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.

The cytolinker plectin regulates nuclear mechanotransduction in keratinocytes

“…The keratin network of intermediate filaments is a major structural and mechanical component of keratinocytes (Ramms et al, 2013;Seltmann et al, 2013). We therefore sought to determine how this cytoskeletal structure contributed to the regulation of nuclear morphology.…”

“…In epidermal keratinocytes, the keratin cytoskeleton contributes substantially to overall cell rigidity and could potentially influence nuclear mechanotransduction (Kröger et al, 2013;Ramms et al, 2013;Seltmann et al, 2013). In this study, we investigated the mechanisms of force transmission to the nucleus in keratinocytes using micro-patterned polymer substrates, which allow for precise control over single-cell adhesion and spreading.…”

Desmosomes and Intermediate Filaments: Their Consequences for Tissue Mechanics

“…Selective disruption of actin filaments and microtubules did not significantly alter keratinocyte mechanics (Lulevich et al 2010). However, application of AFM to keratin-deficient individual keratinocytes revealed a significant softening of keratin-deficient cells (Ramms et al 2013). Magnetic tweezer experiments additionally showed a major contribution of keratins to viscoelastic cell properties.…”

Histological and immunohistochemical practical studies of canine cutaneous tumors

“…Up to 85% of the total content of the keratinocytes is composed of cytokeratins (11,24). Vimentin is an intermediate filament protein that is expressed in most mesenchymal cells, especially in fibroblasts (14).…”