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Modulation of melatonin receptors and G-protein function by microtubules

Jarzynka, MJ; Passey, DK; Ignatius, PF; Melan, MA; Radio, NM; Jockers, R; Rasenick, MM; ... Witt-Enderby, PA; + view all (2006) Modulation of melatonin receptors and G-protein function by microtubules. J PINEAL RES , 41 (4) 324 - 336. 10.1111/j.1600-079X.2006.00371.x.

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Abstract

Chronic melatonin exposure produces microtubule rearrangements in Chinese hamster ovary (CHO) cells expressing the human MT1 melatonin receptor while at the same time desensitizing MT1 receptors. Because microtubule rearrangements parallel MT1 receptor desensitization, we tested whether microtubules modulate receptor responsiveness. We determined whether depolymerization of microtubules by Colcemid, which prevents melatonin-induced outgrowths in MT1-expressing CHO cells, also prevents MT1 receptor desensitization by affecting G(alpha)-GTP exchange on G-proteins. In this study, we found that depolymerization of microtubules in MT1 receptor expressing cells, prevented melatonin-induced receptor desensitization reflected by an increase in the number of high potency sites when compared with melatonin-treated cells. Further examination of the mechanism(s) underlying this desensitization suggested that these effects occurred at the level of G-proteins. Depolymerization of microtubules during melatonin-induced desensitization, attenuated forskolin-induced cAMP accumulation, the opposite of which usually occurs following melatonin exposure alone. Concomitant to this attenuation in the forskolin response was a reduction in the amount of G(i alpha) protein coupled to MT1 receptors and an increase in [P-32] azidoanilido GTP incorporation into G(i) proteins. These data are consistent with the findings that microtubule depolymerization did not affect MT1/G(q) coupling nor did it affect melatonin-induced phosphoinositide hydrolysis following melatonin exposure. However, interestingly, microtubule depolymerization enhanced melatonin-induced protein kinase C activation that was blocked in the presence of pertussis toxin. These data demonstrate that microtubule dynamics can modulate melatonin receptor function through their actions on G(i) proteins and impact on downstream signaling cascades.

Type: Article
Title: Modulation of melatonin receptors and G-protein function by microtubules
DOI: 10.1111/j.1600-079X.2006.00371.x
Keywords: Alzheimer's disease, desensitization, G-proteins, melatonin, melatonin receptors, microtubules, ADRENAL GLOMERULOSA CELLS, CYCLIC-AMP ACCUMULATION, PARS TUBERALIS CELLS, HAMSTER OVARY CELLS, SIGNAL-TRANSDUCTION, ALZHEIMERS-DISEASE, MT(1) MELATONIN, CIRCADIAN-RHYTHMS, PHOSPHOLIPASE-C, RAT-BRAIN
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Pop Health Sciences > Institute of Epidemiology and Health
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Pop Health Sciences > Institute of Epidemiology and Health > Epidemiology and Public Health
URI: http://discovery.ucl.ac.uk/id/eprint/147136
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