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Keratin intermediate filaments form strong mechanical scaffolds that confer structural stability to epithelial tissues, but the reason this function requires a protein family with fifty-four isoforms is not understood. During skin wound healing, a shift in keratin isoform expression alters the composition of keratin filaments. How this change modulates cellular function to support epidermal remodeling remains unclear. We report an unexpected effect of keratin isoform variation on kinase signal transduction. Increased expression of wound-associated keratin 6A, but not of steady-state keratin 5, potentiated keratinocyte migration and wound closure without compromising epidermal stability by activating myosin motors. This pathway depended on isoform-specific interaction between intrinsically disordered keratin head domains and non-filamentous vimentin shuttling myosin-activating kinases. These results substantially expand the functional repertoire of intermediate filaments from their canonical role as mechanical scaffolds to include roles as signaling scaffolds that spatiotemporally organize signal transduction cascades depending on isoform composition.

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Enzyme kinetics is an essential process of life, but it is a concept that challenges introductory biology students. Most enzyme kinetics laboratory activities either use hazardous chemicals to visualize the enzyme product or do not afford quantitative analysis at all. We have designed an inquiry-based activity that provides insight into enzyme function and that is budget friendly, safe, and produces quantitative results. The materials required are household products, so this activity can be adapted even for online classes. Furthermore, we suggest options for a sequential, experiential experiment-design activity for students.

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