Profilaggrin, a high-molecular-weight precursor of filaggrin in human epidermis and cultured keratinocytes.
Filaggrin is a histidine-rich matrix protein of keratinized epidermis. Filaggrin is synthesized as a high-Mr, phosphorylated precursor, profilaggrin, that is processed to form the lower-Mr product present in cornified cells. This study reports the identification of profilaggrin in human epidermis and in unusually well-differentiated cultured human keratinocytes with the use of a polyclonal antihuman filaggrin antiserum. Polyclonal antiserum raised against human filaggrin stained keratohyaline granules and stratum corneum in tissue sections of human skin. Analysis of epidermal extracts showed an immunoreactive low-Mr band (37,000), previously identified as filaggrin, and an immunoreactive high-Mr band (greater than 220,000). Both [32P] phosphate and [3H]histidine were incorporated into the high-Mr band after pulse labeling for 3 h. After a 15-h chase, [3H]histidine, but not [32P]phosphate appeared in filaggrin. Human foreskin keratinocytes cultured on a 3T3 feeder layer were unusually well differentiated. Numerous well-formed keratohyaline granules, complete desmosomes, lamellar granules, and cornified cell envelopes were observed. Immunofluorescence with antihuman filaggrin antiserum showed a granular staining pattern in the more stratified cells. Extracts of cultured cells contained a diffuse high-Mr immunoreactive band but no immunoreactive equivalent of filaggrin. These studies suggest that human skin filaggrin, like rodent filaggrin, is synthesized as a high-Mr, phosphorylated, histidine-rich precursor (profilaggrin) that is processed via posttranslational modification to filaggrin. In human keratinocyte cultures a similar high-Mr precursor is present, but evidence of processing to the lower-Mr product, filaggrin, is lacking.
D000818:Animals; D000911:Antibodies, Monoclonal; D002478:Cells, Cultured; D000091344:Filaggrin Proteins; D005455:Fluorescent Antibody Technique; D006801:Humans; D007231:Infant, Newborn; D007381:Intermediate Filament Proteins / Q000302:isolation & purification*; D008297:Male; D009924:Organ Culture Techniques; D010413:Penis / Q000166:cytology; D011498:Protein Precursors / Q000302:isolation & purification*; D011817:Rabbits / Q000276:immunology; D012867:Skin / Q000032:analysis* / Q000166:cytology
D000911:Antibodies, Monoclonal; C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D011498:Protein Precursors