The VE-cadherin/AmotL2 mechanosensory pathway suppresses aortic inflammation and the formation of abdominal aortic aneurysms

Abstract

Arterial endothelial cells (ECs) have the ability to respond to mechanical forces exerted by fluid shear stress. This response is of importance, as it is protective against vascular diseases such as atherosclerosis and aortic aneurysms. Mechanical forces are transmitted at the sites of adhesion to the basal membrane as well as cell-cell junctions where protein complexes connect to the cellular cytoskeleton to relay force into the cell. Here we present a novel protein complex that connects junctional VE-cadherin and radial actin filaments to the LINC complex in the nuclear membrane. We show that the scaffold protein AmotL2 is essential for the formation of radial actin filaments and the flow-induced alignment of aortic and arterial ECs. The deletion of endothelial AmotL2 alters nuclear shape as well as subcellular positioning. Molecular analysis shows that VE-cadherin is mechanically associated with the nuclear membrane via binding to AmotL2 and Actin. Furthermore, the deletion of AmotL2 in ECs provokes a pro-inflammatory response and abdominal aortic aneurysms (AAA) in the aorta of mice on a normal diet. Remarkably, transcriptome analysis of AAA samples from human patients revealed a negative correlation between AmotL2 expression and aneurysm diameters, as well as a positive correlation between AmotL2 and YAP expression. These findings provide a conceptual framework regarding how mechanotransduction in the junctions is coupled with vascular disease.

The junctional mechanosensor AmotL2 regulates YAP promotor accessibility

“…The notion of nuclear shape as a determinant of chromatin landscape and transcriptional activity is becoming increasingly evident 41 . Deletion of EC AmotL2 leads to mis-shapen nuclei of aortic ECs both in vitro and in vivo 5 , and in agreement with these data, we observed increased presence of nuclear wrinkles in AmotL2 knockdown HUAEC stained for a major structural component of the inner nuclear membrane, lamin A/C (Fig7a). We therefore investigated whether AmotL2 is involved in the regulation of lamins in maintaining nuclear morphology using subcellular fractionation and analysis of lamin A/C by western blotting, which showed a reduction specifically in lamin A expression (Fig7b).…”

“…Previous work from our lab has shown that AmotL2 is highly expressed in aorta compared to inferior vena cava (IVC) 5 . As YAP transcriptionally regulates AmotL2, we hypothesised that this pattern of vascular expression may be due to increased YAP activity exhibited in the aorta 10,11,12 .…”

“…Whole mount staining. Whole mount staining was performed as previously described 5 . Briefly, mice were euthanised and aorta harvested.…”

“…These results confirm that Yap/Taz regulates endothelial AmotL2 expression within the aortic endothelium. Endothelial specific deletion of AmotL2 results in the depletion of junctional actin fibres of the aorta, leading to perturbation in endothelial nuclear morphology and abnormal endothelial sensing of shear flow 5 . Therefore, we hypothesised that as an upstream regulator of AmotL2, the deletion Yap/Taz would phenocopy the morphological dysfunction observed in AmotL2 iDEC.…”

Endothelial dysfunction in Marfan syndrome mice is restored by resveratrol

“…This modulates EC organization, EC shape, nuclear shape, and intracellular organelle positioning 58,59 . A recent study by Zhang et al 60 linked the formation of aortic aneurysms to defective mechanotransduction in ECs, due to distorted nuclear shape and positioning, and reduced EC flow alignment. An ECM-derived aspect participating in altered mechanoresponse is transforming growth factor-β (TGF-β), as fibrillin-1 plays a key role in sequestration of extracellular TGF-β, the EC-vSMC paracrine communication in MFS may involve changes for this growth factor 61 .…”