Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2010 Aug 27;285(35):27302-27313.
doi: 10.1074/jbc.M110.145318. Epub 2010 Jun 21.

Human Tau isoforms assemble into ribbon-like fibrils that display polymorphic structure and stability

Susanne Wegmann  1 , Yu Jin Jung  2 , Subashchandrabose Chinnathambi  3 , Eva-Maria Mandelkow  3 , Eckhard Mandelkow  4 , Daniel J Muller  5
Affiliations

Human Tau isoforms assemble into ribbon-like fibrils that display polymorphic structure and stability

Susanne Wegmann et al. J Biol Chem. .

Abstract

Fibrous aggregates of Tau protein are characteristic features of Alzheimer disease. We applied high resolution atomic force and EM microscopy to study fibrils assembled from different human Tau isoforms and domains. All fibrils reveal structural polymorphism; the "thin twisted" and "thin smooth" fibrils resemble flat ribbons (cross-section approximately 10 x 15 nm) with diverse twist periodicities. "Thick fibrils" show periodicities of approximately 65-70 nm and thicknesses of approximately 9-18 nm such as routinely reported for "paired helical filaments" but structurally resemble heavily twisted ribbons. Therefore, thin and thick fibrils assembled from different human Tau isoforms challenge current structural models of paired helical filaments. Furthermore, all Tau fibrils reveal axial subperiodicities of approximately 17-19 nm and, upon exposure to mechanical stress or hydrophobic surfaces, disassemble into uniform fragments that remain connected by thin thread-like structures ( approximately 2 nm). This hydrophobically induced disassembly is inhibited at enhanced electrolyte concentrations, indicating that the fragments resemble structural building blocks and the fibril integrity depends largely on hydrophobic and electrostatic interactions. Because full-length Tau and repeat domain constructs assemble into fibrils of similar thickness, the "fuzzy coat" of Tau protein termini surrounding the fibril axis is nearly invisible for atomic force microscopy and EM, presumably because of its high flexibility.

