Caricasole Andrea, Ferraro Teresa, Iacovelli Luisa, Barletta Eliana, Caruso Alessandra, Melchiorri Daniela, Terstappen Georg C, Nicoletti Ferdinando
Department of Human Physiology and Pharmacology, University of Rome La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
J Biol Chem. 2003 Sep 26;278(39):37024-31. doi: 10.1074/jbc.M300191200. Epub 2003 Jul 11.
WNT factors represent key mediators of many processes in animal development and homeostasis and act through a receptor complex comprised of members of the Frizzled and low density lipoprotein-related receptors (LRP). In mammals, 19 genes encoding Wingless and Int-related factor (WNTs), 10 encoding Frizzled, and 2 encoding LRP proteins have been identified, but little is known of the identities of individual Frizzled-LRP combinations mediating the effects of specific WNT factors. Additionally, several secreted modulators of WNT signaling have been identified, including at least three members of the Dickkopf family. WNT7A is a WNT family member expressed in the vertebrate central nervous system capable of modulating aspects of neuronal plasticity. Gene knock-out models in the mouse have revealed that WNT7A plays a role in cerebellar maturation, although its function in the development of distal limb structures and of the reproductive tract have been more intensely studied. To identify a receptor complex for this WNT family member, we have analyzed the response of the rat pheochromocytoma cell line PC12 to WNT7A. We find that PC12 cells are capable of responding to WNT7A as measured by increased beta-catenin stability and activation of a T-cell factor-based luciferase reporter construct and that these cells express three members of the Frizzled family (Frizzled-2, -5, and -7) and LRP6. Our functional analysis indicates that WNT7A can specifically act via a Frizzled-5.LRP6 receptor complex in PC12 cells and that this activity can be antagonized by Dickkopf-1 and Dickkopf-3.
WNT因子是动物发育和体内平衡中许多过程的关键调节因子，通过由卷曲蛋白（Frizzled）家族成员和低密度脂蛋白相关受体（LRP）组成的受体复合物发挥作用。在哺乳动物中，已鉴定出19个编码无翅型MMTV整合位点家族（WNTs）的基因、10个编码卷曲蛋白的基因和2个编码LRP蛋白的基因，但对于介导特定WNT因子作用的单个卷曲蛋白-LRP组合的身份了解甚少。此外，还鉴定出了几种WNT信号的分泌调节因子，包括Dickkopf家族的至少三个成员。WNT7A是在脊椎动物中枢神经系统中表达的一种WNT家族成员，能够调节神经元可塑性的多个方面。小鼠基因敲除模型显示，WNT7A在小脑成熟中发挥作用，尽管其在远端肢体结构和生殖道发育中的功能得到了更深入的研究。为了鉴定该WNT家族成员的受体复合物，我们分析了大鼠嗜铬细胞瘤细胞系PC12对WNT7A的反应。我们发现，通过增加β-连环蛋白稳定性和激活基于T细胞因子的荧光素酶报告构建体来衡量，PC12细胞能够对WNT7A作出反应，并且这些细胞表达卷曲蛋白家族的三个成员（卷曲蛋白-2、-5和-7）和LRP6。我们的功能分析表明，WNT7A可以在PC12细胞中通过卷曲蛋白-5.LRP6受体复合物特异性发挥作用，并且这种活性可以被Dickkopf-1和Dickkopf-3拮抗。
