NFAT5 Controls the Integrity of Skin II

The skin protects the human body against dehydration and harmful challenges. Keratinocytes (KCs) are the most frequent epidermal cells, and it is anticipated that KC-mediated transport of Na+ ions creates a physiological barrier of high osmolality against the external environment. We studied in KCs the role of NFAT5, a transcription factor whose activity is controlled by osmotic stress. Cultured KCs from adult mice secrete more than 300 proteins, and upon NFAT5 ablation, the secretion of several matrix proteinases, including metalloproteinase-3 (Mmp3) and kallikrein-related peptidase 7 (Klk7), was markedly enhanced. An increase in Mmp3 and Klk7 RNA levels was also detected in transcriptomes of Nfat5-/- KCs, along with increases of numerous components of ‘Epidermal Differentiation Complex’ (EDC), as proline-rich Sprr and S100 proteins. NFAT5 and Mmp3 are co-expressed in basal KCs from fetal and adult skin but not in skin of newborn mice. This is correlated with a strong increase in Mmp3 and Klk7 expression in KCs of newborn mice and suggests, along with the fragile epidermis of adult Nfat5-/- mice, a suppressive effect of NFAT5 on the expression of matrix proteases in skin. Our data suggest that NFAT5 controls the expression of matrix proteases in skin and contributes to the many fold changes during embryonal skin development and skin integrity in adults. Expression profiling by high throughput sequencing of RNA from murine keratinocytes cultivated in vitro for one or for three weeks. Keratinocytes were prepared from the tail of adult mice (4 independent experiments)

皮肤作为人体的天然屏障，可抵御脱水与各类有害外界刺激。角质形成细胞（Keratinocytes, KCs）是表皮中占比最高的细胞类群，已有研究推测，KC介导的钠离子转运可构建针对外界环境的高渗生理屏障。本研究聚焦于KC中受渗透压应激调控的转录因子NFAT5的生物学功能。从成年小鼠体内分离并体外培养的KC可分泌超过300种蛋白质；当NFAT5基因被敲除后，包括基质金属蛋白酶3（metalloproteinase-3, Mmp3）与激肽释放酶相关肽酶7（kallikrein-related peptidase 7, Klk7）在内的多种基质蛋白酶的分泌水平显著升高。在Nfat5基因纯合敲除（Nfat5-/-）的KC转录组中，不仅检测到Mmp3与Klk7的mRNA水平上调，还发现“表皮分化复合体（Epidermal Differentiation Complex, EDC）”的多种组分表达量显著上升，例如富含脯氨酸的Sprr家族蛋白与S100家族蛋白。NFAT5与Mmp3在胎儿及成年小鼠皮肤的基底KC中存在共表达现象，但在新生小鼠皮肤中未检测到该共表达。该现象与新生小鼠KC中Mmp3与Klk7的表达量大幅升高的结果相一致；结合成年Nfat5基因敲除小鼠存在表皮脆弱的表型，提示NFAT5可抑制皮肤中基质蛋白酶的转录表达。本研究数据表明，NFAT5可精准调控皮肤中基质蛋白酶的表达，进而参与胚胎皮肤发育过程中的诸多分子表达变化，并维持成年个体的皮肤稳态。本研究通过高通量RNA测序技术，对体外培养1周或3周的小鼠角质形成细胞进行表达谱分析；实验所用细胞均取自成年小鼠尾部，共设置4组独立重复实验。