In vivo studies of the gamma subunit of retinal cGMP-phophodiesterase with a substitution of tyrosine-84

Biochem J. 2001 Feb 1;353(Pt 3):467-74. doi: 10.1042/0264-6021:3530467.

Abstract

The inhibitory rod cGMP phosphodiesterase gamma subunit (PDEgamma) is a major component of the photoresponse and is required to support rod integrity. Pdeg(tm1)/Pdeg(tm1) mice (which lack PDEgamma owing to a targeted disruption of the Pdeg gene) suffer from a very rapid and severe photoreceptor degeneration. The Y84G (Tyr(84)-->Gly) allele of PDEgamma has previously been shown in experiments carried out in vitro to reduce the regulatory control of the PDE catalytic core (PDEalphabeta) exerted by the wild-type gamma subunit. To determine the effects of this mutation on in vivo function, the murine opsin promoter was used to direct expression to the photoreceptors of +/Pdeg(tm1) mice of a mutant Y84G and a wild-type PDEgamma control transgene. The transgenic mice were crossed with Pdeg(tm1)/Pdeg(tm1) mice to generate animals able to synthesize only the transgenic PDEgamma. Our results showed that wild-type PDEgamma and Y84G transgenes could complement the Pdeg(tm1)/Pdeg(tm1) mutant for photoreceptor survival. The mutation caused a significant biochemical defect in PDE activation by transducin. However, the Y84G mutation did not fully eliminate the control of PDEgamma on the PDE catalytic core in vivo; the expression of the mutant subunit was associated with only a 10-fold reduction in the amplitude of the a-wave and a 1.5-fold decrease in the b-wave of the corneal electroretinogram. Unexpectedly, the mutation caused a much 'milder' phenotype in vivo than was predicted from the biochemical assays in vitro.

Publication types

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

MeSH terms

  • 3',5'-Cyclic-GMP Phosphodiesterases / chemistry
  • 3',5'-Cyclic-GMP Phosphodiesterases / metabolism*
  • Amino Acid Substitution
  • Animals
  • Cornea / enzymology
  • Cornea / physiology
  • Electroretinography
  • Male
  • Mice
  • Mice, Mutant Strains
  • Mice, Transgenic
  • Rod Cell Outer Segment / enzymology*
  • Tyrosine / metabolism*

Substances

  • Tyrosine
  • 3',5'-Cyclic-GMP Phosphodiesterases