Phosducin regulates the expression of transducin βγ subunits in rod photoreceptors and does not contribute to phototransduction adaptation

Claudia M. Krispel, Maxim Sokolov, Yen Ming Chen, Hongman Song, Rolf Herrmann, Vadim Y. Arshavsky, Marie E Burns

Research output: Contribution to journalArticle

23 Scopus citations


For over a decade, phosducin's interaction with the βγ subunits of the G protein, transducin, has been thought to contribute to light adaptation by dynamically controlling the amount of transducin heterotrimer available for activation by photoexcited rhodopsin. In this study we directly tested this hypothesis by characterizing the dark- and light-adapted response properties of phosducin knockout (Pd-/-) rods. Pd-/- rods were notably less sensitive to light than wild-type (WT) rods. The gain of transduction, as measured by the amplification constant using the Lamb-Pugh model of activation, was 32% lower in Pd-/- rods than in WT rods. This reduced amplification correlated with a 36% reduction in the level of transducin βγ-subunit expression, and thus available heterotrimer in Pd-/- rods. However, commonly studied forms of light adaptation were normal in the absence of phosducin. Thus, phosducin does not appear to contribute to adaptation mechanisms of the outer segment by dynamically controlling heterotrimer availability, but rather is necessary for maintaining normal transducin expression and therefore normal flash sensitivity in rods.

Original languageEnglish (US)
Pages (from-to)303-312
Number of pages10
JournalJournal of General Physiology
Issue number3
StatePublished - Sep 2007


ASJC Scopus subject areas

  • Physiology

Cite this