title: Tau protein binding forms a 1 nm thick layer along protofilaments without affecting the radial elasticity of microtubules.
abstract: Tau is one of the most abundant microtubule-associated proteins involved in kinetic stabilization and bundling of axonal microtubules. Although intense research has revealed much about tau function and its involvement in Alzheimer's disease during the past years, it still remains unclear how exactly tau binds on microtubules and if the kinetic stabilization of microtubules by tau is accompanied, at least in part, by a mechanical reinforcement of microtubules. In this paper, we have used atomic force microscopy to address both aspects by visualizing and mechanically analyzing microtubules in the presence of native tau isoforms. We could show that tau at saturating concentrations forms a 1 nm thick layer around the microtubule, but leaves the protofilament structure well visible. The latter observation argues for tau binding mainly along and not across the protofilaments. The radial elasticity of microtubules was almost unaffected by tau, consistent with tau binding along the tops of the protofilaments. Tau did increase the resistance of microtubules against rupture. Finite-element calculations confirmed our findings.
authors.affiliation: Section Physics of Complex Systems, Department of Physics and Astronomy, Vrije Universiteit Amsterdam, The Netherlands.
authors.forename: Iwan A T
authors.initials: IA
authors.lastname: Schaap
authors.forename: Bernd
authors.initials: B
authors.lastname: Hoffmann
authors.forename: Carolina
authors.initials: C
authors.lastname: Carrasco
authors.forename: Rudolf
authors.initials: R
authors.lastname: Merkel
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D004548:Elasticity; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008869:Microtubule-Associated Proteins / Q000737:chemistry; D008870:Microtubules / Q000737:chemistry*; D011485:Protein Binding; D020033:Protein Isoforms; D013552:Swine / Q000378:metabolism; D016875:tau Proteins / Q000737:chemistry*
chemical_list: D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; D016875:tau Proteins