Liu R, Liu C B, Mohi M G, Arai K, Watanabe S
Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Japan.
Oncogene. 2000 Jan 27;19(4):571-9. doi: 10.1038/sj.onc.1203364.
Human granulocyte-macrophage colony-stimulating factor (hGM-CSF) induces proliferation and sustains viability of the mouse interleukin (IL)-3 dependent lymphoid cell line BA/F3 expressing the hGM-CSF receptor. Caspase-3 like enzyme activity and DNA fragmentation were augmented by depletion of this factor from the cell, and exposure to gamma irradiation accelerated kinetics of these events. Anti gamma irradiation-induced apoptosis occurred through various mutant GM-CSF receptors and only the box1 region was essential while the C terminal region, including tyrosine residues which are required for MAPK cascade activation, was dispensable. Consistent with this notion, the addition of PD98059 had no effect on this activity thereby indicating that activation of MAPK is not essential for the activity. As expected, gamma irradiation increased p53 protein and bax mRNA levels and the presence of hGM-CSF dramatically modulated bax/bcl-X(L) ratio. The PI-3K specific inhibitor wortmannin did not affect hGM-CSF dependent anti gamma irradiation induced apoptosis nor bcl-X(L) induction, thus bcl-X(L) but not PI-3K pathway seems to be involved in hGM-CSF dependent anti gamma irradiation-induced apoptosis. It is well documented that the boxl region is essential for GM-CSF dependent activation of JAK2 and JAK2 specific inhibitor AG490 suppressed anti gamma, irradiation-induced apoptosis by hGM-CSF. An artificial JAK2 activating molecule in which extracellular and the transmembrane of beta(c) fused with whole JAK2 can sustain BA/F3 cells survival and proliferation mIL-3 independently, but these cells are susceptible to gamma irradiation. Furthermore GyrB/Jak2, which can activate STAT5 but not the MAPK cascade nor survival of BA/F3 cells, also could not prevent gamma irradiation-induced apoptosis. Although JAK2 is essential for hGM-CSF dependent anti gamma irradiation-induced apoptosis, it appeared that JAK2 does not seem sufficient for the activity.
人粒细胞巨噬细胞集落刺激因子（hGM-CSF）可诱导表达hGM-CSF受体的小鼠白细胞介素（IL）-3依赖淋巴细胞系BA/F3增殖并维持其活力。从细胞中去除该因子会增强半胱天冬酶-3样酶活性和DNA片段化，而暴露于γ射线会加速这些事件的进程。通过各种突变的GM-CSF受体可发生抗γ射线诱导的凋亡，只有Box1区域是必需的，而包括MAPK级联激活所需酪氨酸残基的C末端区域则是可有可无的。与此观点一致，添加PD98059对该活性无影响，从而表明MAPK的激活对于该活性并非必需。正如预期的那样，γ射线照射会增加p53蛋白和bax mRNA水平，而hGM-CSF的存在会显著调节bax/bcl-X(L)比值。PI-3K特异性抑制剂渥曼青霉素既不影响hGM-CSF依赖的抗γ射线诱导的凋亡，也不影响bcl-X(L)的诱导，因此bcl-X(L)而非PI-3K途径似乎参与了hGM-CSF依赖的抗γ射线诱导的凋亡。有充分的文献记载，Box1区域对于GM-CSF依赖的JAK2激活至关重要，JAK2特异性抑制剂AG490可抑制hGM-CSF诱导的抗γ射线凋亡。一种人工JAK2激活分子，其中β(c)的细胞外和跨膜部分与整个JAK2融合，可独立维持BA/F3细胞在mIL-3存在下的存活和增殖，但这些细胞对γ射线敏感。此外，可激活STAT5但不能激活MAPK级联反应或BA/F3细胞存活的GyrB/Jak2，也无法预防γ射线诱导的凋亡。虽然JAK2对于hGM-CSF依赖的抗γ射线诱导的凋亡至关重要，但似乎JAK2对于该活性并不足够。
