Biology subjects

Garabedian, M. J.

Publications and source records attributed to Garabedian, M. J..

6 recordsLinked to original sources

bioRxiv2026

YAP/TAZ inhibition refines TGF-β signaling to prevent laryngeal fibrosis

Voice disorders affect nearly 20 million Americans and cost more than $13 billion annually. Vocal fold (VF) fibrosis, a major cause of chronic dysphonia, disrupts normal vocal fold vibration by replacing the flexible extracellular matrix with stiff fibrotic tissue. Although TGF-{beta} drives fibrosis, it also activates intrinsic negative feedback mechanisms, including SMAD7 induction and SMAD3 downregulation, to restrain excessive signaling. Broad inhibition of TGF-{beta} or canonical SMAD signaling may disrupt these protective feedback loops and impair normal tissue homeostasis. An ideal anti-fibrotic strategy should differentially target the pro-fibrotic output of TGF-{beta}. Here, we show YAP/TAZ inhibition selectively suppresses pro-fibrotic TGF-{beta} signaling in VF fibroblasts. Pharmacologic inhibition of YAP/TAZ blocked TGF-{beta}-induced fibroblast activation and fibrotic gene expression, while only modestly affecting canonical SMAD feedback responses. Integrated RNA-seq and ChIP-seq analyses demonstrated YAP/TAZ primarily regulate non-canonical TGF-{beta} signaling and pro-fibrotic transcriptional programs. In a rat model of VF fibrosis, YAP/TAZ inhibition reduced nuclear YAP/TAZ localization and attenuated scar formation. Together, these findings identify YAP/TAZ inhibition as a promising therapeutic strategy for VF fibrosis and other fibrotic diseases.

biochemistry↗

bioRxiv2022

Loss of PRMT2 in myeloid cells in normoglycemic mice phenocopies impaired regression of atherosclerosis in diabetic mice

Regression of atherosclerosis is impaired in diabetes. However, the factors mediating this effect remain incomplete. We identified Protein Arginine Methyltransferase 2 (PRMT2) as a protein whose expression in macrophages is reduced in hyperglycemia and diabetes. PRMT2 catalyzes arginine methylation to target proteins to modulate gene expression. Because PRMT2 expression is reduced in cells in hyperglycemia, we wanted to determine whether PRMT2 plays a causal role in the impairment of atherosclerosis regression in diabetes. We therefore examined the consequence of deleting PRMT2 in myeloid cells during regression of atherosclerosis in normal and diabetic mice. Remarkably, we found a significant impairment of atherosclerosis regression under normoglycemic conditions in mice lacking PRMT2 (Prmt2-/-) in myeloid cells that mimics the decrease in regression of atherosclerosis in WT mice under diabetic conditions. This was associated with increased plaque macrophage retention, as well as increased apoptosis and necrosis. PRMT2-deficient plaque CD68+ cells under normoglycemic conditions showed increased expression of genes involved in cytokine signaling and inflammation compared to WT. Consistently Prmt2-/- bone marrow derived macrophages (BMDMs) showed an increased response of pro-inflammatory genes to LPS, and a decreased response of inflammation resolving genes to IL-4. This increased response to LPS in Prmt2-/- BMDMs is via enhanced NF-kappa B activity. Thus, the loss of PRMT2 is causally linked to impaired atherosclerosis regression via a heightened inflammatory response in macrophages. That PRMT2 expression was lower in myeloid cells in plaques from human subjects with diabetes supports the relevance of our findings to human atherosclerosis.

genetics↗

bioRxiv2020

Identification of PIM1 substrates reveals a role for NDRG1 in prostate cancer cellular migration and invasion

PIM1 is an oncogenic serine/threonine kinase that promotes and maintains prostate tumorigenesis. To more fully understand the mechanism by which PIM1 promotes oncogenesis, we performed a chemical genetic screen to identify direct PIM1 substrates in prostate cancer cells. The PIM1 substrates we identified were involved in a variety of oncogenic processes, and included N-Myc Downstream-Regulated Gene 1 (NDRG1), which has reported roles in the suppression of cancer cell invasion and metastasis. NDRG1 is phosphorylated by PIM1 at serine 330 (pS330), and the level of NDRG1 pS330 is associated with high grade compared to low grade prostate tumors. While NDRG1 pS330 is largely cytoplasmic, total NDRG1 is both cytoplasmic and nuclear. Mechanistically, PIM1 phosphorylation of NDRG1 decreases its stability, reducing its interaction with AR, and thereby lowering expression of AR target genes. PIM1-dependent NDRG1 phosphorylation also reduces NDRG1s ability to suppress prostate cancer cell migration and invasion. Our study identifies a novel set of PIM1 substrates in prostate cancer cells using a direct, unbiased chemical genetic screen. It also provides key insights into the mechanisms by which PIM1-mediated phosphorylation of NDRG1 impairs its function, resulting in enhanced cell migration and invasion.

cancer biology↗

bioRxiv2019

Persistence of learning-induced synapses depends on neurotrophic-priming of glucocorticoid receptors

