title: Endolysosomal two-pore channels regulate autophagy in cardiomyocytes.
abstract: Two-pore channels (TPCs) were identified as a novel family of endolysosome-targeted calcium release channels gated by nicotinic acid adenine dinucleotide phosphate, as also as intracellular Na(+) channels able to control endolysosomal fusion, a key process in autophagic flux. Autophagy, an evolutionarily ancient response to cellular stress, has been implicated in the pathogenesis of a wide range of cardiovascular pathologies, including heart failure. We report direct evidence indicating that TPCs are involved in regulating autophagy in cardiomyocytes, and that TPC knockout mice show alterations in the cardiac lysosomal system. TPC downregulation implies a decrease in the viability of cardiomyocytes under starvation conditions. In cardiac tissues from both humans and rats, TPC transcripts and protein levels were higher in females than in males, and correlated negatively with markers of autophagy. We conclude that the endolysosomal channels TPC1 and TPC2 are essential for appropriate basal and induced autophagic flux in cardiomyocytes, and also that they are differentially expressed in male and female hearts.
  
  
  
  Autophagy participates in physiological and pathological remodelling of the heart. The endolysosomal two-pore channels (TPCs), TPC1 and TPC2, have been implicated in the regulation of autophagy. The present study aimed to investigate the role of TPC1 and TPC2 in basal and induced cardiac autophagic activity. In cultured cardiomyocytes, starvation induced a significant increase in TPC1 and TPC2 transcripts and protein levels that paralleled the increase in autophagy identified by increased LC3-II and decreased p62 levels. Small interfering RNA depletion of TPC2 alone or together with TPC1 increased both LC3II and p62 levels under basal conditions and in response to serum starvation, suggesting that, under conditions of severe energy depletion (serum plus glucose starvation), changes in the autophagic flux (as assessed by use of bafilomycin A1) occurred either when TPC1 or TPC2 were downregulated. The knockdown of TPCs diminished cardiomyocyte viability under starvation and simulated ischaemia. Electron micrographs of hearts from TPC1/2 double knockout mice showed that cardiomyocytes contained large numbers of immature lysosomes with diameters significantly smaller than those of wild-type mice. In cardiac tissues from humans and rats, TPC1 and TPC2 transcripts and protein levels were higher in females than in males. Furthermore, transcript levels of TPCs correlated negatively with p62 levels in heart tissues. TPC1 and TPC2 are essential for appropriate basal and induced autophagic flux in cardiomyocytes (i.e. there is a negative effect on cell viability under stress conditions in their absence) and they are differentially expressed in male and female human and murine hearts, where they correlate with markers of autophagy.
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Vanessa
authors.initials: V
authors.lastname: García-Rúa
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: Feijóo-Bandín
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Diego
authors.initials: D
authors.lastname: Rodríguez-Penas
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Mosquera-Leal
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Emad
authors.initials: E
authors.lastname: Abu-Assi
authors.affiliation: Department of Pathology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Andrés
authors.initials: A
authors.lastname: Beiras
authors.affiliation: Department of Endocrine Pathophysiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Luisa
authors.initials: L
authors.lastname: María Seoane
authors.affiliation: Department of Pharmacology, Oxford University, UK.
authors.forename: Pamela
authors.initials: P
authors.lastname: Lear
authors.affiliation: Department of Pharmacology, Oxford University, UK.
authors.forename: John
authors.initials: J
authors.lastname: Parrington
authors.affiliation: La Fe University Hospital, Valencia, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Portolés
authors.affiliation: La Fe University Hospital, Valencia, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Roselló-Lletí
authors.affiliation: La Fe University Hospital, Valencia, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Rivera
authors.affiliation: Department of Neuroendocrine Interactions in Rheumatic and Inflammatory Diseases, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Oreste
authors.initials: O
authors.lastname: Gualillo
authors.affiliation: Department of Internal Medicine (Cardiology) and Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Valentina
authors.initials: V
authors.lastname: Parra
authors.affiliation: Department of Internal Medicine (Cardiology) and Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hill
authors.affiliation: Department of Internal Medicine (Cardiology) and Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Beverly
authors.initials: B
authors.lastname: Rothermel
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: José Ramón
authors.initials: JR
authors.lastname: González-Juanatey
authors.affiliation: Department of Cellular and Molecular Cardiology, Institute of Biomedical Research (IDIS-SERGAS), Santiago de Compostela, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Lago
mesh_terms: D000368:Aged; D000818:Animals; D000831:Animals, Newborn; D020517:Atrial Appendage / Q000502:physiology; D001343:Autophagy / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008247:Lysosomes / Q000502:physiology*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D000097903:Two-Pore Channels
chemical_list: D015220:Calcium Channels; C546784:TPCN1 protein, mouse; D000097903:Two-Pore Channels; C546785:TPCN2 protein, mouse