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UBC Theses and Dissertations

Molecular and pharmacological characterization of mutant (F92A) caveolin-1 : a direction towards increasing nitric oxide bioavailability Sharma, Arpeeta


Nitric Oxide (NO) produced by the endothelium is a critical mediator of vascular function and plays an important role in the protection against various cardiovascular diseases1. In fact, a central feature of most cardiovascular diseases is reduced bioavailability of NO resulting from impaired endothelial function. Consequently, therapies that improve NO synthesis and availability in disease settings are relevant. Endothelial nitric oxide synthase (eNOS) is a membrane enzyme expressed exclusively in vascular endothelial cells and is responsible for NO production. Improper regulation of the enzyme results in production of eNOS-derived superoxide anion (O₂₋) instead of NO. O₂₋ is an oxidative stress mediator and scavenges NO, thereby contributing to lowered NO bioavailability. Extensive research has demonstrated a number of factors involved in positively regulating eNOS activity. However, one of the few proteins that bind to eNOS under basal conditions and inhibit NO release is Caveolin-1 (Cav-1), the major coat protein of plasma membrane lipid-enriched invaginations known as caveolae². Recently, it was demonstrated that a single amino acid substitution of the Cav-1 protein, mutant known as F92A Cav-1, is unable to inhibit eNOS³. Furthermore, preliminary data indicates that high expression of F92A Cav-1 can increase basal NO release. Due to the significance of NO in vascular function, the current work explores the possible mechanisms by which F92A Cav-1 potentiates eNOS activity and NO release. We report that F92A Cav-1 preserves the unique properties of Cav-1, including targeting to caveolae and forming high molecular weight oligomers, which are essential for caveolae organelle biogenesis. Moreover, F92A Cav-1 still retains the ability to bind to eNOS without altering its subcellular localization, indicating that F92A Cav-1 can prevent eNOS binding to endogenous Cav-1, which could rationalize the increased NO release observed. Lastly, we provide evidence that over-expression of F92A Cav-1 reduces the release of basal O₂₋ in endothelial cells as compared to WT Cav-1, revealing another potential positive effect of the mutant Cav-1. Hence, this report compares the biological properties of WT and F92A Cav-1 and the data collected is aimed at describing a therapeutically relevant pharmacological target to increase NO bioavailability in cardiovascular disease settings.

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