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RbFox2 is a RhoBTB1-Cullin-3 Target in Vascular Smooth Muscle Regulating Arterial Stiffness through the Cytoskeleton

ABSTRACT: The RhoBTB1-Cullin3 (CUL3) pathway in smooth muscle cells (SMCs) controls the ubiquitination of target proteins and through this blood pressure (BP) and arterial stiffness. We performed proximity labelling coupled with mass spectrometry to identify RhoBTB1 interacting partners in A7R5 SMCs. We identified 59 proteins which bound to the C-terminal half of RhoBTB1, the region identified as essential for its adapter function to deliver substrates to CUL3. We examined one of these proteins in detail - RbFox2. Co-immunoprecipitation validated the interaction of RbFox2 with RhoBTB1. Expression of RbFox2 was elevated in response to inhibition of the ubiquitination-proteasomal pathway, CUL3-deficiency, and RhoBTB1 inhibition by either siRNA or angiotensin II (ANG). RbFox2 was ubiquitinated in a RhoBTB1- and CUL3-dependent manner suggesting it is regulated through the RhoBTB1-CUL3-dependent ubiquitin-proteasome pathway. Inhibition of RbFox2 impaired the actin cytoskeleton in A7R5 cells and in primary SMC from RbFox2Flox mice and decreased the levels of globular and filamentous actin. ANG increased BP and arterial stiffness of RbFox2Flox mice, but the progression of arterial stiffness was halted after SMC-specific RbFox2 deletion despite a continued rise in BP. We conclude that RhoBTB1 and its target RbFox2 is an important regulator of arterial stiffness through its actions to regulate the cytoskeleton.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE305901 | GEO | 2026/03/24

REPOSITORIES: GEO

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			Action	DRS
		Other
	GSE305901_Control.gene_grouped_counts.tsv.gz	Tabular
	GSE305901_Control.transcript_grouped_counts.tsv.gz	Tabular
	GSE305901_siRbFox2.gene_grouped_counts.tsv.gz	Tabular
	GSE305901_siRbFox2.transcript_grouped_counts.tsv.gz	Tabular

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Project description:SMCs express plasminogen activator inhibitor-1 (PAI-1), which regulates SMC function and vascular remodeling. However, whether PAI-1 controls SMC cytoskeletal dynamics and stiffness is unknown, and the causal role of PAI-1 in arterial stiffening is undefined. SMCs from human coronary arteries and aortae of wild-type vs. PAI-1-deficient mice were cultured with or without PAI-039, a specific PAI-1 inhibitor, after which cell stiffness was measured by atomic force microscopy, filamentous actin structures were assessed by confocal microscopy, and the activities cofilin, LIM domain kinase 1 (LIMK), slingshot homolog 1 (SSH), and AMP-activated protein kinase (AMPK) were measured. RNA sequencing was performed to determine the effects of PAI-039 on SMC gene expression. Effects of PAI-039 on aortic stiffness were assessed by pulse wave velocity. PAI-039 significantly reduced intrinsic stiffness of human SMCs, which was accompanied by significant decreases in cytoplasmic actin filaments. Similar effects were observed in wild-type, but not in PAI-1-deficient SMCs. Mechanistically, PAI-039 significantly increased the activity of cofilin, an actin depolymerase, in SMCs expressing PAI-1, but not in PAI-1-deficient cells. PAI-039 had no significant effects on LIMK or SSH activity. RNA-sequencing analysis suggested that PAI-039 up-regulates AMPK signaling in SMCs, which was confirmed by western blotting. Inhibition of AMPK prevented activation of cofilin by PAI-039. In mice, PAI-039 significantly decreased aortic stiffness without significantly altering peri-aortic fibrosis. PAI-039 decreases intrinsic SMC stiffness by reducing cytoplasmic stress fiber content. These effects are mediated by AMPK-dependent activation of cofilin. PAI-039 also decreases aortic stiffness in vivo. These findings suggest that PAI-1 is an important regulator of the SMC cytoskeleton and that pharmacologic inhibition of PAI-1 has potential to treat cardiovascular diseases mediated by accelerated arterial stiffening.

