LRP6 mediates cAMP generation by G protein-coupled receptors through regulating the membrane targeting of Gα(s)

Sci Signal. 2011 Mar 15;4(164):ra15. doi: 10.1126/scisignal.2001464.

Abstract

Ligand binding to certain heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) stimulates the rapid synthesis of cyclic adenosine monophosphate (cAMP) through the G protein α(s) subunit, which activates adenylyl cyclase (AC). We found that the transmembrane receptor low-density lipoprotein receptor-related protein 6 (LRP6), a co-receptor for Wnt proteins, bound to the Gα(s)βγ heterotrimer and that knockdown of LRP6 attenuated cAMP production by various GPCRs, including parathyroid hormone receptor 1 (PTH1R). Knockdown of LRP6 disrupted the localization of Gα(s) to the plasma membrane, which led to a decrease in the extent of coupling of Gα(s) to PTH1R and inhibited the production of cAMP and the activation of cAMP-dependent protein kinase (PKA) in response to PTH. PKA phosphorylated LRP6, which enhanced the binding of Gα(s) to LRP6, its localization to the plasma membrane, and the production of cAMP in response to PTH. Decreased PTH-dependent cAMP production was observed in single cells in which LRP6 was knocked down or mutated at the PKA site by monitoring the cAMP kinetics. Thus, we suggest that the binding of Gα(s) to LRP6 is required to establish a functional GPCR-Gα(s)-AC signaling pathway for the production of cAMP, providing an additional regulatory component to the current GPCR-cAMP paradigm.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites
  • Cell Line
  • Cell Membrane / metabolism
  • Cyclic AMP / biosynthesis*
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • GTP-Binding Protein alpha Subunits, Gs / metabolism*
  • Gene Knockdown Techniques
  • Humans
  • LDL-Receptor Related Proteins / antagonists & inhibitors
  • LDL-Receptor Related Proteins / genetics
  • LDL-Receptor Related Proteins / metabolism*
  • Ligands
  • Low Density Lipoprotein Receptor-Related Protein-5
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Mice
  • Models, Biological
  • Molecular Sequence Data
  • Phosphorylation
  • RNA, Small Interfering / genetics
  • Rats
  • Receptor, Parathyroid Hormone, Type 1 / metabolism
  • Receptors, G-Protein-Coupled / metabolism*
  • Second Messenger Systems
  • Signal Transduction

Substances

  • LDL-Receptor Related Proteins
  • LRP5 protein, human
  • LRP6 protein, human
  • Ligands
  • Low Density Lipoprotein Receptor-Related Protein-5
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Lrp5 protein, mouse
  • Lrp6 protein, mouse
  • RNA, Small Interfering
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, G-Protein-Coupled
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • GTP-Binding Protein alpha Subunits, Gs