Hernández-Ibarra Jose Anselmo, Laredo-Cisneros Marco Samuel, Mondragón-González Ricardo, Santamaría-Guayasamín Natalie, Cisneros Bulmaro
Departamento de Gen, é, tica y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV- IPN), Mexico City, Mexico.
Departamento de Ciencias de la Vida, Carrera de Ingeniería en Biotecnología, Universidad de las Fuerzas Armadas-ESPE, Sangolquí, Ecuador.
J Cell Biochem. 2015 Dec;116(12):2755-65. doi: 10.1002/jcb.25218.
α-Dystrobrevin (α-DB) is a cytoplasmic component of the dystrophin-associated complex involved in cell signaling; however, its recently revealed nuclear localization implies a role for this protein in the nucleus. Consistent with this, we demonstrated, in a previous work that α-DB1 isoform associates with the nuclear lamin to maintain nuclei morphology. In this study, we show the distribution of the α-DB2 isoform in different subnuclear compartments of N1E115 neuronal cells, including nucleoli and Cajal bodies, where it colocalizes with B23/nucleophosmin and Nopp140 and with coilin, respectively. Recovery in a pure nucleoli fraction undoubtedly confirms the presence of α-DB2 in the nucleolus. α-DB2 redistributes in a similar fashion to that of fibrillarin and Nopp140 upon actinomycin-mediated disruption of nucleoli and to that of coilin after disorganization of Cajal bodies through ultraviolet-irradiation, with relocalization of the proteins to the corresponding reassembled structures after cessation of the insults, which implies α-DB2 in the plasticity of these nuclear bodies. That localization of α-DB2 in the nucleolus is physiologically relevant is demonstrated by the fact that downregulation of α-DB2 resulted in both altered nucleoli structure and decreased levels of B23/nucleophosmin, fibrillarin, and Nopp140. Since α-DB2 interacts with B23/nucleophosmin and overexpression of the latter protein favors nucleolar accumulation of α-DB2, it appears that targeting of α-DB2 to the nucleolus is dependent on B23/nucleophosmin. In conclusion, we show for the first time localization of α-DB2 in nucleoli and Cajal bodies and provide evidence that α-DB2 is involved in the structure of nucleoli and might modulate nucleolar functions.
α-肌营养不良蛋白结合蛋白（α-DB）是肌营养不良蛋白相关复合物的一种胞质成分，参与细胞信号传导；然而，其最近被揭示的核定位表明该蛋白在细胞核中发挥作用。与此一致的是，我们在之前的一项研究中证明，α-DB1亚型与核纤层蛋白结合以维持细胞核形态。在本研究中，我们展示了α-DB2亚型在N1E115神经细胞不同核内亚区室中的分布，包括核仁与卡哈尔体，它分别与B23/核磷蛋白和Nopp140以及卷曲螺旋蛋白在这些区域共定位。在纯核仁组分中的回收无疑证实了α-DB2存在于核仁中。在放线菌素介导的核仁破坏后，α-DB2的重新分布方式与原纤维蛋白和Nopp140相似，而在通过紫外线照射使卡哈尔体解体后，其重新分布方式与卷曲螺旋蛋白相似，在损伤停止后这些蛋白质重新定位到相应的重新组装结构中，这意味着α-DB2在这些核体的可塑性方面发挥作用。α-DB2在核仁中的定位具有生理相关性这一点通过以下事实得以证明：α-DB2的下调导致核仁结构改变以及B23/核磷蛋白、原纤维蛋白和Nopp140水平降低。由于α-DB2与B23/核磷蛋白相互作用，且后者蛋白的过表达有利于α-DB2在核仁中的积累，看来α-DB2靶向核仁依赖于B23/核磷蛋白。总之，我们首次展示了α-DB2在核仁和卡哈尔体中的定位，并提供证据表明α-DB2参与核仁结构并可能调节核仁功能。
