Changes to desmosomal antigens and lectin-binding sites during differentiation in normal human epidermis: a quantitative ultrastructural study.

During epidermal differentiation, desmosomes undergo a series of changes in their abundance, structure and properties, which has previously been defined by conventional electron microscopy and the use of antibodies to desmosomal proteins at the light-microscope level. Such changes in a major adhesive organelle would be expected to have a significant role in the maintenance of epidermal organization, and therefore require more detailed characterization. In the present study, modifications to certain desmosomal components in normal human epidermis have been located and quantified by immunogold electron microscopy.

Relationship of the final alpha-keratin compositions in dyskeratoses to those along the normal keratinization pathway: aetiological and diagnostic significance.

The final alpha-keratin compositions attained in the outer horny layer of 16 dyskeratoses have been compared with the series of compositions which is produced during normal epidermal differentiation. In each case, the abnormal outer horny layer composition corresponded with that of normal basal, spinous, granular or inner horny cells, with, in some cases, the addition of alpha-keratins characteristic of hyperproliferating/regenerating keratinocytes. The results have implications for the aetiology of these diseases.

Epidermal alpha-keratin is neutral-buffer-soluble and forms intermediate filaments under physiological conditions in vitro.

Undenatured bovine epidermal alpha-keratin has been solubilized in a low-ionic-strength buffer at physiological pH (5 mM Tris-HCl/25 mM 2-mercaptoethanol (pH 7.5). The particles in this buffer were multimeric, retaining their characteristic polypeptide chain composition and alpha-helical coiled-coil structure.

Dissection of the bovine epidermal desmosome into cytoplasmic protein and membrane glycoprotein domains.

Epidermal desmosomes contain two main regions. The core consists of a pair of membranes, one on either side of a cross-striated intercellular space bisected by a denser midline. The cytoplasmic compartment comprises a dense plaque deposited on the cytoplasmic surface of each membrane and a diffuse layer occupying the zone between the plaque and attached alpha-keratin filaments.

Tonofilament differentiation in human epidermis, isolation and polypeptide chain composition of keratinocyte subpopulations.

Epidermal tonofilaments are intermediate filaments with an unusually complex polypeptide chain composition which undergoes profound changes during differentiation. Assessment of the possible functional significance of these changes requires their correlation with defined stages of keratinocyte differentiation. Methods have, therefore, been developed for the isolation of the four keratinocyte subpopulations from human epidermis in high yield and purity without detectable damage to tonofilament chains.

A comparative study of psoriatic and non-psoriatic buccal mucosa.

Buccal mucosa biopsies from patients (seven with and seven without psoriasis) were studied using autoradiography and SDS polyacrylamide gel electrophoresis. The flash labelling indices were similar in psoriatic and non-psoriatic patients and the SDS-gel patterns showed variable amounts of 70,000 mol. wt (70K) protein which did not correlate with the presence or absence of psoriasis or with individual labelling indices.

The proteins of living psoriatic epidermis.

Psoriatic epidermis has a rapid rate of turnover and produces a stratum corneum with an abnormal tonofilament composition. One polypeptide chain, (Mr 70,000) is absent or greatly decreased in relative amount and two other chains, (Mr 63,000 and 55,000), which are normally modified in the living cells, persists into the stratum corneum. Increasing the turnover of normal epidermis has been shown to cause the persistence of 63 and 55 kilodalton chains in the stratum corneum but does not affect the relative amount of 70 kilodalton chain.

Protein modifications during the keratinization of normal and psoriatic human epidermis.

Studies on the polypeptide chain compositions of human stratum corneum and callus have shown that characteristic modifications of the epidermal fibrous protein occur during normal eqidermal keratinization. The polypeptide chain composition of psoriatic scale differs from that of both normal stratum corneum and callus. A major constituent, the alpha-chain (Mr = 70 000) of the epidermal fibrous protein is either absent or greatly decreased in amount in psoriatic sacle.