The cell death regulator GRIM-19 is an inhibitor of signal transducer and activator of transcription 3

Non-canonical STAT3 pathway induces alterations of mitochondrial dynamic proteins in the hippocampus of an LPS-induced murine neuroinflammation model

The activation of STAT3 is a crossroads of cellular regulation, induced in its canonical pathway by phosphorylation on a critical tyrosine residue (Y705). The existence of a STAT3 non-canonical signaling mechanisms, induced by phosphorylation at serine 727 (S727), has been recently identified in vitro. After cytoplasmic activation, non-canonical STAT3 could move to the level of mitochondria-endoplasmic reticulum contacts (MERCs). We have previously shown that LPS injections in mouse model induce STAT3 canonical pathway, leading to its nuclear translocation and to neuroinflammation. However, the effects of LPS on activation of the non-canonical pathway and its consequences on protein complexes of MERCs remain to be determined. In an in vivo LPS mouse model, we found that systemic inflammation induces in hippocampus the non-canonical STAT3 pathway. LPS-induced STAT3 affects specifically MERC protein BAP31, and that of a mitochondrial membrane protein known to interact with it, TOM40. These findings shed light on the role of STAT3 on mitochondrial - endoplasmic reticulum interaction under inflammatory conditions, offering new perspectives for targeting mitochondrial function and STAT3 activation in disease contexts.

Low Expression of GRIM-19 Correlates with Poor Prognosis in Patients with Upper Urinary Tract Urothelial Carcinoma

PURPOSE

This study aimed to clarify the expression of a gene associated with Retinoid- Interferon-Induced Mortality-19 (GRIM-19) in Upper Urinary Tract Urothelial Carcinoma (UUTUC) and its prognostic significance for UUTUC patients.

MATERIALS AND METHODS

Immunohistochemical (IHC) staining was used to determine the GRIM-19 expression in 70 paired samples. Progression-Free Survival (PFS) and Cancer-Specific Survival (CSS) were assessed using the Kaplan-Meier method. The independent prognostic factors for PFS and CSS were analyzed by multivariable Cox regression models.

RESULTS

IHC staining showed that GRIM-19 expression was significantly decreased in UUTUC, and its cellular location changed from being both cytoplasmic and nuclear to only cytoplasmic. Kaplan- Meier analysis revealed that the patients with tumors expressing low GRIM-19 had a significantly higher risk for tumor progression (P = 0.002) and cancer-specific mortality (P < 0.001) compared to those with high GRIM-19 levels. The Cox regression showed that both GRIM-19 expression (P = 0.025) and lymph node metastasis (LN) (P = 0.007) were independent predictors of progression in the muscle-invasive (MIC) subgroup. GRIM-19 expressions (entire cohort: P = 0.011; MIC subgroup: P = 0.025), LN (entire cohort: P = 0.019; MIC subgroup: P = 0.007), and progression (entire cohort: P < 0.001; MIC subgroup: P < 0.001) were independent predictors of cancer-specific survival.

CONCLUSION

Low expression of GRIM-19 in patients with UUTUC had significantly shorter PFS or CSS compared to those with high GRIM-19-expressing tumors. High GRIM-19 expression was also strongly associated with longer PFS in MIC patients. It indicates that GRIM-19 might serve as a promising prognostic biomarker for UUTUC patients.

Biallelic NDUFA13 variants lead to a neurodevelopmental phenotype with gradual neurological impairment

Biallelic variants in NADH (nicotinamide adenine dinucleotide (NAD) + hydrogen (H))-ubiquinone oxidoreductase 1 alpha subcomplex 13 have been linked to mitochondrial complex I deficiency, nuclear type 28, based on three affected individuals from two families. With only two families reported, the clinical and molecular spectrum of NADH-ubiquinone oxidoreductase 1 alpha subcomplex 13-related diseases remains unclear. We report 10 additional affected individuals from nine independent families, identifying four missense variants (including recurrent c.170G > A) and three ultra-rare or novel predicted loss-of-function biallelic variants. Updated clinical-radiological data from previously reported families and a literature review compiling clinical features of all reported patients with isolated complex I deficiency caused by 43 genes encoding complex I subunits and assembly factors are also provided. Our cohort (mean age 7.8 ± 5.4 years; range 2.5-18) predominantly presented a moderate-to-severe neurodevelopmental syndrome with oculomotor abnormalities (84%), spasticity/hypertonia (83%), hypotonia (69%), cerebellar ataxia (66%), movement disorders (58%) and epilepsy (46%). Neuroimaging revealed bilateral symmetric T2 hyperintense substantia nigra lesions (91.6%) and optic nerve atrophy (66.6%). Protein modeling suggests missense variants destabilize a critical junction between the hydrophilic and membrane arms of complex I. Fibroblasts from two patients showed reduced complex I activity and compensatory complex IV activity increase. This study characterizes NADH-ubiquinone oxidoreductase 1 alpha subcomplex 13-related disease in 13 individuals, highlighting genotype-phenotype correlations.

