title: Two-pore Channels (TPC2s) and Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) at Lysosomal-Sarcoplasmic Reticular Junctions Contribute to Acute and Chronic β-Adrenoceptor Signaling in the Heart.
abstract: Ca(2+)-permeable type 2 two-pore channels (TPC2) are lysosomal proteins required for nicotinic acid adenine dinucleotide phosphate (NAADP)-evoked Ca(2+) release in many diverse cell types. Here, we investigate the importance of TPC2 proteins for the physiology and pathophysiology of the heart. NAADP-AM failed to enhance Ca(2+) responses in cardiac myocytes from Tpcn2(-/-) mice, unlike myocytes from wild-type (WT) mice. Ca(2+)/calmodulin-dependent protein kinase II inhibitors suppressed actions of NAADP in myocytes. Ca(2+) transients and contractions accompanying action potentials were increased by isoproterenol in myocytes from WT mice, but these effects of β-adrenoreceptor stimulation were reduced in myocytes from Tpcn2(-/-) mice. Increases in amplitude of L-type Ca(2+) currents evoked by isoproterenol remained unchanged in myocytes from Tpcn2(-/-) mice showing no loss of β-adrenoceptors or coupling mechanisms. Whole hearts from Tpcn2(-/-) mice also showed reduced inotropic effects of isoproterenol and a reduced tendency for arrhythmias following acute β-adrenoreceptor stimulation. Hearts from Tpcn2(-/-) mice chronically exposed to isoproterenol showed less cardiac hypertrophy and increased threshold for arrhythmogenesis compared with WT controls. Electron microscopy showed that lysosomes form close contacts with the sarcoplasmic reticulum (separation ∼ 25 nm). We propose that Ca(2+)-signaling nanodomains between lysosomes and sarcoplasmic reticulum dependent on NAADP and TPC2 comprise an important element in β-adrenoreceptor signal transduction in cardiac myocytes. In summary, our observations define a role for NAADP and TPC2 at lysosomal/sarcoplasmic reticulum junctions as unexpected but major contributors in the acute actions of β-adrenergic signaling in the heart and also in stress pathways linking chronic stimulation of β-adrenoceptors to hypertrophy and associated arrhythmias.
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Capel
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Bolton
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Wee K
authors.initials: WK
authors.lastname: Lin
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aston
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Wang
authors.affiliation: the Faculty of Life Science, University of Manchester, Manchester M13 9NT, and.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: the Faculty of Life Science, University of Manchester, Manchester M13 9NT, and.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: the Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Sherrington Road, Oxford OX1 3PT, United Kingdom.
authors.forename: Rebecca-Ann B
authors.initials: RA
authors.lastname: Burton
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Duncan
authors.initials: D
authors.lastname: Bloor-Young
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Kai-Ting
authors.initials: KT
authors.lastname: Shade
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Margarida
authors.initials: M
authors.lastname: Ruas
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: John
authors.initials: J
authors.lastname: Parrington
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Grant C
authors.initials: GC
authors.lastname: Churchill
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Ming
authors.initials: M
authors.lastname: Lei
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT.
authors.forename: Antony
authors.initials: A
authors.lastname: Galione
authors.affiliation: From the Department of Pharmacology, BHF Centre of Research Excellence, University of Oxford, Mansfield Road, Oxford OX1 3QT, derek.terrar@pharm.ox.ac.uk.
authors.forename: Derek A
authors.initials: DA
authors.lastname: Terrar
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D006168:Guinea Pigs; D008247:Lysosomes / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000378:metabolism*; D009249:NADP / Q000031:analogs & derivatives* / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D015220:Calcium Channels; D011943:Receptors, Adrenergic, beta; C546785:TPCN2 protein, mouse; D009249:NADP; C024376:NAADP
keywords: Ca2+/calmodulin-dependent protein kinase II (CaMKII); adrenergic receptor; calcium imaging; calcium intracellular release; cardiac hypertrophy; endoplasmic reticulum (ER); heart; lysosome; nicotinic acid adenine dinucleotide phosphate (NAADP)