involucrin and monodansylcadaverine

Stratified squamous epithelial cells assemble a specialized protective barrier structure on their periphery, termed the cornified envelope. The purpose of this study was to evaluate the presence and distribution of cornified envelope precursors in human corneal epithelium, their expression in human corneal epithelial cell cultures, and the effect of ultraviolet radiation (UVB) and transglutaminase (TG) inhibition on their expression.. Tissue distribution of small proline-rich proteins (SPRRs) and filaggrin and involucrin was studied in human cornea sections by immunofluorescence staining. Primary human corneal epithelial cells (HCECs) from limbal explants were used in cell culture experiments. A single dose of UVB at 20 mJ/cm2 was used to stimulate these cells, in the presence or absence of mono-dansyl cadaverine (MDC), a TG inhibitor. SPRR2 and involucrin protein levels were studied by immunofluorescence staining and Western blot analysis. Gene expression of 12 proteins was investigated by semiquantitative reverse transcription-polymerase chain reaction.. In human cornea tissue, SPRR1, SPRR2, filaggrin, and involucrin protein expression were detected in the central and peripheral corneal and limbal epithelium. In HCECs, SPRR2 and involucrin proteins were detected in the cytosolic fraction, and involucrin levels increased after UVB. Both SPRR2 and involucrin levels accumulated in the presence of MDC. Nine genes including involucrin, SPRR (types 1A, 1B, 2A, 2B, and 3), late envelope protein (LEP) 1 and 16, and filaggrin were expressed by HCECs. SPRR 4, loricrin, and LEP 6 transcripts were not detected. UVB downregulated SPRR (2A, 2B) and LEP 1 transcripts.. Various envelope precursors are expressed in human corneal epithelium and in HCECs, acute UVB stress differentially alters their expression in HCECs. The expression of envelope precursors and their rapid modulation by UVB supports the role of these proteins in the regulation of ocular surface stress. TG function may be relevant in the regulation of soluble precursors in UVB-stimulated corneal epithelium.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Animals; Blotting, Western; Cadaverine; Cells, Cultured; Child; Child, Preschool; Cornified Envelope Proline-Rich Proteins; Down-Regulation; Enzyme Inhibitors; Epithelium, Corneal; Filaggrin Proteins; Fluorescent Antibody Technique, Indirect; Gene Expression Regulation; Humans; Intermediate Filament Proteins; Membrane Proteins; Middle Aged; Polymerase Chain Reaction; Protein Precursors; RNA, Messenger; Swine; Transglutaminases; Ultraviolet Rays

We previously demonstrated that the aspartate protease cathepsin D is activated by ceramide derived from acid sphingomyelinase. Increased expression of cathepsin D in the skin has been reported in wound healing, psoriasis and skin tumors. We explored specific functions of cathepsin D during epidermal differentiation. Protein expression and enzymatic activity of cathepsin D increased in differentiated keratinocytes in both stratified organotypic cultures and in mouse skin during epidermal barrier repair. Treatment of cultured keratinocytes with exogenous cathepsin D increased the activity of transglutaminase 1, known to cross-link the cornified envelope proteins involucrin and loricrin during epidermal differentiation. Inhibition of cathepsin D by pepstatin A suppressed the activity of transglutaminase 1. Cathepsin D-deficient mice revealed reduced transglutaminase 1 activity and reduced protein levels of the cornified envelope proteins involucrin and loricrin. Also, amount and distribution of cornified envelope proteins involucrin, loricrin, filaggrin, and of the keratins K1 and K5 were significantly altered in cathepsin D-deficient mice. Stratum corneum morphology in cathepsin D-deficient mice was impaired, with increased numbers of corneocyte layers and faint staining of the cornified envelope only, which is similar to the human skin disease lamellar ichthyosis. Our findings suggest a functional link between cathepsin D activation, transglutaminase 1 activity and protein expression of cornified envelope proteins during epidermal differentiation.

Topics: Animals; Cadaverine; Cathepsin D; Cell Differentiation; Cells, Cultured; Enzyme Activation; Filaggrin Proteins; Gene Deletion; Intermediate Filament Proteins; Keratinocytes; Keratins; Membrane Proteins; Mice; Pepstatins; Protein Precursors; Protein Processing, Post-Translational; Skin; Transglutaminases; Wound Healing

A method providing more sensitive detection of transglutaminase substrates was developed to localize transglutaminase activity in tissue and to identify in vivo substrates in epidermal extracts. The enhanced sensitivity of this method was achieved via the generation of a monoclonal antibody (designated E7) made to dansylcadaverine. Transglutaminase substrates were visualized by western blot after a 1-min incubation with dansylcadaverine in contrast to the 2 h required when [14C]putrescine incorporation was measured by autoradiography of SDS-polyacrylamide gels. In addition, putative substrates not apparent using conventional methods were readily detected by western analysis. An ELISA assay to measure transglutaminase activity showed similar sensitivity to the traditional radiometric assay (Lorand et al., 1972). The correlation between the ELISA procedure and the radiometric assay was high (r2 = 0.924). Strips of neonatal human and mouse skin incubated in dansylcadaverine-supplemented culture medium were used to localize enzyme activity and to detect substrates in vivo. Transglutaminase activity was demonstrated at the cellular periphery in the upper spinous and granular cell layers of the epidermis. Substrates detected in epidermal extracts were similar to those detected using the in vitro assay. This technique allows for highly sensitive and nonradiometric analysis of both enzymatic activity and the substrates involved. The extension of this methodology to an in vivo system is the first demonstration of a system in which the dynamics of cornified envelope assembly may be further studied.

Topics: Animals; Animals, Newborn; Antibodies, Monoclonal; Autoradiography; Blotting, Western; Cadaverine; Cricetinae; Enzyme-Linked Immunosorbent Assay; Epidermal Cells; Epidermis; Epitopes; Humans; Infant, Newborn; Intracellular Membranes; Keratinocytes; Mice; Mice, Inbred BALB C; Organ Culture Techniques; Protein Precursors; Putrescine; Substrate Specificity; Transglutaminases