Prolonged exposure to dexamethasone alters the proteome and cellular phenotype of human testicular peritubular cells

Human testicular peritubular cells (HTPCs) are smooth muscle cells, which in the testis form a small compartment surrounding the seminiferous tubules. Contractions of HTPCs are responsible for sperm transport, HTPCs contribute to spermatogenesis, have immunological roles and are a site of glucocorticoid receptor expression. Importantly, HTPCs maintain their characteristics in vitro, and thus can serve as an experimental window into the male gonad. Previously we reported consequences of 3-day treatment with Dexamethasone (Dex), a synthetic glucocorticoid and multi-purpose anti-inflammatory drug. However, as glucocorticoid therapies in man often last longer, we now studied consequences of a prolonged 7-day exposure to 1 µM Dex. Combining live cell imaging with quantative proteomics of samples taken from men, we confirmed our recent findings but more importantly, found numerous novel proteomic alterations induced by prolonged Dex treatment. The comparison of the 7-day treatment with the 3-day treatment dataset revealed that extracellular matrix- and focal adhesion-related proteins become more prominent after 7 days of treatment. In contrast, extended stimulation is, for example, associated with a decrease of proteins related to cholesterol and steroid metabolism. Our dataset, which describes phenotypic and proteomic alterations, is a valuable resource for further research projects investigating effects of Dex on human testicular cells.

Structural determinants of mitochondrial STAT3 targeting and function

Signal transducer and activator of transcription (STAT) 3 has been found within mitochondria in addition to its canonical role of shuttling between cytoplasm and nucleus during cytokine signaling. Mitochondrial STAT3 has been implicated in modulation of cellular metabolism, largely through effects on the respiratory electron transport chain. However, the structural requirements underlying mitochondrial targeting and function have remained unclear. Here, we show that mitochondrial STAT3 partitions between mitochondrial compartments defined by differential detergent solubility, suggesting that mitochondrial STAT3 is membrane associated. The majority of STAT3 was found in an SDS soluble fraction copurifying with respiratory chain proteins, including numerous components of the complex I NADH dehydrogenase, while a minor component was found with proteins of the mitochondrial translation machinery. Mitochondrial targeting of STAT3 required the amino-terminal domain, and an internal linker domain motif also directed mitochondrial translocation. However, neither the phosphorylation of serine 727 nor the presence of mitochondrial DNA was required for the mitochondrial localization of STAT3. Two cysteine residues in the STAT3 SH2 domain, which have been previously suggested to be targets for protein palmitoylation, were also not required for mitochondrial translocation, but were required for its function as an enhancer of complex I activity. These structural determinants of STAT3 mitochondrial targeting and function provide potential therapeutic targets for disrupting the activity of mitochondrial STAT3 in diseases such as cancer.

Mitochondrial GRIM-19 loss in parietal cells promotes spasmolytic polypeptide-expressing metaplasia through NLR family pyrin domain-containing 3 (NLRP3)-mediated IL-33 activation via a reactive oxygen species (ROS) -NRF2- Heme oxygenase-1(HO-1)-NF-кB axis

Spasmolytic polypeptide-expressing metaplasia (SPEM), as a pre-neoplastic precursor of intestinal metaplasia (IM), plays critical roles in the development of chronic atrophic gastritis (CAG) and gastric cancer (GC). However, the pathogenetic targets responsible for the SPEM pathogenesis remain poorly understood. Gene associated with retinoid-IFN-induced mortality 19 (GRIM-19), an essential subunit of the mitochondrial respiratory chain complex I, was progressively lost along with malignant transformation of human CAG, little is known about the potential link between GRIM-19 loss and CAG pathogenesis. Here, we show that lower GRIM-19 is associated with higher NF-кB RelA/p65 and NLR family pyrin domain-containing 3 (NLRP3) levels in CAG lesions. Functionally, GRIM-19 deficiency fails to drive direct differentiation of human GES-1 cells into IM or SPEM-like cell lineages in vitro, whereas parietal cells (PCs)-specific GRIM-19 knockout disturbs gastric glandular differentiation and promotes spontaneous gastritis and SPEM pathogenesis without intestinal characteristics in mice. Mechanistically, GRIM-19 loss causes chronic mucosal injury and aberrant NRF2 (Nuclear factor erythroid 2-related factor 2)- HO-1 (Heme oxygenase-1) activation via reactive oxygen species (ROS)-mediated oxidative stress, resulting in aberrant NF-кB activation by inducing p65 nuclear translocation via an IKK/IкB partner, while NRF2-HO-1 activation contributes to GRIM-19 loss-driven NF-кB activation via a positive feedback NRF2-HO-1 loop. Furthermore, GRIM-19 loss did not cause obvious PCs loss but triggers NLRP3 inflammasome activation in PCs via a ROS-NRF2-HO-1-NF-кB axis, leading to NLRP3-dependent IL-33 expression, a key mediator for SPEM formation. Moreover, intraperitoneal administration of NLRP3 inhibitor MCC950 drastically attenuates GRIM-19 loss-driven gastritis and SPEM in vivo. Our study suggests that mitochondrial GRIM-19 maybe a potential pathogenetic target for the SPEM pathogenesis, and its deficiency promotes SPEM through NLRP3/IL-33 pathway via a ROS-NRF2-HO-1-NF-кB axis. This finding not only provides a causal link between GRIM-19 loss and SPEM pathogenesis, but offers potential therapeutic strategies for the early prevention of intestinal GC.

