Serum Sestrin2 and PlGF levels in pregnant women with pre-eclampsia and their correlations with the severity of the disease: A case-control study

Purpose: Sestrin2, a metabolic regulator with antioxidant activity, might have some certain predictability for the occurrence and severity of pre-eclampsia (PE). The purpose of this work was to explore the levels of serum Sestrin2 and PlGF in pregnant women with PE and their correlation with the severity index of the disease.Methods:This was a retrospective case-control study of pregnant women with PE who planned to give birth in our hospital from 05/2017 to 05/2019. Pearson correlation was used to analyze Sestrin2 and PlGF levels with PE severity. Receiver operating characteristic (ROC) curves were used to evaluate the predictive value of Sestrin2 and PlGF for PE.Results: There were 52 women in the control group, 46 in the mild PE group, and 36 in the severe PE group. As the severity of PE increased, the median levels of Sestrin2 increased (8.1, 9.8, and 11.8 ng/ml), and the levels of PlGF decreased (156, 117, and 67 pg/ml) in the three groups of women (all P<0.05).The levels of Sestrin2 and PlGF were strongly correlated with mean arterial pressure,proteinuria, newborn birth weight and gestational weeks at delivery (all P<0.001). Sestrin2 and PlGF had high efficiency of diagnosing PE (cut-off: 8.90 ng/ml, Area Under Curve [AUC]=0.979; cut-off: 122.50 pg/ml, AUC=0.963). Additionally, Sestrin2 and PlGF showed high value of severity prediction (cut-off: 11.15 ng/ml, AUC=0.857; cut-off: 68.50 pg/ml, AUC=0.837).Conclusion: Sestrin2 and PlGF are correlated with the severity of PE. Both Sestrin2 and PlGF had high value for PE diagnosis and severity prediction. Keywords: pre-eclampsia; Sestrin2; placental growth factor; oxidative stress; severity&nbsp

Hepatoprotective role of Sestrin2 against chronic ER stress

Upon prolonged endoplasmic reticulum (ER) stress, cells attenuate protein translation to prevent accumulation of unfolded proteins. Here we show that Sestrin2 is critical for this process. Sestrin2 expression is induced by an ER stress-activated transcription factor CCAATenhancer- binding protein beta (c/EBPβ). Once induced, Sestrin2 halts protein synthesis by inhibiting mammalian target of rapamycin complex 1 (mTORC1). As Sestrin2-deficient cells continue to translate a large amount of proteins during ER stress, they are highly susceptible to ER stress-associated cell death. Accordingly, dietary or genetically induced obesity, which does not lead to any pathological indication other than simple fat accumulation in the liver of wild-type (WT) mice, can provoke Sestrin2-deficient mice to develop severe ER stressassociated liver pathologies such as extensive liver damage, steatohepatitis and fibrosis. These pathologies are suppressed by liver-specific Sestrin2 reconstitution, mTORC1 inhibition or chemical chaperone administration. The Sestrin2-mediated unfolded protein response (UPR) may be a general protective mechanism against ER stress-associated diseases

Sestrin2 promotes LKB1‐mediated AMPK activation in the ischemic heart

The regulation of AMPK in the ischemic heart remains incompletely understood. Recent evidence implicates the role of Sestrin2 in the AMPK signaling pathway, and it is hypothesized that Sestrin2 plays an influential role during myocardial ischemia to promote AMPK activation. Sestrin2 protein was found to be expressed in adult cardiomyocytes and accumulated in the heart during ischemic conditions. Sestrin2 knockout (KO) mice were used to determine the importance of Sestrin2 during ischemia and reperfusion (I/R) injury. When wild‐type (WT) and Sestrin2 KO mice were subjected to in vivo I/R, myocardial infarct size was significantly greater in Sestrin2 KO compared with WT hearts. Similarly, Langendorff perfused hearts indicated exacerbated postischemic contractile function in Sestrin2 KO hearts compared with WT. Ischemic AMPK activation was found to be impaired in the Sestrin2 KO hearts. Immunoprecipitation of Sestrin2 demonstrated an association with AMPK. Moreover, liver kinase B1 (LKB1), a major AMPK upstream kinase, was associated with the Sestrin2‐AMPK complex in a time‐dependent manner during ischemia, whereas this interaction was nearly abolished in Sestrin2 KO hearts. Thus, Sestrin2 plays an important role in cardioprotection against I/R injury, serving as an LKB1‐AMPK scaffold to initiate AMPK activation during ischemic insults.—Morrison, A., Chen, L. Wang, J., Zhang, M., Yang, H., Ma, Y., Budanov, A., Lee, J. H., Karin, M., Li, J. Sestrin2 promotes LKB1‐mediated AMPK activation in the ischemic heart. FASEB J. 29, 408‐417 (2015). www.fasebj.orgPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154534/1/fsb2fj14258814-sup-0001.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154534/2/fsb2fj14258814.pd

