title: Shear stress regulates endothelial nitric oxide synthase expression through c-Src by divergent signaling pathways.
abstract: 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.
authors.affiliation: Division of Cardiology, Emory University, Atlanta, GA, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Davis
authors.forename: H
authors.initials: H
authors.lastname: Cai
authors.forename: G R
authors.initials: GR
authors.lastname: Drummond
authors.forename: D G
authors.initials: DG
authors.lastname: Harrison
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics*; D052250:Nitric Oxide Synthase Type III; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000037:antagonists & inhibitors / Q000502:physiology*; D020871:RNA Stability; D012333:RNA, Messenger / Q000096:biosynthesis; D013314:Stress, Mechanical; D015533:Transcriptional Activation
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D016392:Proto-Oncogene Proteins pp60(c-src); D019908:Proto-Oncogene Proteins c-raf; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D016283:Proto-Oncogene Proteins p21(ras)