Preferences of transmembrane helices for cooperative amplification of G(alpha)s and G (alpha)q signaling of the thyrotropin receptor

Cell Mol Life Sci. 2008 Dec;65(24):4028-38. doi: 10.1007/s00018-008-8530-3.

Abstract

The majority of constitutively activating mutations (CAMs) of the thyroid-stimulating hormone receptor display a partially activated receptor. Thus, full receptor activation requires a multiplex activation process. To define impacts of different transmembrane helices (TMHs) on cooperative signal transduction, we combined single CAMs in particular TMHs to double mutations and measured second messenger accumulation of the G(alpha)s and the G(alpha)q pathway. We observed a synergistic increase for basal activity of the G(alpha)s pathway, for all characterized double mutants except for two combinations. Each double mutation, containing CAMs in TMH2, 6 and 7 showed the highest constitutive activities, suggesting that these helices contribute most to G(alpha)s-mediated signaling. No single CAM revealed constitutive activity for the G(alpha)q pathway. The double mutations with CAMs from TMH1, 2, 3 and 6 also exhibited increase for basal G(alpha)q signaling. Our results suggest that TMH2, 6, 7 show selective preferences towards G(alpha)s signaling, and TMH1, 2, 3, 6 for G(alpha)q signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Chlorocebus aethiops
  • Cyclic AMP / metabolism
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism*
  • GTP-Binding Protein alpha Subunits, Gs / metabolism*
  • Humans
  • Inositol Phosphates / metabolism
  • Models, Molecular
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Mutation / genetics
  • Protein Structure, Secondary
  • Receptors, Thyrotropin / chemistry*
  • Receptors, Thyrotropin / metabolism*
  • Signal Transduction* / drug effects
  • Structure-Activity Relationship
  • Thyrotropin / pharmacology

Substances

  • Inositol Phosphates
  • Mutant Proteins
  • Receptors, Thyrotropin
  • Thyrotropin
  • Cyclic AMP
  • GTP-Binding Protein alpha Subunits, Gq-G11
  • GTP-Binding Protein alpha Subunits, Gs