Human neuroblastoma SH-SY5Y cells treated with okadaic acid express phosphorylated high molecular weight tau-immunoreactive protein species.

•OA treatment of SH-SY5Y cells induced 100 kDa tau-immunoreactive species.•Induced HMW species were reactive to anti-tau-pS202 and anti-tau-p396 antibodies.•HMW species were heat-stable and stable in SDS, urea and guanidine.•OA-induced HMW species could not be detected by several anti-total tau antibodies.•HMW proteins may represent tau oligomers or phosphoproteins cross-reacting with tau.