Cavβ2 transcription start site variants modulate calcium handling in newborn rat cardiomyocytes.
In the heart, the main pathway for calcium influx is mediated by L-type calcium channels, a multi-subunit complex composed of the pore-forming subunit CaV1.2 and the auxiliary subunits CaVα2δ1 and CaVβ2. To date, five distinct CaVβ2 transcriptional start site (TSS) variants (CaVβ2a-e) varying only in the composition and length of the N-terminal domain have been described, each of them granting distinct biophysical properties to the L-type current. However, the physiological role of these variants in Ca(2+) handling in the native tissue has not been explored. Our results show that four of these variants are present in neonatal rat cardiomyocytes. The contribution of those CaVβ2 TSS variants on endogenous L-type current and Ca(2+) handling was explored by adenoviral-mediated overexpression of each CaVβ2 variant in cultured newborn rat cardiomyocytes. As expected, all CaVβ2 TSS variants increased L-type current density and produced distinctive changes on L-type calcium channel (LTCC) current activation and inactivation kinetics. The characteristics of the induced calcium transients were dependent on the TSS variant overexpressed. Moreover, the amplitude of the calcium transients varied depending on the subunit involved, being higher in cardiomyocytes transduced with CaVβ2a and smaller in CaVβ2d. Interestingly, the contribution of Ca(2+) influx and Ca(2+) release on total calcium transients, as well as the sarcoplasmic calcium content, was found to be TSS-variant-dependent. Remarkably, determination of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) messenger RNA (mRNA) abundance and cell size change indicates that CaVβ2 TSS variants modulate the cardiomyocyte hypertrophic state. In summary, we demonstrate that expression of individual CaVβ2 TSS variants regulates calcium handling in cardiomyocytes and, consequently, has significant repercussion in the development of hypertrophy.
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Cristian
C
Moreno
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Tamara
T
Hermosilla
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Danna
D
Morales
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Matías
M
Encina
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Leandro
L
Torres-Díaz
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Pablo
P
Díaz
Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, Santiago, Chile.
Daniela
D
Sarmiento
Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, Santiago, Chile.|Millennium Institute on Immunology and Immunotherapy, Santiago, Chile.
Felipe
F
Simon
Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile. dvarela@bitmed.med.uchile.cl.
Diego
D
Varela
D000200:Action Potentials; D000818:Animals; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000166:cytology / Q000254:growth & development; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D024363:Transcription Initiation Site
D020746:Calcium Channels, L-Type; C493217:calcium channel, l type beta2c subunit, rat
Auxiliary subunits; Calcium transients; Cardiomyocytes; L-type calcium current