A caveolin-binding domain in the HCN4 channels mediates functional interaction with caveolin proteins

Andrea Barbuti, Angela Scavone, Nausicaa Mazzocchi, Benedetta Terragni, Mirko Baruscotti, Dario DiFrancesco

Research output: Contribution to journalArticlepeer-review

Abstract

Pacemaker (HCN) channels have a key role in the generation and modulation of spontaneous activity of sinoatrial node myocytes. Previous work has shown that compartmentation of HCN4 pacemaker channels within caveolae regulates important functions, but the molecular mechanism responsible is still unknown. HCN channels have a conserved caveolin-binding domain (CBD) composed of three aromatic amino acids at the N-terminus; we sought to evaluate the role of this CBD in channel-protein interaction by mutational analysis. We generated two HCN4 mutants with a disrupted CBD (Y259S, F262V) and two with conservative mutations (Y259F, F262Y). In CHO cells expressing endogenous caveolin-1 (cav-1), alteration of the CBD shifted channels activation to more positive potentials, slowed deactivation and made Y259S and F262V mutants insensitive to cholesterol depletion-induced caveolar disorganization. CBD alteration also caused a significant decrease of current density, due to a weaker HCN4-cav-1 interaction and accumulation of cytoplasmic channels. These effects were absent in mutants with a preserved CBD. In caveolin-1-free fibroblasts, HCN4 trafficking was impaired and current density reduced with all constructs; the activation curve of F262V was not altered relative to wt, and that of Y259S displayed only half the shift than in CHO cells. The conserved CBD present in all HCN isoforms mediates their functional interaction with caveolins. The elucidation of the molecular details of HCN4-cav-1 interaction can provide novel information to understand the basis of cardiac phenotypes associated with some forms of caveolinopathies.

Original languageEnglish
Pages (from-to)187-195
Number of pages9
JournalJournal of Molecular and Cellular Cardiology
Volume53
Issue number2
DOIs
Publication statusPublished - Aug 2012

Keywords

  • Caveolae
  • Caveolin binding domain
  • HCN
  • Pacemaker channels
  • Subcellular localization
  • Trafficking

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine

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