Biology subjects

Uldrijan, S.

Publications and source records attributed to Uldrijan, S..

4 recordsLinked to original sources

bioRxiv2025

Translational control of AMPK activity in melanoma

The eIF4F translation initiation complex controls ERK MAPK signaling in malignant melanomas with BRAF and NRAS mutations. It also contributes to the development of melanoma resistance to therapies targeting BRAF and MEK kinases. Here, we uncovered a critical role for eIF4F in regulating the main cellular metabolic sensor, AMP-activated protein kinase (AMPK). In melanoma cells with the most common BRAF V600E mutation, ERK and AMPK pathway activities were reported as mutually exclusive. This is because BRAF-driven ERK activity negatively impacts LKB1-mediated canonical AMPK activation. However, we observed that eIF4F inhibition can stimulate AMPK activity in melanoma cells, both in vitro and in vivo, despite concomitant ERK hyperactivation. Notably, the protein levels of LKB1 and its co-factor MO25 were sensitive to eIF4F inhibition, indicating a non-canonical LKB1-independent mechanism of AMPK activation. In a proteomic screen, we aimed to identify eIF4F roles in melanoma cell physiology beyond the MAPK pathway. We found that the eIF4F function is essential for maintaining cellular levels of key cell cycle and metabolic regulators, including CDK1, CDK2, TYMS, and UHRF1. Importantly, we also identified the protein phosphatase PP2A as a new eIF4F target. Our subsequent analyses showed that inhibition or siRNA-mediated knockdown of PP2A increases AMPK activity in melanoma cells, independent of LKB1. This data shows that PP2A plays a significant role in regulating AMPK activity in melanoma. Thus, eIF4F inhibition not only impairs canonical AMPK activators but also downregulates PP2A, which negatively regulates AMPK dynamics. Collectively, our data highlight a dual role of eIF4F in the control of AMPK in BRAF-mutant melanoma cells. It maintains the canonical AMPK signaling pathway while simultaneously limiting the extent of AMPK activation via the eIF4F-PP2A-AMPK axis. Pharmacological inhibition of this axis can overcome the negative control of AMPK signaling by the ERK pathway. This suggests new therapeutic opportunities to disrupt melanoma growth.

cancer biology↗

bioRxiv2024

Sepsis induces long-term reprogramming of human HSPCs and drives myeloid dysregulation in sepsis survivors

Sepsis is a life-threatening condition characterised by an overwhelming immune response and high fatality. While most research has focused on its acute phase, many sepsis survivors remain immunologically weakened leaving them susceptible to serious complications from even mild infections. The mechanisms underlying this prolonged immune dysregulation remain unclear, limiting effective interventions. Here, we analysed whether sepsis induced long-term "training" in hematopoietic stem and progenitor cells (HSPCs), imprinting changes that persist in their myeloid progeny. Peripheral blood analysis of 8 sepsis survivors, 12 patients with septic shock, and 10 healthy donors revealed a significant expansion of CD38+ progenitors in survivors, with increases in megakaryocyte-erythroid and granulocyte-monocyte progenitors, and reduced mature neutrophil counts. This shift suggests impaired granulopoiesis, favouring immature, immunosuppressive granulocytes. Differentiated macrophages from survivors HSPCs exhibited impaired metabolic pathways after lipopolysaccharide stimulation, with downregulation of tricarboxylic acid cycle and glycolysis genes, indicating altered immune metabolism. Pathway analysis revealed enhanced type-I interferon (IFN) and JAK-STAT signalling in survivors macrophages, reflective of potentially tolerance-prone reprogramming. Finally, exposing healthy donor HSPCs to IFN{beta} during macrophage differentiation reduced HSPC proliferation, increased apoptosis, and induced a metabolic shift towards glycolysis over mitochondrial respiration. Together, these findings suggest that sepsis induces lasting reprogramming in HSPCs leading to myeloid progeny with altered immune memory that might drive immune dysregulation in survivors. These data open avenues to explore potential targets to better manage long-term immune alterations in sepsis survivors. KEY POINTSO_LISepsis induces long-term alterations in HSPCs, leading to the expansion of immature progenitors and metabolic dysregulation of their progeny. C_LIO_LIType-I IFN signalling reprograms macrophage differentiation, affecting their metabolic function and reducing cell proliferation. C_LI

immunology↗

bioRxiv2023

FGF2-induced Redox Signaling: A Mechanism Regulating Pyruvate Dehydrogenase Driven Histone Acetylation and NANOG Upregulation

