title: Keratins as the main component for the mechanical integrity of keratinocytes.
abstract: Keratins are major components of the epithelial cytoskeleton and are believed to play a vital role for mechanical integrity at the cellular and tissue level. Keratinocytes as the main cell type of the epidermis express a differentiation-specific set of type I and type II keratins forming a stable network and are major contributors of keratinocyte mechanical properties. However, owing to compensatory keratin expression, the overall contribution of keratins to cell mechanics was difficult to examine in vivo on deletion of single keratin genes. To overcome this problem, we used keratinocytes lacking all keratins. The mechanical properties of these cells were analyzed by atomic force microscopy (AFM) and magnetic tweezers experiments. We found a strong and highly significant softening of keratin-deficient keratinocytes when analyzed by AFM on the cell body and above the nucleus. Magnetic tweezers experiments fully confirmed these results showing, in addition, high viscous contributions to magnetic bead displacement in keratin-lacking cells. Keratin loss neither affected actin or microtubule networks nor their overall protein concentration. Furthermore, depolymerization of actin preserves cell softening in the absence of keratin. On reexpression of the sole basal epidermal keratin pair K5/14, the keratin filament network was reestablished, and mechanical properties were restored almost to WT levels in both experimental setups. The data presented here demonstrate the importance of keratin filaments for mechanical resilience of keratinocytes and indicate that expression of a single keratin pair is sufficient for almost complete reconstitution of their mechanical properties.
authors.affiliation: Institute of Complex Systems, ICS-7: Biomechanics, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Ramms
authors.forename: Gloria
authors.initials: G
authors.lastname: Fabris
authors.forename: Reinhard
authors.initials: R
authors.lastname: Windoffer
authors.forename: Nicole
authors.initials: N
authors.lastname: Schwarz
authors.forename: Ronald
authors.initials: R
authors.lastname: Springer
authors.forename: Chen
authors.initials: C
authors.lastname: Zhou
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Lazar
authors.forename: Simone
authors.initials: S
authors.lastname: Stiefel
authors.forename: Nils
authors.initials: N
authors.lastname: Hersch
authors.forename: Uwe
authors.initials: U
authors.lastname: Schnakenberg
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Magin
authors.forename: Rudolf E
authors.initials: RE
authors.lastname: Leube
authors.forename: Rudolf
authors.initials: R
authors.lastname: Merkel
authors.forename: Bernd
authors.initials: B
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D001696:Biomechanical Phenomena / Q000502:physiology; D015153:Blotting, Western; D048430:Cell Shape / Q000502:physiology*; D003433:Crosses, Genetic; D055786:Gene Knockout Techniques; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D053547:Keratin-14 / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism; D007633:Keratins / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008846:Micromanipulation; D018625:Microscopy, Atomic Force; D018709:Statistics, Nonparametric
chemical_list: D001426:Bacterial Proteins; C507540:KRT14 protein, human; D053547:Keratin-14; D008164:Luminescent Proteins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; D007633:Keratins