R9AP stabilizes RGS11-G beta5 and accelerates the early light response of ON-bipolar cells

Vis Neurosci. 2010 Mar;27(1-2):9-17. doi: 10.1017/S0952523809990319. Epub 2010 Jan 26.


The rate-limiting step in the recovery of the photoreceptor light response is the hydrolysis of GTP by transducin, a reaction that is accelerated by the RGS9-Gbeta5 complex, and its membrane anchor, R9AP. Similar complexes, including RGS7, RGS11, and Gbeta5, are found in retinal ON-bipolar cell dendrites. Here, we present evidence that R9AP is also expressed in the dendritic tips of ON-bipolar cells. Immunofluorescent staining for R9AP revealed a punctate pattern of labeling in the outer plexiform layer, where it colocalized with mGluR6. In photoreceptors, R9AP is required for proteolytic stability of the entire regulator of G protein signaling complex, and we found that genetic deletion of R9AP also results in a marked reduction in the levels of RGS11 and Gbeta5 in the bipolar cell dendrites; the level of RGS7 was unaffected, suggesting the presence of another interaction partner to stabilize RGS7. To determine the effect of R9AP deletion on the response kinetics of ON-bipolar cells, we compared the electroretinogram (ERG) between wild-type and R9AP-deficient mice. The ERG b-wave, reflecting ON-bipolar cell activity, was delayed and larger in the R9AP-deficient mice. Our data indicate that R9AP is required for stable expression of RGS11-Gbeta5 in ON-bipolar cell dendrites. Furthermore, they suggest that the RGS11-Gbeta5-R9AP complex accelerates the initial ON-bipolar cell response to light.

Publication types

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

MeSH terms

  • Animals
  • Cell Line, Transformed
  • Dendrites / metabolism
  • Dendrites / ultrastructure
  • Electroretinography / methods
  • Evoked Potentials / genetics
  • GTP-Binding Protein beta Subunits / metabolism*
  • Gene Expression Regulation / genetics*
  • Humans
  • Light*
  • Membrane Proteins / deficiency
  • Membrane Proteins / physiology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microscopy, Electron, Transmission / methods
  • Reaction Time / genetics
  • Retina / cytology*
  • Retinal Bipolar Cells / physiology*
  • Retinal Bipolar Cells / ultrastructure
  • Synapses / metabolism
  • Synapses / ultrastructure
  • Transfection / methods


  • GTP-Binding Protein beta Subunits
  • Membrane Proteins
  • R9AP protein, mouse