IL-24 intrinsically regulates Th17 cell pathogenicity in mice

In certain instances, Th17 responses are associated with severe immunopathology. T cell–intrinsic mechanisms that restrict pathogenic effector functions have been described for type 1 and 2 responses but are less well studied for Th17 cells. Here, we report a cell-intrinsic feedback mechanism that controls the pathogenicity of Th17 cells. Th17 cells produce IL-24, which prompts them to secrete IL-10. The IL-10–inducing function of IL-24 is independent of the cell surface receptor of IL-24 on Th17 cells. Rather, IL-24 is recruited to the inner mitochondrial membrane, where it interacts with the NADH dehydrogenase (ubiquinone) 1 α subcomplex subunit 13 (also known as Grim19), a constituent of complex I of the respiratory chain. Together, Grim19 and IL-24 promote the accumulation of STAT3 in the mitochondrial compartment. We propose that IL-24–guided mitochondrial STAT3 constitutes a rheostat to blunt extensive STAT3 deflections in the nucleus, which might then contribute to a robust IL-10 response in Th17 cells and a restriction of immunopathology in experimental autoimmune encephalomyelitis.

GRIM-19 is a target of mycobacterial Zn2+ metalloprotease 1 and indispensable for NLRP3 inflammasome activation

Tuberculosis is a communicable disease caused by Mycobacterium tuberculosis which primarily infects macrophages and establishes intracellular parasitism. A mycobacterial virulence factor Zn²⁺ metalloprotease 1 (Zmp1) is known to suppress interleukin (IL)-1β production by inhibiting caspase-1 resulting in phagosome maturation arrest. However, the molecular mechanism of caspase-1 inhibition by Zmp1 is still elusive. Here, we identified GRIM-19 (also known as NDUFA13), an essential subunit of mitochondrial respiratory chain complex I, as a novel Zmp1-binding protein. Using the CRISPR/Cas9 system, we generated GRIM-19 knockout murine macrophage cell line J774.1 and found that GRIM-19 is essential for IL-1β production during mycobacterial infection as well as in response to NLRP3 inflammasome-activating stimuli such as extracellular ATP or nigericin. We also found that GRIM-19 is required for the generation of mitochondrial reactive oxygen species and NLRP3-dependent activation of caspase-1. Loss of GRIM-19 or forced expression of Zmp1 resulted in a decrease in mitochondrial membrane potential. Our study revealed a previously unrecognized role of GRIM-19 as an essential regulator of NLRP3 inflammasome and a molecular mechanism underlying Zmp1-mediated suppression of IL-1β production during mycobacterial infection.

STAT3β disrupted mitochondrial electron transport chain enhances chemosensitivity by inducing pyroptosis in esophageal squamous cell carcinoma

The clinical efficacy of cisplatin in the treatment of esophageal squamous cell carcinoma (ESCC) is undesirable. Signal transducer and activator of transcription 3β (STAT3β), a splice variant of STAT3, restrains STAT3α activity and enhances chemosensitivity in ESCC. However, the underlying molecular mechanisms remain poorly understood. Here, we found that high expression of STAT3β contributes to cisplatin sensitivity and enhances Gasdermin E (GSDME) dependent pyroptosis in ESCC cells after exposure to cisplatin. Mechanistically, STAT3β was located into the mitochondria and its high expression disrupts the activity of the electron transport chain, resulting in an increase of ROS in cisplatin treatment cells. While high levels of ROS caused activation of caspase-3 and GSDME, and induced cell pyroptosis. STAT3β blocked the phosphorylation of STAT3α S727 in mitochondria by interacting with ERK1/2 following cisplatin treatment, disrupting electron transport chain and inducing activation of GSDME. Clinically, high expression of both STAT3β and GSDME was strongly associated with better overall survival and disease-free survival of ESCC patients. Overall, our study reveals that STAT3β sensitizes ESCC cells to cisplatin by disrupting mitochondrial electron transport chain and enhancing pyroptosis, which demonstrates the prognostic significance of STAT3β in ESCC therapy.