Stress can either promote or impair learning and memory. Such opposing effects depend on whether synapses persist or decay after learning. Maintenance of new synapses formed at the time of learning upon neuronal network activation depends on the stress hormone activated glucocorticoid receptor (GR) and neurotrophic factor release. Whether and how concurrent GR and neurotrophin signaling integrate to modulate synaptic plasticity and learning is unknown. Here we show that deletion of the neurotrophin BDNF-dependent GR phosphorylation sites (GR-PO4) impairs long-term memory retention and maintenance of newly formed postsynaptic dendritic spines in the mouse cortex after motor skills training. Chronic stress and the BDNF polymorphism Val66Met disrupt the BDNF-dependent GR-PO4 pathway necessary for preserving training-induced spines and previously acquired memories. Conversely, enrichment living promotes spine formation but fails to salvage training-related spines in mice lacking BDNF-dependent GR-PO4 sites, suggesting it is essential for spine consolidation and memory retention. Mechanistically, spine maturation and persistence in the motor cortex depend on synaptic mobilization of the glutamate receptor GluA1 mediated by GR-PO4. Together, these findings indicate that regulation of GR-PO4 via activity-dependent BDNF signaling is important for learning-dependent synapses formation and maintenance. They also define a new signaling mechanism underlying these effects.\n\nSIGNIFICANCE STATEMENTSignal transduction of receptors tyrosine kinase and nuclear receptors is essential for homeostasis. Phosphorylation is one of the currencies used by these receptors to support homeostatic reactions in learning and memory. Here we show that consolidation of learning-induced neuroplasticity is made possible via stress activated glucocorticoid nuclear receptor phosphorylation through the brain-derived neurotrophic tyrosine kinase pathway. Crosstalk between these pathways is specific of cell types and behavioral experience (e.g. learning, stress and enrichment living). Disruption of this response may contribute to the pathophysiology of stress-related disorders and treatment resistance.

neuroscience↗

bioRxiv2018

Phosphorylation of LXRα impacts atherosclerosis regression by modulating monocyte/macrophage trafficking

LXR activation in macrophages enhances regression of atherosclerotic plaques in mice by regulating genes crucial for cholesterol efflux, cell motility and inflammation. Diabetes, however, impairs plaque regression in mice. LXR is phosphorylated at serine 198 (pS198), which affects the expression of genes controlling inflammation, lipid metabolism and cell movement. We hypothesize that LXR function is affected by hyperglycemia through changes in LXR pS198. Indeed, macrophages cultured in diabetes relevant high glucose versus normal glucose display alterations in LXR-dependent gene expression and increased LXR pS198. We therefore examined the consequence of disrupting LXR phosphorylation (S196A in mouse LXR) during regression of atherosclerosis in normal and diabetic mice. We find that phosphorylation deficient LXR S196A reduces macrophage retention in plaques in diabetes, which is predicted to be anti-atherogenic and enhance plaque regression. However, this favorable effect on regression is masked by increased monocyte infiltration in the plaque attributed to leukocytosis in LXR S196A mice. RNA-seq of plaque macrophages from diabetic S196A mice shows increased expression of chemotaxis and decreased expression of cell adhesion genes, consistent with reduced macrophage retention by LXR S196A. Thus, the non-phosphorylated form of LXR precludes macrophage retention in the plaque. Our study provides the first evidence for a physiological role of LXR phosphorylation in modulating atherosclerosis regression. Compounds that prevent LXR phosphorylation or ligands that induce the conformation of non-phosphorylated LXR may selectively enhance macrophage emigration from atherosclerotic plaques.

genetics↗

bioRxiv2017

Changes In LXRα Phosphorylation Promote A Novel Diet-Induced Transcriptome That Alters The Transition From Fatty Liver To Steatohepatitis

Understanding the transition from fatty liver or steatosis to more advanced inflammatory and fibrotic stages of non-alcoholic fatty liver disease (steatohepatitis), is key to define strategies that alter or even reverse the progression of this pathology. The Liver X Receptor alpha (LXR) controls hepatic lipid homeostasis and inflammation. Here we show that mice carrying a mutation that abolishes phosphorylation at Ser196 (S196A) in LXR exhibit reduced hepatic inflammation and fibrosis when challenged with a high fat-high cholesterol diet, despite displaying enhanced hepatic lipid accumulation. This protective effect is associated with reduced cholesterol accumulation, a key promoter of lipid-mediated hepatic damage. Reduced steatohepatitis in S196A mice involves the reprogramming of the liver transcriptome by promoting diet-induced changes in the expression of genes involved in endoplasmic reticulum stress, extracellular matrix remodelling, inflammation and lipid metabolism. Unexpectedly, changes in LXR phosphorylation uncover novel diet-specific target genes, whose regulation does not simply mirror ligand-induced LXR activation. These unique LXR phosphorylation-sensitive, diet-responsive target genes are revealed by promoting LXR occupancy and cofactor recruitment in the context of a cholesterol-rich diet. Therefore, LXR phosphorylation at Ser196 critically acts as a novel nutritional sensor that promotes a unique diet-induced transcriptome thereby modulating metabolic, inflammatory and fibrotic responses important in the transition to steatohepatitis.

pathology↗