Hypophosphorylated pRb knock-in mice exhibit hallmarks of aging and vitamin C-preventable diabetes.

Despite extensive analysis of pRB phosphorylation in vitro, how this modification influences development and homeostasis in vivo is unclear. Here, we show that homozygous Rb∆K4 and Rb∆K7 knock-in mice, in which either four or all seven phosphorylation sites in the C-terminal region of pRb, respectively, have been abolished by Ser/Thr-to-Ala substitutions, undergo normal embryogenesis and early development, notwithstanding suppressed phosphorylation of additional upstream sites. Whereas Rb∆K4 mice exhibit telomere attrition but no other abnormalities, Rb∆K7 mice are smaller and display additional hallmarks of premature aging including infertility, kyphosis, and diabetes, indicating an accumulative effect of blocking pRb phosphorylation. Diabetes in Rb∆K7 mice is insulin-sensitive and associated with failure of quiescent pancreatic ß-cells to re-enter the cell cycle in response to mitogens, resulting in induction of DNA damage response (DDR), senescence-associated secretory phenotype (SASP), and reduced pancreatic islet mass and circulating insulin level. Pre-treatment with the epigenetic regulator vitamin C reduces DDR, increases cell cycle re-entry, improves islet morphology, and attenuates diabetes. These results have direct implications for cell cycle regulation, CDK-inhibitor therapeutics, diabetes, and longevity.

Association between family conflict resolution methods and depressive symptoms in South Korea: a longitudinal study.

We investigated the relationship between family conflict resolution and depression, focusing on each component of family conflict resolution to determine which factors have stronger associations with depression. We used data from 2008 to 2015 of the Korea Welfare Panel Study. Our final sample included 3565 participants. For each participant, we included at least 2-8 years of follow-up data with a mean follow-up time of 4.05 ± 2.52 years. To identify the relationship between new-onset depressive symptoms and participants' family conflict resolution styles, we performed generalized estimating equation analysis with autoregressive working correlations to estimate adjusted odds ratios for new-onset depressive symptoms adjusted for covariates. Compared with positive family conflict resolution, negative family conflict resolution had a higher odds ratio for depressive symptoms (aOR 1.80, 95% CI 1.42-2.29). This relationship was strongly founded on participants who were women (aOR 2.35, 95% CI 1.55-3.94) with experience of verbal aggression (aOR 1.84, 95% CI 1.42-2.37) and threatening behaviors (aOR 1.89, 95% CI 1.25-2.85). Negative family conflict resolution has long-term associations with an elevated risk of depressive symptoms. In particular, we observed higher risks of depression with verbal and psychological conflict than with physical conflict. Health care providers and health policymakers should support the management and development of methods for dealing with family conflict to improve mental health at a family level, as well as an individual level.

Cystathionine gamma-lyase/hydrogen sulfide system is essential for adipogenesis and fat mass accumulation in mice.

Hydrogen sulfide (H2S) has been recognized as an important gasotransmitter analogous to nitric oxide and carbon monoxide. Cystathionine gamma-lyase (CSE)-derived H2S is implicated in the regulation of insulin resistance and glucose metabolism, but the involvement of CSE/H2S system in energy homeostasis and fat mass has not been extensively explored. In this study, a potential functional role of the CSE/H2S system in in vitro adipocyte differentiation and in vivo adipogenesis and the underlying mechanism was investigated. CSE expression and H2S production were increased during adipocyte differentiation, and that the pattern of CSE mRNA expression was similar to that of CCAAT/enhancer-binding protein (C/EBP) ß and δ, two key regulators for adipogenesis. C/EBPß and γ bind to the CCAAT box in CSE promoter and stimulate CSE gene transcription. H2S induced PPARγ transactivation activity by S-sulfhydrating all the cysteine residues in the DNA binding domain and stimulated adipogenesis. High fat diet-induced fat mass was lost in CSE deficient mice, and exogenously applied H2S promoted fat mass accumulation in fruit flies. In conclusion, CSE/H2S system is essential for adipogenesis and fat mass accumulation through enhancement of PPARγ function in adipocytes. This study suggests that the CSE/H2S system is involved in the pathogenesis of obesity in mice.

