Laboratory of Biochemistry, Hiroshima International University, Hiroshima, Japan.
Department of Clinical Nutrition, Hiroshima International University, Hiroshima, Japan.
Sci Rep. 2019 Nov 13;9(1):16717. doi: 10.1038/s41598-019-53419-4.
Apoptosis of endothelial cells is a very important event in various diseases and angiogenesis. We recently reported that ras guanyl nucleotide releasing protein 2 (RasGRP2), which is a guanine nucleotide exchange factor, was expressed in the human umbilical vein endothelial cells (HUVECs) and that Rap1 activation by its overexpression inhibited apoptosis by suppressing tumor necrosis factor-α induced-reactive oxygen species (ROS) production. However, other signaling pathways and roles of RasGRP2 not mediated via Rap1 are not well understood. Therefore, we compared the Mock (M) and the RasGRP2-stable overexpression (R) immortalized HUVECs using BAM7 and anisomycin, which are apoptosis inducers. BAM7 and anisomycin induced apoptosis without causing ROS production, and such apoptosis was significantly increased in M cells, but not in R cells. RasGRP2 suppressed BAM7- and anisomycin-induced apoptosis, but not via the Rap1 pathway as observed using Rap1 knockdown. Furthermore, RasGRP2 activated not only Rap1 but also R-Ras, and suppressed apoptosis by activating R-Ras-phosphoinositide 3-kinase (PI3K)-Akt signaling pathway. The phosphorylation of Akt by RasGRP2 inhibited Bax translocation by promoting translocation of hexokinase-2 (HK-2) from cytoplasm to mitochondria. Taken together, it was suggested that RasGRP2 suppresses the Bax activation-induced apoptosis by promoting HK-2 translocation to mitochondria via R-Ras-PI3K-Akt signaling pathway.
内皮细胞的凋亡是各种疾病和血管生成中非常重要的事件。我们最近报道，Ras 鸟嘌呤核苷酸释放蛋白 2（RasGRP2）是一种鸟嘌呤核苷酸交换因子，在人脐静脉内皮细胞（HUVEC）中表达，其过表达激活 Rap1 可抑制肿瘤坏死因子-α诱导的活性氧（ROS）产生，从而抑制细胞凋亡。然而，RasGRP2 不通过 Rap1 介导的其他信号通路和作用尚不清楚。因此，我们使用 BAM7 和anisomycin 比较了 Mock（M）和 RasGRP2 稳定过表达（R）的永生化 HUVEC，这两种物质均可诱导细胞凋亡。BAM7 和 anisomycin 诱导凋亡而不产生 ROS，M 细胞中的这种凋亡明显增加，但在 R 细胞中没有增加。RasGRP2 抑制 BAM7 和 anisomycin 诱导的细胞凋亡，但不通过观察到的 Rap1 通路，因为 Rap1 敲低。此外，RasGRP2 不仅激活 Rap1，还激活 R-Ras，并通过激活 R-Ras-磷酸肌醇 3-激酶（PI3K）-Akt 信号通路抑制细胞凋亡。RasGRP2 通过促进己糖激酶-2（HK-2）从细胞质向线粒体易位来抑制 Bax 易位，从而磷酸化 Akt。总之，这表明 RasGRP2 通过 R-Ras-PI3K-Akt 信号通路促进 HK-2 向线粒体易位，从而抑制 Bax 激活诱导的细胞凋亡。
