In healthy individuals, the controlled release of calcium causes the heart to beat strongly. In heart failure and fatal arrhythmias the release of calcium becomes erratic leading to weakened contraction of heart muscle and cell death. Using a combination of low noise electrophysiological recordings in combination with molecular and biochemical methods, my group investigates intracellular calcium dynamics and the molecular function of ion channels that are involved in the control and regulation of calcium-release from intracellular stores. The aim of our research is to try to understand what happens to channel function under pathophysiological conditions.
Recent research has discovered that a biological agent called “nicotinic acid dinucleotide phosphate” (NAADP) causes the release of calcium by opening a newfamily of pore forming proteins called two pore channels (TPCs) located on acidic intracellular calcium stores. The mechanism of NAADP-regulated signalling via TPCs is not well understood. In humans there are two isoforms of TPC (TPC1 and TPC2) and we are currently investigating the single-channel behaviour of these putative Ca2+-release channels. Owing to their Ca2+-handling properties aberrant TPC function may impact on diseases where disruption of Ca2+-signals are central, including cytotoxicity and cell death, heart failure, and neurodegenerative processes. Furthermore, genetic studies have linked the gene coding TPC2 to hearing defects and cancer.Understanding the role of TPCs in regulating calcium-release will enable the design of drugs that can manipulate the release of calcium via these channels and help combat diseases associated with abnormal calcium-movements.
Reilly-O'Donnell, B, Robertson, GB, Karumbi, A, McIntyre, C, Bal, W, Nishi, M, Takeshima, H
, Stewart, AJ & Pitt, SJ 2017, '
Dysregulated Zn2+ homeostasis impairs cardiac type-2 ryanodine receptor and mitsugumin 23 functions, leading to sarcoplasmic reticulum Ca2+ leakage'
Journal of Biological Chemistry, vol 292, no. 32, pp. 13361-13373. DOI:
10.1074/jbc.M117.781708Jovanovic, A, Obradovic, M, Sudar-Milovanovic, E
, Stewart, AJ, Pitt, SJ, Alvantic, D, Aleksic, E & Isenovic, ER 2017, '
Changes in cardiac Na+/K+-ATPase expression and activity in female rats fed a high fat diet'
Molecular and Cellular Biochemistry, vol First Online. DOI:
10.1007/s11010-017-3077-yZafirovic, S, Obradovic, M, Sudar-Milovanovic, E, Jovanovic, A, Stanimirovic, J
, Stewart, AJ, Pitt, SJ & Isenovic, ER 2017, '
17ß-Estradiol protects against the effects of a high fat diet on cardiac glucose, lipid and nitric oxide metabolism in rats'
Molecular and Cellular Endocrinology, vol 446, pp. 12-20. DOI:
10.1016/j.mce.2017.02.001Jovanovic, A, Sudar-Milovanovic, E, Obradovic, M
, Pitt, SJ, Stewart, AJ, Zafirovic, S, Stanimirovic, J, Radak, D & Isenovic, ER 2017, '
Influence of a high-fat diet on cardiac iNOS in female rats'
Current Vascular Pharmacology, vol 15, no. 5, pp. 491-500. DOI:
10.2174/1570161114666161025101303 Stanimirovic, J, Obradovic, M, Jovanovic, A, Sudar-Milovanovic, E, Zafirovic, S
, Pitt, SJ, Stewart, AJ & Isenovic, ER 2016, '
A high fat diet induces sex-specific differences in hepatic lipid metabolism and nitrite/nitrate in rats'
Nitric Oxide, vol 54, pp. 51-59. DOI:
10.1016/j.niox.2016.02.007Woodier, J, Rainbow, RD
, Stewart, AJ & Pitt, SJ 2016, '
Response to Qian and Colvin: zinc-mediated regulation of the cardiac ryanodine receptor occurs via multiple binding sites'
Journal of Biological Chemistry, vol 291, no. 8, pp. 4267. DOI:
10.1074/jbc.L115.713214Woodier, J, Rainbow, RD
, Stewart, AJ & Pitt, SJ 2015, '
Intracellular zinc modulates cardiac ryanodine receptor-mediated calcium release'