Structural exploration with AlphaFold2-generated STAT3α structure reveals selective elements in STAT3α-GRIM-19 interactions involved in negative regulation

STAT3, an important transcription factor constitutively activated in cancers, is bound specifically by GRIM-19 and this interaction inhibits STAT3-dependent gene expression. GRIM-19 is therefore, considered as an inhibitor of STAT3 and may be an effective anti-cancer therapeutic target. While STAT3 exists in a dimeric form in the cytoplasm and nucleus, it is mostly present in a monomeric form in the mitochondria. Although GRIM-19-binding domains of STAT3 have been identified in independent experiments, yet the identified domains are not the same, and hence, discrepancies exist. Human STAT3-GRIM-19 complex has not been crystallised yet. Dictated by fundamental biophysical principles, the binding region, interactions and effects of hotspot mutations can provide us a clue to the negative regulatory mechanisms of GRIM-19. Prompted by the very nature of STAT3 being a challenging molecule, and to understand the structural basis of binding and interactions in STAT3α-GRIM-19 complex, we performed homology modelling and ab-initio modelling with evolutionary information using I-TASSER and avant-garde AlphaFold2, respectively, to generate monomeric, and subsequently, dimeric STAT3α structures. The dimeric form of STAT3α structure was observed to potentially exist in an anti-parallel orientation of monomers. We demonstrate that during the interactions with both unphosphorylated and phosphorylated STAT3α, the NTD of GRIM-19 binds most strongly to the NTD of STAT3α, in direct contrast to the earlier works. Key arginine residues at positions 57, 58 and 68 of GRIM-19 are mainly involved in the hydrogen-bonded interactions. An intriguing feature of these arginine residues is that these display a consistent interaction pattern across unphosphorylated and phosphorylated monomers as well as unphosphorylated dimers in STAT3α-GRIM-19 complexes. MD studies verified the stability of these complexes. Analysing the binding affinity and stability through free energy changes upon mutation, we found GRIM-19 mutations Y33P and Q61L and among GRIM-19 arginines, R68P and R57M, to be one of the top-most major and minor disruptors of binding, respectively. The proportionate increase in average change in binding affinity upon mutation was inclined more towards GRIM-19 mutants, leading to the surmise that GRIM-19 may play a greater role in the complex formation. These studies propound a novel structural perspective of STAT3α-GRIM-19 binding and inhibitory mechanisms in both the monomeric and dimeric forms of STAT3α as compared to that observed from the earlier experiments, these experimental observations being inconsistent among each other.

Regulation of STAT3 and its role in cardioprotection by conditioning: focus on non-genomic roles targeting mitochondrial function

Ischemia–reperfusion injury (IRI) is one of the biggest challenges for cardiovascular researchers given the huge death toll caused by myocardial ischemic disease. Cardioprotective conditioning strategies, namely pre- and post-conditioning maneuvers, represent the most important strategies for stimulating pro-survival pathways essential to preserve cardiac health. Conditioning maneuvers have proved to be fundamental for the knowledge of the molecular basis of both IRI and cardioprotection. Among this evidence, the importance of signal transducer and activator of transcription 3 (STAT3) emerged. STAT3 is not only a transcription factor but also exhibits non-genomic pro-survival functions preserving mitochondrial function from IRI. Indeed, STAT3 is emerging as an influencer of mitochondrial function to explain the cardioprotection phenomena. Studying cardioprotection, STAT3 proved to be crucial as an element of the survivor activating factor enhancement (SAFE) pathway, which converges on mitochondria and influences their function by cross-talking with other cardioprotective pathways. Clearly there are still some functional properties of STAT3 to be discovered. Therefore, in this review, we highlight the evidence that places STAT3 as a promoter of the metabolic network. In particular, we focus on the possible interactions of STAT3 with processes aimed at maintaining mitochondrial functions, including the regulation of the electron transport chain, the production of reactive oxygen species, the homeostasis of Ca²⁺ and the inhibition of opening of mitochondrial permeability transition pore. Then we consider the role of STAT3 and the parallels between STA3/STAT5 in cardioprotection by conditioning, giving emphasis to the human heart and confounders.

The role of understudied post-translational modifications for the behavior and function of Signal Transducer and Activator of Transcription 3

The Signal Transducer and Activator of Transcription (STAT) family of transcription factors is involved in inflammation, immunity, development, cancer, and response to injury, among other biological phenomena. Canonical STAT signaling is often represented as a 3-step pathway involving the sequential activation of a membrane receptor, an intermediate kinase, and a STAT transcription factor. The rate-limiting phosphorylation at a highly conserved C-terminal tyrosine residue determines the nuclear translocation and transcriptional activity of STATs. This apparent simplicity is actually misleading and can hardly explain the pleiotropic nature of STATs, the existence of various noncanonical STAT pathways, or the key role of the N-terminal domain in STAT functions. More than 80 post-translational modifications (PTMs) have been identified for STAT3, but their functions remain barely understood. Here, we provide a brief but comprehensive overview of these underexplored PTMs and their role on STAT3 canonical and noncanonical functions. A less tyrosine-centric point of view may be required to advance our understanding of STAT signaling.

