FoxO suppresses endoplasmic reticulum stress to inhibit growth of Tsc1-deficient tissues under nutrient restriction

Akt-FoxO signaling drives co-adaptation to insecticide and host plant stresses in an herbivorous insect

INTRODUCTION

Ongoing interactions between host and herbivorous insect trigger a co-evolutionary arms race. Genetic diversity within insects facilitates their adaptation to phytochemicals and their derivatives, including plant-derived insecticides. Cytochrome P450s play important roles in metabolizing phytochemicals and insecticides, due to their diversity and almost perfect evolution.

OBJECTIVES

This study aims to uncover a common molecular mechanism in herbivorous insects by investigating the role of kinase-transcription factor regulation of P450s in conferring tolerance to both insecticides and phytochemicals.

METHODS

RNA interference, transcriptome sequencing, insecticide, and phytochemical bioassays were conducted to validate the functions of Akt, FoxO, and candidate P450s. Dual-luciferase activity assays were employed to identify the regulation of P450s by the Akt-FoxO signaling pathway. Recombinant P450 enzymes were utilized to investigate the metabolism of insecticides and phytochemicals.

RESULTS

We identified an Akt-FoxO signaling cascade, a representative of kinase-transcription factor pathways. This cascade mediates the expression of eight P450 enzymes involved in the metabolism of insecticides and phytochemicals in Nilaparvata lugens. These P450s are from different families and with different substrate selectivity, enabling them to respectively metabolize insecticides and phytochemicals with structure diversity. Nevertheless, the eight P450 genes were up-regulated by FoxO, which was inhibited in a higher cascade by Akt through phosphorylation. The discovery of the Akt-FoxO signaling pathway regulating a series of P450 genes elucidates the finely tuned regulatory mechanism in insects for adapting to phytochemicals and insecticides.

CONCLUSION

These finding sheds light on the physiological balance maintained by these regulatory processes. The work provides the experimental evidence of co-adaptation to the stresses imposed by host plant and insecticide within the model of the kinase-TF involving various P450s. This model provides a comprehensive view of how pests adapt to multiple environmental stresses.

Developmental hazards of 2,2',4,4'-tetrabromodiphenyl ether induced endoplasmic reticulum stress on early life stages of zebrafish (Danio rerio)

Polybrominated diphenyl ether flame retardants are known to have adverse effects on the development of organisms. We investigated the molecular mechanisms associated with the developmental hazards of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in zebrafish, as well as the behavioral and morphological alterations involved, focusing on endoplasmic reticulum stress (ERS), oxidative stress, and apoptosis. Our study revealed behavioral alterations in zebrafish exposed to BDE-47, including impaired motor activity, reduced exploration, and abnormal swimming patterns. In addition, we observed malformations in craniofacial regions and other developmental abnormalities that may be associated with ERS-induced cellular dysfunction. BDE-47 exposure showed apparent changes in ERS, oxidative stress, and apoptosis biomarkers at different developmental stages in zebrafish through gene expression analysis and enzyme activity assays. The study indicated that exposure to BDE-47 results in ERS, as supported by the upregulation of ERS-related genes and increased activity of ERS markers. In addition, oxidative stress-related genes showed different expression patterns, suggesting that oxidative stress is involved in the BDE-47 toxic effects. Moreover, an assessment of apoptotic biomarkers revealed an imbalance in the expression levels of pro- and anti-apoptotic genes, suggesting that BDE-47 exposure activated the apoptotic pathway. These results highlight the complex interactions between ERS, oxidative stress, apoptosis, behavioral alterations, and morphological malformations following BDE-47 exposure in zebrafish. Understanding the mechanisms of toxicity of developmental hazards is essential to elucidate the toxicological effects of environmental contaminants. The knowledge can help develop strategies to mitigate their adverse effects on the health of ecosystems and humans.

The Role of Forkhead Box O in Pathogenesis and Therapy of Diabetes Mellitus

Type 2 diabetes is a disease that causes numerous complications disrupting the functioning of the entire body. Therefore, new treatments for the disease are being sought. Studies in recent years have shown that forkhead box O (FOXO) proteins may be a promising target for diabetes therapy. FOXO proteins are transcription factors involved in numerous physiological processes and in various pathological conditions, including cardiovascular diseases and diabetes. Their roles include regulating the cell cycle, DNA repair, influencing apoptosis, glucose metabolism, autophagy processes and ageing. FOXO1 is an important regulator of pancreatic beta-cell function affecting pancreatic beta cells under conditions of insulin resistance. FOXO1 also protects beta cells from damage resulting from oxidative stress associated with glucose and lipid overload. FOXO has been shown to affect a number of processes involved in the development of diabetes and its complications. FOXO regulates pancreatic β-cell function during metabolic stress and also plays an important role in regulating wound healing. Therefore, the pharmacological regulation of FOXO proteins is a promising approach to developing treatments for many diseases, including diabetes mellitus. In this review, we describe the role of FOXO proteins in the pathogenesis of diabetes and the role of the modulation of FOXO function in the therapy of this disease.