Ethanol-dispersed and antibody-conjugated polymer nanofibers for the selective capture and 3-dimensional culture of EpCAM-positive cells.

Electrospun and ethanol-dispersed polystyrene-poly(styrene-co-maleic anhydride) (PS-PSMA) nanofibers (NFs) were used as a platform for the selective capture and three-dimensional culture of EpCAM-positive cells in cell culture medium and whole blood. The NFs were treated with streptavidin to facilitate bond formation between the amino groups of streptavidin and the maleic anhydride groups of the NFs. A biotinylated anti-EpCAM monoclonal antibody (mAb) was attached to the streptavidin-conjugated NFs via the selective binding of streptavidin and biotin. Upon simple mixing and shaking with EpCAM-positive cancer cells in a wide concentration range from 10 to 1000,000 cells per 10mL, the mAb-attached NFs (mAb-NFs) captured the Ep-CAM positive cells in an efficiency of 59%-67% depending on initial cell concentrations, with minor mechanical capture of 14%-36%. Captured cells were directly cultured, forming cell aggregates, in the NF matrix, which ensures the cell proliferation and follow-up analysis. Furthermore, the capture capacity of mAb-NFs was assessed in the presence of whole blood and blood lysates, indicating cluster formation that captured target cells. It is anticipated that the antibody-attached NFs can be employed for the capture and analysis of very rare EpCAM positive circulating cancer cells.

H2S-Mediated Protein S-Sulfhydration: A Prediction for Its Formation and Regulation.

Protein S-sulfhydration is a newly discovered post-translational modification of specific cysteine residue(s) in target proteins, which is involved in a broad range of cellular functions and metabolic pathways. By changing local conformation and the final activity of target proteins, S-sulfhydration is believed to mediate most cellular responses initiated by H2S, a novel gasotransmitter. In comparison to protein S-sulfhydration, nitric oxide-mediated protein S-nitrosylation has been extensively investigated, including its formation, regulation, transfer and metabolism. Although the investigation on the regulatory mechanisms associated with protein S-sulfhydration is still in its infancy, accumulated evidence suggested that protein S-sulfhydration may share similar chemical features with protein S-nitrosylation. Glutathione persulfide acts as a major donor for protein S-sulfhydration. Here, we review the present knowledge on protein S-sulfhydration, and also predict its formation and regulation mechanisms based on the knowledge from protein S-nitrosylation.

H2S-induced S-sulfhydration of pyruvate carboxylase contributes to gluconeogenesis in liver cells.

BACKGROUND: Cystathionine gamma-lyase (CSE)-derived hydrogen sulfide (H(2)S) possesses diverse roles in the liver, affecting lipoprotein synthesis, insulin sensitivity, and mitochondrial biogenesis. H(2)S S-sulfhydration is now proposed as a major mechanism for H(2)S-mediated signaling. Pyruvate carboxylase (PC) is an important enzyme for gluconeogenesis. S-sulfhydration regulation of PC by H(2)S and its implication in gluconeogenesis in the liver have been unknown. METHODS: Gene expressions were analyzed by real-time PCR and western blotting, and protein S-sulfhydration was assessed by both modified biotin switch assay and tag switch assay. Glucose production and PC activity was measured with coupled enzyme assays, respectively. RESULTS: Exogenously applied H(2)S stimulates PC activity and gluconeogenesis in both HepG2 cells and mouse primary liver cells. CSE overexpression enhanced but CSE knockout reduced PC activity and gluconeogenesis in liver cells, and blockage of PC activity abolished H(2)S-induced gluconeogenesis. H(2)S had no effect on the expressions of PC mRNA and protein, while H(2)S S-sulfhydrated PC in a dithiothreitol-sensitive way. PC S-sulfhydration was significantly strengthened by CSE overexpression but attenuated by CSE knockout, suggesting that H(2)S enhances glucose production through S-sulfhydrating PC. Mutation of cysteine 265 in human PC diminished H(2)S-induced PC S-sulfhydration and activity. In addition, high-fat diet feeding of mice decreased both CSE expression and PC S-sulfhydration in the liver, while glucose deprivation of HepG2 cells stimulated CSE expression. CONCLUSIONS: CSE/H(2)S pathway plays an important role in the regulation of glucose production through S-sulfhydrating PC in the liver. GENERAL SIGNIFICANCE: Tissue-specific regulation of CSE/H(2)S pathway might be a promising therapeutic target of diabetes and other metabolic syndromes.

