Expression Cloning of Human Corneodesmosin Proves Its Identity with the Product of the S Gene and Allows Improved Characterization of Its Processing during Keratinocyte Differentiation

Abstract

In human epidermis and other cornified squamous epithelia, corneodesmosin is located in the desmosomes of the upper living layers, and in related structures of the cornified layers, the corneodesmosomes. During maturation of the cornified layers, the protein undergoes a series of cleavages, thought to be a prerequisite of desquamation. Partial amino acid sequencing of corneodesmosin fragments suggested that it is related to the product of the S gene, previously identified in the human major histocompatibility complex.We report the expression cloning of corneodesmosin cDNA from a human epidermis library screened with monoclonal antibodies. Sequencing demonstrated that corneodesmosin is really the product of the S gene. However, analysis of 20 alleles of the gene revealed that its product is 27 amino acids longer than initially reported. Two additional polymorphic sites were described, and the position of the unique intron was ascertained.Corneodesmosin cDNA expression in COS-7 cells led to secretion of the protein. Precise epitope mapping allowed further characterization of the molecular forms of corneodesmosin present in the most superficial cornified layers, where fragments corresponding to the central region of the protein were detected. This indicated a cleavage of the N-and C-terminal domains of corneodesmosin before desquamation. These serineand glycine-rich domains are proposed to mediate an adhesive function.The late stages of the terminal differentiation program in epidermis correspond to cornification, a particular cell death process transforming keratinocytes into anucleated, flattened corneocytes. Stacking of the corneocytes forms the most superficial epidermal layers, designated as the cornified layers or stratum corneum, and is responsible for the mechanical protection of the body. Corneocytes are continually shed from the epidermis surface in the tightly regulated process of desquamation (1, 2).Corneocyte function is achieved by peculiar structures formed during cornification. The cornified cell envelope, a rigid pericellular shell, consists of covalently linked proteins. Its external side is covered by a monomolecular lipid layer, whereas its internal surface is linked to a cytokeratin-rich fibrous matrix that occupies the entire intracellular volume (3, 4). Intercellular structures derived from desmosomes have been described in the stratum corneum. Indeed, considerable morphological modifications of the desmosomes occur when keratinocytes reach the cornified layers. The desmosomal plaque, thought to be incorporated in the cornified cell envelope, is no longer observed, and the characteristic symmetrical trilamellar structure of the extracellular core becomes transformed into a homogeneous electron dense plug (5-9). These structures, called corneodesmosomes, play a major role in stratum corneum cohesion (9 -15). Their degradation, performed at the skin surface, by the stratum corneum chymotryptic enzyme and other less characterized proteases, is required for desquamation (16 -19). Although corneod...

Temporally controlled targeted somatic mutagenesis in embryonic surface ectoderm and fetal epidermal keratinocytes unveils two distinct developmental functions of BRG1 in limb morphogenesis and skin barrier formation

“…5B and data not shown). Moreover, the transcripts of corneodesmosin, which encode a putative adhesion glycoprotein thought to play a key role in the function of corneodesmosomes and thus in corneocyte cohesion (Guerrin et al, 1998), were fourfold lower in mutant than control skin (Fig. 5C).…”

Corneodesmosin Expression in Psoriasis Vulgaris Differs from Normal Skin and Other Inflammatory Skin Disorders

“…Immunohistochemistry was performed using two monoclonal antibodies to Cdsn, G36-19 and F28-27 (Serre et al, 1991), which label different epitopes in the central domain of the Cdsn protein (Guerrin et al, 1998). Five-micron-thick sections were mounted on glass slides and either fixed in acetone (frozen tissue) or dewaxed in xylene and alcohol and microwave pretreated (paraffin-embedded tissue).…”

“…Some desmosomal proteins are important in maintaining keratinocyte cell-cell adhesion, and it is likely that Cdsn forms part of the adhesive network (Serre et al, 1991). Cdsn has a high glycine content, which implies a potential to form adhesive loop structures at the cell surface, as seen with other epidermal proteins (Guerrin et al, 1998). Progressive proteolytic digestion of Cdsn has been proposed, which would account for the decrease in molecular size between the stratum granulosum and stratum corneum, and the gradual reduction and eventual loss of adhesive function with associated scale formation.…”

Corneodesmosin: Structure, Function and Involvement in Pathophysiology

“…Cloning of its encoding cDNA revealed that CDSN is located on chromosome 6, in PSORS1, the major locus for psoriasis susceptibility. The mRNA encodes a 529-amino acid protein with a N-terminal signal peptide and one putative Nglycosylation site, consistent with the demonstration that it is secreted and glycosylated [7].…”