Ceramides are bound to structural proteins of the human foreskin epidermal cornified cell envelope.
An important component of barrier function in human epidermis is contributed by ceramides that are bound by ester linkages to undefined proteins of the cornified cell envelope (CE). In this paper, we have examined the protein targets for the ceramide attachment. By partial saponification of isolated foreskin epidermal CEs followed by limited proteolysis, we have recovered several lipopeptides. Biochemical and mass spectroscopic characterization revealed that all contained near stoichiometric amounts of ceramides of masses ranging from about 690 to 890 atomic mass units, of which six quantitatively major species were common. The array of ceramides was similar to that obtained from pig skin, the composition of which is known, thereby providing strong indirect data for their fatty acid and sphingosine compositions. The recovered peptides accounted for about 20% of the total foreskin CE ceramides. By amino acid sequencing, about 35% of the peptides were derived from ancestral glutamine-glutamate-rich regions of involucrin, an important CE structural protein. Another 18% derived from rod domain sequences of periplakin and envoplakin, which are also known or suspected CE proteins. Other peptides were too short for unequivocal identification. Together, these data indicate that involucrin, envoplakin, periplakin, and possibly other structural proteins serve as substrates for the attachment of ceramides by ester linkages to the CE for barrier function in human epidermis.
Marekov
L N
LN
Laboratory of Skin Biology, NIAMS, National Institutes of Health, Bethesda, Maryland 20892-2752, USA.
Steinert
P M
PM
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004817:Epidermis / Q000378:metabolism*; D004952:Esters; D006801:Humans; D008074:Lipoproteins / Q000302:isolation & purification / Q000378:metabolism*; D013058:Mass Spectrometry; D008954:Models, Biological; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism
D002518:Ceramides; D004952:Esters; D008074:Lipoproteins; D010455:Peptides; D011498:Protein Precursors; C032253:involucrin