The dynamics of protein kinase B regulation during B cell antigen receptor engagement.
The dynamics of protein kinase B regulation during B cell antigen receptor engagement.
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DOI：
10.1083/jcb.145.7.1511
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发表时间：
1999-06-28
影响因子：
7.8
通讯作者：
Cantrell, D
中科院分区：
文献类型：
--
作者：
Astoul, E;Watton, S;Cantrell, D
本研究利用活细胞中绿色荧光蛋白 (GFP) 标记分子的生物化学和实时共聚焦成像来探索 B 淋巴细胞激活过程中蛋白激酶 B (PKB) 调节的动态。数据显示，B 细胞抗原受体 (BCR) 的触发会诱导 PKB 短暂膜定位，但会持续激活该酶；活性 PKB 存在于活化 B 细胞的胞浆和细胞核中。因此，PKB 在 B 淋巴细胞中具有三个潜在的作用位点： BCR 触发 PKB 后短暂地可以磷酸化质膜局部靶标，而在 B 细胞对抗原的持续反应期间，PKB 在细胞核和细胞质中起作用。 PKB 的膜易位和随后的 PKB 激活依赖于磷脂酰肌醇 3-激酶 (PI3K) 的 BCR 激活。此外，PI3K 信号对于 B 淋巴细胞中 PKB 的持续激活既是必要的也是充分的。然而，在持续 PI3K 激活或 BCR 触发的条件下，PKB 仅短暂地募集到质膜上，表明必须存在一种分子机制将 PKB 从 B 细胞中的 PI3K 活性位点解离。抑制性 Fc 受体 FcγRIIB 通过将肌醇 5 磷酸酶 SHIP 招募到 BCR 复合物中来介导 B 细胞功能的重要稳态控制。在此，我们证明 BCR 与抑制性 FcγRIIB 的结合可防止 PKB 的膜靶向。因此，FcγRIIB可以拮抗PKB定位的BCR信号并阻止BCR对PKB活性的刺激，这证明了FcγRIIB对BCR/PKB反应的抑制作用的机制。
This study has used biochemistry and real time confocal imaging of green fluorescent protein (GFP)-tagged molecules in live cells to explore the dynamics of protein kinase B (PKB) regulation during B lymphocyte activation. The data show that triggering of the B cell antigen receptor (BCR) induces a transient membrane localization of PKB but a sustained activation of the enzyme; active PKB is found in the cytosol and nuclei of activated B cells. Hence, PKB has three potential sites of action in B lymphocytes; transiently after BCR triggering PKB can phosphorylate plasma membrane localized targets, whereas during the sustained B cell response to antigen, PKB acts in the nucleus and the cytosol. Membrane translocation of PKB and subsequent PKB activation are dependent on BCR activation of phosphatidylinositol 3-kinase (PI3K). Moreover, PI3K signals are both necessary and sufficient for sustained activation of PKB in B lymphocytes. However, under conditions of continuous PI3K activation or BCR triggering there is only transient recruitment of PKB to the plasma membrane, indicating that there must be a molecular mechanism to dissociate PKB from sites of PI3K activity in B cells. The inhibitory Fc receptor, the FcγRIIB, mediates vital homeostatic control of B cell function by recruiting an inositol 5 phosphatase SHIP into the BCR complex. Herein we show that coligation of the BCR with the inhibitory FcγRIIB prevents membrane targeting of PKB. The FcγRIIB can thus antagonize BCR signals for PKB localization and prevent BCR stimulation of PKB activity which demonstrates the mechanism for the inhibitory action of the FcγRIIB on the BCR/PKB response.