BAD Investigative Group Meeting, Cardiff, January 1981

Abstract

It is well established that the fibrous protein from stratum corneum (keratin) differs from, and is derived from, that synthesized (prekeratin) in the living epidermis. Plantar stratum corneum (callus) and psoriatic scale keratins are atypical in composition (Baden et al., 1978; Skerrow & Hunter, 1978; Thaler et al., 1978) but there is litde data on the corresponding prekeratins. The aim ofthe present study is to compare keratin and prekeratin from normal and pathological epidermis. Epidermis from scalp skin, heel skin and various psoriatic lesions was extracted with acid buffer and prekeratin obtained by isoelectric precipitation (Skerrow, 1977). Normal stratum corneum, heel callus and psoriatic scale were extracted with neutral 6M urea containing 2% mercaptoethanol, and dialysed against acid buffer. The keratins were obtained by isoelectric precipitation and compared to prekeratin by high resolution SDS-PAGE on gradient slab gels (Bowden & Cunliffe, 1980). Prekeratin from normal epidermis was composed of several polypeptides of molecular weight 45,000-70,000. Callus prekeratin contained three additional polypeptides (mol wt 44,000, 50,000 and 65,000). Psoriatic prekeratin was characterized by a lack of larger polypeptides (mol wt. 67,000-70,000) and the presence of two polypeptides (mol wt 44,000 and 50,000) normally restricted to plantar epidermis. Psoriatic scale demonstrated a prekeratin-like composition and unlike normal stratum corneum, involved callus did not markedly differ in composition from involved scale at other sites. We have demonstrated that prekeratins from plantar and involved psoriatic epidermis differ from each other and from normal prekeratin. These differences may result from changes in keratin gene expression combined with, in psoriatic epidermis, a lack of post-translational modification.