Spagnuolo Raffaella, Corada Monica, Orsenigo Fabrizio, Zanetta Lucia, Deuschle Ulrich, Sandy Peter, Schneider Claudio, Drake Christopher J, Breviario Ferruccio, Dejana Elisabetta
Italian Foundation for Cancer Research (FIRC) Institute of Molecular Oncology, Milan, Italy.
Blood. 2004 Apr 15;103(8):3005-12. doi: 10.1182/blood-2003-07-2459. Epub 2003 Dec 11.
The junctional membrane protein vascular endothelial (VE)-cadherin mediates contact inhibition of growth and inhibits apoptosis of endothelial cells. In this article we show that VE-cadherin induces expression of growth arrest-specific 1 (Gas1), an integral membrane protein up-regulated in nonproliferating cells. By comparing syngenic endothelial cell lines, we found that Gas1 mRNA was increased by 3-fold in VE-cadherin-positive cells in comparison to VE-cadherin-null cells. Ectopic expression of Gas1 in endothelial or 293 cells strongly reduced apoptosis without affecting cell growth. Addition of vascular endothelial growth factor (VEGF) also up-regulated Gas1 and this effect was augmented more so in confluent nonproliferating cells than in sparse cultures. VE-cadherin-blocking antibody partially inhibited VEGF-induced Gas1, suggesting that VE-cadherin clustering is required for an optimal response to this stimulus. Inhibition of phosphoinositole-3-OH kinase (PI3-kinase) pathway by Wortmannin prevented Gas1 synthesis and the antiapoptotic effect of VEGF, but, in cells ectopically expressing Gas1, Wortmannin was ineffective. Furthermore, inhibition of Gas1 expression by short interfering RNA (siRNA) both in vitro and in allantois organ cultures made endothelial cells refractory to the antiapoptotic effect of VEGF. Overall these data indicate that Gas1 induction by VE-cadherin and VEGF in endothelial cells requires activation of PI3-kinase. Gas1 expression positively correlates with inhibition of endothelial cell apoptosis and may contribute to the integrity of resting endothelium.
连接膜蛋白血管内皮（VE）-钙黏蛋白介导生长的接触抑制并抑制内皮细胞凋亡。在本文中，我们表明VE-钙黏蛋白可诱导生长停滞特异性1（Gas1）的表达，Gas1是一种在非增殖细胞中上调的整合膜蛋白。通过比较同基因内皮细胞系，我们发现与缺乏VE-钙黏蛋白的细胞相比，VE-钙黏蛋白阳性细胞中的Gas1 mRNA增加了3倍。Gas1在内皮细胞或293细胞中的异位表达可显著减少细胞凋亡，而不影响细胞生长。添加血管内皮生长因子（VEGF）也可上调Gas1，且这种效应在汇合的非增殖细胞中比在稀疏培养物中增强得更多。VE-钙黏蛋白阻断抗体部分抑制VEGF诱导的Gas1，这表明VE-钙黏蛋白聚集是对该刺激产生最佳反应所必需的。渥曼青霉素对磷酸肌醇-3-OH激酶（PI3-激酶）途径的抑制可阻止Gas1的合成以及VEGF的抗凋亡作用，但在异位表达Gas1的细胞中，渥曼青霉素无效。此外，在体外和尿囊器官培养中，通过小干扰RNA（siRNA）抑制Gas1的表达会使内皮细胞对VEGF的抗凋亡作用产生抗性。总体而言，这些数据表明内皮细胞中VE-钙黏蛋白和VEGF诱导Gas1需要PI3-激酶的激活。Gas1的表达与内皮细胞凋亡的抑制呈正相关，可能有助于静止内皮的完整性。