GRIM19 Impedes Obesity by Regulating Inflammatory White Fat Browning and Promoting Th17/Treg Balance

Obesity, a condition characterized by excessive accumulation of body fat, is a metabolic disorder related to an increased risk of chronic inflammation. Obesity is mediated by signal transducer and activator of transcription (STAT) 3, which is regulated by genes associated with retinoid-interferon-induced mortality (GRIM) 19, a protein ubiquitously expressed in various human tissues. In this study, we investigated the role of GRIM19 in diet-induced obese C57BL/6 mice via intravenous or intramuscular administration of a plasmid encoding GRIM19. Splenocytes from wild-type and GRIM19-overexpressing mice were compared using enzyme-linked immunoassay, real-time polymerase chain reaction, Western blotting, flow cytometry, and histological analyses. GRIM19 attenuated the progression of obesity by regulating STAT3 activity and enhancing brown adipose tissue (BAT) differentiation. GRIM19 regulated the differentiation of mouse-derived 3T3-L1 preadipocytes into adipocytes, while modulating gene expression in white adipose tissue (WAT) and BAT. GRIM19 overexpression reduced diet-induced obesity and enhanced glucose and lipid metabolism in the liver. Moreover, GRIM19 overexpression reduced WAT differentiation and induced BAT differentiation in obese mice. GRIM19-transgenic mice exhibited reduced mitochondrial superoxide levels and a reciprocal balance between Th17 and Treg cells. These results suggest that GRIM19 attenuates the progression of obesity by controlling adipocyte differentiation.

Mitochondrial GRIM-19 deficiency facilitates gastric cancer metastasis through oncogenic ROS-NRF2-HO-1 axis via a NRF2-HO-1 loop

BACKGROUND

NRF2, a prime target of cellular defense against oxidative stress, has shown a dark side profile in cancer progression. GRIM-19, an essential subunit of the mitochondrial MRC complex I, was recently identified as a suppressive role in tumorigenesis of human gastric cancer (GC). However, little information is available on the role of GRIM-19 and its cross-talk with NRF2 in GC metastasis.

METHODS

Online GC database was used to investigate DNA methylation and survival outcomes of GRIM-19. CRISPR/Cas9 lentivirus-mediated gene editing, metastasis mice models and pharmacological intervention were applied to investigate the role of GRIM-19 deficiency in GC metastasis. Quantitative RT-PCR, FACS, Western blot, IHC, IF and reporter gene assay were performed to explore underlying mechanisms.

RESULTS

Low GRIM-19 is correlated with poor survival outcome of GC patients while DNA hypermethylation is associated with GRIM-19 downregulation. GRIM-19 deficiency facilitates GC metastasis and triggers aberrant oxidative stress as well as ROS-dependent NRF2-HO-1 activation. Experimental interventions of specific ROS, NRF2 or HO-1 inhibitor significantly abrogate GRIM-19 deficiency-driven GC metastasis in vitro and in vivo. Moreover, HO-1 inhibition not only reverses GRIM-19 deficiency-driven NRF2 activation, but also feedback blocks NRF2 activator-induced NRF2 signaling, resulting in decreased metastasis-associated genes.

CONCLUSIONS

Our data suggest that GRIM-19 deficiency accelerates GC metastasis through the oncogenic ROS-NRF2-HO-1 axis via a positive-feedback NRF2-HO-1 loop. Therefore, this study not only offers novel insights into the role of oncogenic NRF2 in tumor progression, but also provides new strategies to alleviate the dark side of NRF2 by targeting HO-1.

Stat3 oxidation-dependent regulation of gene expression impacts on developmental processes and involves cooperation with Hif-1α

Reactive oxygen species are bona fide intracellular second messengers that influence cell metabolism and aging by mechanisms that are incompletely resolved. Mitochondria generate superoxide that is dis-mutated to hydrogen peroxide, which in turn oxidises cysteine-based enzymes such as phosphatases, peroxiredoxins and redox-sensitive transcription factors to modulate their activity. Signal Transducer and Activator of Transcription 3 (Stat3) has been shown to participate in an oxidative relay with peroxiredoxin II but the impact of Stat3 oxidation on target gene expression and its biological consequences remain to be established. Thus, we created murine embryonic fibroblasts (MEFs) that express either WT-Stat3 or a redox-insensitive mutant of Stat3 (Stat3-C3S). The Stat3-C3S cells differed from WT-Stat3 cells in morphology, proliferation and resistance to oxidative stress; in response to cytokine stimulation, they displayed elevated Stat3 tyrosine phosphorylation and Socs3 expression, implying that Stat3-C3S is insensitive to oxidative inhibition. Comparative analysis of global gene expression in WT-Stat3 and Stat3-C3S cells revealed differential expression (DE) of genes both under basal conditions and during oxidative stress. Using differential gene regulation pattern analysis, we identified 199 genes clustered into 10 distinct patterns that were selectively responsive to Stat3 oxidation. GO term analysis identified down-regulated genes to be enriched for tissue/organ development and morphogenesis and up-regulated genes to be enriched for cell-cell adhesion, immune responses and transport related processes. Although most DE gene promoters contain consensus Stat3 inducible elements (SIEs), our chromatin immunoprecipitation (ChIP) and ChIP-seq analyses did not detect Stat3 binding at these sites in control or oxidant-stimulated cells, suggesting that oxidised Stat3 regulates these genes indirectly. Our further computational analysis revealed enrichment of hypoxia response elements (HREs) within DE gene promoters, implying a role for Hif-1. Experimental validation revealed that efficient stabilisation of Hif-1α in response to oxidative stress or hypoxia required an oxidation-competent Stat3 and that depletion of Hif-1α suppressed the inducible expression of Kcnb1, a representative DE gene. Our data suggest that Stat3 and Hif-1α cooperate to regulate genes involved in immune functions and developmental processes in response to oxidative stress.

