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

Sprouty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Sprouty蛋白通过RET酪氨酸激酶在细胞内信号转导中的作用。转染Ret和GFRERK-1基因的HEK293T细胞中Sprouty家族蛋白的表达显著降低了α的持续激活，而对p38、Akt和JNK3种蛋白的激活无明显影响。由于胶质细胞源性神经营养因子能有效地诱导表达RET和GFRα-1的人神经母细胞瘤细胞中Sprouty2的表达，我们进一步研究了Sprouty2在TGW细胞生长和分化中的作用。野生型Sprouty2(WT-SPRY2)的表达抑制了TGW细胞的生长。相反，Sprouty2的显性阴性形式(MT-SPRY2，带有突变的酪氨酸残基)的表达促进了细胞的增殖。此外，WT-SPRY2的表达减少了TGW细胞依赖神经生长因子的突起生长，其中…MT-SPRY2的表达增强。综上所述，我们的结果提示Sprouty2调控RET酪氨酸激酶介导的GDNF依赖的TGW神经母细胞瘤细胞的增殖和分化。这些结果已发表在《癌症科学》(癌症科学98：815-821,2007)上。接下来，我们在突变的RET(Y1062F)和Sprouty2之间建立了双基因敲除和敲入小鼠，并观察了它们的表型，特别是在肠道神经系统和肾脏中。Sprouty2缺乏的小鼠表现出肠上皮神经元数量增加和食道失弛缓症样稀释，而Sprouty2缺乏并不影响肾脏的形成，尽管Sprouty2在肾脏中高表达。相比之下，RET纯合子突变的小鼠表现出肠道神经元和小肾脏数量减少，并伴有组织学变化。有趣的是，Sprouty2缺乏部分挽救了纯合子RET突变小鼠的肠道神经系统和肾脏发生的异常表型。这些结果表明，Sprouty2实际上调节了RET酪氨酸激酶的下游信号，并调节了小鼠体内的器官发生。较少

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