The Impact of Oxidative Stress and AKT Pathway on Cancer Cell Functions and Its Application to Natural Products

Oxidative stress and AKT serine-threonine kinase (AKT) are responsible for regulating several cell functions of cancer cells. Several natural products modulate both oxidative stress and AKT for anticancer effects. However, the impact of natural product-modulating oxidative stress and AKT on cell functions lacks systemic understanding. Notably, the contribution of regulating cell functions by AKT downstream effectors is not yet well integrated. This review explores the role of oxidative stress and AKT pathway (AKT/AKT effectors) on ten cell functions, including apoptosis, autophagy, endoplasmic reticulum stress, mitochondrial morphogenesis, ferroptosis, necroptosis, DNA damage response, senescence, migration, and cell-cycle progression. The impact of oxidative stress and AKT are connected to these cell functions through cell function mediators. Moreover, the AKT effectors related to cell functions are integrated. Based on this rationale, natural products with the modulating abilities for oxidative stress and AKT pathway exhibit the potential to regulate these cell functions, but some were rarely reported, particularly for AKT effectors. This review sheds light on understanding the roles of oxidative stress and AKT pathway in regulating cell functions, providing future directions for natural products in cancer treatment.

A coherent FOXO3-SNAI2 feed-forward loop in autophagy

Understanding autophagy regulation is instrumental in developing therapeutic interventions for autophagy-associated disease. Here, we identified SNAI2 as a regulator of autophagy from a genome-wide screen in HeLa cells. Upon energy stress, SNAI2 is transcriptionally activated by FOXO3 and interacts with FOXO3 to form a feed-forward regulatory loop to reinforce the expression of autophagy genes. Of note, SNAI2-increased FOXO3-DNA binding abrogates CRM1-dependent FOXO3 nuclear export, illuminating a pivotal role of DNA in the nuclear retention of nucleocytoplasmic shuttling proteins. Moreover, a dFoxO-Snail feed-forward loop regulates both autophagy and cell size in Drosophila, suggesting this evolutionarily conserved regulatory loop is engaged in more physiological activities.

Autophagy is a highly conserved programmed degradation process that regulates a variety of physiological and pathological activities in health, aging, and disease. To identify additional factors that modulate autophagy, we utilized serum-free starvation or Torin1 to induce autophagy in HeLa cells for unbiased mRNA-sequencing analysis and identified SNAI2, a crucial player in epithelial-to-mesenchymal transition and cancer progression, as a regulator of autophagy. Mechanistically, SNAI2 promotes autophagy by physically interacting with FOXO3 and enhancing FOXO3 binding affinity to its response elements in autophagy-related genes. Intriguingly, binding to the DNA targets appears necessary and sufficient for FOXO3 to antagonize its CRM1-dependent nuclear export, illustrating a critical role of DNA in regulating protein nuclear localization. Moreover, stress-elevated SNAI2 expression is mediated by FOXO3, which activates SNAI2 transcription by directly binding to its promoter. Herein, FOXO3 and SNAI2 form a coherent feed-forward regulatory loop to reinforce autophagy genes induction in response to energy stress. Strikingly, a dFoxO-Snail feed-forward circuit also regulates autophagy in Drosophila, suggesting this mechanism is evolutionarily conserved from fly to human.

ER Stress in Cardiometabolic Diseases: From Molecular Mechanisms to Therapeutics

The endoplasmic reticulum (ER) hosts linear polypeptides and fosters natural folding of proteins through ER-residing chaperones and enzymes. Failure of the ER to align and compose proper protein architecture leads to accumulation of misfolded/unfolded proteins in the ER lumen, which disturbs ER homeostasis to provoke ER stress. Presence of ER stress initiates the cytoprotective unfolded protein response (UPR) to restore ER homeostasis or instigates a rather maladaptive UPR to promote cell death. Although a wide array of cellular processes such as persistent autophagy, dysregulated mitophagy, and secretion of proinflammatory cytokines may contribute to the onset and progression of cardiometabolic diseases, it is well perceived that ER stress also evokes the onset and development of cardiometabolic diseases, particularly cardiovascular diseases (CVDs), diabetes mellitus, obesity, and chronic kidney disease (CKD). Meanwhile, these pathological conditions further aggravate ER stress, creating a rather vicious cycle. Here in this review, we aimed at summarizing and updating the available information on ER stress in CVDs, diabetes mellitus, obesity, and CKD, hoping to offer novel insights for the management of these cardiometabolic comorbidities through regulation of ER stress.