Significance of kallikrein-5 in the formation of filaggrin monomer

丝聚蛋白有助于人类皮肤屏障的形成。聚丝蛋白原被蛋白水解酶切割并转化为功能性聚丝蛋白，但其加工机制尚未完全阐明。激肽释放酶相关肽酶5（KLK 5）是皮肤中发现的主要丝氨酸蛋白酶。我们通过表皮提取物的部分纯化来寻找加工微丝聚集蛋白原的蛋白酶，并发现KLK 5是可能的候选者。我们使用HPLC结合质谱法来显示KLK 5切割聚丝蛋白原。KLK 5还切割含有聚丝蛋白原的连接物的融合蛋白。此外，基于邻位连接试验，免疫组织化学和免疫电子显微镜分析，我们揭示了KLK 5和profilaggrin共定位在人类表皮的颗粒层。在正常培养的人表皮角质形成细胞中KLK 5敲低导致更高水平的聚丝蛋白原，表明KLK 5可能在聚丝蛋白原切割中起作用。

Filaggrin contributes to the formation of the human skin barrier. Profilaggrin is cleaved by proteolytic enzymes and converted to functional filaggrin, but its processing mechanism remains not fully elucidated. Kallikrein-related peptidase 5 (KLK5) is a major serine protease found in the skin. We searched for profilaggrin-processing protease(s) by partial purification of epidermal extracts and found KLK5 as a possible candidate. We used HPLC coupled with mass spectrometry to show that KLK5 cleaves profilaggrin. KLK5 also cleaved fusion protein containing liker of profilaggrin. Furthermore, based on a proximity ligation assay, immunohistochemistry, and immunoelectron microscopy analysis, we reveal that KLK5 and profilaggrin co-localize in the stratum granulosum in human epidermis. KLK5 knockdown in normal cultured human epidermal keratinocytes resulted in higher levels of profilaggrin, indicating that KLK5 potentially functions in profilaggrin cleavage.