Stimulatory effect of CSE-generated H2S on hepatic mitochondrial biogenesis and the underlying mechanisms.

We previously showed that hydrogen sulfide (H2S) upregulates peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α in primary hepatocytes. PGC-1α is a crucial regulator of mitochondrial biogenesis, a process required to maintain cellular energy homeostasis. We investigated the regulation of hepatic mitochondrial biogenesis by cystathionine γ-lyase (CSE)-generated H2S under physiological conditions. Primary hepatocytes isolated from CSE knockout (KO) and wild-type (WT) mice were used in all experiments. Mitochondrial DNA (mtDNA) and mRNA levels were measured via real-time PCR. Protein S-sulfhydration was determined via a modified biotin switch assay. MitoTracker Green was used to quantify mitochondrial content and distribution. CSE-KO hepatocytes produced less mtDNA compared to WT hepatocytes. Mitochondrial content was reduced in CSE-KO hepatocytes compared to WT hepatocytes, which was restored with NaHS (an H2S donor) treatment. CSE-KO hepatocytes exhibited lower levels of mitochondrial transcription factors and the mitochondrial transcription coactivator, peroxisome proliferator-activated receptor-γ coactivator-related protein (PPRC) compared to WT hepatocytes. NaHS administration upregulated PPRC, yet downregulated PGC-1ß protein level in mouse hepatocytes. Exogenous H2S induced the S-sulfhydration of PPRC, which was lower in untreated CSE-KO hepatocytes, but not that of PGC-1ß. Finally, knockdown of either PGC-1α or PPRC significantly decreased NaHS-stimulated mitochondrial biogenesis in hepatocytes, where knockdown of both genes were required to abolish NaHS-induced mitochondrial biogenesis. Endogenous H2S-induced liver mitochondrial biogenesis is dependent upon PGC-1α and PPRC signaling in primary hepatocytes. This study may offer clues to the regulation of energy homeostasis under physiological conditions as well as mitochondrial dysregulation.

S-Sulfhydration of ATP synthase by hydrogen sulfide stimulates mitochondrial bioenergetics.

Mammalian cells can utilize hydrogen sulfide (H2S) to support mitochondrial respiration. The aim of our study was to explore the potential role of S-sulfhydration (a H2S-induced posttranslational modification, also known as S-persulfidation) of the mitochondrial inner membrane protein ATP synthase (F1F0 ATP synthase/Complex V) in the regulation of mitochondrial bioenergetics. Using a biotin switch assay, we have detected S-sulfhydration of the α subunit (ATP5A1) of ATP synthase in response to exposure to H2S in vitro. The H2S generator compound NaHS induced S-sulfhydration of ATP5A1 in HepG2 and HEK293 cell lysates in a concentration-dependent manner (50-300µM). The activity of immunocaptured mitochondrial ATP synthase enzyme isolated from HepG2 and HEK293 cells was stimulated by NaHS at low concentrations (10-100nM). Site-directed mutagenesis of ATP5A1 in HEK293 cells demonstrated that cysteine residues at positions 244 and 294 are subject to S-sulfhydration. The double mutant ATP synthase protein (C244S/C294S) showed a significantly reduced enzyme activity compared to control and the single-cysteine-mutated recombinant proteins (C244S or C294S). To determine whether endogenous H2S plays a role in the basal S-sulfhydration of ATP synthase in vivo, we compared liver tissues harvested from wild-type mice and mice deficient in cystathionine-gamma-lyase (CSE, one of the three principal mammalian H2S-producing enzymes). Significantly reduced S-sulfhydration of ATP5A1 was observed in liver homogenates of CSE-/- mice, compared to wild-type mice, suggesting a physiological role for CSE-derived endogenous H2S production in the S-sulfhydration of ATP synthase. Various forms of critical illness (including burn injury) upregulate H2S-producing enzymes and stimulate H2S biosynthesis. In liver tissues collected from mice subjected to burn injury, we detected an increased S-sulfhydration of ATP5A1 at the early time points post-burn. At later time points (when systemic H2S levels decrease) S-sulfhydration of ATP5A1 decreased as well. In conclusion, H2S induces S-sulfhydration of ATP5A1 at C244 and C294. This post-translational modification may be a physiological mechanism to maintain ATP synthase in a physiologically activated state, thereby supporting mitochondrial bioenergetics. The sulfhydration of ATP synthase may be a dynamic process, which may be regulated by endogenous H2S levels under various pathophysiological conditions.

