Hyperphosphorylated tau in SY5Y cells: similarities and dissimilarities toabnormally hyperphosphorylated tau from Alzheimer disease brain

Unlike normal tau, abnormally hyperphosphorylated tau (AD P-tau) from Alzhe imer disease (AD) does not promote but instead inhibits microtubule assembl y and disrupts already formed microtubules, Tau in the human neuroblastoma cell line SH-SY5Y is hyperphosphorylated at several of the same sites as AD P-tau, and accumulates in the cell body without any association to the cel lular microtubule network. The aim of the present study was to elucidate wh y the SY5Y tau does not affect the viability of the cells, We found that, l ike AD P-tau, SY5Y tau because of hyperphosphorylation does not bind to mic rotubules and inhibits the tau-promoted assembly of microtubules. However, the tau/HMW MAP ratio is about 10 times less in SY5Y cells than in AD brain . These findings suggest that the hyperphosphorylated tau from SY5Y cells h as similar biological characteristics as AD P-tau from AD brain, but is not lethal to the SY5Y cells because of its ion tau/HMW MAP ratio. (C) 1999 Fe deration of European Biochemical Societies.