Biology subjects

Morrell, N.

Publications and source records attributed to Morrell, N..

5 recordsLinked to original sources

bioRxiv2026

Interrogation of the glycolytic axis in pulmonary arterial hypertension models and how modifying these can lead to potential therapeutic options.

IntroductionPulmonary arterial hypertension (PAH) describes diseases characterized by increased pulmonary vessel pressures that lead to right ventricular failure and death if left untreated. Dysregulated metabolic function has been reported in endothelial cells from PAH patients. Healthy endothelial cells can rapidly shift from quiescence to proliferative and apoptotic states, partly due to a greater utilization of glycolysis for ATP production, rather than the slower oxidative phosphorylation more commonly relied on by other cell types. However, in PAH patients, pulmonary artery endothelial cells demonstrate an even greater shift towards glycolytic ATP production. This phenomenon, which was first described in cancer as the Warburg effect, is an adaptation for optimizing both energy production and biosynthetic processes for maximum proliferative potential. Hypothesis and MethodsWe hypothesize that targeting the PKM2 axis in endothelial cells may shift the balance to favor oxidative phosphorylation, in effect reversing the Warburg effect; and that this would have beneficial effects in cell and rodent models of PAH. To this end we have tested TEPP-46, an allosteric PKM2 activator that stabilizes the tetrameric form, blocking its translocation into the nucleus and increasing canonical enzymatic activity, in blood outgrowth endothelial cells (BOECs) and in a rat Sugen-hypoxia model. ResultsTEPP-46 treatment reduced levels of nuclear PKM2 (the homodimer form which promotes anabolic effects and proliferation). Cytoplasmic levels of PKM2 and levels of PKM1 were unaffected. Exposure to TEPP-46 lowered levels of polypyrimidine tract-binding protein 1 (PTPB1), which controls alternative splicing of the PKM gene to promote PKM2 expression; and reduced LDHA, which converts pyruvate to lactate, preventing its utilization for oxidative phosphorylation. In the Sugen-hypoxia rat model, administration of TEPP-46 significantly ameliorated the elevated right ventricular systolic pressures, reduced the loss of body weight and increased survival. The increased muscularization of the smaller blood arteries and arterioles in the lungs of rats due to Sugen-hypoxia were also improved by concurrent administration of TEPP-46. ConclusionWe have shown that TEPP-46 treatment reduces nuclear PKM2 and represses PKM2-driven gene expression, with the functional effect of ameliorating the Sugen-hypoxia phenotype. This suggests that antagonizing the Warburg effect may offer a novel therapeutic avenue for PAH.

physiology↗

bioRxiv2025

A GCN1-independent activator of the kinase GCN2

Mutations of EIF2AK4, which encodes the eIF2 kinase GCN2, cause a severe inherited form of pulmonary hypertension called pulmonary veno-occlusive disease (PVOD). Some pathogenic variants of GCN2 are amenable to pharmacological reactivation by low concentrations of ATP-pocket binding inhibitors. Kinase inhibition at modestly elevated concentrations limits the clinical utility of these drugs against PVOD. We therefore performed an in cellulo chemical screen for GCN2 activators and identified three structurally distinct compounds with low micromolar stimulatory activities. Unlike previously described GCN2 activators, one of these molecules activated GCN2 independently of GCN1. Modelling supported by structure activity screens suggested it binds within the ATP-pocket of GCN2, but unlike existing ligands does not protrude inward into the allosteric pocket or outward into the solvent. This overcomes a key requirement of other GCN2 activators.

cell biology↗

bioRxiv2025

Interleukin-6 is critical in the development of gcn2-mutation associated pulmonary vascular disease in mice

Biallelic mutations in eukaryotic translation initiation factor 2 kinase 4, EIF2AK4 (which encodes general control nonderepressible 2, GCN2) underpin heritable forms of pulmonary veno-occlusive disease (PVOD), a rare and fatal form of pulmonary hypertension. The mechanisms linking these are mostly uncharacterised. We demonstrate for the first time that homozygous loss of gcn2 is sufficient to cause mild pulmonary hypertension in mice. Single-cell transcriptomics of mouse lungs identified adventitial fibroblasts as having the greatest GCN2-dependent transcriptional differences, implicating them as key players in this model of PVOD. The most significantly upregulated pathways in gcn2-/- adventitial fibroblasts were inflammatory. Therefore, we went on to demonstrate a pro-inflammatory phenotype in gcn2-/- mouse embryonic fibroblasts and gcn2-/- mice. In a novel murine model of pulmonary hypertension induced by exposure to mitomycin C, deletion of interleukin-6 rescued the pulmonary vascular phenotype. When chronically exposed to lipopolysaccharide, the pulmonary hypertensive phenotype of gcn2-/- mice is exaggerated. Genetic ablation of interleukin-6 completely rescues both the baseline and LPS-exaggerated pulmonary hypertensive phenotype. Targeting Il6-dependent pathways may be useful in treating this deadly disease.

