The Type I Keratin 19 Possesses Distinct and Context-Dependent Assembly Properties

The study investigated the assembly properties of keratin 19 (K19) compared to keratin 14 (K14) in both in vitro and in vivo settings. K19, a smaller intermediate filament protein expressed in a subpopulation of basal cells with stem-cell-like characteristics, was found to form less stable tetramers and shorter, narrower filaments than K14 when paired with K5. In cultured cells, K5 and K19 did not form a filamentous array, unlike K5-K14 and K8-K19 combinations. However, K19 integrated into the keratin network of epithelial cell lines with minimal disruption. These findings suggested that K19 had distinct assembly properties, potentially imparting unique characteristics to the basal cells expressing it in skin epithelia.