phosphate (NAADP) levels. Biochem. J. 380:449-454.

Yamasaki, M., J.T.Thomas, G.C.Churchill, C.Garnham, A.L.Lewis, J.M.Cancela, S.Patel, and A.Galione. 2005. Role of NAADP and cADPR in the induction and maintenance of agonist-evoked Ca2+ Spiking in mouse pancreatic acinar cells. Curr. Biol. 15:874-878.

Brailoiu, E., J.L.Hoard, C.M.Filipeanu, G.C.Brailoiu, S.L.Dun, S.Patel, and N.J.Dun. 2005. Nicotinic acid adenine dinucleotide phosphate potentiates neurite outgrowth. J. Biol. Chem. 280:5646-5650.

Churamani, D., M.J.Boulware, T.J.Geach, A.C.Martin, G.W.Moy, Y.H.Su, V.D.Vacquier, J.S.Marchant, L.Dale, and S.Patel. 2007. Molecular characterization of a novel intracellular ADP-ribosyl cyclase. PLoS. ONE. 2:e797.

Pandey, V., C.C.Chuang, A.M.Lewis, P.Aley, E.Brailoiu, N.Dun, G.C.Churchill, and S.Patel. 2009. Recruitment of NAADP-sensitive acidic Ca2+ stores by glutamate. Biochem. J. 422:503-512.

The two-pore channels (TPCs)

In 2009, we were one of three groups that converged on the TPCs as the long-sought-after target channels for NAADP. TPCs have a duplicated domain architecture comprising two concatenated voltage-gated ion channel-like repeats, each containing 6 transmembrane regions and a re-entrant pore loop. They likely dimerise to form the characteristic pseudotetrameric arrangement typical of the voltage-gated ion channel superfamily to which TPCs belong. We showed that TPCs localise to the endolysosomal system and applied loss- and gain-of function approaches, together with Ca2+ imaging and electrophysiology (with Rahman and Muallem), to show that TPCs are likely the pore-forming subunit of NAADP-gated, Ca2+-permeable channels. Our work with Marchant suggests that NAADP does not bind directly to TPCs, but instead to closely associated NAADP-binding protein(s). Modifiers of voltage-gated Ca2+ and Na+ channels also block TPCs, possibly though a common binding site. We are currently performing structure-function analyses of TPCs.

Researchfig2

Brailoiu, E., D.Churamani, X.Cai, M.G.Schrlau, G.C.Brailoiu, X.Gao, R.Hooper, M.J.Boulware, N.J.Dun, J.S.Marchant, and S.Patel. 2009. Essential requirement for two-pore channel 1 in NAADP-mediated calcium signaling. J. Cell Biol. 186:201-209.

Brailoiu, E., T.Rahman, D.Churamani, D.L.Prole, G.C.Brailoiu, R.Hooper, C.W.Taylor, and S.Patel. 2010b. An NAADP-gated two-pore channel targeted to the plasma membrane uncouples triggering from amplifying Ca2+ signals. J. Biol. Chem. 285:38511-38516.

Hooper, R., D.Churamani, E.Brailoiu, C.W.Taylor, and S.Patel. 2011. Membrane topology of NAADP-sensitive two-pore channels and their regulation by N-linked glycosylation. J. Biol. Chem. 286:9141-9149.

Churamani, D., R.Hooper, E.Brailoiu, and S.Patel. 2012. Domain assembly of NAADP-gated two-pore channels. Biochem. J. 441:317-323.

Lin-Moshier, Y., T.F.Walseth, D.Churamani, S.M.Davidson, J.T.Slama, R.Hooper, E.Brailoiu, S.Patel, and J.S.Marchant. 2012. Photoaffinity labeling of nicotinic acid adenine dinucleotide phosphate (NAADP) targets in mammalian cells. J. Biol. Chem. 287:2296-2307.

Jha, A., M.Ahuja, S.Patel, E.Brailoiu, and S.Muallem. 2014. Convergent Regulation of the Lysosomal Two-Pore Channel-2 by Mg2+, NAADP, PI(3,5)P2 and Multiple Protein Kinases. EMBO J. 33:501-511

Rahman, T., X.Cai, G.C.Brailoiu, M.E.Abood, E.Brailoiu, and S.Patel. 2014. Two-pore channels provide insight into the evolution of voltage-gated Ca2+ and Na+ channels. Sci. Signal. 7:ra109.

Inter-organellar crosstalk

NAADP is often described as “trigger” for Ca2+ signalling. This is because the Ca2+ signals it evokes from acidic organelles can be amplified by neighbouring channels on the ER, likely through the process of Ca2+-induced Ca2+-release. We have proposed that such “chatter” might occur at membrane contact sites between the ER and the endolysosomal system. Membrane contact sites are regions of close apposition where different membranes come in close contact (<30 nm) but do not fuse. With Futter we have identified membrane contact sites between the lysosomes and ER. Computational modelling with Sneyd has provided insight into Ca2+ signalling at these junctions. We are currently investigating the properties of these junctions.

Researchfig3

Patel, S., and E.Brailoiu. 2012. Triggering of Ca2+ signals by NAADP-gated two-pore channels. A role for membrane contact sites? Biochem. Soc. Trans. 40:153-157.

Kilpatrick, B.S., E.R.Eden, A.H.Schapira, C.E.Futter, and S.Patel. 2013. Direct mobilisation of lysosomal Ca2+ triggers complex Ca2+ signals. J. Cell Sci. 126:60-66.

