Phosphatidylinositol 3 kinase-Akt signaling serves as a circadian output in the retina

J Neurochem. 2009 Mar;108(6):1607-20. doi: 10.1111/j.1471-4159.2009.05931.x. Epub 2009 Jan 24.

Abstract

The daily rhythm of L-type voltage-gated calcium channels (L-VGCCs) is part of the cellular mechanism underlying the circadian regulation of retina physiology and function. However, it is not completely understood how the circadian clock regulates L-VGCC current amplitudes without affecting channel gating properties. The phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt) signaling pathway has been implicated in many vital cellular functions especially in trophic factor-induced ion channel trafficking and membrane insertion. Here, we report that PI3K-Akt signaling participates in the circadian phase-dependent modulation of L-VGCCs. We found that there was a circadian regulation of Akt phosphorylation on Thr308 that peaked at night. Inhibition of PI3K or Akt significantly decreased L-VGCC current amplitudes and the expression of membrane-bound L-VGCCalpha1D subunit only at night but not during the subjective day. Photoreceptors transfected with a dominant negative Ras had significantly less expression of phosphorylated Akt and L-VGCCalpha1D subunit compared with non-transfected photoreceptors. Interestingly, both PI3K-Akt and extracellular signal-related kinase were downstream of Ras, and they appeared to be parallel and equally important pathways to regulate L-VGCC rhythms. Inhibition of either pathway abolished the L-VGCC rhythm indicating that there were multiple mechanisms involved in the circadian regulation of L-VGCC rhythms in retina photoreceptors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biophysical Phenomena / physiology
  • Biotinylation
  • Calcium Channels, L-Type / physiology
  • Cells, Cultured
  • Chick Embryo
  • Circadian Rhythm / physiology*
  • Electric Stimulation
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / physiology
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Oncogene Protein v-akt / metabolism*
  • Patch-Clamp Techniques / methods
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Protein Transport / drug effects
  • Protein Transport / physiology
  • Retina / drug effects
  • Retina / physiology*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Transfection

Substances

  • Calcium Channels, L-Type
  • Enzyme Inhibitors
  • Phosphatidylinositol 3-Kinases
  • Oncogene Protein v-akt