DISTRIBUTION OF ISOFORMS OF THE MICROTUBULE-ASSOCIATED PROTEIN-TAU INGREY AND WHITE-MATTER AREAS OF HUMAN BRAIN - A 2-DIMENSIONAL GELELECTROPHORETIC ANALYSIS

The microtubule-associated protein tan in human brain consists of six molecular isoforms derived from a single gene by alternative mRNA-spli cing and further modified by posttranslational processing. In the pres ent study, the distribution of tan isoforms in grey and white matter o f human temporal cortex was investigated by two-dimensional gelelectro phoresis. More than 80 isoforms were defected. The pattern of isoforms obtained after treatment with alkaline phosphatase was still more com plex than those of recombinant tau, indicating that posttranslational modifications other than phosphorylation contribute to the molecular h eterogeneity of tan. The tau isoform D according to Goedert [1] contai ning four tubulin-binding regions shown to promote tubulin polymerisat ion most efficiently was present in higher amounts in white as compare d to grey matter. The pattern of isoform distribution was not signific antly altered in Alzheimer's disease. It is concluded that molecular i soforms that differ in their tubulin-binding characteristics are diffe rentially distributed in subcellular neuronal compartments and/or neur onal types.