Abdullah Ash-Shafie, Foong Charlene, Murata-Hori Maki
Mammalian Cell Biology Group, Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore.
Temasek Junior College, 22 Bedok South Road, 469278, Singapore.
Cancer Cell Int. 2005 Nov 9;5:31. doi: 10.1186/1475-2867-5-31.
It is known that aurora B, a chromosomal passenger protein responsible for the proper progression of mitosis and cytokinesis, is overexpressed throughout the cell cycle in cancer cells. Overexpression of aurora B produced multinuclearity and induced aggressive metastasis, suggesting that overexpressed aurora B has multiple functions in cancer development. However, the detailed dynamics and functions of overexpressed aurora B are poorly understood.
We overexpressed GFP fused aurora B kinase in normal rat kidney epithelial cells. Using spinning disk confocal microscopy, we found that overexpressed aurora B-GFP was predominantly localized in the nucleus and along the cortex as a dot-like or short filamentous structure during interphase. Time-lapse imaging revealed that a cytoplasmic fraction of overexpressed aurora B-GFP was incorporated into the nucleus after cell division. Immunofluorescence showed that the nuclear fraction of overexpressed aurora B did not induce ectopic phosphorylation of histone H3 after cell division. The cytoplasmic fraction of overexpressed aurora B-GFP was mainly associated with cortical actin filaments but not stress fibers. Myosin II regulatory light chain, one of the possible targets for aurora B, did not colocalize with cortical aurora B-GFP, suggesting that overexpressed aurora B did not promote phosphorylation of myosin II regulatory light chain in interphase cells.
We conclude that overexpressed aurora B has a specific localization pattern in interphase cells. Based on our findings, we propose that overexpressed aurora B targets the nuclear and cortical proteins during interphase, which may contribute to cancer development and tumor metastasis.
已知极光B是一种负责有丝分裂和胞质分裂正常进行的染色体乘客蛋白，在癌细胞的整个细胞周期中均有过表达。极光B的过表达导致多核形成并诱导侵袭性转移，这表明过表达的极光B在癌症发展中具有多种功能。然而，对于过表达的极光B的详细动态变化和功能，人们了解甚少。
我们在正常大鼠肾上皮细胞中过表达了绿色荧光蛋白（GFP）融合的极光B激酶。使用转盘共聚焦显微镜，我们发现过表达的极光B-GFP在间期主要定位于细胞核以及沿皮质呈点状或短丝状结构。延时成像显示，过表达的极光B-GFP的细胞质部分在细胞分裂后被纳入细胞核。免疫荧光显示，过表达的极光B的细胞核部分在细胞分裂后不会诱导组蛋白H3的异位磷酸化。过表达的极光B-GFP的细胞质部分主要与皮质肌动蛋白丝相关，但与应力纤维无关。肌球蛋白II调节轻链是极光B的可能靶标之一，它与皮质极光B-GFP不共定位，这表明过表达的极光B在间期细胞中不会促进肌球蛋白II调节轻链的磷酸化。
我们得出结论，过表达的极光B在间期细胞中具有特定的定位模式。基于我们的研究结果，我们提出过表达的极光B在间期靶向细胞核和皮质蛋白，这可能有助于癌症发展和肿瘤转移。
