Zinc promotes liquid–liquid phase separation of tau protein

Abstract

Tau is a microtubule-associated protein that plays a major role in Alzheimer's disease (AD) and other tauopathies. Recent reports indicate that, in the presence of crowding agents, tau can undergo liquid-liquid phase separation (LLPS), forming highly dynamic liquid droplets. Here, using recombinantly expressed proteins, turbidimetry, fluorescence microscopy imaging, and fluorescence recovery after photobleaching (FRAP) assays, we show that the divalent transition metal zinc strongly promotes this process, shifting the equilibrium phase boundary to lower protein or crowding agent concentrations. We observed no tau LLPS-promoting effect for any other divalent transition metal ions tested, including Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , and Cu 2+ . We also demonstrate that multiple zinc-binding sites on tau are involved in the LLPS-promoting effect and provide insights into the mechanism of this process. Zinc concentration is highly elevated in AD brains, and this metal ion is believed to be an important player in the pathogenesis of this disease. Thus, the present findings bring a new dimension to understanding the relationship between zinc homeostasis and the pathogenic process in AD and related neurodegenerative disorders. ____________________________________ https://www.jbc.org/cgi/

Zinc and Copper Ions Differentially Regulate Prion-Like Phase Separation Dynamics of Pan-Virus Nucleocapsid Biomolecular Condensates

“…It was later shown that Cu 2+ and Zn 2+ bind to the same Aβ histidine residues, where Zn 2+ precipitates at least two peptides to induce spherical structures, whereas Cu 2+ outcompetes Zn 2+ to inhibit intra-protein contacts [ 139 ]. Indeed, from numerous metal ions tested (including Cu 2+ ), Zn 2+ alone could induce Tau protein condensates, another prime causative agent of neurodegenerative disease deposits [ 14 ]. The cellular prion protein also binds to both Zn 2+ and Cu 2+ , with both metals inducing structural changes and decreased solubility [ 140 ] and differentially affecting its fold variants [ 141 , 142 ], where Cu 2+ -binding induces protease resistant variants [ 143 , 144 ].…”

“…Indeed, self-aggregating mutated proteins that are hallmarks of neurological diseases, including SOD1, G3BP1, TIAR, TIA-1, DDX6, TDP-43, FUS/TLS, Tau, Amyloid β (Aβ), and hnRNP proteins [ 9 ], are also characterized as RNA-binding proteins, as helicases or chaperones, and as components of SGs or processing bodies (PBs) [ 10 , 11 ]. These proteins can be Zn- [ 12 , 13 , 14 , 15 ] or Cu- [ 15 , 16 , 17 , 18 , 19 , 20 ] regulated or regulating, and can undergo LLPS due to their low-complexity, intrinsically disordered prion-like disordered protein domains (PrLDs) [ 21 , 22 ]. These proteins also represent commonly used markers of SG assembly blockade imposed by numerous viruses that also co-opt them towards their replication [ 11 , 23 , 24 ].…”

Late Embryogenesis Abundant Protein–Client Protein Interactions

“…; [ 45 , 120 ]). There are other possible associations in which the LEAPs may play a role (e.g., proteinaceous membrane-less organelles/ liquid-liquid phase separation), the stability and timing of formation of which may lead to pathology [ 57 , 121 ]. The expanded polyQ tracts associated with the severity and time of onset of, for example, Huntington’s disease, are disordered, polar, and soluble regions [ 122 , 123 ] that, when they persist, cause endoplasmic reticular stress [ 122 ] among other dysfunctions.…”

Tau conformers in FTLD-MAPT undergo liquid-liquid phase separation and perturb the nuclear envelope

“…Zhang et al, 2015) and the interactions of DPRs with proteins harboring LCDs or RRMs disturb multiple MLOs such as nucleoli, NPCs and stress granules (SGs) (Lee et al, 2016). For tau, recent studies have shown that this intrinsically disordered protein, although lacking predicted LCDs and RRMs, nonetheless has some propensity to undergo LLPS (Ambadipudi, Biernat, Riedel, Mandelkow, & Zweckstetter, 2017; Boyko, Qi, Chen, Surewicz, & Surewicz, 2019; Singh, Xu, Boyko, Surewicz, & Surewicz, 2020; Vega, Umstead, & Kanaan, 2019; Wegmann et al, 2018; X. Zhang et al, 2017).…”