Rod-type transducin alpha-subunit mediates a phototransduction pathway in the chicken pineal gland

J Neurochem. 2000 Jul;75(1):217-24. doi: 10.1046/j.1471-4159.2000.0750217.x.


The chicken pineal gland is a photosensitive neuroendocrine organ producing melatonin in circadian clock-regulated and light-sensitive manners. To understand the relationship between the photoreceptive molecule pinopsin and the light-dependent melatonin suppression that is sensitive to pertussis toxin treatment, we have searched for pertussis toxin-sensitive G protein alpha-subunits expressed in the chicken pineal gland. Here we report the cDNA cloning of the pineal transducin alpha-subunit (Gtalpha), which is highly homologous to human retinal rod cell-specific Gt(1)alpha. Concurrent cDNA cloning of chicken retinal Gt(1)alpha and Gt(2)alpha (rod and cone cell-specific alpha-subunits of transducin, respectively) revealed that the chicken pineal Gtalpha is identical to the retinal Gt(1)alpha. Double-immunostaining analysis of the chicken pineal sections localized Gt(1)alpha-immunoreactivity in the rudimentary outer segments of both follicular and parafollicular pinealocytes that were immunopositive to anti-pinopsin antibody. To examine whether pineal Gt(1)alpha is involved in the pineal phototransduction pathway, trypsin protection assay was applied for detecting the conversion of GDP-bound Gt(1)alpha into the guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS)-bound form in the pineal membrane homogenate. It was clearly demonstrated that the pineal Gt(1)alpha is activated in a light-dependent manner in the presence of GTPgammaS. These data together suggest strongly that pineal Gt(1)alpha mediates the phototransduction pathway triggered by pinopsin in the chicken pinealocytes.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Avian Proteins
  • Chickens*
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Guanosine Diphosphate / metabolism
  • Light
  • Light Signal Transduction*
  • Male
  • Molecular Sequence Data
  • Nerve Tissue Proteins / analysis
  • Nerve Tissue Proteins / physiology
  • Pineal Gland / chemistry
  • Pineal Gland / physiology*
  • Rod Opsins / analysis
  • Rod Opsins / physiology
  • Sequence Homology
  • Transducin / analysis
  • Transducin / chemistry
  • Transducin / physiology*


  • Avian Proteins
  • Nerve Tissue Proteins
  • Rod Opsins
  • pinopsin protein, chicken
  • Guanosine Diphosphate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Transducin