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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 laminar 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 endothelial cells. 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 provoked 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 inflammation of the aortic intima. These findings provide a conceptual framework regarding how mechanotransduction in the junctions is coupled with vascular diseases.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Bos Taurus (bovine) Mus Musculus (mouse)

SUBMITTER: Georgios Mermelekas

LAB HEAD: Janne Lehtio

PROVIDER: PXD042661 | Pride | 2023-08-21

REPOSITORIES: Pride

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Project description:Background: Palmdelphin (PALMD), a protein of unknown function, belongs to the family of Paralemmin proteins implicated in cytoskeletal regulation. Single nucleotide polymorphisms (SNPs) in the PALMD locus, which reduce its expression, are strong risk factors for development of calcific aortic valve stenosis (CAVS) and for severity of the disease. Methods: Public database screening and immunodetection of PALMD showed dominant expression in endothelial cells (ECs). Mass spectrometry allowed identification of PALMD partners. The consequence of loss of PALMD expression was assessed in siRNA silenced EC cultures, in knockout mice and in human valve samples and EC cultures from patients. RNA sequencing on siRNA silenced cells and transcript arrays on valve samples from a Swedish SNP rs7543130 patient cohort informed about gene regulatory changes. Results: ECs express the cytoplasmic PALMD-KKVI splice variant, which was shown to exist in complex with RAN GTPase activating protein1 (RANGAP1). RANGAP1 regulates the activity of the GTPase RAN and thereby, nucleocytoplasmic shuttling via Exportin1 (XPO1). Reduced PALMD expression resulted in subcellular relocalization of RANGAP1 and XPO1, providing a mechanism for the gene regulatory changes established in PALMD-deficiency. Gene ontology analysis showed enrichment of actin and RHO GTPAse related terms in PALMD-silenced ECs. In accordance, PALMD-silenced ECs showed multiple changes in adhesive and migratory properties and cells were softer. In particular, PALMD-deficient ECs failed to form a perinuclear actin cap when exposed to flow. The perinuclear actin cap is known to provide protection against mechanical stress. Lack of the actin cap correlated with tilting of the nuclear long axis relative to the cell body, which was established in PALMD-deficient ECs, mice and patient valve samples. The loss of the actin cap may contribute to further dysregulated gene transcription eventually promoting calcific precipitations and inflammation in CAVS. Conclusions: We identify RANGAP1 as a PALMD partner in ECs. Disrupting the PALMD/RANGAP1 complex changes the subcellular localization of essential nucleocytoplasmic shuttling components, thereby instigating the loss of actin-dependent nuclear resilience, which in turn promotes further deterioration of gene expression patterns predisposing to the establishment of CAVS.

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

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