Mannell Hanna, Hammitzsch Ariane, Mettler Ramona, Pohl Ulrich, Krötz Florian
Cardiology, Medical Policlinic, Ludwig-Maximilians-University, Ziemssenstrasse 1, 80336 Munich, Germany.
Cell Signal. 2010 Jan;22(1):88-96. doi: 10.1016/j.cellsig.2009.09.015. Epub 2009 Sep 23.
Angiogenesis initiation is crucially dependent on endothelial proliferation and can be stimulated by the fibroblast growth factor 2 (FGF-2). The DNA dependent protein kinase (DNA-PK), long known for its importance in repairing DNA double strand breaks, belongs to the phosphatidylinositol-3 kinase (PI3-K) super family and has recently been identified as one of the enzymes phosphorylating and activating Akt. Due to its similarity with PI3-K, we hypothesized that DNA-PK may have similar effects on endothelial angiogenic processes and signalling. We used primary endothelial cells (HUVEC and PAEC) and human microvascular endothelial cells (HMEC) to study the role of DNA-PK in endothelial proliferation and signalling. DNA-PKcs suppression with the compound NU7026 or with siRNA induced basal endothelial cell proliferation as well as enhanced FGF-2 dependent proliferation. This was associated with an increase in phosphorylated Akt. Tube formation was not affected by DNA-PKcs clearly showing that the role of DNA-PK in endothelial processes differs from that of PI3-K. Our findings indicate DNA-PK as an important enzyme maintaining the quiescent endothelial phenotype by actively inhibiting Akt thus restraining endothelial cell proliferation preventing excessive growth.
血管生成的起始关键依赖于内皮细胞增殖，且可被成纤维细胞生长因子2（FGF-2）刺激。DNA依赖性蛋白激酶（DNA-PK），长期以来因其在修复DNA双链断裂中的重要性而闻名，属于磷脂酰肌醇-3激酶（PI3-K）超家族，最近被鉴定为磷酸化并激活Akt的酶之一。由于其与PI3-K相似，我们推测DNA-PK可能对内皮血管生成过程和信号传导有类似作用。我们使用原代内皮细胞（人脐静脉内皮细胞和肺动脉内皮细胞）和人微血管内皮细胞来研究DNA-PK在内皮细胞增殖和信号传导中的作用。用化合物NU7026或小干扰RNA抑制DNA-PK催化亚基可诱导基础内皮细胞增殖以及增强FGF-2依赖性增殖。这与磷酸化Akt的增加有关。成管不受DNA-PK催化亚基的影响，这清楚地表明DNA-PK在内皮过程中的作用与PI3-K不同。我们的研究结果表明，DNA-PK是一种重要的酶，通过积极抑制Akt来维持静止的内皮细胞表型，从而抑制内皮细胞增殖，防止过度生长。