Sestrin2 Phosphorylation by ULK1 Induces Autophagic Degradation of Mitochondria Damaged by Copper-Induced Oxidative Stress

Selective autolysosomal degradation of damaged mitochondria, also called mitophagy, is an indispensable process for maintaining integrity and homeostasis of mitochondria. One well-established mechanism mediating selective removal of mitochondria under relatively mild mitochondria-depolarizing stress is PINK1-Parkin-mediated or ubiquitin-dependent mitophagy. However, additional mechanisms such as LC3-mediated or ubiquitin-independent mitophagy induction by heavy environmental stress exist and remain poorly understood. The present study unravels a novel role of stress-inducible protein Sestrin2 in degradation of mitochondria damaged by transition metal stress. By utilizing proteomic methods and studies in cell culture and rodent models, we identify autophagy kinase ULK1-mediated phosphorylation sites of Sestrin2 and demonstrate Sestrin2 association with mitochondria adaptor proteins in HEK293 cells. We show that Ser-73 and Ser-254 residues of Sestrin2 are phosphorylated by ULK1, and a pool of Sestrin2 is strongly associated with mitochondrial ATP5A in response to Cu-induced oxidative stress. Subsequently, this interaction promotes association with LC3-coated autolysosomes to induce degradation of mitochondria damaged by Cu-induced ROS. Treatment of cells with antioxidants or a Cu chelator significantly reduces Sestrin2 association with mitochondria. These results highlight the ULK1-Sestrin2 pathway as a novel stress-sensing mechanism that can rapidly induce autophagic degradation of mitochondria under severe heavy metal stress

Sestrin2 is induced by glucose starvation via the unfolded protein response and protects cells from non-canonical necroptotic cell death

Sestrin2 is a member of a family of stress responsive proteins, which controls cell viability via antioxidant activity and regulation of the mammalian target of rapamycin protein kinase (mTOR). Sestrin2 is induced by different stress insults, which diminish ATP production and induce energetic stress in the cells. Glucose is a critical substrate for ATP production utilized via glycolysis and mitochondrial respiration as well as for glycosylation of newly synthesized proteins in the endoplasmic reticulum (ER) and Golgi. Thus, glucose starvation causes both energy deficiency and activation of ER stress followed by the unfolding protein response (UPR). Here, we show that UPR induces Sestrin2 via ATF4 and NRF2 transcription factors and demonstrate that Sestrin2 protects cells from glucose starvation-induced cell death. Sestrin2 inactivation sensitizes cells to necroptotic cell death that is associated with a decline in ATP levels and can be suppressed by Necrostatin 7. We propose that Sestrin2 protects cells from glucose starvation-induced cell death via regulation of mitochondrial homeostasis

Sestrin2 is a leucine sensor for the mTORC1 pathway

Leucine is a proteogenic amino acid that also regulates many aspects of mammalian physiology, in large part by activating the mTOR complex 1 (mTORC1) protein kinase, a master growth controller. Amino acids signal to mTORC1 through the Rag guanosine triphosphatases (GTPases). Several factors regulate the Rags, including GATOR1, aGTPase-activating protein; GATOR2, a positive regulator of unknown function; and Sestrin2, a GATOR2-interacting protein that inhibits mTORC1 signaling. We find that leucine, but not arginine, disrupts the Sestrin2-GATOR2 interaction by binding to Sestrin2 with a dissociation constant of 20 micromolar, which is the leucine concentration that half-maximally activates mTORC1. The leucine-binding capacity of Sestrin2 is required for leucine to activate mTORC1 in cells. These results indicate that Sestrin2 is a leucine sensor for the mTORC1 pathway.United States. National Institutes of Health (R01CA103866)United States. National Institutes of Health (AI47389)United States. Department of Defense (W81XWH-07-0448)United States. National Institutes of Health (T32 GM007753)United States. National Institutes of Health (F30 CA189333)United States. National Institutes of Health (F31 CA180271

