Davis M E, Cai H, Drummond G R, Harrison D G
Division of Cardiology, Emory University, Atlanta, GA, USA.
Circ Res. 2001 Nov 23;89(11):1073-80. doi: 10.1161/hh2301.100806.
In this study, we defined the signaling cascade responsible for increased eNOS mRNA expression in response to laminar shear stress. This pathway depends on the tyrosine kinase c-Src because shear induction of eNOS mRNA is blocked by the c-Src inhibitors PP1 and PP2, as well as an adenovirus encoding kinase inactive c-Src. After activation of c-Src, this pathway diverges. One arm is responsible for the short-term (6 hour) increase in eNOS mRNA. This involves a transient, 1-hour increase in eNOS transcription, as detected by nuclear run-on, that is dependent on activation of Ras and is blocked by adenoviral infection with dominant negative Ras. Downstream of Ras, MEK1/2 and ERK1/2 are important in this pathway, as 2 inhibitors of MEK1/2, PD98059 and UO126, completely prevented this early increase in eNOS mRNA. ERK1/2 was rapidly phosphorylated in response to shear, and this was prevented by c-Src and Ras inhibition. Further, Raf is phosphorylated in response to shear stress, and this is prevented by c-Src inhibition, suggesting that Raf may transduce the signal between Ras and ERK1/2. The second arm of the pathway linking activation of c-Src to eNOS expression involves stabilization of eNOS mRNA by shear stress. This response to shear is completely abrogated by the c-Src inhibitor PP1 but not altered by Ras or MEK1/2 inhibition. Thus, c-Src plays a central role in modulation of eNOS expression in response to shear stress via divergent pathways involving a short-term increase in eNOS transcription and a longer-term stabilization of eNOS mRNA.
在本研究中，我们确定了响应层流切应力时负责eNOS mRNA表达增加的信号级联。该途径依赖于酪氨酸激酶c-Src，因为eNOS mRNA的切应力诱导被c-Src抑制剂PP1和PP2以及编码激酶失活型c-Src的腺病毒所阻断。c-Src激活后，该途径发生分支。其中一条分支负责eNOS mRNA的短期（6小时）增加。这涉及通过核转录分析检测到的eNOS转录短暂增加1小时，其依赖于Ras的激活，并被显性负性Ras的腺病毒感染所阻断。在Ras的下游，MEK1/2和ERK1/2在该途径中很重要，因为MEK1/2的两种抑制剂PD98059和UO126完全阻止了eNOS mRNA的这种早期增加。ERK1/2响应切应力而迅速磷酸化，而c-Src和Ras抑制可阻止这种磷酸化。此外，Raf响应切应力而磷酸化，而c-Src抑制可阻止这种磷酸化，这表明Raf可能在Ras和ERK1/2之间传导信号。将c-Src激活与eNOS表达联系起来的途径的第二条分支涉及切应力对eNOS mRNA的稳定作用。c-Src抑制剂PP1可完全消除这种对切应力的反应，但Ras或MEK1/2抑制不会改变这种反应。因此，c-Src在通过涉及eNOS转录短期增加和eNOS mRNA长期稳定的不同途径调节响应切应力的eNOS表达中起核心作用。
