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Signal transduction of eNOS activation.
1Institut für Kardiovaskuläre Physiologie, Klinikum der J.W. Goethe-Universität, Frankfurt am Main, Germany. Fleming@em.uni-frankfurt.de
Cardiovascular Research
|February 26, 2000
Summary
Endothelial nitric oxide synthase (eNOS) activation can occur independently of calcium. Shear stress stimulates NO production via Ca2+-independent pathways involving tyrosine phosphorylation, highlighting novel regulatory mechanisms.
Area of Science:
- Biochemistry
- Cell Biology
- Physiology
Background:
- Endothelial nitric oxide synthase (eNOS) is a Ca2+/calmodulin-dependent enzyme.
- eNOS activity is regulated by Ca2+ influx, calmodulin binding, and post-translational modifications.
- Fluid shear stress typically induces transient Ca2+ increases and NO production in endothelial cells.
Purpose of the Study:
- To investigate the mechanisms of Ca2+-independent eNOS activation by fluid shear stress.
- To identify signaling pathways involved in shear stress-induced NO production independent of intracellular Ca2+.
Main Methods:
- Experiments were conducted on native and cultured endothelial cells.
- Studies involved manipulating extracellular Ca2+ concentrations and using calmodulin antagonists.
- Pharmacological inhibitors targeting tyrosine kinases, Hsp90-binding proteins, phosphatidylinositol 3-kinase, and protein tyrosine phosphatases were employed.
Main Results:
- Shear stress induced maintained NO production in the absence of extracellular Ca2+ and in the presence of calmodulin antagonists.
- This Ca2+-independent NO production was insensitive to extracellular Ca2+ removal.
- The activation was sensitive to tyrosine kinase inhibitors, Hsp90-binding proteins, and PI3K inhibitors, and mimicked by protein tyrosine phosphatase inhibitors.
Conclusions:
- eNOS can be activated by Ca2+-independent mechanisms, particularly under fluid shear stress.
- Phosphorylation of eNOS and/or associated proteins is crucial for this Ca2+-independent activation.
- These findings reveal novel regulatory pathways for NO production in endothelial cells.