Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L-3N6, Canada.
Cancers (Basel). 2015 Jan 7;7(1):96-111. doi: 10.3390/cancers7010096.
Mesenchymal cells employ actin-based membrane protrusions called podosomes and invadopodia for cross-tissue migration during normal human development such as embryogenesis and angiogenesis, and in diseases such as atherosclerosis plaque formation and cancer cell metastasis. The Akt isoforms, downstream effectors of phosphatidylinositol 3 kinase (PI3K), play crucial roles in cell migration and invasion, but their involvement in podosome formation and cell invasion is not known. In this study, we have used Akt1 and/or Akt2 knockout mouse embryonic fibroblasts and Akt3-targeted shRNA to determine the roles of the three Akt isoforms in Src and phorbol ester-induced podosome formation, and extracellular matrix (ECM) digestion. We found that deletion or knockdown of Akt1 significantly reduces Src-induced formation of podosomes and rosettes, and ECM digestion, while suppression of Akt2 has little effect. In contrast, Akt3 knockdown by shRNA increases Src-induced podosome/rosette formation and ECM invasion. These data suggest that Akt1 promotes, while Akt3 suppresses, podosome formation induced by Src, and Akt2 appears to play an insignificant role. Interestingly, both Akt1 and Akt3 suppress, while Akt2 enhances, phorbol ester-induced podosome formation. These data show that Akt1, Akt2 and Akt3 play different roles in podosome formation and ECM invasion induced by Src or phorbol ester, thus underscoring the importance of cell context in the roles of Akt isoforms in cell invasion.
间质细胞利用肌动蛋白为基础的膜突，称为足突和侵袭伪足，在正常的人类发育过程中进行跨组织迁移，如胚胎发生和血管生成，以及在动脉粥样硬化斑块形成和癌细胞转移等疾病中。磷脂酰肌醇 3 激酶（PI3K）的下游效应物 Akt 同工型在细胞迁移和侵袭中发挥着关键作用，但它们在足突形成和细胞侵袭中的参与情况尚不清楚。在这项研究中，我们使用 Akt1 和/或 Akt2 基因敲除的小鼠胚胎成纤维细胞和 Akt3 靶向的 shRNA，以确定三种 Akt 同工型在Src 和佛波酯诱导的足突形成和细胞外基质（ECM）消化中的作用。我们发现，Akt1 的缺失或敲低显著减少了 Src 诱导的足突和玫瑰花结的形成以及 ECM 的消化，而 Akt2 的抑制作用则很小。相比之下，shRNA 下调 Akt3 会增加 Src 诱导的足突/玫瑰花结形成和 ECM 侵袭。这些数据表明 Akt1 促进Src 诱导的足突形成，而 Akt3 抑制 Akt1，Akt2 似乎作用不大。有趣的是，Akt1 和 Akt3 均抑制，而 Akt2 增强佛波酯诱导的足突形成。这些数据表明，Akt1、Akt2 和 Akt3 在 Src 或佛波酯诱导的足突形成和 ECM 侵袭中发挥不同的作用，因此强调了细胞背景在 Akt 同工型在细胞侵袭中的作用的重要性。
