Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

The endothelial nitric oxide synthase (eNOS) exists in endothelial cells, not as an isolated protein, but as part of a complex with other proteins. For example, we and others have shown that eNOS is subject to negative allosteric regulation by the plasmalemmal caveolae structural protein, caveolin-1. Caveolin-1 interacts directly with eNOS and inhibits eNOS catalytic activity. eNOS-activating agonists promote dissociation of eNOS from caveolin-1, an event which may be important in the agonist-stimulated eNOS activation process. In the present study, we show that eNOS also participates in direct and inhibitory interactions with the G-protein-coupled receptors for three different eNOS-activating agonists. Glutathione S-transferase fusion proteins containing intracellular domain 4 of either the bradykinin B2 receptor, the angiotensin II AT1 receptor, or the endothelin-1 ETB receptor are all bound by purified recombinant eNOS in in vitro binding assays. Synthetic peptides corresponding to a 20-residue membrane-proximal portion of intracellular domain 4 of each of the receptors are also potent inhibitors of eNOS catalytic activity. In vitro interactions of eNOS with the B2 receptor appear to have relevance for the existence of an eNOS-B2 receptor complex in endothelial cells because eNOS and the receptor are coimmunoprecipitated from endothelial cell lysates by antibodies directed against either of the two proteins. Furthermore, treatment of endothelial cells with bradykinin or Ca2+ ionophore promotes a rapid dissociation of the eNOS-B2 receptor complex. We propose that dissociation of eNOS from inhibitory interactions with the B2 receptor may be an important and necessary component of bradykinin signal transduction leading to eNOS activation.

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Presentation Number SAvenema0471
Keywords: eNOS, caveolin, nitric oxide, bradykinin