Torigoe T, O'Connor R, Santoli D, Reed J C
Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia.
Blood. 1992 Aug 1;80(3):617-24.
The lymphokine interleukin-3 (IL-3) promotes the growth and survival of immature hematopoietic cells. Previous studies have shown that IL-3 induces rapid increases in protein-tyrosine kinase (PTK) activity in IL-3--dependent cells. Unlike some other hematopoietic growth factor receptors (eg, c-fms and c-kit), however, the known subunits of the IL-3 receptor (IL-3R) lack intrinsic kinase activity. Recently, it was reported that the IL-2R (whose p75 beta-subunit shares sequence homology with a known murine IL-3R subunit and a common beta-subunit of the human IL-3R and granulocyte-macrophage colony-stimulating factor [GM-CSF] receptors) can physically associate with and regulate the activity of the SRC-family PTK, p56-LCK. Because most IL-3--dependent cells contain p53/56-LYN, but not p56-LCK, we explored the effects of IL-3 on the activities of LYN and other SRC-like PTKs in two human leukemic cell lines, AML-193 and TALL-101, which are phenotypically myeloid, and whose in vitro growth is dependent on IL-3. These cells expressed four of the eight known SRC-family proto-oncogenes: lyn, fyn, yes, and hck. When these factor-dependent leukemic cell lines were deprived of lymphokine to achieve cellular quiescence and then restimulated with IL-3, rapid increases (detectable within 1 minute and maximal by 10 minutes) were observed in the activity of the p53/56-LYN kinase, as assessed by in vitro kinase assays. In contrast, no alteration in the activities of other SRC-family PTKs present in these cells was detected after restimulation with IL-3 under the same conditions. This effect of IL-3 reflected an increase in the specific activity of the LYN kinase, because levels of the 53-Kd and 56-Kd LYN proteins were unaltered by IL-3 stimulation, as assessed by immunoblotting. Furthermore, the magnitude of these inducible increases in LYN kinase activity was dependent on the concentration of IL-3, and correlated with IL-3--induced proliferation. The IL-3--induced upregulation of LYN kinase activity may be mediated by the 120-Kd common subunit of the human IL-3 and GM-CSF receptors, because GM-CSF also stimulated marked increases in the activity of the LYN kinase, whereas granulocyte-CSF (G-CSF) did not, despite inducing cellular proliferation. These observations provide the first example of an IL-3--regulable PTK, and strongly suggest that the p53/56-LYN kinase participates in early IL-3--initiated signalling events, at least in some human leukemic cell lines.
淋巴因子白细胞介素-3（IL-3）可促进未成熟造血细胞的生长和存活。以往研究表明，IL-3可使IL-3依赖细胞中的蛋白酪氨酸激酶（PTK）活性迅速升高。然而，与其他一些造血生长因子受体（如c-fms和c-kit）不同，IL-3受体（IL-3R）的已知亚基缺乏内在激酶活性。最近有报道称，IL-2R（其p75β亚基与已知的小鼠IL-3R亚基以及人IL-3R和粒细胞-巨噬细胞集落刺激因子[GM-CSF]受体的共同β亚基具有序列同源性）可与SRC家族PTK p56-LCK发生物理结合并调节其活性。由于大多数IL-3依赖细胞含有p53/56-LYN，但不含p56-LCK，我们研究了IL-3对两种人白血病细胞系AML-193和TALL-101中LYN及其他SRC样PTK活性的影响，这两种细胞系在表型上为髓样，其体外生长依赖于IL-3。这些细胞表达了8种已知SRC家族原癌基因中的4种：lyn、fyn、yes和hck。当这些因子依赖的白血病细胞系被剥夺淋巴因子以实现细胞静止，然后用IL-3重新刺激时，通过体外激酶测定评估，观察到p53/56-LYN激酶活性迅速升高（1分钟内可检测到，10分钟时达到最大值）。相比之下，在相同条件下用IL-3重新刺激后，未检测到这些细胞中存在的其他SRC家族PTK活性有改变。IL-3的这种作用反映了LYN激酶比活性的增加，因为通过免疫印迹评估，53-Kd和56-Kd LYN蛋白的水平未因IL-3刺激而改变。此外，LYN激酶活性的这些诱导性增加的幅度取决于IL-3的浓度，并与IL-3诱导的增殖相关。IL-3诱导的LYN激酶活性上调可能由人IL-3和GM-CSF受体的120-Kd共同亚基介导，因为GM-CSF也刺激LYN激酶活性显著增加，而粒细胞集落刺激因子（G-CSF）尽管诱导细胞增殖，但却没有这种作用。这些观察结果提供了第一个IL-3可调节PTK的例子，并强烈表明p53/56-LYN激酶至少在一些人白血病细胞系中参与了早期IL-3启动的信号事件。
