Slowed recovery of rod photoresponse in mice lacking the GTPase accelerating protein RGS9-1.
Timely deactivation of the alpha-subunit of the rod G-protein transducin (Galphat) is essential for the temporal resolution of rod vision. Regulators of G-protein signalling (RGS) proteins accelerate hydrolysis of GTP by the alpha-subunits of heterotrimeric G proteins in vitro. Several retinal RGS proteins can act in vitro as GTPase accelerating proteins (GAP) for Galphat. Recent reconstitution experiments indicate that one of these, RGS9-1, may account for much of the Galphat GAP activity in rod outer segments (ROS). Here we report that ROS membranes from mice lacking RGS9-1 hydrolyse GTP more slowly than ROS membranes from control mice. The Gbeta5-L protein that forms a complex with RGS9-1 was absent from RGS9-/- retinas, although Gbeta5-L messenger RNA was still present. The flash responses of RGS9-/- rods rose normally, but recovered much more slowly than normal. We conclude that RGS9-1, probably in a complex with Gbeta5-L, is essential for acceleration of hydrolysis of GTP by Galphat and for normal recovery of the photoresponse.
Pubmed ID: 10676965 RIS Download
3',5'-Cyclic-GMP Phosphodiesterases | Animals | Cyclic Nucleotide Phosphodiesterases, Type 6 | GTP Phosphohydrolases | Guanosine Triphosphate | Hydrolysis | Mice | Mice, Inbred Strains | Mice, Knockout | Mice, Transgenic | RGS Proteins | Retinal Rod Photoreceptor Cells | Rod Cell Outer Segment | Transducin | Vision, Ocular