The Small Heat Shock Protein Hsp27 Affects Assembly Dynamics and
Structure of Keratin Intermediate Filament Networks
Jona Kayser,
Martin Haslbeck,
Lisa Dempfle,
Maike Krause,
Carsten Grashoff,
Johannes Buchner,
Harald Herrmann,
Andreas R. Bausch
BIOPHYSICAL JOURNAL
105
(8)
1778-1785
(2013)
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The mechanical properties of living cells are essential for many<br> processes. They are defined by the cytoskeleton, a composite network of<br> protein fibers. Thus, the precise control of its architecture is of<br> paramount importance. Our knowledge about the molecular and physical<br> mechanisms defining the network structure remains scarce, especially for<br> the intermediate filament cytoskeleton. Here, we investigate the effect<br> of small heat shock proteins on the keratin 8/18 intermediate filament<br> cytoskeleton using a well-controlled model system of reconstituted<br> keratin networks. We demonstrate that Hsp27 severely alters the<br> structure of such networks by changing their assembly dynamics.<br> Furthermore, the C-terminal tail domain of keratin 8 is shown to be<br> essential for this effect. Combining results from fluorescence and<br> electron microscopy with data from analytical ultracentrifugation<br> reveals the crucial role of kinetic trapping in keratin network<br> formation.
Neurofilament sidearms modulate parallel and crossed-filament
orientations inducing nematic to isotropic and re-entrant birefringent
hydrogels
Joanna Deek,
Peter J. Chung,
Jona Kayser,
Andreas R. Bausch,
Cyrus R. Safinya
Neurofilaments are intermediate filaments assembled from the subunits<br> neurofilament-low, neurofilament-medium and neurofilament-high. In<br> axons, parallel neurofilaments form a nematic liquid-crystal hydrogel<br> with network structure arising from interactions between the<br> neurofilaments' C-terminal sidearms. Here we report, using small-angle<br> X-ray-scattering, polarized-microscopy and rheometry, that with<br> decreasing ionic strength, neurofilament-low-high,<br> neurofilament-low-medium and neurofilament-low-medium-high hydrogels<br> transition from the nematic hydrogel to an isotropic hydrogel (with<br> random, crossed-filament orientation) and to an unexpected new<br> re-entrant liquid-crystal hydrogel with parallel filaments-the<br> bluish-opaque hydrogel-with notable mechanical and water retention<br> properties reminiscent of crosslinked hydrogels. Significantly, the<br> isotropic gel phase stability is sidearm-dependent:<br> neurofilament-low-high hydrogels exhibit a wide ionic strength range,<br> neurofilament-low-medium hydrogels a narrow ionic strength range,<br> whereas neurofilament-low hydrogels lack the isotropic gel phase. This<br> suggests a dominant regulatory role for neurofilament-high sidearms in<br> filament reorientation plasticity, facilitating organelle transport in<br> axons. Neurofilament-inspired biomimetic hydrogels should therefore<br> exhibit remarkable structure-dependent moduli and slow and fast<br> water-release properties.
Salt-Responsive Liquid Crystal Hydrogels: Neurofilament Network Structure and Mechanical Modulation
Joanna Deek,
Peter J. Chung,
Jona Kayser,
Andreas Bausch,
Cyrus R. Safinya
Towards constructing extracellular matrix-mimetic hydrogels: An elastic
hydrogel constructed from tandem modular proteins containing tenascin
FnIII domains
Shanshan Lv,
Tianjia Bu,
Jona Kayser,
Andreas Bausch,
Hongbin Li
Protein-based hydrogels have been developed for various biomedical<br> applications where they provide artificial extracellular<br> microenvironments that mimic the physical and biochemical<br> characteristics of natural extracellular matrices (ECMs). In natural<br> ECMs, a large number of proteins are tandem modular proteins consisting<br> of many individually folded functional domains that confer structural<br> and biological functionalities. Such tandem modular proteins are<br> promising building blocks for constructing ECM-mimetic biomaterials.<br> However, their use for such purposes has not been explored extensively.<br> Tenascin-C (TNC) is an ECM tandem modular protein and plays an important<br> role in mechanotransduction by regulating important cell matrix<br> interactions. The third FnIII domain of TNC (TNfn3) contains an RGD<br> sequence and is known to bind integrins. Here we use the TNfn3 domain<br> and resilin sequence-based tandem modular protein FRF4RF4R (F represents<br> the TNfn3 domain and R represents the resilin sequence, respectively) as<br> a building block to construct protein-based ECM-mimetic hydrogels. The<br> tandem modular protein-based building block FRF4RF4R closely mimics the<br> architecture of the naturally occurring tandem modular ECM protein TNC<br> and incorporates intact RGD-containing FnIII domains. Our results<br> demonstrate that tandem modular proteins containing TNfn3 can be readily<br> photochemically crosslinked into elastic hydrogels, whose Young's<br> modulus can be tuned by the concentration of the tandem modular protein<br> solution. In vitro studies demonstrate that none of the photochemical<br> crosslinking reaction components are cytotoxic at the level tested, and<br> the hydrogel supports the spread of human lung fibroblast cells. Our<br> results demonstrate that FRF4RF4R-based hydrogel is a novel ECM-mimetic<br> hydrogel. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All<br> rights reserved.
Contact
Research Group Jona Kayser
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
