AIM: To explore the protective effects of melatonin (Mel) on the abnormal phosphorylation of neuronal cytoskeletal proteins. METHODS: We generated a neuroblastoma (SH-SY5Y) cell system in which cytoskeletal proteins are abnormally phosphorylated resulting in microtubule disruption due to the marked inhibition of protein phosphatase activities by okadaic acid (OA). RESULTS: OA-induced declines in cell viability and mitochondrial metabolic activity were remarkably prevented by Mel. In addition, the hyperphosphorylation/accumulation of neurofilament- (NF-) H/M subunits and the disruption of microtubules, induced by OA, were significantly inhibited by Mel. CONCLUSION: Our results suggest multiple protective functions of Mel against a series of pathological lesions known to culminate in AD, including abnormal phosphorylation of cytoskeletal proteins, microtubule disassembly and mitochondrion-initiated cell toxicity. AIM: To explore the protective effects of melatonin (Mel) on the abnormal phosphorylation of neuronal cytoskeletal proteins. METHODS: We generated a neuroblastoma (SH-SY5Y) cell system in which cytoskeletal proteins are abnormally phosphorylated resulting in microtubule disruption due to the marked inhibition of protein phosphatase activities by okadaic acid (OA). RESULTS: OA-induced declines in cell viability and mitochondrial metabolic activity were remarkably prevented by Mel. In addition, the hyperphosphorylation / accumulation of neurofilament- (NF-) H / M subunits and the disruption of microtubules, induced by OA, were significantly inhibited by Mel. CONCLUSION: Our results suggest multiple protective functions of Mel against a series of pathological lesions known to culminate in AD, including abnormal phosphorylation of cytoskeletal proteins, microtubule disassembly and mitochondrion-initiated cell toxicity.