Alibardi Lorenzo, Tschachler Erwin, Eckhart Leopold
Department of Biology, University of Bologna, Bologna, Italy.
Anat Rec A Discov Mol Cell Evol Biol. 2005 Oct;286(2):962-73. doi: 10.1002/ar.a.20234.
Caspase-14, a member of the caspase family of cysteine proteases, is almost exclusively expressed in the epidermis. Studies on human and mouse cells and tissues have implicated caspase-14 in terminal differentiation of epidermal keratinocytes and in the formation of the stratum corneum. Here we investigated evolutionary aspects of the role of caspase-14 by analyzing its distribution in the epidermis and hair follicles of representative species of placental mammals, marsupials, and monotremes. Immunocytochemical staining showed that caspase-14 is consistently expressed in the granular and corneous layer of the epidermis of all mammalian species investigated. Ultrastructural analysis using gold-labeled anticaspase-14 antibodies revealed that caspase-14 is associated preferentially with keratin bundles and amorphous material of keratohyalin granules, but is also present in nuclei of transitional cells of the granular layer and in corneocytes. In hair follicles, caspase-14 was diffusely present in cornifying cells of the outer root sheath, in the companion layer, and, most abundantly, in the inner root sheath of all mammalian species here analyzed. In Henle and Huxley layers of the inner root sheath, labeling was seen in nuclei and, more diffusely, among trichohyalin granules of cornifying cells. In summary, the tissue expression pattern and the intracellular localization of caspase-14 are highly conserved among diverse mammalian species, suggesting that this enzyme is involved in a molecular process that appeared early in the evolution of mammalian skin. The association of caspase-14 with keratohyalin and trichohyalin granules may indicate a specific role of caspase-14 in the maturation of these keratinocyte-specific structures.
半胱天冬酶 -14是半胱氨酸蛋白酶半胱天冬酶家族的成员，几乎只在表皮中表达。对人和小鼠细胞及组织的研究表明，半胱天冬酶 -14与表皮角质形成细胞的终末分化及角质层的形成有关。在此，我们通过分析其在胎盘哺乳动物、有袋类动物和单孔目动物的代表性物种的表皮和毛囊中的分布，研究了半胱天冬酶 -14作用的进化方面。免疫细胞化学染色显示，在所研究的所有哺乳动物物种的表皮颗粒层和角质层中，半胱天冬酶 -14持续表达。使用金标抗半胱天冬酶 -14抗体的超微结构分析表明，半胱天冬酶 -14优先与角蛋白束和透明角质颗粒的无定形物质相关，但也存在于颗粒层过渡细胞的细胞核和角质形成细胞中。在毛囊中，半胱天冬酶 -14广泛存在于外根鞘的角质化细胞、陪伴层中，在此分析的所有哺乳动物物种中，在内根鞘中含量最为丰富。在内根鞘的亨勒层和赫胥黎层中，在细胞核中可见标记，在角质化细胞的毛透明蛋白颗粒中标记更为广泛。总之，半胱天冬酶 -14的组织表达模式和细胞内定位在不同哺乳动物物种中高度保守，表明该酶参与了哺乳动物皮肤进化早期出现的分子过程。半胱天冬酶 -14与透明角质颗粒和毛透明蛋白颗粒的关联可能表明半胱天冬酶 -14在这些角质形成细胞特异性结构的成熟中具有特定作用。
