Sciandra Francesca, Morlacchi Simona, Allamand Valérie, De Benedetti Giacomo, Macchia Gianfranco, Petrucci Tamara C, Bozzi Manuela, Brancaccio Andrea
Istituto di Chimica del Riconoscimento Molecolare (CNR) c/o Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore L.go F. Vito 1, 00168 Rome, Italy.
Matrix Biol. 2008 May;27(4):360-70. doi: 10.1016/j.matbio.2007.12.003. Epub 2007 Dec 23.
Keratoepithelin (KE) is an extracellular matrix protein that binds collagens, fibronectin, decorin, biglycan and integrins, interconnecting extracellular matrix components with resident cells in several tissues. KE has a molecular mass of 68 kDa and harbours four FAS1 domains named after those identified in the insect cell adhesion molecule fasciclin I. In humans, KE is preferentially expressed by the corneal epithelial layer and liberated towards the corneal stroma but it was also detected in the lung and in the bladder smooth muscle. No detailed information is available on the distribution of this protein in other human tissues. In this work, we have raised a polyclonal antibody against the recombinantly expressed human fourth FAS1 domain which is able to specifically detect KE in human skeletal muscle tissue extracts. Immunofluorescence experiments indicate that KE is localized around the perimysium and endomysium of each skeletal muscle fiber. The same kind of analysis shows that in muscle sections from patients affected by different forms of muscular dystrophy KE is upregulated and widely distributed in fibrotic tissues. The muscle specific expression of KE was also demonstrated by RT-PCR. In human skeletal muscle, KE may help to build up a bridge between collagen VI and yet unidentified muscle receptor(s), adding to the complexity of the adhesive molecular network established between muscle fibers and the surrounding basement membrane.
角蛋白上皮素（KE）是一种细胞外基质蛋白，它能结合胶原蛋白、纤连蛋白、核心蛋白聚糖、双糖链蛋白聚糖和整合素，在多个组织中将细胞外基质成分与驻留细胞相互连接起来。KE的分子量为68 kDa，含有四个FAS1结构域，以在昆虫细胞黏附分子成束蛋白I中鉴定出的结构域命名。在人类中，KE优先由角膜上皮层表达并释放到角膜基质中，但在肺和膀胱平滑肌中也有检测到。关于这种蛋白质在其他人体组织中的分布尚无详细信息。在这项研究中，我们制备了一种针对重组表达的人第四FAS1结构域的多克隆抗体，该抗体能够特异性检测人骨骼肌组织提取物中的KE。免疫荧光实验表明，KE定位于每条骨骼肌纤维的肌束膜和肌内膜周围。同样的分析表明，在患有不同形式肌营养不良症患者的肌肉切片中，KE上调并广泛分布于纤维化组织中。KE的肌肉特异性表达也通过逆转录聚合酶链反应（RT-PCR）得到证实。在人类骨骼肌中，KE可能有助于在胶原蛋白VI和尚未确定的肌肉受体之间建立桥梁，从而增加了肌肉纤维与周围基底膜之间建立的黏附分子网络的复杂性。
