Effect of Vascular Heterogeneity, Aging, and Exercise Training on eNOS ? Associated Protein:Protein Interactions

Endothelial dysfunction is a major risk factor for the development of cardiovascular diseases, and aging is associated with a gradual decline in endothelial function. Furthermore, endothelial dysfunction in arteries and arterioles supplying skeletal muscle has been implicated in the decline in exercise capacity with aging. Defined as an imbalance between the production and degradation of nitric oxide (NO), limited NO bioavailability is the hallmark characteristic of endothelial dysfunction. Production of NO is controlled by the enzyme endothelial nitric oxide synthase (eNOS), which is regulated in part by post-translational protein modifications.

The purpose of this research was to examine the effect of vascular heterogeneity, aging, and endurance exercise training on eNOS-associated protein:protein interactions. Caveolin-1 (Cav1) is a negative regulator of eNOS activity, so that NO production is suppressed when Cav1 is bound to eNOS. Conversely, calmodulin (CaM) and heat-shock protein 90 (Hsp90) are positive regulators of eNOS activity, thus increasing eNOS activity and NO production when either are bound to eNOS. Co-immunoprecipitation was used to determine protein:protein interactions among eNOS and its regulatory proteins throughout the arterial network, from the aorta to third order skeletal muscle arterioles. Results show that eNOS-associated protein:protein interactions vary throughout the arterial network, and Cav1:eNOS and CaM:eNOS interactions are altered with aging. Additionally, endurance exercise training has no effect on the protein:protein interactions examined. In conclusion, eNOS regulation via protein:protein interactions appears to be vessel-specific, and aging has a heterogeneous effect on protein:protein interactions throughout the arterial network.