S-sulfhydration of MEK1 leads to PARP-1 activation and DNA damage repair.

The repair of DNA damage is fundamental to normal cell development and replication. Hydrogen sulfide (H2S) is a novel gasotransmitter that has been reported to protect cellular aging. Here, we show that H2S attenuates DNA damage in human endothelial cells and fibroblasts by S-sulfhydrating MEK1 at cysteine 341, which leads to PARP-1 activation. H2S-induced MEK1 S-sulfhydration facilitates the translocation of phosphorylated ERK1/2 into nucleus, where it activates PARP-1 through direct interaction. Mutation of MEK1 cysteine 341 inhibits ERK phosphorylation and PARP-1 activation. In the presence of H2S, activated PARP-1 recruits XRCC1 and DNA ligase III to DNA breaks to mediate DNA damage repair, and cells are protected from senescence.

Continuous exposure to 60 Hz magnetic fields induces duration- and dose-dependent apoptosis of testicular germ cells.

To evaluate duration- and dose-dependent effects of continuous exposure to a 60 Hz magnetic field (MF) on the testes in mice, BALB/c male mice were exposed to a 60 Hz MF at 100 µT for 24 h a day for 2, 4, 6, or 8 weeks, and at 2, 20, or 200 µT for 24 h a day for 8 weeks. Any exposures to MF did not significantly affect body or testicular masses. However, the apoptotic cells among testicular germ cells were increased duration-dependent at exposures of 100 µT for 6 and 8 weeks and dose-dependent at exposures of 20 and 200 µT for 8 weeks. The number of sperm in epididymis and the diameter of seminiferous tubule decreased in mice exposed to 100 and 200 µT for 8 weeks, respectively. To induce the apoptosis of testicular germ cell in mice, the minimum dose is 20 µT at continuous exposure to a 60 Hz MF for 8 weeks and the minimum duration is 6 weeks at continuous exposure of 100 µT. Taken together, these results suggest that continuous exposure to a 60 Hz MF might affect, duration- and dose-dependent biological processes including apoptotic cell death and spermatogenesis in the male reproductive system of mice.

H(2)S signaling in redox regulation of cellular functions.

Hydrogen sulfide (H(2)S) is traditionally recognized as a toxic gas with a rotten-egg smell. In just the last few decades, H(2)S has been found to be one of a family of gasotransmitters, together with nitric oxide and carbon monoxide, and various physiologic effects of H(2)S have been reported. Among the most acknowledged molecular mechanisms for the cellular effects of H(2)S is the regulation of intracellular redox homeostasis and post-translational modification of proteins through S-sulfhydration. On the one side, H(2)S can promote an antioxidant effect and is cytoprotective; on the other side, H(2)S stimulates oxidative stress and is cytotoxic. This review summarizes our current knowledge of the antioxidant versus pro-oxidant effects of H(2)S in mammalian cells and describes the Janus-faced properties of this novel gasotransmitter. The redox regulation for the cellular effects of H(2)S through S-sulfhydration and the role of H(2)S in glutathione generation is also recapitulated. A better understanding of H(2)S-regualted redox homeostasis will pave the way for future design of novel pharmacological and therapeutic interventions for various diseases.

