Department of Molecular Biology, School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey, Stratford, NJ 08084, USA.
Biochem Biophys Res Commun. 2010 Apr 16;394(4):1075-81. doi: 10.1016/j.bbrc.2010.03.129. Epub 2010 Mar 24.
In yeast, the hexokinase type II enzyme (HXKII) translocates to the nucleus in the presence of excess glucose, and participates in glucose repression. However, no evidence has suggested a nuclear function for HXKII in mammalian cells. Herein, we present data showing nuclear localization of HXKII in HeLa cells, both by immunocytochemistry and subcellular fractionation. HXKII is extruded from the nucleus, at least in part, by the activity of the exportin 1/CrmA system, as demonstrated by increased nuclear expression and decreased cytoplasmic expression after incubation with leptomycin B, a bacterially-derived exportin inhibitor. Furthermore, cytoplasmic localization of HXKII is dependent on its enzymatic activity, as inhibiting HXKII activity using 2-deoxy-D-glucose (2DG) increased nuclear localization. This effect was more significant in cells incubated in the absence of glucose for 24 h prior to addition of 2DG. Regulated translocation of HXKII to the nucleus of mammalian cells could represent a previously unknown glucose-sensing mechanism.
在酵母中，己糖激酶 II 型酶（HXKII）在过量葡萄糖存在的情况下会转移到细胞核中，并参与葡萄糖抑制。然而，没有证据表明 HXKII 在哺乳动物细胞中有核功能。在此，我们通过免疫细胞化学和亚细胞分级分离，提供了 HXKII 在 HeLa 细胞中定位于核内的证据。HXKII 至少部分通过输出蛋白 1/CrmA 系统的活性从核内挤出，这一点通过用细菌衍生的出口抑制剂莱普霉素 B 孵育后核内表达增加和细胞质表达减少得到证明。此外，HXKII 的细胞质定位依赖于其酶活性，因为用 2-脱氧-D-葡萄糖（2DG）抑制 HXKII 活性会增加核定位。在添加 2DG 之前，将细胞在无葡萄糖的情况下孵育 24 小时，这种效应更为显著。HXKII 到哺乳动物细胞核内的调节性易位可能代表了一种以前未知的葡萄糖感应机制。
