EFFECT OF MELATONIN ON BETA-TUBULIN AND MAP2 EXPRESSION IN NIE-115 CELLS

Physiological concentrations of the pineal hormone melatonin induce an increase of microtubules in neuroblastoma NIE-115 cells. This effect is due to an increase in the polymerization state of tubulin. Concomit antly, higher levels of soluble beta P-tubulin are present in the trea ted cells. Unexpectedly, no significant changes in the levels of beta- tubulin or its mRNA occur in the presence of melatonin reflecting perh aps a strict control of its steady state in a physiological context. I n contrast, higher amounts of microtubule-associated-protein 2 are fou nd when the cells are exposed to me latonin. These findings support th e idea that tubulin polymerization process is one of the targets of me latonin action. Furthermore, our results might explain the increase in the length and number of neurites present in these cells when they ar e treated with this hormone.