SNTS--DEVELOPMENTAL FUNCTIONS AND RECEPTOR INTERACTIONS

描述（改编自申请人的摘要）：SNT（Suc 1结合神经营养因子诱导的酪氨酸磷酸化靶）蛋白是最近发现的衔接分子，其在被包括神经营养因子（NGF、BDNF、NT 3）和FGF的生长因子而不是胰岛素和EGF刺激后经历快速酪氨酸磷酸化。他们与国税局关系密切。SNT是豆蔻酰化的，膜锚定的，并且具有N-末端磷酸酪氨酸结合（PTB）结构域，其介导弱的但功能上重要的SNT-受体相互作用。SNT的配体依赖性酪氨酸磷酸化使得SNT能够与至少两种不同的含SH 2结构域的部分Grb 2/Sos和Shp 2相互作用。由于Grb 2/Sos的激活和随后的Ras激活以及Shp 2磷酸酶已被证明是广泛的FGF和神经营养因子诱导的生物反应所需的，因此SNT可能是激活两种生物学关键途径所需的。在本申请中提出了三个目的来阐明SNTs的生物化学和生物学特性。目的1提出了通过使用NMR和诱变方法的组合来确定SNT PTB结构域之间的相互作用的性质。还将测试SNTs与另一种受体酪氨酸激酶Ret之间可能的直接相互作用。在具体目标2中，将阐述SNT 1和SNT 2的生物学功能。为此，将采取两种办法：1）SNT的显性负突变体将在培养的细胞中过表达，并且2.）将产生在SNT基因中具有无效突变、超效突变和条件性无效突变的小鼠。最后，在具体目标3中，将测试SNTs作为潜在生物特异性决定因素的想法。为此，将产生嵌合SNT-IRS以及胰岛素受体-Trk杂合体，以确定它们是否可以将胰岛素应答转变为神经营养因子或FGF的应答。

DESCRIPTION (Adapted from applicant's abstract): SNT (Suc1-binding Neurotrophic factor-induced Tyrosine-phosphorylated target) proteins are recently discovered adaptor molecules that undergo rapid tyrosine phosphorylation following stimulation by growth factors including neurotrophins (NGF, BDNF, NT3) and FGFs but not by insulin and EGF. They are distantly related to IRS. SNTs are myristoylated and membrane-anchored and bear an N-terminal phosphotyrosine-binding (PTB) domain that mediates weak, but functionally significant SNT-receptor interactions. The ligand- dependent tyrosine phosphorylation of SNTs enables SNTs to interact with at least two different SH2 domain-containing moieties, Grb2/Sos and Shp2. As activation of both the Grb2/Sos and the subsequent Ras activation as well as the Shp2 phosphatase has been shown to be required for a wide-range of FGF- and neurotrophin- induced biological responses, SNTs may be required for activation of two biologically critical pathways. Three aims are proposed in this application to elucidate the biochemical and biological properties of SNTs. Aim 1 is proposed to determine the nature of the interaction between SNT PTB domains by using a combination of NMR and mutagenesis approaches. A possible direct interaction between SNTs and another receptor tyrosine kinase Ret will also be tested. In specific aim 2, the biological function of SNT1 and SNT2 will be addressed. Two approaches will be undertaken for this purpose: 1.) Dominant negative mutants of SNTs will be overexpressed in cultured cells and 2.) Mice with null, hypmerorphs and conditional null mutations in SNT genes will be generated. Finally, in specific aim 3, the idea of SNTs serving as potential biological specificity determinants will be tested. To this end, chimeric SNT-IRS as well as insulin receptor-Trk hybrids will be produced to determine if they can turn insulin response to that of neurotrophins or FGFs.