Project description:Objective: Angiotensin-II (Ang-II) drives pathological vascular wall remodeling in hypertension and abdominal aortic aneurysm (AAA). Previous studies showed that the phosphatase activity of calcineurin (Cn) mediates Ang-II-induced AAA, but the cell type involved in the action of Cn in AAA formation remained unknown. Methods: Smooth muscle cell (SMC)-specific and endothelial cell (EC)-specific Cn-deficient mice (SM-Cn-/- and EC-Cn-/- mice, respectively) were created and assessed for Ang-II-induced AAA formation and hypertension vs controls. Osmotic minipumps were used to administer Ang-II and cyclosporine A (CsA), a pharmaceutical Cn inhibitor. AAA formation and hypertension were monitored by ultrasonography, arterial blood pressure monitoring, and histological analysis. Deep RNA sequencing was used to identify the Ang-II-regulated transcriptome sensitive to Cn deletion or pharmacological inhibition. Arterial and SMC contractility were also assessed. Results: Cn expressed in SMCs, but not ECs, was required for Ang-II-induced AAA. SMC Cn also played an unexpected structural role in the early onset and maintenance of Ang-II-induced hypertension independently of Cn phosphatase activity. Nearly 90% of the genes regulated by Ang-II in the aorta required Cn expression in SMCs. Cn orchestrated, independently of its enzymatic activity, the induction by Ang-II of a gene expression program closely related to SMC contractility and hypertension. Cn deletion in SMCs, but not its pharmacological inhibition, impaired the regulation of arterial contractility. Among the genes whose regulation by Ang-II required Cn expression but not its phosphatase activity, Serpine1 was critical for Ang-II-induced hypertension. Indeed, pharmacological inhibition of PAI-1, the protein encoded by Serpine1, impaired SMCs contractility and regressed hypertension. Conclusions: Whereas the phosphatase activity of Cn mediates Ang-II-induced AAA, a phosphatase-independent action of SMC Cn underlies blood pressure regulation by orchestrating a gene expression program closely related to contractility regulation and hypertension.

Project description:Tissue Factor Pathway Inhibitor-2 is Induced by Fluid Shear Stress in Vascular Smooth Muscle Cells and Affects Cell Proliferation and Survival Introduction: Vascular smooth muscle cells (SMCs) are exposed to fluid shear stress (FSS) after interventional procedures such as balloon-angioplasty. Whereas the effects of hemodynamic forces on endothelial cells are explored in detail, the influence of FSS on smooth muscle cell function is poorly characterized. Here, we investigated the effect of FSS on SMC gene expression and function. Methods: Laminar FSS of arterial level (14 dynes/cm2) was applied to SMC cultures for 24 h in a parallel-plate flow chamber. The effect of FSS on gene expression was first screened with microarray technology and the results further verified by real time (RT) PCR and immunoblotting. Protein expression was also studied in the rat carotid artery after balloon-injury and DNA synthesis and apoptosis was examined in SMCs in vitro. Results: Microarrays identified tissue-pathway inhibitor-2 (TFPI-2) as the most differentially expressed gene by FSS in cultured SMCs. The regulatory effect of FSS on the expression of TFPI-2 was confirmed by RT-PCR and immunobloting demonstrating a more than 400-fold increase in TFPI-2 expression in SMCs exposed to FSS compared to static controls and a consistent upregulation at the protein level. Functionally, SMC proliferation was decreased by FSS and recombinant TFPI-2 was found to inhibit SMC proliferation and induce SMC apoptosis as indicated by activation of caspase-3. In vivo, TFPI-2 expression was found to be up-regulated 5, 10 and 20 h after rat carotid balloon-injury and immunohistochemistry demonstrated TFPI-2 protein in luminal SMCs exposed to FSS in rat carotid intimal hyperplasia 10 days after balloon-injury. Conclusion: FSS strongly influence gene expression in cultured SMCs and induce TFPI-2 expression, which is also expressed after rat carotid balloon injury in luminal SMCs exposed to FSS. Functionally, TFPI-2 may play an important role in vessel wall repair by regulating SMC proliferation and survival. Further studies are needed to elucidate the mechanisms by which TFPI-2 control SMC function. 3 x 2 samples from a paired fluid shear stress experiment on smooth muscle cells.

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RbFox2 is a RhoBTB1-Cullin-3 Target in Vascular Smooth Muscle Regulating Arterial Stiffness through the Cytoskeleton

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