Near-atomic model of microtubule-tau interactions

Abstract

Tau is a developmentally regulated axonal protein that stabilizes and bundles microtubules (MTs). Its hyperphosphorylation is thought to cause detachment from MTs and subsequent aggregation into fibrils implicated in Alzheimer’s disease. It is unclear which tau residues are crucial for tau-MT interactions, where tau binds on MTs, and how it stabilizes them. We used cryo–electron microscopy to visualize different tau constructs on MTs, and computational approaches to generate atomic models of tau-tubulin interactions. The conserved tubulin-binding repeats within tau adopt similar extended structures along the crest of the protofilament, stabilizing the interface between tubulin dimers. Our structures explain the effect of phosphorylation on MT affinity and lead to a model of tau repeats binding in tandem along protofilaments, tethering together tubulin dimers and stabilizing polymerization interfaces.

Site‐Specific Hyperphosphorylation Inhibits, Rather than Promotes, Tau Fibrillization, Seeding Capacity, and Its Microtubule Binding

“…This is consistent with ar ecent report on the atomic structure of tubulin and tau interactions,w hich shows that both residues S262 and S258 of tau are directly involved in hydrogen bonding interactions with tubulin residue E434 (Figure S18 B), which further highlights the role of S262 in MT binding. [33] Introducing phosphorylation at S262 and S258 would disrupt the hydrogen bonding and further introduce electrostatic repulsion between pS262 or pS258 of tau and tubulin E434, which could potentially destabilize the tau-MT interaction. These attributes clearly support our experimental results that K18 phosphorylated at S262 and S258 significantly disrupts MT assembly and MT binding ( Figure S17).…”

Structural characterization of tau in fuzzy tau:tubulin complexes

“…Here we use an environmentally sensitive fluorophore, in combination with a published structural model (Kellogg et al, 2018), to interrogate the structural features of tau in tau:tubulin complexes and gain insight into tau-mediated polymerization of tubulin.…”

“…Cysteine mutations were introduced individually throughout R2 to allow for sitespecific labeling with acrylodan ( Figure 1A), in order to compare with our previous work with R3 (Li et al, 2015), as well as the published tau:MT structure ( Figure 1C) (Kellogg et al, 2018). Anisotropy measurements comparing tau labeled with acrylodan (tauacrylodan) at two different sites within R2 with tauA488 labeled at the N-terminus show that labeling with acrylodan in the MTBR does not significantly impair tubulin binding ( Figure S2A).…”

“…Numerous studies have identified putative binding sites of tau on soluble tubulin and the MT lattice, as well as characterized structural features of bound tau (Al-Bassam et al, 2002;Chau et al, 1998;Kadavath et al, 2018;Kadavath et al, 2015;Kar et al, 2003;Martinho et al, 2018;Santarella et al, 2004;Serrano et al, 1985). Most recently, cryo-EM and computational modeling revealed the first near-atomic level model of MTbound tau (Kellogg et al, 2018). Tandem repeats of R1 and R2 were used to improve resolution of the cryo-EM map, which showed segments of the repeats decorating the outer surface of each MT protofilament.…”

Site-specific hyperphosphorylation of tau inhibits its fibrillization in vitro, blocks its seeding capacity in cells, and disrupts its microtubule binding; Implications for the native state stabilization of tau

“…6B), which further highlights the role of S262 in MT binding. 43 Introducing phosphorylation at S262 and S258 would disrupt the hydrogen bonding and further introduce electrostatic repulsion between pS262 or pS258 of tau and tubulin E434, which could potentially destabilize the tau-MT interaction. These attributes clearly support our experimental results that K18 phosphorylated at S262…”