Tumors recycle glucocorticoids to drive Treg-mediated immunosuppression.

Suppression of antitumor immunity is a prominent feature of the tumor microenvironment. In this issue of the JCI, Taves, Otsuka, and authors show that glucocorticoids (GCs), which are potent immunosuppressive hormones mainly produced by the adrenals, can be reconverted from their inactive form to active metabolites via the 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme expressed by murine tumor cell lines. In the tumor microenvironment, GCs acted on CD4+ regulatory T cells to enhance their immunosuppressive function and promote tumor growth. The findings suggest that targeting GC recycling as a strategy for modulating tumor immunosuppression has the potential to improve therapeutic efficacy of immune checkpoint blockade.

Thinking (Metastasis) outside the (Primary Tumor) Box.

The metastasis of tumor cells into vital organs is a major cause of death from diverse types of malignancies [...].

Distinct shared and compartment-enriched oncogenic networks drive primary versus metastatic breast cancer.

Metastatic breast-cancer is a major cause of death in women worldwide, yet the relationship between oncogenic drivers that promote metastatic versus primary cancer is still contentious. To elucidate this relationship in treatment-naive animals, we hereby describe mammary-specific transposon-mutagenesis screens in female mice together with loss-of-function Rb, which is frequently inactivated in breast-cancer. We report gene-centric common insertion-sites (gCIS) that are enriched in primary-tumors, in metastases or shared by both compartments. Shared-gCIS comprise a major MET-RAS network, whereas metastasis-gCIS form three additional hubs: Rho-signaling, Ubiquitination and RNA-processing. Pathway analysis of four clinical cohorts with paired primary-tumors and metastases reveals similar organization in human breast-cancer with subtype-specific shared-drivers (e.g. RB1-loss, TP53-loss, high MET, RAS, ER), primary-enriched (EGFR, TGFß and STAT3) and metastasis-enriched (RHO, PI3K) oncogenic signaling. Inhibitors of RB1-deficiency or MET plus RHO-signaling cooperate to block cell migration and drive tumor cell-death. Thus, targeting shared- and metastasis- but not primary-enriched derivers offers a rational avenue to prevent metastatic breast-cancer.

Bacteriophage EK99P-1 alleviates enterotoxigenic Escherichia coli K99-induced barrier dysfunction and inflammation.

Bacteriophages, simply phages, have long been used as a potential alternative to antibiotics for livestock due to their ability to specifically kill enterotoxigenic Escherichia coli (ETEC), which is a major cause of diarrhea in piglets. However, the control of ETEC infection by phages within intestinal epithelial cells, and their relationship with host immune responses, remain poorly understood. In this study, we evaluated the effect of phage EK99P-1 against ETEC K99-infected porcine intestinal epithelial cell line (IPEC-J2). Phage EK99P-1 prevented ETEC K99-induced barrier disruption by attenuating the increased permeability mediated by the loss of tight junction proteins such as zonula occludens-1 (ZO-1), occludin, and claudin-3. ETEC K99-induced inflammatory responses, such as interleukin (IL)-8 secretion, were decreased by treatment with phage EK99P-1. We used a IPEC-J2/peripheral blood mononuclear cell (PBMC) transwell co-culture system to investigate whether the modulation of barrier disruption and chemokine secretion by phage EK99P-1 in ETEC K99-infected IPEC-J2 would influence immune cells at the site of basolateral. The results showed that phage EK99P-1 reduced the mRNA expression of ETEC K99-induced pro-inflammatory cytokines, IL-1ß and IL-8, from PBMC collected on the basolateral side. Together, these results suggest that phage EK99P-1 prevented ETEC K99-induced barrier dysfunction in IPEC-J2 and alleviated inflammation caused by ETEC K99 infection. Reinforcement of the intestinal barrier, such as regulation of permeability and cytokines, by phage EK99P-1 also modulates the immune cell inflammatory response.

