J. Biochem, 2001, Vol. 129, No. 1 51-59
© 2001 Japanese Biochemical Society
other |
Effect of Brefeldin A on Melatonin Secretion of Chick Pineal Cells1
,
,2,,3,3
*Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033
CREST, Japan Science and Technology Corporation, National Institute for Physiological Sciences Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585
Laboratory of Ultrastructure Research, Department of Molecular Physiology, National Institute for Physiological Sciences Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585
3Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033. Tel/Fax: +81-3-5802-8871, E-mail: sfukada{at}mail.ecc.u-tokyo.ac.jp (Y.F.) or Laboratory of Ultrastructure Research, Department of Molecular Physiology, National Institute for Physiological Sciences, Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585. Tel: +81-564-55-7815, Fax: +81-564-52-7913, E-mail: mmurata{at}nips.ac.jp (M.M.)
Melatonin is secreted from the pineal gland in a circadian manner. It is well established that the synthesis of melatonin shows a diurnal rhythm reflecting a daily change in serotonin N-acetyltransferase (NAT) activity, and the overall secretion of melatonin requires a cellular release process, which is poorly understood. To investigate the possible involvement of Golgi-derived vesicles in the release, we examined the effect of brefeldin A (BFA), a reversible inhibitor of Golgi-mediated secretion, on melatonin secretion of cultured chick pineal cells. We show here that treatment with BFA completely disassembles the Golgi apparatus and reduces melatonin secretion. In more detailed time course experiments, however, the inhibition of melatonin secretion is only observed after the removal of BFA in parallel with the reassembly of the Golgi apparatus. This inhibition of melatonin secretion is not accompanied by accumulation of melatonin in the cells. These observations indicate that chick pineal melatonin is released independently of the Golgi-derived vesicles, and suggest inhibition of melatonin synthesis after the removal of BFA. By measuring the activities and mRNA levels of melatonin-synthesizing enzymes, we found that the removal of BFA specifically inhibits NAT activity at the protein level. On the other hand, BFA causes no detectable phase-shift of the chick pineal oscillator regulating the circadian rhythm of melatonin secretion. The results presented here suggest that the Golgi-mediated vesicular transport is involved in neither the melatonin release nor the time-keeping mechanism of the circadian oscillator, but rather contributes to the regulation of NAT activity.
1This work was supported in part by Grants-in-Aid from the Ministry of Education, Science, Sports and Culture of Japan. T.H. and T.K. are supported by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists.
2Present address: Department of Biological Sciences, Nara Women's University, Nara 630-8506.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  M. L. Ko, Y. Liu, L. Shi, D. Trump, and G. Y.-P. Ko Circadian Regulation of Retinoschisin in the Chick Retina Invest. Ophthalmol. Vis. Sci., April 1, 2008; 49(4): 1615 - 1621. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Hirota, T. Okano, K. Kokame, H. Shirotani-Ikejima, T. Miyata, and Y. Fukada Glucose Down-regulates Per1 and Per2 mRNA Levels and Induces Circadian Gene Expression in Cultured Rat-1 Fibroblasts J. Biol. Chem., November 8, 2002; 277(46): 44244 - 44251. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Doi, Y. Nakajima, T. Okano, and Y. Fukada Light-induced phase-delay of the chicken pineal circadian clock is associated with the induction of cE4bp4, a potential transcriptional repressor of cPer2 gene PNAS, July 3, 2001; 98(14): 8089 - 8094. [Abstract] [Full Text] [PDF]
|
|