Department of Dermatology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Department of Dermatology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; Division of Skin Surface Sensing, Department of Dermatology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
J Dermatol Sci. 2014 Mar;73(3):225-31. doi: 10.1016/j.jdermsci.2013.10.008. Epub 2013 Oct 30.
Neuronatin (Nnat), which is a neuronal developmental and differentiation molecule, is expressed in the endoplasmic reticulum of non-neuronal cells and is involved in insulin secretion from pancreatic β-cells by plausibly modulating their intracellular calcium concentration. However, the role of Nnat in keratinocyte differentiation remains unclear.
To unveil a possible integration of Nnat in controlling the keratinocyte differentiation markers such as involucrin, cytokeratin1, filaggrin, loricrin and S100A7.
Immunohistological staining was done using psoriasis, chronic eczema, lichen planus and normal skin. Immunofluorescence staining, Western blotting and semi-quantitative real-time PCR were performed for detecting Nnat, involucrin, cytokeratin1, filaggrin, loricrin and S100A7 using human keratinocytes with or without Nnat gene transfection. Small interference RNA was applied to knockdown the Nnat gene expression.
Nnat existed in normal human epidermis and cultured keratinocytes. In the hyperplastic epidermis of psoriasis, chronic eczema and lichen planus, over-expression of Nnat was evident along with involucrin and cytokeratin1 expression. Coordinate up-regulation of Nnat and involucrin, but not cytokeratin1, was demonstrated in cultured keratinocytes under differentiation stimuli such as extracellular calcium elevation, exposure to phorbol myristate acetate, and increased cell density. Transfection of small intereference RNA for Nnat decreased the mRNA levels of Nnat and involucrin, but not of cytokeratin1. Furthermore, a gene transfection assay showed increased involucrin expression in the Nnat-transfected keratinocytes than in mock-transfected counterparts, without any appreciable influence on cytokeratin1, filaggrin, loricrin and S100A7 expression.
These data indicate that Nnat is related to keratinocyte differentiation by up-regulating involucrin expression.
神经元特有的分泌蛋白（Nnat）是一种神经元发育和分化分子，在非神经元细胞的内质网中表达，通过调节细胞内钙离子浓度来参与胰岛β细胞的胰岛素分泌。然而，Nnat 在角质形成细胞分化中的作用尚不清楚。
揭示 Nnat 可能整合在控制角蛋白细胞分化标志物中，如兜甲蛋白、细胞角蛋白 1、丝聚合蛋白、板层素和 S100A7。
采用免疫组织化学染色法对银屑病、慢性湿疹、扁平苔藓和正常皮肤进行染色。采用免疫荧光染色、Western blot 和半定量实时 PCR 检测 Nnat、兜甲蛋白、细胞角蛋白 1、丝聚合蛋白、板层素和 S100A7，同时对转染 Nnat 基因或 Nnat 基因沉默的人角质形成细胞进行检测。
Nnat 存在于正常人类表皮和培养的角质形成细胞中。在银屑病、慢性湿疹和扁平苔藓的过度增生表皮中，Nnat 与兜甲蛋白和细胞角蛋白 1 的表达均明显上调。在分化刺激下，如细胞外钙升高、佛波醇肉豆蔻酸酯（PMA）暴露和细胞密度增加，培养的角质形成细胞中 Nnat 与兜甲蛋白的协同上调，但与细胞角蛋白 1 无关。Nnat 的小干扰 RNA 转染降低了 Nnat 和兜甲蛋白的 mRNA 水平，但对细胞角蛋白 1 没有影响。此外，基因转染试验显示，Nnat 转染的角质形成细胞中兜甲蛋白的表达增加，而对细胞角蛋白 1、丝聚合蛋白、板层素和 S100A7 的表达没有明显影响。
这些数据表明，Nnat 通过上调兜甲蛋白的表达与角质形成细胞分化有关。
