CALMODULIN MEDIATES MELATONIN CYTOSKELETAL EFFECTS

In this article, we review the data concerning melatonin interactions with calmodulin. The kinetics of melatonin-calmodulin binding suggest that the hormone modulates cell activity through intracellular binding to the protein at physiological concentration ranges. Melatonin inter action with calmodulin may allow the hormone to modulate rhythmically many cellular functions. Melatonin's effect on tubulin polymerization, and cytoskeletal changes in MDCK and N1E-115 cells cultured with mela tonin, suggest that at low concentrations (10(-9) M) cytoskeletal effe cts are mediated by its antagonism to Ca2+-calmodulin. At higher conce ntrations (10(-5) M), non-specific binding of melatonin to tubulin occ urs thus overcoming the specific melatonin antagonism to Ca2+-calmodul in. Since the structures of melatonin and calmodulin are phylogenetica lly well preserved, calmodulin-melatonin interaction probably represen ts a major mechanism for regulation and synchronization of cell physio logy.