title: L-type Cav1.3 channels regulate ryanodine receptor-dependent Ca2+ release during sino-atrial node pacemaker activity.
abstract: OBJECTIVE
  Sino-atrial node (SAN) automaticity is an essential mechanism of heart rate generation that is still not completely understood. Recent studies highlighted the importance of intracellular Ca(2+) ([Ca(2+)]i) dynamics during SAN pacemaker activity. Nevertheless, the functional role of voltage-dependent L-type Ca(2+) channels in controlling SAN [Ca(2+)]i release is largely unexplored. Since Cav1.3 is the predominant L-type Ca(2+) channel isoform in SAN cells, we studied [Ca(2+)]i dynamics in isolated cells and ex vivo SAN preparations explanted from wild-type (WT) and Cav1.3 knockout (KO) mice (Cav1.3(-/-)).
  
  
  RESULTS
  We found that Cav1.3 deficiency strongly impaired [Ca(2+)]i dynamics, reducing the frequency of local [Ca(2+)]i release events and preventing their synchronization. This impairment inhibited the generation of Ca(2+) transients and delayed spontaneous activity. We also used action potentials recorded in WT SAN cells as voltage-clamp commands for Cav1.3(-/-) cells. Although these experiments showed abolished Ca(2+) entry through L-type Ca(2+) channels in the diastolic depolarization range of KO SAN cells, their sarcoplasmic reticulum Ca(2+) load remained normal. β-Adrenergic stimulation enhanced pacemaking of both genotypes, though, Cav1.3(-/-) SAN cells remained slower than WT. Conversely, we rescued pacemaker activity in Cav1.3(-/-) SAN cells and intact tissues through caffeine-mediated stimulation of Ca(2+)-induced Ca(2+) release.
  
  
  CONCLUSIONS
  Cav1.3 channels play a critical role in the regulation of [Ca(2+)]i dynamics, providing an unanticipated mechanism for triggering local [Ca(2+)]i releases and thereby controlling pacemaker activity. Our study also provides an additional pathophysiological mechanism for congenital SAN dysfunction and heart block linked to Cav1.3 loss of function in humans.
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France matteo.mangoni@igf.cnrs.fr angelotorrente@hotmail.com.
authors.forename: Angelo Giovanni
authors.initials: AG
authors.lastname: Torrente
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France.
authors.forename: Pietro
authors.initials: P
authors.lastname: Mesirca
authors.affiliation: UMR-S 1180, Inserm, Univ. Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France Department of Pharmacology and Toxicology, Institute of Pharmacy.
authors.forename: Patricia
authors.initials: P
authors.lastname: Neco
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Rizzetto
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France.
authors.forename: Stefan
authors.initials: S
authors.lastname: Dubel
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Barrere
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Pharmacy Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Sinegger-Brauns
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Pharmacy Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Joerg
authors.initials: J
authors.lastname: Striessnig
authors.affiliation: INSERM, U1046, Montpellier, France CNRS UMR 9214, PhyMedExp, University of Montpellier, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Richard
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France.
authors.forename: Joël
authors.initials: J
authors.lastname: Nargeot
authors.affiliation: UMR-S 1180, Inserm, Univ. Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France Department of Pharmacology and Toxicology, Institute of Pharmacy.
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Gomez
authors.affiliation: Département de Physiologie, CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier F-34000, France INSERM, U1191, Montpellier F-34000, France Université de Montpellier, UMR-5203, Montpellier F-34000, France matteo.mangoni@igf.cnrs.fr angelotorrente@hotmail.com.
authors.forename: Matteo Elia
authors.initials: ME
authors.lastname: Mangoni
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010138:Pacemaker, Artificial; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D012849:Sinoatrial Node / Q000378:metabolism
chemical_list: C485995:Cacna1d protein, mouse; D020746:Calcium Channels, L-Type; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium
keywords: Ca2+ dynamics; Cav1.3; L-type Ca2+ channels; Pacemaker activity; Sino-atrial node