Tau–RNA complexes inhibit microtubule polymerization and drive disease-relevant conformation change

Abstract

Alzheimer’s disease and related disorders feature neurofibrillary tangles and other neuropathological lesions composed of detergent-insoluble tau protein. In recent structural biology studies of tau proteinopathy, aggregated tau forms a distinct set of conformational variants specific to the different types of tauopathy disorders. However, the constituents driving the formation of distinct pathological tau conformations on pathway to tau-mediated neurodegeneration remain unknown. Previous work demonstrated RNA can serve as a driver of tau aggregation, and RNA associates with tau containing lesions, but tools for evaluating tau/RNA interactions remain limited. Here we employ molecular interaction studies to measure the impact of tau/RNA binding on tau microtubule binding and aggregation. To investigate the importance of tau/RNA complexes (TRCs) in neurodegenerative disease, we raised a monoclonal antibody (mAb TRC35) against aggregated tau/RNA complexes. Here we show native tau binds RNA with high affinity but low specificity, and tau binding to RNA competes with tau mediated microtubule assembly functions. Tau/RNA interaction in vitro promotes the formation of higher molecular weight tau/RNA complexes which represent an oligomeric tau species. Co-expression of tau and poly(A)45 RNA transgenes in Caenorhabditis elegans exacerbates tau related phenotypes including neuronal dysfunction and pathological tau accumulation. TRC35 exhibits specificity for Alzheimer’s disease-derived detergent insoluble tau relative to soluble recombinant tau. Immunostaining with TRC35 labels a wide variety of pathological tau lesions in animal models of tauopathy, which are reduced in mice lacking the RNA binding protein MSUT2. TRC-positive lesions are evident in many human tauopathies including Alzheimer’s disease, progressive supranuclear palsy, corticobasal degeneration, and Pick’s disease. We also identify ocular pharyngeal muscular dystrophy as a novel tauopathy disorder where loss of function in the poly(A) RNA binding protein (PABPN1) causes accumulation of pathological tau in tissue from postmortem human brain. Tau/RNA binding drives tau conformational change and aggregation inhibiting tau mediated microtubule assembly. Our findings implicate cellular tau/RNA interactions as modulators of both normal tau function and pathological tau toxicity in tauopathy disorders, and suggest feasibility for novel therapeutic approaches targeting TRCs.

Long non-coding RNA SNHG8 drives stress granule formation in tauopathies

“…In AD, the association of tau with RNA-binding proteins is increased, which may contribute to the dysregulation of RNA metabolism [ 65 ]. LncRNAs have also been shown to interact with a wide range of RNA-binding proteins, which can impact posttranslational modification, stability, subcellular localization, and activity of interacting partners [ 46 , 66 ]. The 15 common lncRNAs identified in our study were predicted to interact with several RNA-binding proteins that have been previously implicated in neurodegeneration.…”

Long non-coding RNASNHG8drives stress granule formation in tauopathies

“…In AD, the association of tau with RNA-binding proteins is increased, which may contribute to the dysregulation of RNA metabolism (Meier et al 2016). LncRNAs have also been shown to interact with a wide range of RNA-binding proteins, which can impact posttranslational modification, stability, subcellular localization, and activity of interacting partners (McMillan et al 2023; Yang, Wen, and Zhu 2015). The 15 common lncRNAs identified in our study were predicted to interact with several RNA-binding proteins that have been previously implicated in neurodegeneration.…”

Biochemical approaches to assess the impact of post-translational modifications on pathogenic tau conformations using recombinant protein

“…For oligomeric tau, three antibodies are used extensively in literature: tau oligomeric complex 1 (TOC1) [ 56 ], tau oligomer monoclonal antibody-1 (TOMA-1) [ 63 ], and T22 [ 55 ]. Other oligomeric or aggregated conformation tau antibodies also exist and will undoubtedly prove useful in studying tau conformation [ 181 , 182 ]. In addition, a set of antibodies called tau N-terminal antibodies (TNTs) are also available that detect conformation-dependent PAD exposure in tau [ 64 , 183 ].…”