Keratohyalin

Dockal

Reinisch

et al. 2004

J Histochem Cytochem.

Caspase-14 has been implicated in the formation of stratum corneum because of its specific expression and activation in terminally differentiating keratinocytes. However, its precise physiological role and its protein substrate are elusive. We studied the ultrastructural localization of caspase-14 in human epidermis to compare its distribution pattern with that of well-characterized differentiation markers. Immunogold cytochemistry confirmed that caspase-14 is nearly absent in basal and spinous layers. In the granular, layer nuclei and keratohyalin granules were labeled with increasing intensity towards the transitional layer. Particularly strong caspase-14 labeling was associated with areas known to be occupied by involucrin and loricrin, whereas F-granules, occupied by profilaggrin/filaggrin, were much less labeled. A high density of gold particles was also present at the forming cornified cell envelope, including desmosomes. In corneocytes, intense labeling was both cytoplasmic and associated with nuclear remnants and corneodesmosomes. These observations will allow focusing efforts of biochemical substrate screening on a subset of proteins localizing to distinct compartments of terminally differentiated keratinocytes.

Section: Discussionsupporting

confidence: 93%

“…Profilaggrin, a histidin-rich protein that aggregates keratins, is present in F-granules of composite keratohyalin (Fukuyama and Epstein 1986; Holbrook 1989; Steven et al 1990; Manabe et al 1991). F-granules have been described for both rodents and human keratohyalin (Yoneda et al 1992; Ishida-Yamamoto et al 1993).…”

mentioning

confidence: 99%

Ultrastructural Localization of Caspase-14 in Human Epidermis

Dockal

Reinisch

et al. 2004

J Histochem Cytochem.

“…This pattern is produced by paler keratin filaments of 8-10 nm embedded within electrondenser matrix material [Baden and Maderson, 1970;Frazer et al, 1972]. The latter derives from the production of matrix proteins (mainly filaggrin in mammals) that keep keratin filaments together to form the dense corneous bundles of mature corneocytes [Fukuyama and Epstein, 1986;Resing and Dale, 1991].…”

Section: Proteins Of Cornification In Interfollicular and Apteric Epimentioning

confidence: 99%

Localization and Characterization of Specific Cornification Proteins in Avian Epidermis

Toni

2004

Cells Tissues Organs

Little is known about proteins involved in the formation of the stratum corneum in the avian apteric epidermis. The present immunocytochemical, autoradiographic and electrophoretic study shows that antibodies against characteristic proteins of mammalian cornification (α-keratins, loricrin, sciellin, filaggrin, transglutaminase) recognize avian epidermal proteins. This suggests the presence of avian protein with epitopes common to related mammalian proteins. These proteins may also be involved in the formation of the cornified core and cell envelope of mature avian corneocytes. The immunoblotting study suggests that protein bands, cross-reactive for antibodies against loricrin (45, 52–57 kDa), sciellin (54, 84 kDa), filaggrin (32, 38, 45–48 kDa), and transglutaminase (40, 50, 58 kDa), are present in the avian epidermis. Immunocytochemistry shows that immunoreactivity for the above proteins is localized in the transitional and lowermost corneous layer of apteric epidermis. Their epitopes are rapidly masked/altered in cornifying cells and are no longer detectable in mature corneocytes. In scaled epidermis a thick layer made of β-keratins of 14–18, 20–22, and 33 kDa is formed. Only in feathered epidermis (not in scale epidermis), an antifeather chicken β-keratin antibody recognized a protein band at 8–12 kDa. This small β-keratin is probably suitable for the formation of long, axial filaments in elongated barb, barbule and calamus cells. Conversely, the larger β-keratins in scales are irregularly deposited forming flat plates. Tritiated histidine coupled to autoradiography show an absence of both keratohyalin and histidine-rich proteins in adult feathered and scaled epidermis. Most of the labeling appears in proteins within the range of β- and α-keratins. These data on apteric epidermis support the hypothesis of an evolution of the apteric and interfollicular epidermis from the expansion of hinge regions of protoavian archosaurians.

“…At least some of these granules may be confused with previously identified mucous granules (Landmann, 1979(Landmann, , 1986. The granules merge one to another and with other components, including lipid droplets (Fukuyama and Epstein, 1986;Alibardi, 1999). The phosphorous peak of large KHLGs is likely derived from incorporated phospholipids, which is different from mammalian keratohyalin, where the phosphorous component is mainly derived from phosphorylated profilaggrin (Resing and Dale, 1991).…”

Section: Discussionmentioning

confidence: 98%

Loricrin‐like immunoreactivity during keratinization in lizard epidermis

2002

Journal of Morphology

Two modalities of keratinization are present in lizard epidermis: alpha (soft-pliable corneous layers) and beta (hard and inflexible corneous layers). While beta-keratinization is probably due to the synthesis of a new (beta)-keratin gene product, alpha keratinization resembles in part that of mammalian epidermis. The goal of this study was to test whether a sulfur-rich molecule similar to the mammalian corneous cell envelope protein loricrin is also present in lizard epidermis. This was done using X-ray microanalysis and immunocytochemical and ultrastructural methods. In the epidermis of the lizard Podarcis muralis small (0.1-0.3 microm) to large (1-5 microm) keratohyalin-like granules (KHLGs) are produced in alpha-keratinizing cells, especially in the clear layer. Small KHLGs contain sulfur and show weak filaggrin-like and stronger loricrin-like immunoreactivities. The latter is also present in keratinizing alpha-layers but is absent in the beta layers. Large KHLGs in the clear layer derive from the aggregation of the small granules with other components, including lipid material. These large granules show some loricrin-like immunoreactivity and contain sulfur and phosphorous, histidine, but not filaggrin-like immunoreactivity. It is suggested here that phosphorous derives from their phospholipid component. The present study shows that the modality of alpha-keratinization of lizard epidermis resembles that of mammals and suggests that the basic molecular mechanisms of keratin aggregation and formation of the corneous cell envelope were already present in the therapsid line of reptiles from which mammals evolved.