Change of Dendritic Cell Subsets Involved in Protection Against Listeria monocytogenes Infection in Short-Term-Fasted Mice.

The gastrointestinal tract is the first organ directly affected by fasting. However, little is known about how fasting influences the intestinal immune system. Intestinal dendritic cells (DCs) capture antigens, migrate to secondary lymphoid organs, and provoke adaptive immune responses. We evaluated the changes of intestinal DCs in mice with short-term fasting and their effects on protective immunity against Listeria monocytogenes (LM). Fasting induced an increased number of CD103+CD11b- DCs in both small intestinal lamina propria (SILP) and mesenteric lymph nodes (mLN). The SILP CD103+CD11b- DCs showed proliferation and migration, coincident with increased levels of GM-CSF and C-C chemokine receptor type 7, respectively. At 24 h post-infection with LM, there was a significant reduction in the bacterial burden in the spleen, liver, and mLN of the short-term-fasted mice compared to those fed ad libitum. Also, short-term-fasted mice showed increased survival after LM infection compared with ad libitum-fed mice. It could be that significantly high TGF-ß2 and Aldh1a2 expression in CD103+CD11b- DCs in mice infected with LM might affect to increase of Foxp3+ regulatory T cells. Changes of major subset of DCs from CD103+ to CD103- may induce the increase of IFN-γ-producing cells with forming Th1-biased environment. Therefore, the short-term fasting affects protection against LM infection by changing major subset of intestinal DCs from tolerogenic to Th1 immunogenic.

Inactivated Vibrio cholerae Strains That Express TcpA via the toxT-139F Allele Induce Antibody Responses against TcpA.

Cholera remains a major global public health problem, for which oral cholera vaccines (OCVs) being a valuable strategy. Patients, who have recovered from cholera, develop antibody responses against LPS, cholera toxin (CT), toxin-coregulated pilus (TCP) major subunit A (TcpA) and other antigens; thus, these responses are potentially important contributors to immunity against Vibrio cholerae infection. However, assessments of the efficacy of current OCVs, especially inactivated OCVs, have focused primarily on O-antigen-specific antibody responses, suggesting that more sophisticated strategies are required for inactivated OCVs to induce immune responses against TCP, CT, and other antigens. Previously, we have shown that the toxT-139F allele enables V. cholerae strains to produce CT and TCP under simple laboratory culture conditions. Thus, we hypothesized that V. cholerae strains that express TCP via the toxT-139F allele induce TCP-specific antibody responses. As anticipated, V. cholerae strains that expressed TCP through the toxT-139F allele elicited antibody responses against TCP when the inactivated bacteria were delivered via a mouse model. We have further developed TCP-expressing V. cholerae strains that have been used in inactivated OCVs and shown that they effect an antibody response against TcpA in vivo, suggesting that V. cholerae strains with the toxT-139F allele are excellent candidates for cholera vaccines.

Early onset senescence and cognitive impairment in a murine model of repeated mTBI.

