Proteolytic cleavage and PKA phosphorylation of α1C subunit are not required for adrenergic regulation of CaV1.2 in the heart Academic Article uri icon

Overview

MeSH Major

  • Arrhythmias, Cardiac
  • Fibroblast Growth Factors
  • Genetic Predisposition to Disease
  • Ion Channels
  • Myocytes, Cardiac

abstract

  • Calcium influx through the voltage-dependent L-type calcium channel (CaV1.2) rapidly increases in the heart during "fight or flight" through activation of the β-adrenergic and protein kinase A (PKA) signaling pathway. The precise molecular mechanisms of β-adrenergic activation of cardiac CaV1.2, however, are incompletely known, but are presumed to require phosphorylation of residues in α1C and C-terminal proteolytic cleavage of the α1C subunit. We generated transgenic mice expressing an α1C with alanine substitutions of all conserved serine or threonine, which is predicted to be a potential PKA phosphorylation site by at least one prediction tool, while sparing the residues previously shown to be phosphorylated but shown individually not to be required for β-adrenergic regulation of CaV1.2 current (17-mutant). A second line included these 17 putative sites plus the five previously identified phosphoregulatory sites (22-mutant), thus allowing us to query whether regulation requires their contribution in combination. We determined that acute β-adrenergic regulation does not require any combination of potential PKA phosphorylation sites conserved in human, guinea pig, rabbit, rat, and mouse α1C subunits. We separately generated transgenic mice with inducible expression of proteolytic-resistant α1C Prevention of C-terminal cleavage did not alter β-adrenergic stimulation of CaV1.2 in the heart. These studies definitively rule out a role for all conserved consensus PKA phosphorylation sites in α1C in β-adrenergic stimulation of CaV1.2, and show that phosphoregulatory sites on α1C are not redundant and do not each fractionally contribute to the net stimulatory effect of β-adrenergic stimulation. Further, proteolytic cleavage of α1C is not required for β-adrenergic stimulation of CaV1.2.

publication date

  • August 22, 2017

Research

keywords

  • Academic Article

Identity

Language

  • eng

PubMed Central ID

  • PMC5576811

Digital Object Identifier (DOI)

  • 10.1073/pnas.1706054114

PubMed ID

  • 28784807

Additional Document Info

start page

  • 9194

end page

  • 9199

volume

  • 114

number

  • 34