Precise control of pluripotency is a requirement for the safe and effective use of hPSCs in research and therapies. Here we report that pyruvate dehydrogenase upregulates histone H3 pan acetylation and levels of pluripotency marker NANOG in 5% O2. Pyruvate dehydrogenase (PDH) is an essential metabolic switch and a bottleneck for the glycolytic production of acetyl-CoA. Silencing of gene expression showed that PDH is regulated by the activity of its phosphatase PDP1. We show that PDP1 is sensitive to reactive oxygen species-mediated inactivation, leading to the downregulation of H3 pan acetylation and NANOG levels. Furthermore, we show that FGF2, a cytokine commonly used to maintain pluripotency activates pyruvate dehydrogenase through MEK1/2-ERK1/2 signaling pathway-mediated downregulation of ROS in 5% O2, thus promoting histone acetylation. Our results show the importance of pyruvate dehydrogenase in regulating energy metabolism and its connection to pluripotency. Furthermore, our data highlight the role of reactive oxygen species and redox homeostasis in pluripotency maintenance and differentiation. Highlights- PDP1-induced activation of PDH leads to increased histone H3 pan acetylation and NANOG levels in hPSCs - Reactive oxygen species (ROS) inactivate PDP1 and decrease histone H3 pan acetylation and NANOG levels in hPSCs - MEK1/2-ERK1/2 signaling-mediated downregulation of ROS in 5% O2 activates PDH in hPSCs Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=129 SRC="FIGDIR/small/524871v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@133f8dcorg.highwire.dtl.DTLVardef@1176d94org.highwire.dtl.DTLVardef@11b153corg.highwire.dtl.DTLVardef@10f2e4d_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2022

A forskolin-mediated increase in cAMP promotes T helper cell differentiation into the Th1 and Th2 subsets rather than into the Th17 subset

The cyclic adenosine monophosphate (cAMP) signaling pathway is involved in various physiological and pathophysiological processes. Forskolin (FSK), a labdane diterpene well known as an activator of cAMP production, is suggested to possess significant immunomodulatory potential. However, the specific effects of elevated cAMP levels caused by the FSK-mediated activation of adenylate cyclase (AC) on T helper (Th) cell differentiation and functions are still unclear. We speculated that the increased levels of cAMP in Th cells affect the differentiation program of distinct Th populations differently, in particular the development of Th1, Th2, and Th17 subsets. Only minor changes in the expressions of isoforms of ACs and phosphodiesterases (PDE), enzymes responsible for the degradation of cAMP, were observed in differentiating human Th cells with prevailing ADCY1, ADCY3, ADCY7, and ADCY9 and PDE3B, PDE4A/B/D, PDE7A/B, and PDE8A isoforms. FSK mediated elevation in Th1-specific markers reinforcing the Th1 cell phenotype. The differentiation of Th2 was not altered by FSK, though cell metabolism was affected. In contrast, the Th17 immunophenotype was severely suppressed leading to the highly specific upregulation of the level of CXCL13. The causality between FSK-elicited cAMP production and the observed modulation of Th2 differentiation was proven by using cAMP inhibitor 2,5-dideoxyadenosine that reverted the FSK effects. Overall, an FSK-mediated cAMP increase has an effect on Th1, Th2 and Th17 differentiation and can contribute to the identification of novel therapeutic targets for the treatment of Th cell-related pathological processes.

cell biology↗