Branched-Chain Amino Acid Negatively Regulates KLF15 Expression via PI3K-AKT Pathway.

Recent studies have linked branched-chain amino acid (BCAA) with numerous metabolic diseases. However, the molecular basis of BCAA's roles in metabolic regulation remains to be established. KLF15 (Krüppel-like factor 15) is a transcription factor and master regulator of glycemic, lipid, and amino acids metabolism. In the present study, we found high concentrations of BCAA suppressed KLF15 expression while BCAA starvation induced KLF15 expression, suggesting KLF15 expression is negatively controlled by BCAA.Interestingly, BCAA starvation induced PI3K-AKT signaling. KLF15 induction by BCAA starvation was blocked by PI3K and AKT inhibitors, indicating the activation of PI3K-AKT signaling pathway mediated the KLF15 induction. BCAA regulated KLF15 expression at transcriptional level but not post-transcriptional level. However, BCAA starvation failed to increase the KLF15-promoter-driven luciferase expression, suggesting KLF15 promoter activity was not directly controlled by BCAA. Finally, fasting reduced BCAA abundance in mice and KLF15 expression was dramatically induced in muscle and white adipose tissue, but not in liver. Together, these data demonstrated BCAA negatively regulated KLF15 expression, suggesting a novel molecular mechanism underlying BCAA's multiple functions in metabolic regulation

Sestrins are evolutionarily conserved mediators of exercise benefits.

Exercise is among the most effective interventions for age-associated mobility decline and metabolic dysregulation. Although long-term endurance exercise promotes insulin sensitivity and expands respiratory capacity, genetic components and pathways mediating the metabolic benefits of exercise have remained elusive. Here, we show that Sestrins, a family of evolutionarily conserved exercise-inducible proteins, are critical mediators of exercise benefits. In both fly and mouse models, genetic ablation of Sestrins prevents organisms from acquiring metabolic benefits of exercise and improving their endurance through training. Conversely, Sestrin upregulation mimics both molecular and physiological effects of exercise, suggesting that it could be a major effector of exercise metabolism. Among the various targets modulated by Sestrin in response to exercise, AKT and PGC1α are critical for the Sestrin effects in extending endurance. These results indicate that Sestrin is a key integrating factor that drives the benefits of chronic exercise to metabolism and physical endurance

Role of activating transcription factor 4 in the hepatic response to amino acid depletion by asparaginase

The anti-leukemic agent asparaginase activates the integrated stress response (ISR) kinase GCN2 and inhibits signaling via mechanistic target of rapamycin complex 1 (mTORC1). The study objective was to investigate the protective role of activating transcription factor 4 (ATF4) in controlling the hepatic transcriptome and mediating GCN2-mTORC1 signaling during asparaginase. We compared global gene expression patterns in livers from wildtype, Gcn2 -/-, and Atf4 -/- mice treated with asparaginase or excipient and further explored selected responses in livers from Atf4 +/- mice. Here, we show that ATF4 controls a hepatic gene expression profile that overlaps with GCN2 but is not required for downregulation of mTORC1 during asparaginase. Ingenuity pathway analysis indicates GCN2 independently influences inflammation-mediated hepatic processes whereas ATF4 uniquely associates with cholesterol metabolism and endoplasmic reticulum (ER) stress. Livers from Atf4 -/- or Atf4 +/- mice displayed an amplification of the amino acid response and ER stress response transcriptional signatures. In contrast, reduction in hepatic mTORC1 signaling was retained in Atf4 -/- mice treated with asparaginase