Keratin and other stratum corneum proteins (SC proteins)

The stratum corneum is the outermost layer of the epidermis, acting as the body's primary physical and chemical barrier against environmental insults. It consists of corneocytes, which are dead, flattened cells filled with a dense network of keratin intermediate filaments (primarily KRT1 and KRT10) and encased in a highly cross-linked cornified envelope composed of proteins like filaggrin, loricrin, and involucrin (StatPearls, NBK513299). These proteins provide structural rigidity and are essential for maintaining skin hydration and preventing transepidermal water loss (PubMed, 23945662). In various dermatological conditions such as psoriasis and ichthyosis, abnormal keratinization leads to the accumulation of these proteins, resulting in thickened, scaly skin (NIH, Filaggrin). Therapeutic strategies targeting these proteins often utilize keratolytic agents like salicylic acid or urea, which chemically disrupt the protein structures or the 'intercellular cement' to promote the shedding of excess cornified tissue (PubChem, Salicylic acid). Additionally, retinoids are used to modulate the gene expression of these proteins to normalize the differentiation process of keratinocytes (Journal of Clinical and Aesthetic Dermatology, Keratolytics).

Other names

Stratum corneum proteinsCornified envelope proteinsEpidermal keratinsCorneocyte proteins

Keratolytic agents interact with these proteins by increasing hydration, which causes the cornified epithelium to swell and soften, or by disrupting the intercellular desmosomes and protein-lipid matrices that hold corneocytes together, thereby facilitating desquamation.