Numb independently antagonizes Sanpodo membrane targeting and Notch signaling in Drosophila sensory organ precursor cells.
Numb independently antagonizes Sanpodo membrane targeting and Notch signaling in Drosophila sensory organ precursor cells.
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DOI：
10.1091/mbc.e09-09-0831
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发表时间：
2010-03-01
影响因子：
3.3
通讯作者：
Roegiers F
中科院分区：
文献类型：
--
作者：
Tong X;Zitserman D;Serebriiskii I;Andrake M;Dunbrack R;Roegiers F
Numb如何调控细胞不对称分裂后的Notch信号尚不清楚。Numb直接结合和阻断Sanpodo的膜定位，Sanpodo是果蝇Notch信号转导所必需的蛋白质。解偶联Sanpodo和Numb会导致Sanpodo在细胞膜上积累，但令人惊讶的是，这似乎并没有促进Notch信号转导。在果蝇中，有丝分裂的神经前体细胞不对称地分离细胞命运决定因素Numb，以便仅在两个子细胞中的一个细胞中阻断Notch信号。Sanpodo是Notch信号转导所需的一种膜蛋白，在神经前体细胞有丝分裂后，它以数量依赖的方式从质膜隔离到细胞内的小泡。然而，麻木依赖的Sanpodo调控的意义尚不清楚。在这项研究中，我们进行了结构-功能分析，以确定Sanpodo体内靶向的决定因素。我们在Sanpodo的氨基末端细胞质尾部发现了一个NPAF基序，该基序在昆虫Sanpodo同源物中是保守的。Sanpodo NPAF基序被预测直接与Numb磷酸酪氨酸结合结构域结合，并且在体外对Numb结合是关键的。NPAF基序的缺失或突变导致体内Numb阳性细胞质膜上Sanpodo的积聚。对Sanpodo NPAF突变体的遗传分析表明，数目依赖的Sanpodo内吞靶向可以从Notch信号调节中解偶联。我们的发现表明，Sanpodo包含一个进化保守的基序，该基序与脊椎动物的Numb依赖的调控有关，并进一步支持Numb调节Notch信号的模型，该模型独立于Sanpodo神经前体细胞的膜运输。
How Numb regulates Notch signaling following asymmetric cell division is unclear. Numb directly binds and blocks membrane localization of Sanpodo, a protein essential for Notch signaling in Drosophila. Uncoupling Sanpodo from Numb results in accumulation of Sanpodo at the membrane, but this surprisingly does not appear to promote Notch signaling. In Drosophila, mitotic neural progenitor cells asymmetrically segregate the cell fate determinant Numb in order to block Notch signaling in only one of the two daughter cells. Sanpodo, a membrane protein required for Notch signaling in asymmetrically dividing cells, is sequestered from the plasma membrane to intracellular vesicles in a Numb-dependent way after neural progenitor cell mitosis. However, the significance of Numb-dependent Sanpodo regulation is unclear. In this study, we conducted a structure–function analysis to identify the determinants of Sanpodo targeting in vivo. We identified an NPAF motif in the amino-terminal cytoplasmic tail of Sanpodo, which is conserved among insect Sanpodo homologues. The Sanpodo NPAF motif is predicted to bind directly to the Numb phosphotyrosine-binding domain and is critical for Numb binding in vitro. Deletion or mutation of the NPAF motif results in accumulation of Sanpodo at the plasma membrane in Numb-positive cells in vivo. Genetic analysis of Sanpodo NPAF mutants shows that Numb-dependent Sanpodo endocytic targeting can be uncoupled from Notch signaling regulation. Our findings demonstrate that Sanpodo contains an evolutionarily conserved motif that has been linked to Numb-dependent regulation in vertebrates and further support the model that Numb regulates Notch signaling independently of Sanpodo membrane trafficking in neural progenitor cells.
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