Tau dephosphorylation at tau-1 site correlates with its association to cell membrane.

It has been considered that tau protein is mainly a cytoplasmic protein since it is a microtubule associated protein. However, it has also been suggested that tau could be located in the cell nucleus and membrane. In our work, the cellular distribution of tau has been studied by immunofluorescence and western blot analysis, after subcellular fractionation in neuroblastoma cells and in tau-transfected non neural cells using, mainly, two types of tau antibodies; antibody 7.51 (that recognizes tau independent of its phosphorylation level); and antibody Tau-1 (that recognizes tau only in its dephosphorylated form). Also, tau was expressed in COS-1 cells to test for the features involved in the sorting of tau to different cell localizations. Our results show that tau associated to cell membrane has a lower phosphorylation level in its proline-rich region. Additionally, in differentiated neuroblastoma cells, tau phosphorylation, at that region, decreases and the amount of tau associated to cell membrane increases.