Minshall C, Arkins S, Dantzer R, Freund G G, Kelley K W
Laboratory of Immunophysiology, Department of Animal Sciences, College of Medicine, Department of Pathology, University of Illinois, Urbana 61801, USA.
J Immunol. 1999 Apr 15;162(8):4542-9.
Phosphatidylinositol 3'-kinase (PI 3-kinase) catalyzes the formation of 3' phosphoinositides and has been implicated in an intracellular signaling pathway that inhibits apoptosis in both neuronal and hemopoietic cells. Here, we investigated two potential downstream mediators of PI 3-kinase, the serine/threonine p70 S6-kinase (S6-kinase) and the antiapoptotic protein B cell lymphoma-2 (Bcl-2). Stimulation of factor-dependent cell progenitor (FDCP) cells with either IL-4 or insulin-like growth factor (IGF)-I induced a 10-fold increase in the activity of both PI 3-kinase and S6-kinase. Rapamycin blocked 90% of the S6-kinase activity but did not affect PI 3-kinase, whereas wortmannin and LY294002 inhibited the activity of both S6-kinase and PI 3-kinase. However, wortmannin and LY294002, but not rapamycin, blocked the ability of IL-4 and IGF-I to promote cell survival. We next established that IL-3, IL-4, and IGF-I increase expression of Bcl-2 by >3-fold. Pretreatment with inhibitors of PI 3-kinase, but not rapamycin, abrogated expression of Bcl-2 caused by IL-4 and IGF-I, but not by IL-3. None of the cytokines affected expression of the proapoptotic protein Bax, suggesting that all three cytokines were specific for Bcl-2. These data establish that inhibition of PI 3-kinase, but not S6-kinase, blocks the ability of IL-4 and IGF-I to increase expression of Bcl-2 and protect promyeloid cells from apoptosis. The requirement for PI 3-kinase to maintain Bcl-2 expression depends upon the ligand that activates the cell survival pathway.
磷脂酰肌醇3'-激酶（PI 3-激酶）催化3'磷酸肌醇的形成，并参与一条细胞内信号通路，该通路在神经元细胞和造血细胞中均能抑制细胞凋亡。在此，我们研究了PI 3-激酶的两种潜在下游介质，即丝氨酸/苏氨酸p70 S6-激酶（S6-激酶）和抗凋亡蛋白B细胞淋巴瘤-2（Bcl-2）。用白细胞介素-4（IL-4）或胰岛素样生长因子（IGF）-I刺激因子依赖性细胞祖细胞（FDCP），可使PI 3-激酶和S6-激酶的活性增加10倍。雷帕霉素可阻断90%的S6-激酶活性，但不影响PI 3-激酶，而渥曼青霉素和LY294002可抑制S6-激酶和PI 3-激酶的活性。然而，渥曼青霉素和LY294002（而非雷帕霉素）可阻断IL-4和IGF-I促进细胞存活的能力。接下来我们证实，IL-3、IL-4和IGF-I可使Bcl-2的表达增加3倍以上。用PI 3-激酶抑制剂预处理可消除IL-4和IGF-I（而非IL-3）引起的Bcl-2表达，但雷帕霉素无此作用。这些细胞因子均不影响促凋亡蛋白Bax的表达，提示这三种细胞因子对Bcl-2具有特异性。这些数据表明，抑制PI 3-激酶而非S6-激酶，可阻断IL-4和IGF-I增加Bcl-2表达并保护早幼粒细胞免受凋亡的能力。维持Bcl-2表达对PI 3-激酶的需求取决于激活细胞存活通路的配体。
