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KMID : 0984920010030010035
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Journal of Skin Barrier Research
2001 Volume.3 No. 1 p.35 ~ p.39
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Corneocyte Lipid Envelope
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Lim Ok-Hwan
Lee Jeong-Deuk
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Abstract
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Cells of the stratum granulosum are enclosed by a phospholipid-enriched plasma membrane, which transforms during cornification into a novel hydrophobic envelope, corneocyte lipid envelope(CLE), that lies external to the outer surface of the cornified envelope. This structure is enriched in ω-hydroxyceramide(ω-OHCer), which appear to be linked covalently by ester bonds to glutamine and glutamic acid residues within the involucrin-enriched, outer portion of the conrified envelope. Ultrastructural studies and molecular models generally portray the CLE as a unifrom, electron-lucent gap between the cornified envelope and the most proximate polar leaflet of the extracellular lamellar membrane system. Treatment with the dipolar organic solvent, pyridine, yields electron-dense-lucent-dense images of the CLE in which a distinct, electron-dense inner leaflet can be seen contiguous to the cornified envelope. Not only the in situ structure and composition, but also the function of the CLE is not known. Although the CLE alone is assumed to lack water barrier properties, it could; a) serve as a scaffold necessary for the deposition and anchorage of the extracellular lamellae; b)play a role in corneocyte cohesion and desquamation; or c)serve as a molecular sieve, allowing transmembrane water movement, but restricting passage of larger molecules. The CLE is presumed to originate from epidermal lamellar bodies. Yet, CLE lipids could originate from the limiting membrane of the lamellar body, rather than its contents; however, fusion of the lamellar body limiting membrane with the apical plasma membrane of the outermost stratum granulosum cell would allow covalent attachment of ceramide to cornified envelope proteins by transglutamase 1.
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KEYWORD
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corneocyte lipid envelope, ω-hydroxyceramide
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