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 α- subunits expressed in the chicken pineal gland. Here we report the cDNA cloning of the pineal transducin α-subunit (Gtα), which is highly homologous to human retinal rod cell-specific Gt1α. Concurrent cDNA cloning of chicken retinal Gt1α and Gt2α (rod and cone cell-specific α-subunits of transducin, respectively) revealed that the chicken pineal Gtα is identical to the retinal Gt1α. Double-immunostaining analysis of the chicken pineal sections localized Gt1α-immunoreactivity in the rudimentary outer segments of both follicular and parafollicular pinealocytes that were immunopositive to anti-pinopsin antibody. To examine whether pineal Gt1α is involved in the pineal phototransduction pathway, trypsin protection assay was applied for detecting the conversion of GDP-bound Gt1α into the guanosine 5'-O-(3-thiotriphosphate) (GTPγS)-bound form in the pineal membrane homogenate. It was clearly demonstrated that the pineal Gt1α is activated in a light-dependent manner in the presence of GTPγS. These data together suggest strongly that pineal Gt1α mediates the phototransduction pathway triggered by pinopsin in the chicken pinealocytes.
|ジャーナル||Journal of neurochemistry|
|出版ステータス||Published - 2000|
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