Cul3-Klhl18 ubiquitin ligase modulates rod transducin translocation during light-dark adaptation

EMBO J. 2019 Dec 2;38(23):e101409. doi: 10.15252/embj.2018101409. Epub 2019 Nov 7.


Adaptation is a general feature of sensory systems. In rod photoreceptors, light-dependent transducin translocation and Ca2+ homeostasis are involved in light/dark adaptation and prevention of cell damage by light. However, the underlying regulatory mechanisms remain unclear. Here, we identify mammalian Cul3-Klhl18 ubiquitin ligase as a transducin translocation modulator during light/dark adaptation. Under dark conditions, Klhl18-/- mice exhibited decreased rod light responses and subcellular localization of the transducin α-subunit (Tα), similar to that observed in light-adapted Klhl18+/+ mice. Cul3-Klhl18 promoted ubiquitination and degradation of Unc119, a rod Tα-interacting protein. Unc119 overexpression phenocopied Tα mislocalization observed in Klhl18-/- mice. Klhl18 weakly recognized casein kinase-2-phosphorylated Unc119 protein, which is dephosphorylated by Ca2+ -dependent phosphatase calcineurin. Calcineurin inhibition increased Unc119 expression and Tα mislocalization in rods. These results suggest that Cul3-Klhl18 modulates rod Tα translocation during light/dark adaptation through Unc119 ubiquitination, which is affected by phosphorylation. Notably, inactivation of the Cul3-Klhl18 ligase and calcineurin inhibitors FK506 and cyclosporine A that are known immunosuppressant drugs repressed light-induced photoreceptor damage, suggesting potential therapeutic targets.

Keywords: G protein; cilium; post-translational modification; protein transport; retina.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cullin Proteins / physiology*
  • Dark Adaptation*
  • Female
  • Light*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Phosphorylation
  • Photoreceptor Cells, Vertebrate / metabolism
  • Protein Transport
  • Retina / injuries
  • Retina / metabolism
  • Retina / pathology
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Transducin / genetics
  • Transducin / metabolism*
  • Ubiquitin / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • Cul3 protein, mouse
  • Cullin Proteins
  • Gnat1 protein, mouse
  • Klhl18 protein, mouse
  • Ubiquitin
  • Unc119 protein, mouse
  • Transducin