Dual expression of constitutively active Gα s-protein-coupled receptors differentially establishes the resting activity of the cAMP-gated HCN2 channel in a single compartment

Biochem Biophys Res Commun. 2017 Dec 9;494(1-2):76-81. doi: 10.1016/j.bbrc.2017.10.082. Epub 2017 Oct 17.

Abstract

The hyperpolarization-activated cyclic nucleotide-gated 2 (HCN2) channel is a major subtype of the HCN channel family expressed in the nervous system that sets the membrane potential, regulates cell excitability and senses changes in the extracellular environment. Neurons express various Gαs-protein-coupled receptors (GPCRs), many of which show ligand-independent constitutive activity. These membrane-bound proteins are expressed in various subcellular compartments of neurons. Therefore, some proportion of HCN2 channels opens in response to the basal cAMP pool size produced by constitutively active GPCRs. Here, we employed an exogenous HEK293 expression system and voltage-clamp patch-clamp recordings to investigate basal HCN2 channel activity in the presence of two GPCRs with diverse basal activities in a single compartment. We utilized the β2-adrenoceptor (β2AR) together with odorant receptors (ORs), as both GPCR families are known to show strong basal activity. Consequently, β2AR alone strongly enhanced the activity of HCN2 channels, and co-expression of ORs further diversified the HCN2 channel activity, which was totally abolished by an adenylate cyclase inhibitor. Thus, we conclude that the dual expression of constitutively active GPCRs establishes the diverse range of the basal cAMP pool size in resting cells through mutual additive or suppressive interactions, even in the absence of external stimulation.

Keywords: Basal cAMP pool; Constitutively active GPCRs; HCN channel; Single compartment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cyclic AMP / metabolism*
  • GTP-Binding Protein alpha Subunits, Gs / metabolism*
  • HEK293 Cells
  • Humans
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / genetics
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / metabolism*
  • Ion Channel Gating
  • Patch-Clamp Techniques
  • Potassium Channels / genetics
  • Potassium Channels / metabolism*
  • Receptors, Adrenergic, beta-2 / genetics
  • Receptors, Adrenergic, beta-2 / metabolism
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, Odorant / genetics
  • Receptors, Odorant / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism

Substances

  • HCN2 protein, human
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
  • Potassium Channels
  • Receptors, Adrenergic, beta-2
  • Receptors, G-Protein-Coupled
  • Receptors, Odorant
  • Recombinant Proteins
  • Cyclic AMP
  • GTP-Binding Protein alpha Subunits, Gs