The B cell-specific major raft protein, Raftlin, is necessary for the integrity of lipid raft and BCR signal transduction
The B cell-specific major raft protein, Raftlin, is necessary for the integrity of lipid raft and BCR signal transduction
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DOI：
10.1093/emboj/cdg293
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发表时间：
2003-06-16
期刊：
影响因子：
11.4
通讯作者：
Yoshimura, A
中科院分区：
文献类型：
--
作者：
Saeki, K;Miura, Y;Yoshimura, A
最近的证据表明，膜微结构域，称为脂筏，在b细胞活化中作为b细胞抗原受体（BCR）信号起始的平台起作用。为了深入了解脂筏在B细胞中的可能功能，我们应用液相色谱-电喷雾电离串联质谱（LC-ESI-MS/MS）方法鉴定了与Raji细胞脂筏共纯化的蛋白质。在这些raft蛋白中，我们发现了一种新的蛋白，称为Raftlin （raft-linking protein）。与Src家族激酶一样，Raftlin仅通过n端Gly2和Cys3的脂肪酰化定位于脂筏中，并且在BCR刺激前后与BCR共定位。在DT40 b细胞系中，破坏Raftlin基因导致脂质筏组分（包括Lyn和神经节苷脂GM1）的数量明显减少，而过表达Raftlin则增加了筏蛋白的含量。此外，bcr介导的酪氨酸磷酸化和钙动员因缺乏Raftlin而受损，并实际上因Raftlin的过表达而增强。这些数据表明，Raftlin在脂筏的形成和/或维持中起关键作用，因此调节bcr介导的信号传导。
Recent evidence indicates that membrane microdomains, termed lipid rafts, have a role in B-cell activation as platforms for B-cell antigen receptor (BCR) signal initiation. To gain an insight into the possible functioning of lipid rafts in B cells, we applied liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) methodologies to the identification of proteins that co-purified with lipid rafts of Raji cells. Among these raft proteins, we characterized a novel protein termed Raftlin (raft-linking protein). Like the Src family kinase, Raftlin is localized exclusively in lipid rafts by fatty acylation of N-terminal Gly2 and Cys3, and is co-localized with BCR before and after BCR stimulation. Disruption of the Raftlin gene in the DT40 B-cell line resulted in a marked reduction in the quantity of lipid raft components, including Lyn and ganglioside GM1, while overexpression of Raftlin increased the content of raft protein. Moreover, BCR-mediated tyrosine phosphorylation and calcium mobilization were impaired by the lack of Raftlin and actually potentiated by overexpression of Raftlin. These data suggest that Raftlin plays a pivotal role in the formation and/or maintenance of lipid rafts, therefore regulating BCR-mediated signaling.