Prolonged photoresponses and defective adaptation in rods of Gbeta5-/- mice

J Neurosci. 2003 Aug 6;23(18):6965-71. doi: 10.1523/JNEUROSCI.23-18-06965.2003.


Timely deactivation of G-protein signaling is essential for the proper function of many cells, particularly neurons. Termination of the light response of retinal rods requires GTP hydrolysis by the G-protein transducin, which is catalyzed by a protein complex that includes regulator of G-protein signaling RGS9-1 and the G-protein beta subunit Gbeta5-L. Disruption of the Gbeta5 gene in mice (Gbeta5-/-) abolishes the expression of Gbeta5-L in the retina and also greatly reduces the expression level of RGS9-1. We examined transduction in dark- and light-adapted rods from wild-type and Gbeta5-/- mice. Responses of Gbeta5-/- rods were indistinguishable in all respects from those of RGS9-/- rods. Loss of Gbeta5-L (and RGS9-1) had no effect on the activation of the G-protein cascade, but profoundly slowed its deactivation and interfered with the speeding of incremental dim flashes during light adaptation. Both RGS9-/- and Gbeta5-/- responses were consistent with another factor weakly regulating GTP hydrolysis by transducin in a manner proportional to the inward current. Our results indicate that a complex containing RGS9-1-Gbeta5-L is essential for normal G-protein deactivation and rod function. In addition, our light adaptation studies support the notion than an additional weak GTPase-accelerating factor in rods is regulated by intracellular calcium and/or cGMP.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptation, Ocular / physiology*
  • Animals
  • Darkness
  • GTP-Binding Protein beta Subunits*
  • Heterotrimeric GTP-Binding Proteins / deficiency*
  • Heterotrimeric GTP-Binding Proteins / genetics
  • In Vitro Techniques
  • Light
  • Macromolecular Substances
  • Mice
  • Mice, Knockout
  • Photic Stimulation
  • RGS Proteins / deficiency
  • RGS Proteins / genetics
  • Reaction Time
  • Retina / cytology
  • Retina / physiology
  • Retinal Rod Photoreceptor Cells / metabolism
  • Retinal Rod Photoreceptor Cells / physiology*
  • Retinal Rod Photoreceptor Cells / radiation effects
  • Sensory Thresholds
  • Transducin / metabolism
  • Vision, Ocular / genetics
  • Vision, Ocular / physiology*
  • Vision, Ocular / radiation effects


  • GTP-Binding Protein beta Subunits
  • Gnb5 protein, mouse
  • Macromolecular Substances
  • RGS Proteins
  • regulator of g-protein signaling 9
  • Heterotrimeric GTP-Binding Proteins
  • Transducin