Dynamics of galectin-3 in the nucleus and cytoplasm.
Dynamics of galectin-3 in the nucleus and cytoplasm.
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DOI：
10.1016/j.bbagen.2009.07.005
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发表时间：
2010-02
影响因子：
3
通讯作者：
Arnoys, Eric J.
中科院分区：
文献类型：
--
作者：
Haudek, Kevin C.;Spronk, Kimberly J.;Voss, Patricia G.;Patterson, Ronald J.;Wang, John L.;Arnoys, Eric J.
本文综述了半乳糖凝集素-3(Galectin-3，Gal3)作为碳水化合物结合蛋白在细胞质和细胞核中的动态行为的部分研究。在由15个成员组成的Galectin蛋白家族中，Gal3(Mr~30,000)是嵌合体亚类的唯一代表，在嵌合体亚类中，富含脯氨酸和甘氨酸的NH2末端结构域与负责结合含半乳糖的糖共轭的COOH末端碳水化合物识别结构域融合。蛋白质根据靶向信号在细胞质和细胞核之间穿梭，这些靶向信号被Importin(S)识别用于核定位，Exportin-1(CRM1)识别用于核出口。根据细胞类型、特定的体外实验条件或组织位置的不同，已有报道称Gal3完全是细胞质的，主要是核的，或者分布在两个隔室之间。因此，蛋白质的核质分布必须反映出核输入和输出之间的某种平衡，以及细胞质锚定或与核成分结合的机制。事实上，据报道，Gal3在细胞质和细胞核中有许多配体。然而，大多数配体似乎是通过蛋白质-蛋白质相互作用而不是通过蛋白质-碳水化合物识别来结合Gal3。例如，在细胞质中，Gal3与凋亡抑制因子Bcl2相互作用，这种相互作用可能参与了Gal3‘S的抗凋亡活性。在细胞核中，Gal3是一种必需的前mRNA剪接因子；该蛋白通过与U1小核核糖核蛋白(SnRNP)复合体结合而进入剪接体。尽管这些相互作用大部分是通过Gal3的碳水化合物识别结构域发生的，而且乳糖等糖配体可以干扰其中一些相互作用，但蛋白质的碳水化合物结合活性本身的重要性仍然是未来研究的一个挑战。
This review summarizes selected studies on galectin-3 (Gal3) as an example of the dynamic behavior of a carbohydrate-binding protein in the cytoplasm and nucleus of cells. Within the 15-member galectin family of proteins, Gal3 (Mr ~30,000) is the sole representative of the chimera subclass in which a proline- and glycine-rich NH2-terminal domain is fused onto a COOH-terminal carbohydrate recognition domain responsible for binding galactose-containing glycoconjugates. The protein shuttles between the cytoplasm and nucleus on the basis of targeting signals that are recognized by importin(s) for nuclear localization and exportin-1 (CRM1) for nuclear export. Depending on the cell type, specific experimental conditions in vitro, or tissue location, Gal3 has been reported to be exclusively cytoplasmic, predominantly nuclear, or distributed between the two compartments. The nuclear versus cytoplasmic distribution of the protein must reflect, then, some balance between nuclear import and export, as well as mechanisms of cytoplasmic anchorage or binding to a nuclear component. Indeed, a number of ligands have been reported for Gal3 in the cytoplasm and in the nucleus. Most of the ligands appear to bind Gal3, however, through protein-protein interactions rather than through protein-carbohydrate recognition. In the cytoplasm, for example, Gal3 interacts with the apoptosis repressor Bcl-2 and this interaction may be involved in Gal3’s anti-apoptotic activity. In the nucleus, Gal3 is a required pre-mRNA splicing factor; the protein is incorporated into spliceosomes via its association with the U1 small nuclear ribonucleoprotein (snRNP) complex. Although the majority of these interactions occur via the carbohydrate recognition domain of Gal3 and saccharide ligands such as lactose can perturb some of these interactions, the significance of the protein’s carbohydrate-binding activity, per se, remains a challenge for future investigations.
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