Dephosphorylation by protein phosphatase 2A regulates visual pigment regeneration and the dark adaptation of mammalian photoreceptors

Alexander V. Kolesnikov, Tivadar Orban, Hui Jin, Celine Brooks, Lukas Hofmann, Zhiqian Dong, Maxim Sokolov, Krzysztof Palczewski, Vladimir J. Kefalov

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Resetting of G-protein–coupled receptors (GPCRs) from their active state back to their biologically inert ground state is an integral part of GPCR signaling. This “on–off” GPCR cycle is regulated by reversible phosphorylation. Retinal rod and cone photoreceptors arguably represent the best-understood example of such GPCR signaling. Their visual pigments (opsins) are activated by light, transduce the signal, and are then inactivated by a GPCR kinase and arrestin. Although pigment inactivation by phosphorylation is well understood, the enzyme(s) responsible for pigment dephosphorylation and the functional significance of this reaction remain unknown. Here, we show that protein phosphatase 2A (PP2A) acts as opsin phosphatase in both rods and cones. Elimination of PP2A substantially slows pigment dephosphorylation, visual chromophore recycling, and ultimately photoreceptor dark adaptation. These findings demonstrate that visual pigment dephosphorylation regulates the dark adaptation of photoreceptors and provide insights into the role of this reaction in GPCR signaling.

Original languageEnglish
Pages (from-to)E9675-E9684
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number45
DOIs
StatePublished - Nov 7 2017

Keywords

  • Dark adaptation
  • GPCRs
  • PP2A
  • Photoreceptors
  • Visual cycle

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