pathology↗

bioRxiv2024

Functional validation of EIF2AK4 (GCN2) missense variants associated with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a disorder with a large genetic component. Biallelic mutations of EIF2AK4, which encodes the kinase GCN2, are causal in two ultra-rare subtypes of PAH, pulmonary veno-occlusive disease and pulmonary capillary haemangiomatosis. EIF2AK4 variants of unknown significance have also been identified in patients with classical PAH, though their relationship to disease remains unclear. To provide patients with diagnostic information and enable family testing, the functional consequences of such rare variants must be determined, but existing computational methods are imperfect. We applied a suite of bioinformatic and experimental approaches to sixteen EIF2AK4 variants that had been identified in patients. By experimentally testing the functional integrity of the integrated stress response (ISR) downstream of GCN2, we determined that existing computational tools have insufficient sensitivity to reliably predict impaired kinase function. We determined experimentally that several EIF2AK4 variants identified in patients with classical PAH had preserved function and are therefore likely to be non-pathogenic. The dysfunctional variants of GCN2 that we identified could be subclassified into three groups: misfolded, kinase-dead, and hypomorphic. Intriguingly, members of the hypomorphic group were amenable to paradoxical activation by a type-1.5 GCN2 kinase inhibitor. This experiment approach may aid in the clinical stratification of EIF2AK4 variants and potentially identify hypomorophic alleles receptive to pharmacological activation.

cell biology↗

bioRxiv2019

Transforming growth factor-beta signaling via ALK1 and ALK5 regulates distinct functional pathways in vein graft intimal hyperplasia

RationaleTransforming growth factor-beta (TGF{beta}) is tightly regulated at multiple levels, with regulation at the receptor level now recognized as a key determinant of the cellular response to this pleiotropic cytokine. TGF{beta} promotes saphenous vein graft neointima formation after coronary artery bypass graft (CABG) surgery, inducing smooth muscle cell (SMC) hyperplasia and fibrosis by signaling via activin receptor-like kinase 5(ALK5). However, the role of the alternate TGF{beta} receptor ALK1 remains completely unknown. ObjectiveTo define the receptor pathways activated by TGF{beta} in SMCs and their mechanistic importance during CABG neointima formation. Methods and resultsRadioligand co-IP assays revealed direct interactions between TGF{beta}, ALK5 and ALK1 in primary saphenous vein graft SMC (HSVSMC) from patients undergoing CABG. Knockdown and pharmacological inhibition of ALK5 or ALK1 in HSVSMC significantly attenuated TGF{beta}-induced phosphorylation of receptor-regulated (R)-Smads 2/3 and 1/5, respectively. Microarray profiling followed by qRT-PCR validation showed that TGF{beta} induced distinct transcriptional networks downstream of ALK5 or ALK1, associated with HSVSMC contractility and migration, respectively and confirmed using migration assays as well as qRT-PCR and western blot assays of contractile SMC markers. scRNAseq analysis of TGF{beta}-treated HSVSMC identified distinct subgroups of cells showing ALK5 or ALK1 transcriptional responses, while RNA velocity analyses indicated divergence in differentiation towards ALK5 or ALK1-dominant lineages. ALK1, ALK5 and their downstream effectors pSmad1/5 and pSmad2/3 were localized to SMA+ neointimal SMCs in remodelled mouse vein grafts. Pharmacological inhibition or genetic ablation of Smad1/5 substantially reducing neointima formation following acute vascular injury. Notably, expression and activation of ALK1, ALK5 and their respective downstream R-Smads was already evident in hyperplastic saphenous veins prior to grafting. ConclusionsWhilst canonical TGF{beta} signaling via ALK5 promotes a contractile HSVSMC phenotype, transactivation of ALK1 by TGF{beta} induces neointima formation by driving cell migration. Restoring the balance between ALK1 and ALK5 in HSVSMC may represent a novel therapeutic strategy for vein graft failure.

cell biology↗