Keratinization, epidermal

Postsynthetic modifications of cytoskeletal microfilaments can also occur. For example, epidermal keratin has been found to contain lanthionine, (y-gluta-myllysine) and lysinoalanine, both presumably arising from crosslinkages.306... 

The head domain in trichocyte (or hair) keratins has been characterized by Parry and North (1998) and Parry et al. (2002) and shown to consist of two domains—a basic one (NB) at the N-terminal end of the head domain (27 and 70 residues long, respectively, for Type I and Type II chains) and an acidic one (NA) lying between the rod and NB. The latter is 29 and 34 residues long for Type I and Type II chains, respectively. Importantly, however, NA is homologous to HI in the respective chain types of epidermal keratins. There can therefore be little, if any, doubt that the role of these regions in trichocyte and epidermal keratins is... 

Fig. 2. (a) Schematic diagram of the subdomain structure in epidermal keratin... 

One aspect of the assembly of IF molecules that has received scant attention thus far relates to the small head-to-tail overlap that occurs between similarly directed molecules. This is defined by mode AcN. Its value is generally about 7 hcc (7.03 hcc or 1.04 nm in epidermal keratin,... 

The epidermal keratins have a tail subdomain structure closely parallel to that described for the heads in Section II.A.l. Immediately C-terminal to the rod domain exists a stretch of highly conserved sequence across Type II chains (Steinert et al., 1985). This is termed the H2 subdomain and is 20 residues long. An equivalent conserved region in Type I chains, however, is totally absent. C-terminal to H2 lies a sequence that varies between chains within a particular type, but which is rich in glycine and serine residues. This V2 subdomain, present in both Type I and Type II chains, has a length that lies in the range 0-110 and 25-125 residues in the two chain types, respectively. Human K1 and K10 chains both show... 

It is evident that specific residue-related features observed in the rod domain of one particular IF chain type are frequently not observed in the same place (if at all) in the other chain types and, of course, the large differences in head and tail structure and sequence between chain types preclude identical roles from occurring there as well. The highly specialized sequence characteristics thus define unique structural assemblies and functions, while still maintaining a high degree of structural uniformity, particularly in the manner of rod domain assembly. Even in this case, small but important differences in the An, A22, and A12 modes occur. Distinct IF structures have been identified for (1) unoxidized trichocyte keratin and epidermal keratin (2) oxidized trichocyte keratin (3) Type III and IV IF proteins and (4) the nuclear lam ins. 

Parry, D. A. D. (1995). Hard u-keratin IF A structural model lacking a head-lo-lail molecular overlap but having hybrid features characteristic of both epidermal keratin and vimentin IF. Proteins 22, 267-272. 

Parry, D. A. D. (1997). Protein chains in hair and epidermal keratin IF Structural features and spatial arrangements. In Formation and Structure of Human Hair (P. Jolles, H. Zahn, and H. Hocker, Eds.), pp. 177-207. Birkhauser, Basel. 

Figure 8.8 Proposed assembly of keratin polypeptide chains to form keratin filaments. (Reproduced by permission from Eichner R, Rew P, Engel A, Aebi U. Human epidermal keratin filaments studies on their structure and assembly. Ann NY Acad Sri 455 381-401, 1985.)...

Uitto, J., Richard, G., McGrath, J.A. (2007). Diseases of epidermal keratins and their linker proteins. Exp. Cell Res. 313 1995-2009. 

Swanbeck, G. (1959). Macromolecular oiganization of epidermal keratin. Acta Der-mato-Venereologica 39(Supl. 43) 5. 

Epidermal keratinization and mucous membrane squamous metaplasia respond to both oral and topical vitamin A therapy. Vitamin A exists in three forms retinol, retinal, and retinoic acid.VitaminA increases the mucous production of goblet cells and perhaps the aqueous and lipid components of the tears as well. Tretinoin is a normal metabolite and the carboxylic form of retinol. Retinol is present in tears and the lacrimal gland appears to be its major provider. Retinoic acid has been shown to be effective in ocular surfece disorders such as squamous metaplasia by reversing the corneal and conjunctival keratinization and improving epithelium wound healing rate. 

Membrane Thickening. Cell envelopes are usually neglected in discussions of skin penetration, although Matoltsy (65) wrote, the cell membrane can be looked on as the specific protective element of each comified cell, since it is much more resistant than the epidermal keratin. He also observed that loss of barrier function is maximum when SC is treated with reagents that aflEect membranes (66). 

Swanbeck, G., Macromolecular Organization of Epidermal Keratin, Acta... 

F27. Fukuyama, K., and Epstein, W. L., Epidermal keratinization Localization of iso topically labelled amino acids. J. Invest. Dermatol. 47, 551-560 (1966). 

Keratin AE1 /AE3 Keratins—Moll numbers 1-5, 6, 8, 9, 10, 14-16, and 18 Human epidermal keratin Dako 1 200 HIER... 

The TBA method has been used not only to assay glycosylated hemoglobin, but also almost exclusively for the following glycosylated proteins plasma albumin (D22, El, NIO, M12), plasma proteins and albumin (K6), capillary whole-blood protein collected on filter paper (L14), erythrocyte spectrin (M13), skin collagen (P2), lens basement membrane (M5), and crystallins (M28). In assays on hair and epidermal keratin, cyclohexanone extraction of the color developed with TBA and reading the absorbance of the cyclohexanone layer at 433 nm has provided increased sensitivity and accuracy (T4). A possible objection to the procedure is the use of oxalic and thiobarbituric acids, which are potentially toxic chemicals. 

T4. Thomas, D. P., Delbridge, L., Morris, D., and Howell, M. J., Cyclohexanone extraction an improvement in the thiobarbituric acid method for the determination of nonenzymatic glycosylation of hair and epidermal keratin. Scand. J. Clin. Lah. Invest. 44, 457-461 (1984). 

Compared with the hard ketatins like hair, wool, etc., the epidermal keratins show three main differences. The cystine and arginine contents... 

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