Sprouty family of proteins regulates organogenesis and carcinogenesis through the signaling caused by RET tyrosine kinase

斯普罗蒂蛋白家族包括由受体酪氨酸激酶启动的下游信号的重要调节因子。在本研究中，我们研究了通过RET酪氨酸激酶的胞内信号传导中Sprouty蛋白的作用。在转染RET和GFRα1基因的HEK293T细胞中，表达Sprouty家族蛋白可显著降低ERK的持续激活，而对p38、Akt和JNK的激活无显著影响。由于GDNF能在表达RET和GFRα1的TGW人神经母细胞瘤细胞中有效诱导Sprouty2的表达，我们进一步研究了Sprouty2在TGW细胞生长分化中的作用。野生型Sprouty2 （WT-SPRY2）的表达降低了TGW细胞的生长。相反，Sprouty2显性阴性形式（MT-SPRY2，酪氨酸残基突变）的表达增强了细胞增殖。此外，WT-SPRY2的表达减少了TGW细胞gdnf依赖性神经突的生长，其中MT-SPRY2的表达增强了gdnf依赖性神经突的生长。综上所述，我们的研究结果表明Sprouty2调节由RET酪氨酸激酶介导的gdnf依赖性的TGW神经母细胞瘤细胞的增殖和分化。这些研究结果发表在《癌症科学》杂志上（癌症科学98:815-821,2007）。接下来，我们在突变RET （Y1062F）和Sprouty2之间产生了双敲除和敲入小鼠，并观察了它们在肠神经系统和肾脏中的表型。Sprouty2缺乏小鼠表现出肠神经元数量增加和食管贲门失弛缓症样稀释，而Sprouty2缺乏不影响肾脏发生，尽管Sprouty2在肾脏中高表达。纯合突变RET小鼠肠道神经元数量减少，肾脏变小，组织学改变。有趣的是，Sprouty2缺失部分挽救了纯合子RET突变小鼠肠神经系统和肾发生中的异常表型。这些结果表明Sprouty2实际上在体内调节RET酪氨酸激酶的下游信号，调控小鼠器官发生。少

The Sprouty family of proteins includes important regulators of downstream signaling initiated by receptor tyrosine kinases. In the present study, we investigated the role of Sprouty proteins in intracellular signaling via RET tyrosine kinase. Expression of Sprouty family proteins in HEK293T cells transfected with RET and GFRα1 genes significantly reduced sustained activation of ERK, whereas their expression had no remarkable influence on the activation of p38, Akt and JNK. Since expression of Sprouty2 was efficiently induced by GDNF in TGW human neuroblastoma cells expressing RET and GFRα1, we further investigated the role of Sprouty2 in growth and differentiation of TGW cells. Expression of wild-type Sprouty2 (WT-SPRY2) decreased the growth of TGW cells. In contrast, expression of a dominant negative form of Sprouty2 (MT-SPRY2, with a mutated tyrosine residue) enhanced cell proliferation. In addition, expression of WT-SPRY2 reduced GDNF-dependent neurite outgrowth of TGW cells, where … More as expression of MT-SPRY2 enhanced it. Taken together, our results suggest that Sprouty2 regulates GDNF-dependent proliferation and differentiation of TGW neuroblastoma cells mediated by RET tyrosine kinase. These results have been reported in Cancer Science (Cancer Sci 98: 815-821, 2007). We next generated double knocli-out and knock-in mice between mutant RET (Y1062F) and Sprouty2 and observed their phenotype especially in the enteric nervous system and the kidney. Sprouty2-defficient mice demonstrated increased number of enteric neurons and achalasia-like dilution of esophagus, whereas Sprouty2 deficiency did not affect nephrogenesis even though high expression of Sprouty2 in the kidney. In contrast, mice with homozygous mutant RET demonstrated the decreased number of enteric neurons and small kidneys accompanying histological change. Interesting, Sprouty2 deficiency partially rescued the abnormal phenotype both in the enteric nervous system and nephrogenesis in homozygous RET mutant mice. These results suggest that Sprouty2 actually modulates the downstream signaling of RET tyrosine kinase and regulates mouse organogenesis in vivo. Less