Epidermal barrier dysfunction is associated with a wide range of highly prevalent inflammatory skin diseases. However, the molecular processes that drive epidermal barrier maintenance are still largely unknown. Here, using quantitative proteomics, lipidomics, and mouse genetics, we characterize epidermal barrier maintenance versus a newly established barrier and functionally identify differential ceramide synthase 4 protein expression as one key difference. We show that epidermal loss of ceramide synthase 4 first disturbs epidermal lipid metabolism and adult epidermal barrier function, ultimately resulting in chronic skin barrier disease characterized by acanthosis, hyperkeratosis, and immune cell accumulation. Importantly, prolonged barrier dysfunction induced by loss of ceramide synthase 4 induced a barrier repair response that largely recapitulates molecular programs of barrier establishment. Collectively, this study provides an unbiased temporal proteomic characterization of barrier maintenance and disturbed homeostasis and shows that lipid homeostasis is essential to maintain adult skin barrier function to prevent disease.

表皮屏障功能障碍与多种高度流行的炎性皮肤疾病有关。然而，驱动表皮屏障维持的分子过程仍然是未知的。在这里，使用定量蛋白质组学，脂质组学和小鼠遗传学，我们表征了表皮屏障维持与新建立的屏障之间的关系，并在功能上将差异性神经酰胺合酶4蛋白表达鉴定为一个关键差异。我们表明，神经酰胺合酶4的表皮丧失首先会干扰表皮脂质代谢和成人表皮屏障功能，最终导致以棘皮病，角化过度和免疫细胞蓄积为特征的慢性皮肤屏障疾病。重要的，由神经酰胺合酶4丧失引起的延长的屏障功能障碍，诱导了屏障修复反应，从而在很大程度上概括了屏障建立的分子程序。总的来说，这项研究提供了屏障维持和紊乱的体内平衡的无偏态的蛋白质组学表征，并显示脂质体内平衡对于维持成人皮肤屏障功能以预防疾病至关重要。