Nucleoporin93 (Nup93) Promotes Vascular Health by Limiting Endothelial Cell Aging and Dysfunction

Endothelial cells (ECs) serve as a selective monolayer to mediate blood vessel integrity for vascular function, and EC health is in turn increasingly acknowledged as a crucial factor in limiting age-induced vessel dysfunction. Conversely, chronic inflammation and natural aging drive pro-inflammatory endothelial changes, resulting in EC activation and vessel leakage to precipitate vascular disease. Recent studies report increased nuclear leakiness with aging, displaying the significance of proper nucleocytoplasmic transport for cellular health. As the major regulator of molecular transport across the nuclear envelope, the nuclear pore complex (NPC) in ECs may also be compromised with age to drive vascular disease. Our exciting studies implicate nucleoporin93 (Nup93), a crucial structural NPC protein, as an indispensable player for EC health and vascular protection. We observe a significant reduction in endothelial Nup93 expression in the coronary vasculature of aged mice. Moreover, we find that endothelial loss of Nup93 induces cellular senescence and promotes the surface expression of pro-inflammatory adhesion molecules for enhanced EC-monocyte interaction. Mechanistically, endothelial Nup93 deficiency leads to nuclear leakiness for increased nuclear localization of Yap, a transcription co-factor known to activate EC inflammation. Pharmacological inhibition of Yap activity in Nup93-null ECs reverses the senescence and inflammatory phenotypes, indicating Yap hyperactivation as a major consequence of Nup93 deficiency in ECs. Furthermore, Nup93 loss in human ECs leads to actin stress fiber formation, impaired eNOS-dependent nitric oxide (NO) bioavailability, and enhanced in vitro paracellular permeability. Mechanistically, endothelial Nup93 depletion significantly decreases Sun1 levels, a component of the linker of the nucleoskeleton and cytoskeleton (LINC) complex necessary to connect the nucleus with the cytoskeleton. Endothelial loss of Nup93 also results in a concomitant increase in RhoA activity, where the re-introduction of Sun1 in Nup93-deficient ECs mitigates RhoA activation to restore endothelial barrier function and NO production. Our studies not only show Sun1 as a negative regulator of endothelial RhoA activity, but also implicate Nup93 as a necessary component in preventing aberrant RhoA signaling. Overall, the dissertation herein highlights the previously unrecognized role of NPC proteins in limiting endothelial senescence and dysfunction, thus providing novel insight into the molecular mechanisms underlying vascular aging and disease progression.