Colocalization of pinopsin with two types of G-protein alpha-subunits in the chicken pineal gland

Cell Tissue Res. 2000 Feb;299(2):245-51. doi: 10.1007/s004419900145.


Pinopsin is a photoreceptive molecule present in the outer segments of chicken pinealocytes. In this paper, the localization of alpha-subunits of G-proteins, rod transducin (Gt1) and Gq/11, was examined by immunoelectron microscopy to investigate whether these G-proteins colocalize with pinopsin in the outer segments. Ultrathin sections of the chicken pineal gland were double-immunolabeled with antibodies to pinopsin and either Gt1alpha or Gq/11alpha. As shown previously, the outer segments around the follicular lumen exhibited divergent morphology with ciliary, bulbous, or lamellate shapes, and most of them displayed pinopsin immunoreactivity. The majority (>90%) of pinopsin-immunopositive outer segments were labeled by anti-Gt1alpha and/or anti-Gq/11alpha antibodies. Application of double-immunolabeling to serial sections demonstrated that a large number of the pinopsin-immunopositive outer segments contained both Gt1alpha and Gq/11alpha immunoreactivities. These results suggest that Gt1alpha and Gq/11alpha are functionally coupled with light-activated pinopsin within a single outer segment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Avian Proteins
  • Chickens
  • Circadian Rhythm
  • Heterotrimeric GTP-Binding Proteins / analysis*
  • Microscopy, Immunoelectron
  • Nerve Tissue Proteins / analysis*
  • Pineal Gland / chemistry*
  • Pineal Gland / cytology
  • Pineal Gland / ultrastructure
  • Rod Opsins / analysis*
  • Transducin / analysis


  • Avian Proteins
  • Nerve Tissue Proteins
  • Rod Opsins
  • pinopsin protein, chicken
  • Heterotrimeric GTP-Binding Proteins
  • Transducin