PubMed Disclaimer

Figures

FIGURE 1.
FIGURE 1.
Survey of Tau isoforms, constructs, and fibril assembly. A, sequences of Tau isoforms and constructs assembled into fibrils in the presence of heparin are sketched in a bar diagram. The two hexapeptide motifs (black bars) involved in PHF core formation are located in repeat 2 and 3 (R2 and R3). The position of the Lys280 deletion in hTau40ΔK280 and K18ΔK280 is indicated by red dots. B, EM image of K18ΔK280 fibrils with the typical appearance of PHFs. C, nonselective EM images of hTau40 fibril preparations show a heterogeneous mixture of fibril shapes. D, AFM topographs of the same fibril preparation confirm the heterogeneity of fibril structures but reveal details with superior contrast. Fibril morphologies differ in length, bending, internal twist, periodicity, and thickness (★ for thick fibrils (bright yellow on the color scale) and ○ for thin fibrils (brown on the color scale)). This structural heterogeneity was largely independent of the Tau isoform and construct from which the fibrils self-assembled (supplemental Figs. S1–S3). Notably, although the fibril thickness in EM images is given by the apparent width of the structure, it is reflected by the fibril height in AFM topographs. AFM topographs were recorded in imaging buffer (10 mm Tris-HCl, pH 7.4, 50 mm KCl) and exhibit a full color range that corresponds to vertical scale of 25 nm as indicated by the color scale bar. Length scale bars in B, C, and D correspond to 100 nm.
FIGURE 2.
FIGURE 2.
Morphologies of fibrils assembled from full-length Tau and repeat domain. A–F, fibrils from hTau40. G–M, fibrils from the shortened Tau 3-repeat domain K19. With both Tau proteins, a variety of fibril morphologies can be observed by AFM. However, overall the collection of fibrillar structures is remarkably similar, despite the large size difference of hTau40 and K19 (441 versus 99 residues, respectively). There are thin straight fibrils (A and B, labeled ○), thin spiral or wave-like shapes (A, D, E, H, and I, labeled □), and thin fibrils with different degrees of internal twisting (C, G, J, K, and L, labeled ▵). Some fibrils are thicker (indicated by ★, e.g. F and M) than others. To discriminate thick and thin fibrils, their height was quantified from AFM topographs. The ratio of thick to thin fibrils (∼20–75%) depends on the Tau protein and assembly conditions. Different twists can occur in the same fibril (L). Thin fibrils may appear as a stack of smaller subunits (A, green arrowheads, B–E, H–J, and L, with typical spacing of 15–20 nm). On top of this beaded substructure, thin fibrils can have an internal twist (G, purple arrowheads, e.g. C and J) of various periodicities. All thick fibrils show pronounced internal twisting (e.g. A, blue arrowheads, B, F, and M). Periodicities of hTau40 and K19 fibrils were obtained from Fourier transform spectra measured along the fibril axis and correspond to the maxima in the power spectrum (asterisks). N, Fourier transform spectrum obtained for a single thin hTau40 fibril, in this case showing a stack periodicity of 22 nm (*) and a twist periodicity of 77 nm (**). O, most probable periodicities for twisted thin (n = 38) and thick (n = 12) hTau40 fibrils and twisted thin (n = 47) and thick (n = 20) K19 fibrils were attained from Gaussian fits to periodicity distributions. The periodicities of stacked subunits in smooth thin fibrils of hTau40 (n = 16) and K19 (n = 11) were determined in the same way. AFM topographs were recorded in imaging buffer (10 mm Tris-HCl, pH 7.4, 50 mm KCl) and exhibit a full color range that corresponds to a vertical scale of 30 nm. Length scale bars equal 200 nm in A and G and 50 nm in B–F and H–N.
FIGURE 3.
FIGURE 3.
Analysis of Tau fibril thickness. Fibrils with a clear difference in thickness (height) coexist in the same preparation of hTau40 (A) and K19 (C). AFM topographs were taken to perform height measurements of thin (A and C, labeled ○) and thick fibrils (A and C, labeled ★) assembled from hTau40 (B) and K19 (D). The difference in height between thin and thick fibrils ranges from ∼2 nm (lower heights) to ∼4.5 nm (higher heights) for hTau40 fibrils and from ∼2.5 nm (higher heights) to ∼3 nm (lower heights) for K19 fibrils. Full color range corresponds to a vertical scale of 35 nm. Length of scale bars in A and C correspond to 50 nm.
FIGURE 4.
FIGURE 4.
Mechanically and chemically induced disassembly of Tau fibrils. A and B, mechanical stress can induce the disassembly of hTau40 fibrils into smaller fragments. This phenomenon was observed for fibrils of every Tau protein when increasing the force applied to the AFM stylus to ∼150–200 pN. This disassembly emerges in the AFM fast scanning direction (dashed horizontal lines in topographs) where the lateral interaction forces between AFM stylus and fibril are highest. Repeatedly imaging the same surface area (A, panels I–III, and B, panels I–III) shows the consecutive fragmentation of hTau40 fibrils. Changes in fibril structure are indicated by arrowheads before and after fragmentation. Green arrowheads in A indicate the dislocation of a fibril accompanied by fragmentation and extension. C, spontaneous disassembly of hTau40 fibrils upon exposure to a hydrophobic surface (HOPG). As in the case of mechanical fragmentation, fibrils disassemble into smaller fragments typically 15–25 nm in length. D and E, high resolution AFM topographs of mechanically disassembled fibrils on mica highlight thread-like connections between the fragments. The cross-section plotted along a disassembled fibril (E) indicates a pronounced height difference between fragments (9.0 ± 2.0 nm; mean ± S.D.) and thread-like connections (2.6 ± 1.0 nm). F, histogram of fragment lengths (n = 224). The multimodal distribution shows three major peaks at 14.9, 21.3, and 26.2 nm (all maxima indicated on right). AFM topographs were recorded in imaging buffer and exhibit full color ranges that correspond to a vertical scale of 20 nm (A and B) or 10 nm (C and E). The length of all scale bars corresponds to 100 nm.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Ballatore C., Lee V. M., Trojanowski J. Q. (2007) Nat. Rev. Neurosci. 8, 663–672 - PubMed
    1. Finder V. H., Glockshuber R. (2007) Neurodegener Dis. 4, 13–27 - PubMed
    1. Iqbal K., Liu F., Gong C. X., Alonso Adel C., Grundke-Iqbal I. (2009) Acta Neuropathol. 118, 53–69 - PMC - PubMed
    1. Krebs M. R., Domike K. R., Donald A. M. (2009) Biochem. Soc. Trans. 37, 682–686 - PubMed
    1. Mandelkow E., von Bergen M., Biernat J., Mandelkow E. M. (2007) Brain Pathol. 17, 83–90 - PubMed

Publication types

MeSH terms

LinkOut - more resources

-