Identification and characterization of a novel BASH N terminus-associated protein, BNAS2
Identification and characterization of a novel BASH N terminus-associated protein, BNAS2
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DOI：
10.1074/jbc.m403685200
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发表时间：
2004-06-18
影响因子：
4.8
通讯作者：
Kitamura, D
中科院分区：
文献类型：
--
作者：
Imamura, Y;Katahira, T;Kitamura, D
B细胞特异性接头蛋白Bash(也称为BLNK或SLP-65)对B细胞受体(BCR)信号转导至关重要。Bash通过其定义明确的基序与多种信号中间体结合，如BTK、PLCGamma2、Vav和Grb2。虽然这种相互作用的功能意义已经被证明，但Bash介导的信号转导机制并不完全清楚。利用酵母双杂交系统，我们鉴定了一个与Bash保守的N末端结构域结合的新蛋白，我们将其命名为BNAS2(Bash N末端相关蛋白2)。根据其推导的氨基酸序列，推测BNAS2含有四个跨膜结构域，它们位于中央Marvel结构域中，并定位于内质网。BNAS2与BASH、BTK和ERK2从小鼠B细胞株的裂解液中共沉淀。在转基因细胞中，外源BNAS2定位于细胞质中的网状结构，类似于内质网和核膜。Bash与BNAS2以依赖于其N-末端结构域的方式共定位。RT-PCR分析表明，除浆细胞外，BNAS2基因在肿瘤细胞中广泛表达。在鸡B细胞系DT40中，BNAS2的过表达导致BCR连接介导的ELK1的转录激活增强，但对NF-kappaB的转录激活没有增强作用，这种增强作用依赖于BNAS2的剂量。因此，BNAS2可能作为Bash、BTK和ERK等信号蛋白在内质网和核膜上的支架，并可能通过细胞表面受体的信号促进ERK的激活。
A B cell-specific adaptor protein, BASH ( also known as BLNK or SLP-65), is crucial for B cell receptor (BCR) signaling. BASH binds to various signaling intermediates, such as Btk, PLCgamma2, Vav, and Grb2, through its well defined motifs. Although functional significance of such interactions has been documented, BASH-mediated signal transduction mechanism is not fully understood. Using the yeast two-hybrid system, we have identified a novel protein that binds to a conserved N-terminal domain of BASH, which we named BNAS2 (BASH N terminus associated protein 2). From its deduced amino acid sequence, BNAS2 is presumed to contain four transmembrane domains, which are included in a central MARVEL domain, and to localize to endoplasmic reticulum. BNAS2 was co-precipitated with BASH as well as Btk and ERK2 from a lysate of mouse B cell line. In the transfected cells, the exogenous BNAS2 was localized in a mesh-like structure in the cytoplasm resembling that of endoplasmic reticulum ( ER) and nuclear membrane. BASH was co-localized with BNAS2 in a manner dependent on its N-terminal domain. RT-PCR analysis indicated that BNAS2 mRNA is expressed ubiquitously except for plasma cells. In chicken B cell line DT40, overexpression of BNAS2 resulted in an enhancement of BCR ligation-mediated transcriptional activation of Elk1, but not of NF-kappaB, in a manner dependent on the dose of BNAS2. Thus BNAS2 may serve as a scaffold for signaling proteins such as BASH, Btk, and ERK at the ER and nuclear membrane and may facilitate ERK activation by signaling from cell-surface receptors.