Novel Antibodies that Target Tau Tyrosine Nitration in Alzheimer's Disease and Related Tauopathies

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the pathological association of the microtubule-associated protein (MAP) tau into neurofibrillary tangles (NFTs) and amyloid beta into senile plaques. The association of tau into NFT formation is thought to be induced by numerous modifications within the molecule including phosphorylation, proteolytic cleavage, or conformational changes. Notably, the aggregation of the amyloid beta into plaques is thought to play a major role in inducing AD-associated inflammation and promoting the formation of peroxynitrite (ONOO-), a powerful compound capable of modifying tyrosine residues in proteins by adding nitrogen dioxide groups (-NO2) to the phenolic ring, a modification known as tyrosine nitration. Protein tyrosine nitration is thought to affect protein folding and function. To date, several laboratories have reported an increase in the levels of nitrated proteins within the cerebrospinal fluid and immunological probes to detect the nitrotyrosine modifications localize to the NFTs in AD as well as the fibrillar tau inclusions in other tauopathies. However, these probes also labeled the Lewy bodies in Parkinson's disease which are composed mainly of alpha-synuclein proteins, suggesting that these probes are not specific for tau. In this dissertation, we examine the nitrative modifications of the tau protein during the pathological progression of tau into NFTs in AD and related tauopathies. We hypothesize that tau is nitrated at specific tyrosine sites during in AD pathogenesis. To test this hypothesis; we generated site-specific tau antibodies to nitrative modifications at each tyrosine site within the tau molecule. Using these specific immunological probes, we determined the spatial and temporal evolution of nitration events during the pathogenesis of AD and non-AD tauopathies. Our data indicate that tau tyrosine nitration may be a a highly controlled post-translational modification that could have normal biological functions and that nitration at specific residues may be up-regulated in a disease- and lesion-specific manner.