Biology subjects

Karp, A.

Publications and source records attributed to Karp, A..

4 recordsLinked to original sources

bioRxiv2026

An Ovol1 Variant in Endothelial Cells Regulates Slug and is Essential for Pathological Angiogenesis

During development, the blood vasculature expands by sprouting angiogenesis, but the programs that guide this process can become dysregulated in the pathological angiogenesis of neovascular diseases leading to excessive disorganized blood vessels. We previously reported that in endothelial cells, the pro-mesenchymal transcription factor Slug critically regulates angiogenesis through a partial and reversible endothelial-to-mesenchymal transition (pEndoMT); however, the upstream regulators that activate Slug and may contribute to pathological activation of the pEndoMT pathway in disease are still poorly understood. Here, we show that endothelial cells express an unusual low molecular weight variant of Ovol1 - a zinc-finger transcription factor that regulates mesenchymal transition in epithelial cells. Ovol1 and Slug are co-expressed in angiogenic endothelial cells, and using ChIP, we confirm direct Ovol1 binding to the endogenous Slug gene at a species-conserved binding motif. Whereas Ovol1 is typically a transcriptional repressor in epithelial cells, we find using a combination of silencing RNA and lentiviral overexpression constructs that the endothelial Ovol1 variant upregulates Slug, and is sufficient to drive pEndoMT marker expression and enhance endothelial cell migratory capacity. Silencing of Ovol1 abolished sprouting angiogenesis in a 3D in vitro sprouting angiogenesis assay, whereas constitutive overexpression of Ovol1 produced overaggressive and disorganized hypersprouting that depends upon Slug. We generated Ovol1 or Slug endothelial-specific knockout mice (Ovol1ECKO and SlugECKO) and found that healthy developmental angiogenesis of the neonatal mouse retina proceeds relatively normally in knockout animals. By contrast, Ovol1 was reduced in established post-natal blood vessels but became strongly re-expressed in tumor endothelial cells, and we found that colorectal cancer syngraft growth was significantly reduced in both Ovol1ECKO and SlugECKO mice alongside a failure of tumor angiogenesis. Lastly, neovascularization in the oxygen-induced retinopathy (OIR) model was also reduced in SlugECKO mice. In conclusion, we report that an endothelial Ovol1 variant upregulates Slug and drives a mesenchymal-like state, and that this Ovol1-Slug pEndoMT signaling axis is essential for pathological angiogenesis in neovascular disease models.

cell biology↗

bioRxiv2025

Molnupiravir inhibits Bourbon virus infection and disease-associated pathology in mice

Bourbon virus (BRBV) is an emerging tick-borne virus that can cause severe and fatal disease in humans. BRBV is vectored via the Amblyomma americanum tick, which is widely distributed throughout the central, eastern, and southern United States. Serosurveillance studies in Missouri and North Carolina identified BRBV-neutralizing antibodies in approximately 0.6% of tested individuals. To date, no specific antiviral therapy exists. Molnupiravir, an antiviral drug with oral bioavailability, has shown broad-spectrum antiviral activity against RNA viruses, including SARS-CoV-2. Here, we investigated the antiviral activity of molnupiravir against BRBV infection in cell culture and a mouse model of BRBV disease. Molnupiravir suppressed BRBV production in cells. In vivo, pre-exposure administration of molnupiravir protected susceptible type I interferon receptor knockout (Ifnar1-/-) mice against lethal BRBV infection. The protection by molnupiravir was associated with lower virus burden in mouse tissues, improvement of T cell (CD4+, CD8+) and B cell (follicular) profiles in the spleen, improvement of severe thrombocytopenia, and reduced pathology in the spleen and liver of BRBV-infected animals. Finally, therapeutic administration of molnupiravir starting 24 or 48 hours after infection ameliorated weight loss, clinical signs of disease, and lethality associated with BRBV infection. Overall, our experiments suggest that molnupiravir as a potential antiviral therapy for evaluation in humans with BRBV infections.

microbiology↗

bioRxiv2024

ERK5 Signaling is Required for Type III IFN-mediated Mucosal Antiviral Responses

Type III interferons (IFN{lambda}) are innate immune cytokines that limit viral replication and coordinate tissue repair through the induction of interferon stimulated genes (ISGs). This response must be tightly regulated to avoid excessive responses that result in the disruption of tissue barrier integrity or inefficient responses that allow for pathogen escape. Here we examine the contribution of Mitogen Activated Protein Kinase (MAPK) signaling on IFN{lambda}-mediated antiviral activity. We find that extracellular-signal-regulated kinase 5 (ERK5), a poorly characterized member of the conventional MAPK family, potentiates the antiviral efficacy of IFN{lambda}. Chemical inhibition and genetic targeting of ERK5 during IFN{lambda} treatment of cells results in a decrease in ISG induction and impaired control of viral infections. This decrease in IFN{lambda} antiviral efficacy in the absence of ERK5 kinase activity corresponded to lowered STAT1 phosphorylation, revealing a noncanonical role for ERK5 in STAT1 activation downstream of IFN{lambda}. In contrast, type I IFN antiviral signaling is largely resistant to ERK5 modulation. Altogether, we identify ERK5 as a potentiator of STAT1 activation, ISG expression, and antiviral activity following type III IFN stimulation. SIGNIFICANCERegulation of type III interferons (IFN{lambda}) at mucosal barriers in response infection to mitigate viral replication and support barrier integrity. The specific mechanistic requirements for MAPK signaling to sustain IFN{lambda}-mediated gene expression have remained elusive. Amongt the least characterized members of the MAPK family, the role of ERK5 in regulating host inflammatory responses has been hampered by off-target effects of kinase inhibitors. Here, we combine pharmacological and genetic approaches to specifically demonstrate that ERK5 promotes antiviral immunity in epithelial cells. Mechanistically, ERK5 enhances the activation of STAT1 in response to IFN stimulation to augment the transcription of IFN-stimulated genes. Our work demonstrates that therapeutic modulation of MAPK and IFN signaling pathway co-integration could distinguish between the protective and deleterious outcomes of IFN expression. One-sentence summaryERK5 potentiates IFN lambda responses.

immunology↗

bioRxiv2022

MEF2A suppresses replicative stress responses that trigger DDX41-dependent IFN production

Interferons (IFN) are induced by sensing of self- and non-self DNA or genomic lesions by pathogen recognition receptors (PRR) that activate STING. These pathways must be kept in check by negative regulators to prevent unscheduled activation of IFN, which contributes to autoinflammation. Here we show that MEF2A as a novel negative regulator of inflammation that suppresses homeostatic induction of IFNs. Indeed, MEF2A deficiency results in the spontaneous production of type I IFN and robust downstream IFN-stimulated gene expression that coincided with a robust cellular antiviral state. Mechanistically, MEF2A depletion promoted the accumulation of R-loops that activate the DDX41/STING pathway. This pro-inflammatory pathway was dependent on ATR kinase activity, hallmark of the replicative stress response, was necessary for the activation of STING upon loss of MEF2A expression. Thus, our study connects MEF2A with protection from maladaptive type I IFN responses triggered by R-loop accumulation and links the DDX41-dependent activation of STING to the DNA damage response.

immunology↗