Association of Nucleophosmin Negatively Regulates CXCR4-Mediated G Protein Activation and Chemotaxis
Association of Nucleophosmin Negatively Regulates CXCR4-Mediated G Protein Activation and Chemotaxis
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DOI：
10.1124/mol.107.037119
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发表时间：
2007-11
影响因子：
3.6
通讯作者：
Wen-bo Zhang;J. Navenot;Nicole Frilot;N. Fujii;S. Peiper
中科院分区：
文献类型：
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作者：
Wen-bo Zhang;J. Navenot;Nicole Frilot;N. Fujii;S. Peiper
CXCR 4是CXCL 12的主要受体，通过介导前体细胞的定向迁移在造血、血管、中枢神经和免疫系统的发育中起关键作用。该机制促进肿瘤细胞归巢至分泌CXCL 12的转移部位，并且CXCR 4表达是急性髓性白血病（AML）的负性预后因子。为了阐明调节CXCR 4信号传导的机制，我们使用蛋白质组学方法来鉴定与CXCR 4物理相关的蛋白质。CXCR 4免疫复合物的分析鉴定了核磷蛋白（NPM），这通过NPM的相互免疫共沉淀来证实。组成型活性CXCR 4变体与比野生型受体更高水平的NPM结合，这被反向激动剂T140逆转。NPM与CXCR 4的结合将相互作用定位于C末端和胞质环（CL）-3，但不与CL-1或CL-2结合。丙氨酸扫描诱变表明，CL-3中带正电荷的氨基酸对NPM结合至关重要。重组NPM降低了CXCL 12激活CXCR 4后膜组分中的GTP结合。抑制NPM的表达增强趋化反应CXCL 12，相反，过表达的胞质NPM突变体减少趋化诱导CXCL 12。这项研究为NPM作为CXCL 12诱导的CXCR 4信号传导的负调节剂的新作用提供了证据，这可能与AML的生物学相关。
CXCR4, the primary receptor for CXCL12, plays a critical role in the development of hematopoietic, vascular, central nervous, and immune systems by mediating directional migration of precursor cells. This mechanism promotes homing of tumor cells to metastatic sites that secrete CXCL12, and CXCR4 expression is a negative prognostic factor in acute myelogenous leukemia (AML). To elucidate mechanisms that regulate CXCR4 signaling, we used a proteomic approach to identify proteins physically associated with CXCR4. Analysis of CXCR4 immune complexes identified nucleophosmin (NPM), which was confirmed by reciprocal coimmunoprecipitation for NPM. Constitutively active CXCR4 variants bound higher levels of NPM than the wild-type receptor, which was reversed by T140, an inverse agonist. NPM binding to CXCR4 localized interactions to the C terminus and cytoplasmic loop (CL)-3, but not CL-1 or CL-2. Alanine scanning mutagenesis demonstrated that positively charged amino acids in CL-3 were critical for NPM binding. Recombinant NPM decreased GTP binding in membrane fractions after activation of CXCR4 by CXCL12. Suppression of NPM expression enhanced chemotactic responses to CXCL12, and, conversely, overexpression of a cytosolic NPM mutant reduced chemotaxis induced by CXCL12. This study provides evidence for a novel role for NPM as a negative regulator of CXCR4 signaling induced by CXCL12 that may be relevant to the biology of AML.