Penny, C.J., B.S.Kilpatrick, J.M.Han, J.Sneyd, and S.Patel. 2014. A computational model of lysosome-ER Ca2+ microdomains. J. Cell Sci. 127:2934-2943.

Membrane trafficking

It is likely that the local Ca2+ signals derived from acidic organelles might act in their own right to drive physiological processes. Indeed, it has been known for some time that local Ca2+ signals regulate various trafficking events within the endolysosomal system. With Marchant, we have shown that TPCs associate with a variety of proteins involved in membrane trafficking (such as Rab GTPases) to regulate endolysosomal morphology. We are currently defining the mechanisms by which TPCs regulate membrane traffic. Researchfig4.1


Lin-Moshier, Y., M.V.Keebler, R.Hooper, M.J.Boulware, X.Liu, D.Churamani, M.E.Abood, T.F.Walseth, E.Brailoiu, S.Patel, and J.S.Marchant. 2014. The two-pore channel (TPC) interactome unmasks isoform-specific roles for TPCs in endolysosomal morphology and cell pigmentation. Proc. Natl. Acad. Sci. 111:13087-13092.

Parkinson disease

There is an increasing appreciation of the role of lysosomal dysfunction in neurodegenerative disorders such as Alzheimer’s and Parkinson disease. With Schapira, we have recently identified Ca2+-dependent lysosomal trafficking defects in fibroblasts from Parkinson disease patients. We showed that chemical or molecular inhibition of the NAADP pathway restores endocytic “well-being”. We are currently exploring whether the NAADP-signalling pathway might therefore represent a novel therapeutic target in Parkinson disease. Researchfig5

Hockey, L. N., Kilpatrick, B. S., Eden, E. R., Lin-Moshier, Y., Brailoiu, G. C., Brailoiu, E., Futter, C., Schapira, A. H., Marchant, J. S. and Patel, S. (2015) Dysregulation of lysosomal morphology by pathogenic LRRK2 is corrected by two-pore channel 2 inhibition. J.Cell Sci. 128, 232-238

Evolution

Despite their diversity, acidic Ca2+ stores may function similarly across the natural world in processes such as signalling, membrane traffic and secretion. TPCs are particularly interesting in an evolutionary context in terms of their phylogenomic profile (ie the presence of their genes in specific organisms) and their putative structure. Most deuterostome animals possess three TPC isoforms but there is highly unusual, lineage-specific loss of TPC3 in certain primates (including humans) and rodents. Their duplicated domain organisation indicates that they may be descendants of the key evolutionary intermediate between one- and four-domain members of the voltage-gated ion channel superfamily. With Cai, we have established the phylogenetic relationship between multi-domain voltage-gated ion channels, and recently identified a novel clade of TPCs in unicellular organisms with predicted properties similar to voltage-gated Ca2+ channels. We are exploring the evolutionary trajectory for TPCs and their related channels.

Researchfig6

Patel, S., and R.Docampo. 2010. Acidic calcium stores open for business: expanding the potential for intracellular Ca2+ signaling. Trends Cell Biol. 20:277-286.

Brailoiu, E., R.Hooper, X.Cai, G.C.Brailoiu, M.V.Keebler, N.J.Dun, J.S.Marchant, and S.Patel. 2010. An ancestral deuterostome family of two-pore channels mediate nicotinic acid adenine dinucleotide phosphate-dependent calcium release from acidic organelles. J. Biol. Chem. 285:2897-2901.

Cai, X., and S.Patel. 2010. Degeneration of an intracellular ion channel in the primate lineage by relaxation of selective constraints. Mol. Biol. Evol. 27:2352-2359.

Patel, S., and S.Muallem. 2011. Acidic Ca2+ stores come to the fore. Cell Calcium 50:109-112.

Rahman, T., X.Cai, G.C.Brailoiu, M.E.Abood, E.Brailoiu, and S.Patel. 2014. Two-pore channels provide insight into the evolution of voltage-gated Ca2+ and Na+ channels. Sci. Signal. 7:ra109.

Patel, S., and X.Cai. 2015. Evolution of acid Ca2+ stores and their resident Ca2+-permeable channels. Cell Calcium.

Sandip Patel

patel


Principal investigator

Bethan S. Kilpatrick

Bethan Kilpatrick


Post doc

Manuela Melchionda

Melchionda


Post doc

Stephen Mullin

Stephen Mullin


PhD student (Primary supervisor: Anthony. H. Schapira)

Christopher J. Penny

Christopher Penny


PhD student

Elizabeth Yates

PhD student

Alumini

Leanne Hockey (MSc student, 2011 – 2012)

Dev Churamani, (PhD student, 2002 – 2005; Post doc, 2006 – 2012)

Suchita Deo (MSc student, 2010 – 2011)

Robert Hooper (PhD student; 2008 – 2011)

Latha Ramakrishnan (PhD student; 2007 – 2010)

George Dickinson (Post doc, 2002 - 2004; Post doc 2008 – 2010)

Vinita Pandey (Post doc, 2004 – 2006)

George Dickinson (Post doc, 2002 – 2004)

Dayle Hogg (Post doc, 2000 – 2001)

Georgina Berridge (Research assistant; 2000 – 2001)

Page last modified on 29 jan 15 15:17 by Sonja Van Praag (WAMS)