IMMUNOCHEMICAL EVIDENCE THAT FRAGMENTS OF PHOSPHORYLATED MAP5 (MAP1B) ARE BOUND TO NEUROFIBRILLARY TANGLES IN ALZHEIMERS-DISEASE

To test the hypothesis that cortical neurons undergo massive sprouting in Alzheimer's disease brain, we investigated whether neurofibrillary tangles contain fetal antigens. Two monoclonal antibodies to tangles specifically labeled an ∼300 kd protein in the neonatal brain homogenate, which was subsequently identified as MAP5 (MAP1B). Conversely, two monoclonal antibodies to MAP5 were found to stain tangles. All four reacted with only a phosphorylated species of MAP5. By careful immunochemical analysis, at least three independent phosphorylated epitopes that should have distinct conformations were shown to be shared by tangles and MAP5. However, several monoclonal antibodies to non-phosphorylated MAP5 did not stain tangles. From these observations, we conclude that fragments of phosphorylated MAP5 are bound to tangles. Since MAP5, in particular, a phosphorylated species, is known to be involved in neurite outgrowth, this result supports the sprouting hypothesis. © 1990.