c-Cbl binding and ubiquitin-dependent lysosomal degradation of membrane-associated Notch1
c-Cbl binding and ubiquitin-dependent lysosomal degradation of membrane-associated Notch1
复制标题
DOI：
10.1074/jbc.m108552200
复制
发表时间：
2002-03-08
影响因子：
4.8
通讯作者：
Bielke, W
中科院分区：
文献类型：
--
作者：
Jehn, BM;Dittert, I;Bielke, W
Notch1活性的调节对细胞命运的决定和骨骼肌母细胞的分化至关重要。我们利用骨骼肌成肌细胞系C2C12来研究Notch1蛋白在肌肉发生过程中的翻译后调节。尽管激活的细胞内Notch1片段的主要降解途径似乎涉及泛素化和26 S蛋白酶体的降解，但我们提供了另一种催化途径的证据，即内源性的跨膜形式的Notch1以溶酶体室为靶点。免疫沉淀分析显示，溶酶体抑制剂氯喹处理后，跨膜Notch1蛋白依赖泛素积聚，而不同蛋白酶体抑制剂处理后，Notch1蛋白没有。这一发现得到了以下观察的支持：跨膜形式的Notch1是酪氨酸磷酸化的，并与泛素连接酶c-Cbl特异性地共沉淀。我们的数据表明，一种调控机制下调了细胞表面已经存在的Notch1蛋白水平，可能在末端分化过程中影响Notch依赖的信号转导。
Regulation of Notch1 activity is critical for cell fate decisions and differentiation of skeletal myoblasts. We have employed the skeletal myoblast cell line C2C12 to study posttranslational regulation of Notch1 protein levels during myogenesis. Although the major degradation pathway of the activated intracellular Notch1 fragment appears to involve ubiquitination and degradation by the 26 S proteasome, we provide evidence for an alternative catalytic pathway where the endogenous, transmembrane form of Notch1 is targeted to the lysosomal compartment. Immunoprecipitation analysis revealed ubiquitin-dependent accumulation of transmembrane Notch1 protein after treatment with the lysosomal inhibitor chloroquine but not after treatment with various proteasome inhibitors. This finding was supported by the observation that the transmembrane form of Notch1 was tyrosine-phosphorylated and specifically coprecipitated with the ubiquitin ligase c-Cbl. Our data suggest a regulatory mechanism down-regulating Notch1 protein levels already at the cellular surface, possibly with consequences for Notch-dependent signal transduction during terminal differentiation processes.