Activation-dependent hindrance of photoreceptor G protein diffusion by lipid microdomains

J Biol Chem. 2008 Oct 31;283(44):30015-24. doi: 10.1074/jbc.M803953200. Epub 2008 Aug 18.


The dynamics of G protein-mediated signal transduction depend on the two-dimensional diffusion of membrane-bound G proteins and receptors, which has been suggested to be rate-limiting for vertebrate phototransduction, a highly amplified G protein-coupled signaling pathway. Using fluorescence recovery after photobleaching (FRAP), we measured the diffusion of the G protein transducin alpha-subunit (Galpha(t)) and the G protein-coupled receptor rhodopsin on disk membranes of living rod photoreceptors from transgenic Xenopus laevis. Treatment with either methyl-beta-cyclodextrin or filipin III to disrupt cholesterol-containing lipid microdomains dramatically accelerated diffusion of Galpha(t) in its GTP-bound state and of the rhodopsin-Galphabetagamma(t) complex but not of rhodopsin or inactive GDP-bound Galphabetagamma. These results imply an activity-dependent sequestration of G proteins into cholesterol-dependent lipid microdomains, which limits diffusion and exclude the majority of free rhodopsin and the free G protein heterotrimer. Our data offer a novel demonstration of lipid microdomains in the internal membranes of living sensory neurons.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cholesterol / metabolism
  • Densitometry
  • GTP-Binding Proteins / chemistry*
  • GTP-Binding Proteins / metabolism
  • Guanosine Triphosphate / chemistry
  • Insecta
  • Lipids / chemistry*
  • Membrane Microdomains / chemistry*
  • Microscopy, Fluorescence
  • Neurons / metabolism
  • Photoreceptor Cells / metabolism
  • Protein Structure, Tertiary
  • Rhodopsin / chemistry
  • Signal Transduction
  • Xenopus laevis


  • Lipids
  • Guanosine Triphosphate
  • Rhodopsin
  • Cholesterol
  • GTP-Binding Proteins