Instability of GGL Domain-containing RGS Proteins in Mice Lacking the Fifth Member of the G-protein Beta Subunit

Abstract

Abstract: : Purpose: Gß5-L interacts with the GGL domain of RGS9-1 in retinal photoreceptors. In the retina of RGS9^-/- mouse the Gß5-L protein is lost but its mRNA is present. This study aims to examine the effects of removing Gß5 on RGS9-1 level in the photoreceptors and on other GGL domain-containing RGS proteins in other tissues. Methods: Standard gene targeting approach was employed to delete a 2.7 Kb XhoI fragment containing the exon3 of the Gß5 gene in mouse. Rabbit polyclonal antibodies against RGS6, RGS7 and RGS11 were generated and used in Western Blot analyses to determine endogenous GGL domain-containing RGS protein levels from various mouse tissues. The mRNA levels of these RGS proteins were determined by Northern Blot analyses. Results: We generated Gß5 heterozygous knockout (Gß5^+/-) mice in a mixed background of C57BLACK/6 and 129SEVE. The homozygous knockout (Gß5^-/-) mice were derived from inbreeding of the Gß5^+/- mice. Approximately two thirds of the Gß5^-/- pups derived from the heterozygous mating (Gß5^+/- X Gß5^+/-) died before weaning. We were able to establish Gß5^-/- mouse lines by mating the surviving homozygous knockout individuals. The loss of both Gß5-S and Gß5-L in the Gß5^-/- mice was confirmed by Western Blot. In retinas of Gß5^-/- mice, <5% of the RGS9-1 protein was left but RGS7, RGS6 and RGS11 were all undetectable. The mRNA levels for all four GGL domain-containing RGS proteins were found comparable to the wild-type level. The level of other proteins involved in phototransduction was normal. In the striatum of Gß5^-/- mice, RGS9-2 and RGS7 proteins were undetectable while their mRNA levels remained normal. RGS4 and G_γ2 protein levels were unaffected in the absence of Gß5. Conclusions: Our results indicate that Gß5 interacts with all GGL domain-containing RGS proteins in vivo and such interactions are essential for their stability. The Gß5^-/- mice are thus useful to study the physiological roles of GGL domain-containing RGS proteins in vivo.

Keywords: animal model • gene/expression • photoreceptors