Florica Roxana Oriana, Hipolito Victoria, Bautista Stephen, Anvari Homa, Rapp Chloe, El-Rass Suzan, Asgharian Alimohammad, Antonescu Costin N, Killeen Marie T
Graduate Program in Molecular Science Program, Ryerson University, 350 Victoria St., Toronto, Ont., Canada M5B 2K3; Dept. of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto, Ont., Canada M5B 2K3.
Dept. of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto, Ont., Canada M5B 2K3.
Dev Biol. 2017 Oct 1;430(1):249-261. doi: 10.1016/j.ydbio.2017.06.036. Epub 2017 Jul 8.
The axons of the DA and DB classes of motor neurons fail to reach the dorsal cord in the absence of the guidance cue UNC-6/Netrin or its receptor UNC-5 in C. elegans. However, the axonal processes usually exit their cell bodies in the ventral cord in the absence of both molecules. Strains lacking functional versions of UNC-6 or UNC-5 have a low level of DA and DB motor neuron axon outgrowth defects. We found that mutations in the genes for all six of the ENU-3 proteins function to enhance the outgrowth defects of the DA and DB axons in strains lacking either UNC-6 or UNC-5. A mutation in the gene for the MIG-14/Wntless protein also enhances defects in a strain lacking either UNC-5 or UNC-6, suggesting that the ENU-3 and Wnt pathways function parallel to the Netrin pathway in directing motor neuron axon outgrowth. Our evidence suggests that the ENU-3 proteins are novel members of the Wnt pathway in nematodes. Five of the six members of the ENU-3 family are predicted to be single-pass trans-membrane proteins. The expression pattern of ENU-3.1 was consistent with plasma membrane localization. One family member, ENU-3.6, lacks the predicted signal peptide and the membrane-spanning domain. In HeLa cells ENU-3.6 had a cytoplasmic localization and caused actin dependent processes to appear. We conclude that the ENU-3 family proteins function in a pathway parallel to the UNC-6/Netrin pathway for motor neuron axon outgrowth, most likely in the Wnt pathway.
在秀丽隐杆线虫中，如果没有导向信号分子UNC-6/Netrin或其受体UNC-5，DA和DB类运动神经元的轴突就无法到达背侧神经索。然而，在这两种分子都不存在的情况下，轴突通常会从腹侧神经索中的细胞体发出。缺乏功能性UNC-6或UNC-5的菌株中，DA和DB运动神经元轴突生长缺陷的水平较低。我们发现，ENU-3蛋白的所有六个基因发生突变，都会增强缺乏UNC-6或UNC-5的菌株中DA和DB轴突的生长缺陷。MIG-14/Wntless蛋白基因的突变也会增强缺乏UNC-5或UNC-6的菌株中的缺陷，这表明ENU-3和Wnt信号通路在指导运动神经元轴突生长方面与Netrin信号通路平行发挥作用。我们的证据表明，ENU-3蛋白是线虫Wnt信号通路中的新成员。ENU-3家族的六个成员中有五个预计是单次跨膜蛋白。ENU-3.1的表达模式与质膜定位一致。一个家族成员ENU-3.6缺乏预测的信号肽和跨膜结构域。在HeLa细胞中，ENU-3.6定位于细胞质，并导致肌动蛋白依赖性过程出现。我们得出结论，ENU-3家族蛋白在与UNC-6/Netrin信号通路平行的途径中发挥作用，促进运动神经元轴突生长，最有可能是在Wnt信号通路中。
