Keratin 14-dependent disulfides regulate epidermal homeostasis and barrier function via 14-3-3σ and YAP1.

Yajuan Guo,Vinod Jaskula-Ranga,Margarita V Brovkina,Pierre A Coulombe,Catherine J Redmond,Krystynne A Leacock,Suyun Ji

doi:10.7554/elife.53165

Yajuan Guo, Vinod Jaskula-Ranga + Show 5 more

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https://doi.org/10.7554/elife.53165

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Abstract

The intermediate filament protein keratin 14 (K14) provides vital structural support in basal keratinocytes of epidermis. Recent studies evidenced a role for K14-dependent disulfide bonding in the organization and dynamics of keratin IFs in skin keratinocytes. Here we report that knock-in mice harboring a cysteine-to-alanine substitution at Krt14's codon 373 (C373A) exhibit alterations in disulfide-bonded K14 species and a barrier defect secondary to enhanced proliferation, faster transit time and altered differentiation in epidermis. A proteomics screen identified 14-3-3 as K14 interacting proteins. Follow-up studies showed that YAP1, a transcriptional effector of Hippo signaling regulated by 14-3-3sigma in skin keratinocytes, shows aberrant subcellular partitioning and function in differentiating Krt14 C373A keratinocytes. Residue C373 in K14, which is conserved in a subset of keratins, is revealed as a novel regulator of keratin organization and YAP function in early differentiating keratinocytes, with an impact on cell mechanics, homeostasis and barrier function in epidermis.

Highlights

The epidermis covering our skin and body maintains a vital and multidimensional barrier to water and the outside environment while renewing itself with rapid kinetics, even under normal physiological conditions (Kubo et al, 2012)
These findings indicate that mice homozygous for Krt14 C373A allele are viable and appear macroscopically normal, biochemically they exhibit a strikingly altered pattern of keratin 14 (K14)-dependent disulfide bonding, in ear and tail skin
Our findings support the conclusion that K14-dependent disulfide bonding involving the conserved ‘stutter cysteine’ residue impacts cell architecture, mechanosensing and Hippo signaling at an early stage of epithelial differentiation in the epidermis

Summary

Introduction

The epidermis covering our skin and body maintains a vital and multidimensional barrier to water and the outside environment while renewing itself with rapid kinetics, even under normal physiological conditions (Kubo et al, 2012). The mechanisms through which new progenitor cells are produced at the base of this stratified epithelium, pace themselves through differentiation, and maintain tissue architecture and function in spite of a high rate of cell loss at the skin surface are only partially understood (Wells and Watt, 2018). Keratin intermediate filaments are major protein constituents in epithelial cells and are encoded by a large family of 54 conserved genes that are individually regulated in a tissue- and differentiation-specific fashion (Schweizer et al, 2006). An outstanding question is the extent to which keratin, and other types of intermediate filaments (IFs), participate in basic processes such as cell differentiation and tissue homeostasis. Two main roles have so far been ascribed to K5-K14

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