Transcriptomic and Quantitative Proteomic Profiling Reveals Signaling Pathways Critical for Pancreatic Islet Maturation

Pancreatic β-cell dysfunction and reduced insulin secretion play a key role in the pathogenesis of diabetes. Fetal and neonatal islets are functionally immature and have blunted glucose responsiveness and decreased insulin secretion in response to stimuli and are far more proliferative. However, the mechanisms underlying functional immaturity are not well understood. Pancreatic islets are composed of a mixture of different cell types, and the microenvironment of islets and interactions between these cell types are critical for β-cell development and maturation. RNA sequencing and quantitative proteomic data from intact islets isolated from fetal (embryonic day 19) and 2-week-old Sprague-Dawley rats were integrated to compare their gene and protein expression profiles. Ingenuity Pathway Analysis (IPA) was also applied to elucidate pathways and upstream regulators modulating functional maturation of islets. By integrating transcriptome and proteomic data, 917 differentially expressed genes/proteins were identified with a false discovery rate of less than 0.05. A total of 411 and 506 of them were upregulated and downregulated in the 2-week-old islets, respectively. IPA revealed novel critical pathways associated with functional maturation of islets, such as AMPK (adenosine monophosphate-activated protein kinase) and aryl hydrocarbon receptor signaling, as well as the importance of lipid homeostasis/signaling and neuronal function. Furthermore, we also identified many proteins enriched either in fetal or 2-week-old islets related to extracellular matrix and cell communication, suggesting that these pathways play critical roles in islet maturation. Our present study identified novel pathways for mature islet function in addition to confirming previously reported mechanisms, and provided new mechanistic insights for future research on diabetes prevention and treatment.

GRIM-19 Ameliorates Multiple Sclerosis in a Mouse Model of Experimental Autoimmune Encephalomyelitis with Reciprocal Regulation of IFNγ/Th1 and IL-17A/Th17 Cells

The protein encoded by the Gene Associated with Retinoid-Interferon-Induced Mortality-19 (GRIM-19) is located in the mitochondrial inner membrane and is homologous to the NADH dehydrogenase 1-alpha subcomplex subunit 13 of the electron transport chain. Multiple sclerosis (MS) is a demyelinating disease that damages the brain and spinal cord. Although both the cause and mechanism of MS progression remain unclear, it is accepted that an immune disorder is involved. We explored whether GRIM-19 ameliorated MS by increasing the levels of inflammatory cytokines and immune cells; we used a mouse model of experimental autoimmune encephalomyelitis (EAE) to this end. Six-to-eight-week-old male C57BL/6, IFNγ-knockout (KO), and GRIM-19 transgenic mice were used; EAE was induced in all strains. A GRIM-19 overexpression vector (GRIM19 OVN) was electrophoretically injected intravenously. The levels of Th1 and Th17 cells were measured via flow cytometry, immunofluorescence, and immunohistochemical analysis. IL-17A and IFNγ expression levels were assessed via ELISA and quantitative PCR. IL-17A expression decreased and IFNγ expression increased in EAE mice that received injections of the GRIM19 OVN. GRIM-19 transgenic mice expressed more IFNγ than did wild-type mice; this inhibited EAE development. However, the effect of GRIM-19 overexpression on the EAE of IFNγ-KO mice did not differ from that of the empty vector. GRIM-19 expression was therapeutic for EAE mice, elevating the IFNγ level. GRIM-19 regulated the Th17/Treg cell balance.

The proinflammatory cytokines IL-1β and TNF-α modulate corneal epithelial wound healing through p16Ink4a suppressing STAT3 activity

The proinflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are involved in the corneal inflammatory response and wound healing following corneal injuries. However, the mechanism by which proinflammatory cytokines modulate corneal epithelial wound healing remains unclear. In this study, we found that IL-1β or TNF-α was transiently elevated during corneal epithelial wound healing in mice. After corneal epithelial debridement, persistent treatment with IL-1β or TNF-α restrained the level of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) and boosted the level of cell cycle inhibitor p16^Ink4a , resulting in impaired corneal epithelial repair. When p16^Ink4a was deleted, the p-STAT3 level in corneal epithelium was enhanced and corneal epithelial wound healing was clearly accelerated. In diabetic mice, IL-1β, TNF-α, and p16^Ink4a appeared a sustained and strong expression in the corneal epithelium, and p16^Ink4a knockdown partially reverted the defective diabetic corneal epithelial repair. Furthermore, immunoprecipitation proved that p16^Ink4a interacted with p-STAT3 and thus possibly suppressed the STAT3 activity. Our findings revealed a novel mechanism that the proinflammatory cytokines modulate corneal epithelial wound healing via the p16^Ink4a -STAT3 signaling.