Journal of Biological Chemistry, vol 290, no. 28, pp. 17599-17610. DOI:
10.1074/jbc.M115.661280Pitt, SJ, Lam, AKM, Rietdorf, K, Galione, A & Sitsapesan, R 2014, '
Reconstituted human TPC1 is a proton-permeable ion channel and is activated by NAADP or Ca2+'
Science signaling, vol 7, no. 326, ra46. DOI:
10.1126/scisignal.2004854 Obradovic, M
, Stewart, AJ, Pitt, SJ, Labudovic-Borovic, M, Sudar, E, Petrovic, V, Zafirovic, S, Maravic-Stojkovic, V, Vasic, V & Isenovic, ER 2014, '
In vivo effects of 17β-estradiol on cardiac Na+/K+-ATPase expression and activity in rat heart'
Molecular and Cellular Endocrinology, vol 388, no. 1-2, pp. 58-68. DOI:
10.1016/j.mce.2014.03.005Venturi, E, Galfre, E, O'Brien, F
, Pitt, SJ, Bellamy, S, Sessions, RB & Sitsapesan, R 2014, '
FKBP12.6 activates RyR1: investigating the amino acid residues critical for channel modulation'
Biophysical Journal, vol 106, no. 4, pp. 824-833. DOI:
10.1016/j.bpj.2013.12.041Pitt, SJ, Lam, A, Galione, A & Sitsapesan, R 2014, '
TPC1 is a proton permeable channel that can be independently activated by cytosolic calcium or NAADP'
Biophysical Journal, vol 106, no. 2, pp. 642A-642A. DOI:
10.1016/j.bpj.2013.11.3555 Venturi, E, Matyjaszkiewicz, A
, Pitt, SJ, Tsaneva-Atanasova, K, Nishi, M, Yamazaki, D, Takeshima, H & Sitsapesan, R 2013, '
TRIC-B channels display labile gating: evidence from the TRIC-A knockout mouse model'
Pflügers Archiv: European Journal of Physiology, vol 465, no. 8, pp. 1135-1148. DOI:
10.1007/s00424-013-1251-yGalfre, E
, Pitt, SJ, Venturi, E, Sitsapesan, M, Zaccai, NR, Tsaneva-Atanasova, K, O'Neill, S & Sitsapesan, R 2012, '
FKBP12 activates the cardiac ryanodine receptor Ca2+-release channel and is antagonised by FKBP12.6'
PLoS One, vol 7, no. 2, e31956. DOI:
10.1371/journal.pone.0031956Venturi, E
, Pitt, SJ, Galfre, E & Sitsapesan, R 2012, '
From eggs to hearts: what is the link between cyclic ADP-ribose and ryanodine receptors?'
Cardiovascular Therapeutics, vol 30, no. 2, pp. 109-16. DOI:
10.1111/j.1755-5922.2010.00236.xCarter, S
, Pitt, SJ, Colyer, J & Sitsapesan, R 2011, '
Ca2+-dependent phosphorylation of RyR2 can uncouple channel gating from direct cytosolic Ca2+ regulation'
Journal of Membrane Biology, vol 240, no. 1, pp. 21-33. DOI:
10.1007/s00232-011-9339-9Venturi, E, Mio, K, Nishi, M, Ogura, T, Moriya, T
, Pitt, SJ, Okuda, K, Kakizawa, S, Sitsapesan, R, Sato, C & Takeshima, H 2011, '
Mitsugumin 23 forms a massive bowl-shaped assembly and cation-conducting channel.'
Biochemistry, vol 50, no. 13, pp. 2623-32. DOI:
10.1021/bi1019447Pitt, SJ, Funnell, TM, Sitsapesan, M, Venturi, E, Rietdorf, K, Ruas, M, Ganesan, A, Gosain, R, Churchill, GC, Zhu, MX, Parrington, J, Galione, A & Sitsapesan, R 2010, '
TPC2 is a novel NAADP-sensitive Ca2+ release channel, operating as a dual sensor of luminal pH and Ca2+'
Journal of Biological Chemistry, vol 285, no. 45, pp. 35039-35046. DOI:
10.1074/jbc.M110.156927 Pitt, SJ, Park, K-H, Nishi, M, Urashima, T, Aoki, S, Yamazaki, D, Ma, J, Takeshima, H & Sitsapesan, R 2010, '
Charade of the SR K+-channel: two ion-channels, TRIC-A and TRIC-B, masquerade as a single K+-channel'
Biophysical Journal, vol 99, no. 2, pp. 417-426. DOI:
10.1016/j.bpj.2010.04.051 Pitt, SJ, Martinez-Pinna, J, Barnard, EA & Mahaut-Smith, MP 2005, '
Potentiation of P2Y receptors by physiological elevations of extracellular K+ via a mechanism independent of Ca2+ influx.'
Molecular Pharmacology, vol 67, no. 5, pp. 1705-13. DOI:
10.1124/mol.104.009902 Vial, C
, Pitt, SJ, Roberts, JA, Rolf, MG, Mahaut-Smith, MP & Evans, RJ 2003, '
Lack of evidence for functional ADP-activated human P2X1 receptors supports a role for ATP during hemostasis and thrombosis.'
Blood, vol 102, no. 10, pp. 3646-51. DOI:
10.1182/blood-2003-06-1963
