Immunolocalization of Alpha-keratins and Associated Beta-proteins in Lizard Epidermis Shows That Acidic Keratins Mix with Basic Keratin-associated Beta-proteins

Overview

Journal Protoplasma

Publisher Springer

Specialty Biology

Date 2013 Nov 27

PMID 24276370

Citations 1

Authors

Lorenzo Alibardi

Affiliations

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Abstract

The differentiation of the corneous layers of lizard epidermis has been analyzed by ultrastructural immunocytochemistry using specific antibodies against alpha-keratins and keratin associated beta-proteins (KAbetaPs, formerly indicated as beta-keratins). Both beta-cells and alpha-cells of the corneous layer derive from the same germinal layer. An acidic type I alpha-keratin is present in basal and suprabasal layers, early differentiating clear, oberhautchen, and beta-cells. Type I keratin apparently disappears in differentiated beta- and alpha-layers of the mature corneous layers. Conversely, a basic type II alpha-keratin rich in glycine is absent or very scarce in basal and suprabasal layers and this keratin likely does not pair with type I keratin to form intermediate filaments but is weakly detected in the pre-corneous and corneous alpha-layer. Single and double labeling experiments show that in differentiating beta-cells, basic KAbetaPs are added and replace type-I keratin to form the hard beta-layer. Epidermal alpha-keratins contain scarce cysteine (0.2-1.4 %) that instead represents 4-19 % of amino acids present in KAbetaPs. Possible chemical bonds formed between alpha-keratins and KAbetaPs may derive from electrostatic interactions in addition to cross-linking through disulphide bonds. Both the high content in glycine of keratins and KAbetaPs may also contribute to increase the hydrophobicy of the beta- and alpha-layers and the resistance of the corneous layer. The increase of gly-rich KAbetaPs amount and the bonds to the framework of alpha-keratins give rise to the inflexible beta-layer while the cys-rich KAbetaPs produce a pliable alpha-layer.

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References

Sybert V, Dale B, Holbrook K . Ichthyosis vulgaris: identification of a defect in synthesis of filaggrin correlated with an absence of keratohyaline granules. J Invest Dermatol. 1985; 84(3):191-4. DOI: 10.1111/1523-1747.ep12264813. View

Alibardi L . Immunolocalization of keratin-associated beta-proteins (beta-keratins) in the regenerating lizard epidermis indicates a new process for the differentiation of the epidermis in lepidosaurians. J Morphol. 2012; 273(11):1272-9. DOI: 10.1002/jmor.20057. View

Bragulla H, Homberger D . Structure and functions of keratin proteins in simple, stratified, keratinized and cornified epithelia. J Anat. 2009; 214(4):516-59. PMC: 2736122. DOI: 10.1111/j.1469-7580.2009.01066.x. View

Fraser R, Parry D . The structural basis of the filament-matrix texture in the avian/reptilian group of hard β-keratins. J Struct Biol. 2010; 173(2):391-405. DOI: 10.1016/j.jsb.2010.09.020. View

Sun T, Eichner R, Nelson W, Tseng S, Weiss R, Jarvinen M . Keratin classes: molecular markers for different types of epithelial differentiation. J Invest Dermatol. 1983; 81(1 Suppl):109s-15s. DOI: 10.1111/1523-1747.ep12540831. View

Alibardi L . Cornification in reptilian epidermis occurs through the deposition of keratin-associated beta-proteins (beta-keratins) onto a scaffold of intermediate filament keratins. J Morphol. 2012; 274(2):175-93. DOI: 10.1002/jmor.20086. View

Valle L, Michieli F, Benato F, Skobo T, Alibardi L . Molecular characterization of alpha-keratins in comparison to associated beta-proteins in soft-shelled and hard-shelled turtles produced during the process of epidermal differentiation. J Exp Zool B Mol Dev Evol. 2013; 320(7):428-41. DOI: 10.1002/jez.b.22517. View

Wyld J, Brush A . The molecular heterogeneity and diversity of reptilian keratins. J Mol Evol. 1979; 12(4):331-47. DOI: 10.1007/BF01732028. View

Scala C, Cenacchi G, Ferrari C, Pasquinelli G, Preda P, Manara G . A new acrylic resin formulation: a useful tool for histological, ultrastructural, and immunocytochemical investigations. J Histochem Cytochem. 1992; 40(11):1799-804. DOI: 10.1177/40.11.1431065. View

10.

Oguin W, Galvin S, Schermer A, Sun T . Patterns of keratin expression define distinct pathways of epithelial development and differentiation. Curr Top Dev Biol. 1987; 22:97-125. DOI: 10.1016/s0070-2153(08)60100-3. View

11.

Alibardi L . Adaptation to the land: The skin of reptiles in comparison to that of amphibians and endotherm amniotes. J Exp Zool B Mol Dev Evol. 2003; 298(1):12-41. DOI: 10.1002/jez.b.24. View

12.

Alibardi L . Immunolocalization of specific keratin associated beta-proteins (beta-keratins) in the adhesive setae of Gekko gecko. Tissue Cell. 2013; 45(4):231-40. DOI: 10.1016/j.tice.2013.01.002. View

13.

Alibardi L, Toni M, Dalla Valle L . Hard cornification in reptilian epidermis in comparison to cornification in mammalian epidermis. Exp Dermatol. 2007; 16(12):961-76. DOI: 10.1111/j.1600-0625.2007.00609.x. View

14.

Dalla Valle L, Nardi A, Bonazza G, Zucal C, Zuccal C, Emera D . Forty keratin-associated beta-proteins (beta-keratins) form the hard layers of scales, claws, and adhesive pads in the green anole lizard, Anolis carolinensis. J Exp Zool B Mol Dev Evol. 2009; 314(1):11-32. DOI: 10.1002/jez.b.21306. View

15.

Hallahan D, Keiper-Hrynko N, Shang T, Ganzke T, Toni M, Dalla Valle L . Analysis of gene expression in gecko digital adhesive pads indicates significant production of cysteine- and glycine-rich beta-keratins. J Exp Zool B Mol Dev Evol. 2008; 312(1):58-73. DOI: 10.1002/jez.b.21242. View

16.

Alibardi L, Toni M . Cytochemical, biochemical and molecular aspects of the process of keratinization in the epidermis of reptilian scales. Prog Histochem Cytochem. 2006; 40(2):73-134. DOI: 10.1016/j.proghi.2006.01.001. View

17.

Baden H, Maderson P . Morphological and biophysical identification of fibrous proteins in the amniote epidermis. J Exp Zool. 1970; 174(2):225-32. DOI: 10.1002/jez.1401740211. View

18.

Coulombe P, Omary M . 'Hard' and 'soft' principles defining the structure, function and regulation of keratin intermediate filaments. Curr Opin Cell Biol. 2002; 14(1):110-22. DOI: 10.1016/s0955-0674(01)00301-5. View

19.

Vandebergh W, Bossuyt F . Radiation and functional diversification of alpha keratins during early vertebrate evolution. Mol Biol Evol. 2011; 29(3):995-1004. DOI: 10.1093/molbev/msr269. View

20.

Kirfel J, Magin T, Reichelt J . Keratins: a structural scaffold with emerging functions. Cell Mol Life Sci. 2003; 60(1):56-71. PMC: 11146072. DOI: 10.1007/s000180300004. View