Mild traumatic brain injury (mTBI) results in broad neurological symptoms and an increased risk of being diagnosed with a neurodegenerative disease later in life. While the immediate oxidative stress response and post-mortem pathology of the injured brain has been well studied, it remains unclear how early pathogenic changes may drive persistent symptoms and confer susceptibility to neurodegeneration. In this study we have used a mouse model of repeated mTBI (rmTBI) to identify early gene expression changes at 24 h or 7 days post-injury (7 dpi). At 24 h post-injury, gene expression of rmTBI mice shows activation of the DNA damage response (DDR) towards double strand DNA breaks, altered calcium and cell-cell signalling, and inhibition of cell death pathways. By 7 dpi, rmTBI mice had a gene expression signature consistent with induction of cellular senescence, activation of neurodegenerative processes, and inhibition of the DDR. At both timepoints gliosis, microgliosis, and axonal damage were evident in the absence of any gross lesion, and by 7 dpi rmTBI also mice had elevated levels of IL1ß, p21, 53BP1, DNA2, and p53, supportive of DNA damage-induced cellular senescence. These gene expression changes reflect establishment of processes usually linked to brain aging and suggests that cellular senescence occurs early and most likely prior to the accumulation of toxic proteins. These molecular changes were accompanied by spatial learning and memory deficits in the Morris water maze. To conclude, we have identified DNA damage-induced cellular senescence as a repercussion of repeated mild traumatic brain injury which correlates with cognitive impairment. Pathways involved in senescence may represent viable treatment targets of post-concussive syndrome. Senescence has been proposed to promote neurodegeneration and appears as an effective target to prevent long-term complications of mTBI, such as chronic traumatic encephalopathy and other related neurodegenerative pathologies.

Inhibition of eEF2K synergizes with glutaminase inhibitors or 4EBP1 depletion to suppress growth of triple-negative breast cancer cells.

The eukaryotic elongation factor-2 kinase, eEF2K, which restricts protein translation elongation, has been identified as a potential therapeutic target for diverse types of malignancies including triple negative breast cancer (TNBC). However, the contexts in which eEF2K inhibition is essential in TNBC and its consequences on the proteome are largely unknown. Here we show that genetic or pharmacological inhibition of eEF2K cooperated with glutamine (Gln) starvation, and synergized with glutaminase (GLS1) inhibitors to suppress growth of diverse TNBC cell lines. eEF2K inhibition also synergized with depletion of eukaryotic translation initiation factor 4E-binding protein 1 (eIF4EBP1; 4EBP1), a suppressor of eukaryotic protein translation initiation factor 4E (eIF4E), to induce c-MYC and Cyclin D1 expression, yet attenuate growth of TNBC cells. Proteomic analysis revealed that whereas eEF2K depletion alone uniquely induced Cyclin Dependent Kinase 1 (CDK1) and 6 (CDK6), combined depletion of eEF2K and 4EBP1 resulted in overlapping effects on the proteome, with the highest impact on the 'Collagen containing extracellular matrix' pathway (e.g. COL1A1), as well as the amino-acid transporter, SLC7A5/LAT1, suggesting a regulatory loop via mTORC1. In addition, combined depletion of eEF2K and 4EBP1 indirectly reduced the levels of IFN-dependent innate immune response-related factors. Thus, eEF2K inhibition triggers cell cycle arrest/death under unfavourable metabolic conditions such as Gln-starvation/GLS1 inhibition or 4EBP1 depletion, uncovering new therapeutic avenues for TNBC and underscoring a pressing need for clinically relevant eEF2K inhibitors.

STAT1 maintains naïve CD8+ T cell quiescence by suppressing the type I IFN-STAT4-mTORC1 signaling axis.

Naïve CD8+ T cell quiescence is maintained at a steady state. Although this state of quiescence involves various cell-intrinsic and cell-extrinsic regulators, the mechanisms underlying this regulation remain incompletely understood. Here, we found that signal transducer and activator of transcription 1 (STAT1), a key transcription factor downstream of interferon receptor (IFNR) signaling, plays a cell-intrinsic role in maintaining naïve CD8+ T cell quiescence. STAT1-deficient mice showed enhanced proliferation of peripheral naïve CD8+ T cells, which resulted in an abnormal increase in the number of CD44hi memory/activated phenotype cells and an enlargement of secondary lymphoid tissues. This phenomenon was not observed in IFNR-deficient mice but was paradoxically dependent on type I interferon and its alternative signaling pathway via the STAT4­RagD­lysosomal mTORC1 axis. Collectively, these findings underline the importance of STAT1 in regulating the homeostasis of peripheral naïve CD8+ T cells by suppressing their responsiveness to homeostatic cues at a steady state.