Heterogeneity of GRIM-19 Expression in the Adult Mouse Brain

Gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) is a subunit of the mitochondrial respiratory chain complex I that has a significant effect on ATP production. The brain is particularly susceptible to ATP deficiency due to its limited energy storage capability and its high rate of oxygen consumption. Thus, GRIM-19 might be involved in regulating ATP level in the brain or cell death caused by several neurological disorders. To understand the physiological and pathophysiological roles of GRIM-19 in the brain, a thorough investigation of the neuroanatomic distribution of GRIM-19 in the normal brain is necessary. Therefore, the present study examined the distribution patterns of GRIM-19 in the adult C57BL/6 mouse brain using immunohistochemistry and identified cell types expressing GRIM-19 using double immunofluorescence staining. We found that GRIM-19 was ubiquitously but not homogenously expressed throughout the brain. GRIM-19 immunoreactivity was predominantly observed in neurons, but not in astrocytes, microglia, or oligodendrocytes under normal physiological conditions. Following transient global cerebral ischemia, GRIM-19-positive immunoreactivity was, however, observed in neurons as well as glial cells including astrocytes in the hippocampus. Furthermore, GRIM-19 was weakly expressed in the hippocampal subgranular zone, in which neural stem and progenitor cells are abundant, but highly expressed in the immature and mature neuronal cells in the granular cell layer of the normal brain, suggesting an inverse correlation between expression of GRIM-19 and stemness activity. Collectively, our study demonstrating widespread and differential distribution of GRIM-19 in the adult mouse brain contributes to investigating the functional and pathophysiological roles of this protein.

OLFM4 Enhances STAT3 Activation and Promotes Tumor Progression by Inhibiting GRIM19 Expression in Human Hepatocellular Carcinoma

Olfactomedin 4 (OLFM4) induces signal transducer and activator of transcription 3 (STAT3) activation by inhibiting gene associated with retinoid-interferon-induced mortality 19 (GRIM19), a strong STAT3 suppressor gene; however, the mechanisms of OLFM4 for regulating GRIM19-STAT3 cascade in hepatocellular carcinoma (HCC) remain unclear. The functions and regulations of OLFM4, GRIM19, and STAT3 activation in HCC progression were evaluated using surgical specimens collected from 111 HCC patients or 2 HCC cell lines in vitro. Moreover, the cancer stem cell-like property of OLFM4 mediated by leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), known as an intestinal stem cell marker, was investigated. OLFM4 was increased in HCC compared with adjacent liver tissue. The multivariate analysis revealed that high OLFM4 expression was an independent factor for poor prognosis. OLFM4 expression was negatively correlated with GRIM19 expression and positively correlated with STAT3 activation in HCC, thereby increasing cell cycle progression. OLFM4 knockdown in HCC cells increased GRIM19 expression and inhibited STAT3 activation; however, after double knockdown of GRIM19 and OLFM4, STAT3 activation decreased by OLFM4 knockdown was increased again. OLFM4 knockdown increased cell apoptosis, inhibited cell proliferation, and suppressed cancer stem cell-like property in HCC cells. The incidence of hematogenous recurrence was higher in HCC patients with high OLFM4 expression, suggesting that anoikis resistance of HCC was enhanced by OLFM4. In clinical cases, LGR5 expression and CD133 expression was correlated with OLFM4 expression in HCC, leading to poor patient prognosis. In vitro, LGR5 enhanced cancer stem cell-like property by up-regulating OLFM4 through the Wnt signaling pathway. Conclusion: OLFM4 is induced by the LGR5-Wnt signaling pathway and is strongly associated with aggressive tumor progression and poor prognosis in HCC by regulating STAT3-induced tumor cell proliferation and cancer stem cell-like property. Therefore, OLFM4 is a novel prognostic predictor and a potential therapeutic target for patients with HCC.

Fine-Tuning Cytokine Signals

Cytokines are secreted or otherwise released polypeptide factors that exert autocrine and/or paracrine actions, with most cytokines acting in the immune and/or hematopoietic system. They are typically pleiotropic, controlling development, cell growth, survival, and/or differentiation. Correspondingly, cytokines are clinically important, and augmenting or attenuating cytokine signals can have deleterious or therapeutic effects. Besides physiological fine-tuning of cytokine signals, altering the nature or potency of the signal can be important in pathophysiological responses and can also provide novel therapeutic approaches. Here, we give an overview of cytokines, their signaling and actions, and the physiological mechanisms and pharmacologic strategies to fine-tune their actions. In particular, the differential utilization of STAT proteins by a single cytokine or by different cytokines and STAT dimerization versus tetramerization are physiological mechanisms of fine-tuning, whereas anticytokine and anticytokine receptor antibodies and cytokines with altered activities, including cytokine superagonists, partial agonists, and antagonists, represent new ways of fine-tuning cytokine signals.

