Studying AMPK in an Evolutionary Context

Fus3 Interacts with Gal83, Revealing the MAPK Crosstalk to Snf1/AMPK to Regulate Secondary Metabolic Substrates in Aspergillus flavus

Aflatoxins (AFs), highly carcinogenic natural products, are produced by the secondary metabolism of fungi such as Aspergillus flavus. Essential for the fungi to respond to environmental changes and aflatoxin synthesis, the pheromone mitogen-activated protein kinase (MAPK) is a potential regulator of aflatoxin biosynthesis. However, the mechanism by which pheromone MAPK regulates aflatoxin biosynthesis is not clear. Here, we showed Gal83, a new target of Fus3, and identified the pheromone Fus3-MAPK signaling pathway as a regulator of the Snf1/AMPK energy-sensing pathway modulating aflatoxins synthesis substrates. The screening for Fus3 target proteins identified the β subunit of Snf1/AMPK complexes using tandem affinity purification and multiomics. This subunit physically interacted with Fus3 both in vivo and in vitro and received phosphorylation from Fus3. Although the transcript levels of aflatoxin synthesis genes were not noticeably downregulated in both gal83 and fus3 deletion mutant strains, the levels of aflatoxin B1 and its synthesis substrates and gene expression levels of primary metabolizing enzymes were significantly reduced. This suggests that both the Fus3-MAPK and Snf1/AMPK pathways respond to energy signals. In conclusion, all the evidence unlocks a novel pathway of Fus3-MAPK to regulate AFs synthesis substrates by cross-talking with the Snf1/AMPK complexes.

Modulation of AMPK Significantly Alters Uveal Melanoma Tumor Cell Viability

INTRODUCTION

Uveal melanoma (UM) responds poorly to targeted therapies or immune checkpoint inhibitors. Adenosine monophosphate-activated protein kinase (AMPK) is a pivotal serine/threonine protein kinase that coordinates vital processes such as cell growth. Targeting AMPK pathway, which represents a critical mechanism mediating the survival of UM cells, may prove to be a novel treatment strategy for UM. We aimed to demonstrate the effects of AMPK modulation on UM cells.

METHODS

In silico analyses were performed to compare UM and normal melanocyte cells via Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA). The effects of AMPK modulation on cell viability and proliferation in UM cell lines with different molecular profiles (i.e., 92-1, MP46, OMM2.5, and Mel270) were investigated via XTT cell viability and proliferation assays after treating the cells with varying concentrations of A-769662 (AMPK activator) or dorsomorphin (AMPK inhibitor).

RESULTS

KEGG/GSEA studies demonstrated that genes implicated in the AMPK signaling pathway were differentially regulated in UM. Gene sets comprising genes involved in AMPK signaling and genes involved in energy-dependent regulation of mammalian target of rapamycin by liver kinase B1-AMPK were downregulated in UM. We observed gradual decreases in the numbers of viable UM cells as the concentration of A-769662 treatment increased. All UM cells demonstrated statistically significant decreases in cell viability when treated with 200 µm A-769662. Moreover, the effects of AMPK inhibition on UM cells were potent, since low doses of dorsomorphin treatment resulted in significant decreases in viabilities of UM cells. The half maximal inhibitory concentration (IC50) values confirmed the potency of dorsomorphin treatment against UM in vitro.

CONCLUSION

AMPK may act like a friend or a foe in cancer depending on the context. As such, the current study contributes to the literature in determining the effects of therapeutic strategies targeting AMPK in several UM cells. We propose a new perspective in the treatment of UM. Targeting AMPK pathway may open up new avenues in developing novel therapeutic approaches to improve overall survival in UM.

Adjustment of photosynthetic activity to drought and fluctuating light in wheat

Drought is a major cause of losses in crop yield. Under field conditions, plants exposed to drought are usually also experiencing rapid changes in light intensity. Accordingly, plants need to acclimate to both, drought and light stress. Two crucial mechanisms in plant acclimation to changes in light conditions comprise thylakoid protein phosphorylation and dissipation of light energy as heat by non-photochemical quenching (NPQ). Here, we analyzed the acclimation efficacy of two different wheat varieties, by applying fluctuating light for analysis of plants, which had been subjected to a slowly developing drought stress as it usually occurs in the field. This novel approach allowed us to distinguish four drought phases, which are critical for grain yield, and to discover acclimatory responses which are independent of photodamage. In short-term, under fluctuating light, the slowdown of NPQ relaxation adjusts the photosynthetic activity to the reduced metabolic capacity. In long-term, the photosynthetic machinery acquires a drought-specific configuration by changing the PSII-LHCII phosphorylation pattern together with protein stoichiometry. Therefore, the fine-tuning of NPQ relaxation and PSII-LHCII phosphorylation pattern represent promising traits for future crop breeding strategies.