Small GTPase Ras and Rho expression in rat osteoblasts during spaceflight
Small GTPase Ras and Rho expression in rat osteoblasts during spaceflight
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DOI：
10.1196/annals.1397.032
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发表时间：
2007-01-01
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影响因子：
--
通讯作者：
Morita, Sadao
中科院分区：
文献类型：
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作者：
Kumei, Yasuhiro;Shimokawa, Hitoyata;Morita, Sadao
大鼠成骨细胞在航天飞机上培养 4 和 5 天，并在用 1α、25 二羟基维生素 D-3 处理 24 小时后溶解。定量RT-PCR测定Ras上游和下游信号分子的mRNA水平。小 GTP 酶被鸟嘌呤核苷酸交换蛋白 (GEF) 激活，并被 GTP 酶激活蛋白 (GAP) 失活。当外部刺激转变成细胞内信号时，会调用多种途径：粘着斑激酶 (FAK) 与整合素-β 相关，并指导下游底物的酪氨酸磷酸化，包括磷脂酶 C-gamma (PLC-gamma) 和 Sevenless 之子 (SOS，Ras GEF)。飞行培养物中FAK和PLC-gamma 1和-gamma 2的mRNA水平比地面对照增加了150%和250%。飞行培养物中的 SOS mRNA 水平比地面对照增加了 520% 和 320%。 G 蛋白偶联受体的信号通过 PLC(3 和 Ras GRF（另一种 Ras GEF）进行传输。激活的 Ras 会刺激 Raf、丝裂原激活蛋白激酶 (MAPK) 级联。Raf、MAPK 家族细胞外信号调节蛋白激酶（ERK-1 和 -2）以及 PLC-beta 的 mRNA 水平在太空飞行期间增加。飞行培养物中的 Rho GAP 表达增加了地面对照的两倍。自 Rho GAP 使 Rho 失活，微重力可能抑制 Rho 信号，调节肌动蛋白丝重排。微重力信号可能涉及激活大鼠成骨细胞中 Ras、Raf 和 MAPK 级联的两条途径（G 蛋白偶联受体介导的途径和酪氨酸磷酸化介导的途径）。
Rat osteoblasts were cultured for 4 and 5 days aboard a space shuttle and solubilized after a 24-h treatment with 1 alpha,25 dihydroxyvitamin D-3. The quantitative RT-PCR determined the mRNA levels of signaling molecules upstream and downstream Ras. The small GTPase is activated by guanine nucleotide exchange protein (GEF) and deactivated by GTPase-activating protein (GAP). When external stimuli are transduced into intracellular signals, various pathways are recruited: focal adhesion kinase (FAK) is associated with integrin-beta, and directs tyrosine phosphorylation of downstream substrates, including phospholipase C-gamma (PLC-gamma) and son of sevenless (SOS, a Ras GEF). The mRNA levels of FAK and PLC-gamma 1 and -gamma 2 in the flight cultures were increased 150% and 250% of the ground controls. The SOS mRNA levels in the flight cultures were increased 520% and 320% of the ground controls. Signals via G protein-coupled receptors are transmitted through PLC(3 and Ras GRF (another Ras GEF). Activated Ras then stimulates Raf, mitogen-activated protein kinase (MAPK) cascades. The mRNA levels of Raf, extracellular signal-regulated protein kinase of MAPK family (ERK-1 and -2), and PLC-beta were increased during spaceflight. Rho GAP expression in the flight cultures was increased twofold of the ground controls. Since Rho GAP deactivates Rho, microgravity may suppress Rho signals, regulating actin filament rearrangement. Microgravity signals may involve two pathways (G protein-coupled receptor-mediated pathway and tyrosine phosphorylation-mediated pathway) that activate Ras, Raf, and MAPK cascades in rat osteoblasts.