Department of Pharmacology, University of Illinois College of Medicine, Chicago, IL 60612, USA.
Blood. 2010 May 27;115(21):4237-46. doi: 10.1182/blood-2009-11-255323. Epub 2010 Mar 23.
In neutrophils, the phosphoinositide 3-kinase/Akt signaling cascade is involved in migration, degranulation, and O(2)(-) production. However, it is unclear whether the Akt kinase isoforms have distinct functions in neutrophil activation. Here we report functional differences between the 2 major Akt isoforms in neutrophil activation on the basis of studies in which we used individual Akt1 and Akt2 knockout mice. Akt2(-/-) neutrophils exhibited decreased cell migration, granule enzyme release, and O(2)(-) production compared with wild-type and Akt1(-/-) neutrophils. Surprisingly, Akt2 deficiency and pharmacologic inhibition of Akt also abrogated phorbol ester-induced O(2)(-) production, which was unaffected by treatment with the phosphoinositide 3-kinase inhibitor LY294002. The decreased O(2)(-) production in Akt2(-/-) neutrophils was accompanied by reduced p47(phox) phosphorylation and its membrane translocation, suggesting that Akt2 is important for the assembly of phagocyte nicotinamide adenine dinucleotide phosphate oxidase. In wild-type neutrophils, Akt2 but not Akt1 translocated to plasma membrane upon chemoattractant stimulation and to the leading edge in polarized neutrophils. In the absence of Akt2, chemoattractant-induced Akt protein phosphorylation was significantly reduced. These results demonstrate a predominant role of Akt2 in regulating neutrophil functions and provide evidence for differential activation of the 2 Akt isoforms in neutrophils.
在中性粒细胞中，磷酸肌醇 3-激酶/Akt 信号级联参与迁移、脱颗粒和 O(2)(-)产生。然而，Akt 激酶同工型在中性粒细胞激活中的是否具有不同的功能尚不清楚。在此，我们根据使用单个 Akt1 和 Akt2 敲除小鼠的研究，报告了中性粒细胞激活中 2 种主要 Akt 同工型之间的功能差异。与野生型和 Akt1(-/-)中性粒细胞相比，Akt2(-/-)中性粒细胞的细胞迁移、颗粒酶释放和 O(2)(-)产生减少。令人惊讶的是，Akt2 缺陷和 Akt 的药理学抑制也消除了佛波酯诱导的 O(2)(-)产生，而这种产生不受磷酸肌醇 3-激酶抑制剂 LY294002 的影响。Akt2(-/-)中性粒细胞中 O(2)(-)产生的减少伴随着 p47(phox)磷酸化及其膜转位减少，表明 Akt2 对于吞噬细胞烟酰胺腺嘌呤二核苷酸磷酸氧化酶的组装很重要。在野生型中性粒细胞中，Akt2 而不是 Akt1 在趋化因子刺激时向质膜易位，并在极化的中性粒细胞中向前缘易位。在 Akt2 缺失的情况下，趋化因子诱导的 Akt 蛋白磷酸化显著减少。这些结果表明 Akt2 在调节中性粒细胞功能中起着主要作用，并为 2 种 Akt 同工型在中性粒细胞中的差异激活提供了证据。
