Rhythmic expression of microRNA-26a regulates the L-type voltage-gated calcium channel alpha1C subunit in chicken cone photoreceptors

J Biol Chem. 2009 Sep 18;284(38):25791-803. doi: 10.1074/jbc.M109.033993. Epub 2009 Jul 16.

Abstract

MicroRNAs (miRNAs) modulate gene expression by degrading or inhibiting translation of messenger RNAs (mRNAs). Here, we demonstrated that chicken microRNA-26a (gga-mir-26a) is a key posttranscriptional regulator of photoreceptor L-type voltage-gated calcium channel alpha1C subunit (L-VGCCalpha1C) expression, and its own expression has a diurnal rhythm, thereby explaining the rhythmic nature of L-VGCCalpha1Cs. Circadian oscillators in retinal photoreceptors provide a mechanism that allows photoreceptors to anticipate daily illumination changes. In photoreceptors, L-VGCC activities are under circadian control, which are higher at night and lower during the day. Interestingly, the mRNA level of VGCCalpha1D oscillates, but those for VGCCalpha1C do not. However, the protein expression of both VGCCalpha1C and alpha1D are higher at night in cone photoreceptors. The underlying mechanism regulating L-VGCCalpha1C protein expression was not clear until now. In vitro targeting reporter assays verified that gga-mir-26a specifically targeted the L-VGCCalpha1C 3'-untranslated region, and gga-mir-26a expression in the retina peaked during the day. After transfection with gga-mir-26a, L-VGCCalpha1C protein expression and L-VGCC current density decreased. Therefore, the rhythmic expression of gga-mir-26a regulated the protein expression of the L-VGCCalpha1C subunit. Additionally, both CLOCK (circadian locomoter output cycles kaput) and CREB (cAMP-response element-binding protein-1) activated gga-mir-26a expression in vitro. This result implies that gga-mir-26a might be a downstream target of circadian oscillators. Our work has uncovered new functional roles for miRNAs in the regulation of circadian rhythms in cone photoreceptors. Circadian regulated miRNAs could serve as the link between the core oscillator and output signaling that further govern biological functions.

Publication types

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

MeSH terms

  • 3' Untranslated Regions / genetics
  • 3' Untranslated Regions / metabolism
  • Animals
  • Biological Clocks / physiology*
  • CLOCK Proteins
  • COS Cells
  • Calcium Channels, L-Type / biosynthesis*
  • Calcium Channels, L-Type / genetics
  • Chickens / genetics
  • Chickens / metabolism*
  • Chlorocebus aethiops
  • Circadian Rhythm / physiology*
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • Gene Expression Regulation / physiology*
  • MicroRNAs / biosynthesis*
  • MicroRNAs / genetics
  • Retinal Cone Photoreceptor Cells / cytology
  • Retinal Cone Photoreceptor Cells / metabolism*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism

Substances

  • 3' Untranslated Regions
  • Calcium Channels, L-Type
  • Cyclic AMP Response Element-Binding Protein
  • MicroRNAs
  • Trans-Activators
  • CLOCK Proteins