6] Purification of paired helical filament tau and normal tau from human brain tissue

Abstract

Publisher Summary Paired helical filaments (PHF) are the major structural components of the neurofibrillary tangles (NFTs) that form in neurons, which subsequently degenerate in the brains of patients with Alzheimer's disease (AD), Down syndrome, amyotrophic lateral sclerosis/parkinsonism–dementia complex of Guam (ALS/PDC), dementia pugilistica, and several other neurodegenerative disorders. Paired helical filaments (PHFs) contain modified forms of central nervous system (CNS) tau proteins known collectively as PHF–tau (previously referred to as A68). Tau proteins are a group of microtubule-associated proteins that are expressed predominantly in axons. Some of the known functions of tau proteins are to bind to microtubules (MTs), to promote the assembly of tubulin monomers into MTs, and to stabilize polymerized MTs. Although the biological significance of glycosylation remains to be elucidated, phosphorylation regulates the binding of tau to MT—that is, increasing tau phosphorylation reduces MT binding. Although previous studies have demonstrated that PHF–tau is hyperphosphorylated relative to normal human tau, normal human tau isolated from biopsy brain samples is much more phosphorylated than normal human tau isolated from autopsy brain samples. This chapter describes a procedure to effectively purify PHF–tau and soluble normal tau preparations from human brain.