Townsend P V, Crouch M F, Mak N K, Hapel A J
Division of Clinical Science, John Curtin School of Medical Research, Australian National University, Canberra.
Growth Factors. 1993;9(1):21-30. doi: 10.3109/08977199308991579.
We have examined the role of Gi alpha in haemopoietic cells using the myelomonocytic progenitor cell lines FDC-P1 and WEHI-3B (JCS). During growth factor-dependent proliferation of FDC-P1 cells Gi alpha was found predominantly in the nucleus and associated with the plasma membrane. Following removal of growth factor, Gi alpha accumulated in the cytoplasm and at the plasma membrane. Treatment of FDC-P1 cells with pertussis toxin (PT) completely inhibited translocation of Gi alpha to the nucleus and reduced the sensitivity of FDC-P1 cells to the proliferative effects of growth factors, indicating that translocation of Gi alpha plays a regulatory role in, but may not be essential for, cell division. Gi alpha initially associated with DNA during S/G2 of the FDC-P1 cell cycle but separated from condensing chromosomes during mitosis. In contrast to FDC-P1 cells, WEHI-3B (JCS) cells proliferate in the absence of added growth factors but can be induced to differentiate by TNF-alpha. In proliferating JCS cells Gi alpha was again associated with the nucleus but when proliferation was inhibited by TNF-alpha, Gi alpha accumulated in the cytoplasm with none detected in the nucleus. Thus the cytokine regulated accumulation of Gi alpha at different intracellular sites correlated with the ability of the cell to progress through the proliferative cycle. When the tyrosine kinase inhibitor genistein was added to FDC-P1 cells prior to stimulation with IL-3 or GM-CSF, proliferation was almost completely inhibited but translocation of Gi alpha was not affected, suggesting that tyrosine phosphorylation was not involved in G protein translocation but was essential for cytokine induced cell division. Cholera toxin (CT) also inhibited proliferation of FDC-P1 cells but had no effect on translocation of Gi alpha to the nucleus. The near complete inhibition of cell division by genistein and CT without a corresponding effect on Gi alpha movement indicates that Gi alpha can be regulated independently of tyrosine kinase and adenylyl cyclase activities, respectively.
我们利用骨髓单核细胞祖细胞系FDC-P1和WEHI-3B（JCS）研究了Giα在造血细胞中的作用。在FDC-P1细胞依赖生长因子的增殖过程中，发现Giα主要位于细胞核并与质膜相关联。去除生长因子后，Giα在细胞质和质膜处积累。用百日咳毒素（PT）处理FDC-P1细胞可完全抑制Giα向细胞核的转位，并降低FDC-P1细胞对生长因子增殖作用的敏感性，表明Giα的转位在细胞分裂中起调节作用，但可能不是细胞分裂所必需的。在FDC-P1细胞周期的S/G2期，Giα最初与DNA相关联，但在有丝分裂期间与浓缩染色体分离。与FDC-P1细胞不同，WEHI-3B（JCS）细胞在不添加生长因子的情况下增殖，但可被肿瘤坏死因子-α（TNF-α）诱导分化。在增殖的JCS细胞中，Giα再次与细胞核相关联，但当增殖被TNF-α抑制时，Giα在细胞质中积累，细胞核中未检测到。因此，细胞因子调节的Giα在不同细胞内位点的积累与细胞通过增殖周期的能力相关。在用白细胞介素-3（IL-3）或粒细胞-巨噬细胞集落刺激因子（GM-CSF）刺激之前，将酪氨酸激酶抑制剂染料木黄酮添加到FDC-P1细胞中，增殖几乎完全被抑制，但Giα的转位不受影响，这表明酪氨酸磷酸化不参与G蛋白转位，但对细胞因子诱导的细胞分裂至关重要。霍乱毒素（CT）也抑制FDC-P1细胞的增殖，但对Giα向细胞核的转位没有影响。染料木黄酮和CT对细胞分裂的近乎完全抑制而对Giα移动没有相应影响，表明Giα可以分别独立于酪氨酸激酶和腺苷酸环化酶活性进行调节。
