Analysis of Isoform-specific Tau Aggregates Suggests a Common Toxic Mechanism Involving Similar Pathological Conformations and Axonal Transport Inhibition

• Published in: Neurobiology of aging Vol. 47; pp. 113 - 126
• Main Authors: Cox, Kristine, Combs, Benjamin, Abdelmesih, Brenda, Morfini, Gerardo, Brady, Scott T, Kanaan, Nicholas M
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-11-2016
• Subjects: Aggregation; Alzheimer Disease - etiology; Alzheimer Disease - metabolism; Alzheimer's disease; Animals; Axon; Axonal Transport; Decapodiformes; Humans; In Vitro Techniques; Internal Medicine; Microtubule-associated protein; Neurology; Oligomer; Pathological conformations; Polymerization; Protein Aggregates; Protein Domains; Protein Isoforms; Signal Transduction; tau Proteins - chemistry; tau Proteins - metabolism; tau Proteins - toxicity; Tauopathies - etiology; Tauopathies - metabolism; Tauopathy; tauopathy; Alzheimer’s disease; oligomer; aggregation; axon; microtubule-associated protein; pathological conformations; Aggregation; Pathological conformations; Axon; Tauopathy; Oligomer; Microtubule-associated protein; Alzheimer's disease
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/j.neurobiolaging.2016.07.015

Abstract Misfolded tau proteins are characteristic of tauopathies, but the isoform composition of tau inclusions varies by tauopathy. Using aggregates of the longest tau isoform (containing four microtubule-binding repeats, 4-repeat tau), we recently described a direct mechanism of toxicity that involves exposure of the N-terminal phosphatase-activating domain (PAD) in tau, which triggers a signaling pathway that disrupts axonal transport. However, the impact of aggregation on PAD exposure for other tau isoforms was unexplored. Here, results from immunochemical assays indicate that aggregation-induced increases in PAD exposure and oligomerization are common features among all tau isoforms. The extent of PAD exposure and oligomerization was larger for tau aggregates composed of 4-repeat isoforms compared to those made of 3-repeat isoforms. Importantly, aggregates of all isoforms exhibited enough PAD exposure to significantly impair axonal transport in the squid axoplasm. We also show that PAD exposure and oligomerization represent common pathological characteristics in multiple tauopathies. Collectively, these results suggest a mechanism of toxicity common to each tau isoform that likely contributes to degeneration in different tauopathies.