Shin Won-Sik, Maeng Yong-Sun, Jung Jae-Won, Min Jeong-Ki, Kwon Young-Guen, Lee Seung-Taek
Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea.
Biochem Biophys Res Commun. 2008 Jul 11;371(4):793-8. doi: 10.1016/j.bbrc.2008.04.168. Epub 2008 May 8.
Human PTK7 is a defective receptor protein tyrosine kinase and its expression is upregulated in various cancers including colorectal carcinomas. To determine whether PTK7 functions in angiogenesis, we have expressed and purified the extracellular domain of PTK7 (soluble PTK7; sPTK7) as a decoy receptor to counteract the effects of endogenous PTK7. Capillary-like tube formation of human umbilical vascular endothelial cells (HUVECs) was accompanied by modulation in the PTK7 mRNA level. Neutralization of endogenous PTK7 with sPTK7 inhibited vascular endothelial growth factor (VEGF)-induced tube formation, migration, and invasion of HUVECs in a dose-dependent manner. sPTK7 reduced VEGF-induced phosphorylation of focal adhesion kinase (FAK) and paxillin, relocalization of paxillin to focal adhesions, and formation of stress fibers. Moreover, sPTK7 inhibited VEGF-induced angiogenesis in vivo. Knockdown of PTK7 using siRNA also inhibited VEGF-induced tube formation, supporting that sPTK7 specifically blocks function of the endogenous PTK7. These results demonstrate that PTK7 plays an important role not only in tube formation, migration, and invasion of endothelial cells but also in angiogenesis.
人PTK7是一种缺陷型受体蛋白酪氨酸激酶，其在包括结直肠癌在内的多种癌症中表达上调。为了确定PTK7是否在血管生成中发挥作用，我们表达并纯化了PTK7的细胞外结构域（可溶性PTK7；sPTK7）作为诱饵受体，以抵消内源性PTK7的作用。人脐静脉血管内皮细胞（HUVECs）的毛细血管样管形成伴随着PTK7 mRNA水平的调节。用sPTK7中和内源性PTK7以剂量依赖的方式抑制血管内皮生长因子（VEGF）诱导的HUVECs管形成、迁移和侵袭。sPTK7降低了VEGF诱导的粘着斑激酶（FAK）和桩蛋白的磷酸化、桩蛋白重新定位到粘着斑以及应力纤维的形成。此外，sPTK7在体内抑制VEGF诱导的血管生成。使用siRNA敲低PTK7也抑制了VEGF诱导的管形成，支持sPTK7特异性阻断内源性PTK7的功能。这些结果表明，PTK7不仅在内皮细胞的管形成、迁移和侵袭中起重要作用，而且在血管生成中也起重要作用。