GRIM-19 repressed hypoxia-induced invasion and EMT of colorectal cancer by repressing autophagy through inactivation of STAT3/HIF-1α signaling axis

Hypoxia leads to cancer progression and promotes the metastatic potential of cancer cells. Thereby, the aim of the present study was to investigate the detailed effects of gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) in colorectal cancer (CRC) cell lines under hypoxia conditions and explore the potential molecular mechanisms. Here, we observed that GRIM-19 expression was downregulated in several CRC cell lines as well as in HCT116 and Caco-2 cells under a hypoxic microenvironment. Additionally, the introduction of GRIM-19 obviously suppressed cell invasive ability and epithelial-mesenchymal transition (EMT) through modulating EMT markers as reflected by the upregulation of E-cadherin along with the downregulation of vimentin and N-cadherin under hypoxic conditions. Moreover, the addition of GRIM-19 repressed hypoxia-induced autophagy through modulating autophagy associated proteins as reflected by the downregulation of LC3-II/LC3-I ratio and Beclin-1 expression, as well as the increased of p62 expression. Interestingly, overexpression of GRIM-19 markedly ameliorated the accumulation of HIF-1α triggered by hypoxia accompanied by an inhibition of vascular endothelial growth factor (VEGF) production and phospho-signal transducer and activator of transcription 3 (p-STAT3) expression. Further data demonstrated that GRIM-19 have a negative feedback effect on the expression of HIF-1α. Mechanistically, re-expression of HIF-1α completely reversed the inhibitory effects of GRIM-19 on hypoxia-induced invasion and EMT. Taken all data together, our findings established that GRIM-19 suppresses hypoxia-triggered invasion and EMT by inhibiting hypoxia-induced autophagy through inactivation HIF-1α/STAT3 signaling pathway, indicating that GRIM-19 may serve as a potential predictive factor and therapeutic target for CRC treatment.

STAT3 Interactors as Potential Therapeutic Targets for Cancer Treatment

Signal transducers and activators of transcription (STATs) mediate essential signaling pathways in different biological processes, including immune responses, hematopoiesis, and neurogenesis. Among the STAT members, STAT3 plays crucial roles in cell proliferation, survival, and differentiation. While STAT3 activation is transient in physiological conditions, STAT3 becomes persistently activated in a high percentage of solid and hematopoietic malignancies (e.g., melanoma, multiple myeloma, breast, prostate, ovarian, and colon cancers), thus contributing to malignant transformation and progression. This makes STAT3 an attractive therapeutic target for cancers. Initial strategies aimed at inhibiting STAT3 functions have focused on blocking the action of its activating kinases or sequestering its DNA binding ability. More recently, the diffusion of proteomic-based techniques, which have allowed for the identification and characterization of novel STAT3-interacting proteins able to modulate STAT3 activity via its subcellular localization, interact with upstream kinases, and recruit transcriptional machinery, has raised the possibility to target such cofactors to specifically restrain STAT3 oncogenic functions. In this article, we summarize the available data about the function of STAT3 interactors in malignant cells and discuss their role as potential therapeutic targets for cancer treatment.

STAT3: a multifaceted oncoprotein

Signal transducer and activator of transcription (STAT) 3 is a key signalling protein engaged by a multitude of growth factors and cytokines to elicit diverse biological outcomes including cellular growth, differentiation, and survival. The complete loss of STAT3 is not compatible with life and even partial loss of function mutations lead to debilitating pathologies like hyper IgE syndrome. Conversely, augmented STAT3 activity has been reported in as many as 50% of all human tumours. The dogma of STAT3 activity posits that it is a tyrosine phosphorylated transcription factor which modulates the expression of hundreds of genes. However, the regulation and biological consequences of STAT3 activation are far more complex. In addition to tyrosine phosphorylation, STAT3 is decorated with a plethora of post-translational modifications which regulate STAT3's nuclear function in addition to its non-genomic activities. In addition to these emerging complexities in the biochemical regulation of STAT3 activity, recent studies reveal that STAT3 is either oncogenic or a tumour suppressor. This review will explore these complexities.

Mechanisms of Mitochondrial Redox Signaling in Psychosocial Stress-Responsive Systems: New Insights into an Old Story

SIGNIFICANCE

Psychosocial stress is associated with alterations in serum glucocorticoids and cytokines, such as interleukin-6 (IL-6) and IL-1β, which functionally interact. However, the molecular mechanisms and physiological relationship between the two systems within the context of stress exposure are not well characterized. Recent Advances: Extracellular IL-6, which stimulates the release of cortisol from the zona fasciculata of the adrenal cortex, mediates its intracellular effects by tyrosine phosphorylation of the transcription factor signal transducer and activator of transcription 3 (STAT3). Mitochondrial electron transfer reactions are involved in both STAT3-driven ATP production in oxidative respiration and adrenocortical steroid biosynthesis.

CRITICAL ISSUES

The role of STAT3 in oxidative respiration and steroidogenesis suggests that it integrates both nuclear and mitochondrial actions, thereby preserving main steps of glucocorticoid biosynthesis in the adrenal gland under psychosocial stress. This review discusses the notion that these two pathways are together simultaneously involved in protection against chronic stressors.

FUTURE DIRECTIONS

Linking the function of cytokines and main components of the hypothalamic-pituitary-adrenal (HPA) axis to molecular mechanisms of mitochondrial redox signaling will be essential for a better understanding of the relevant stress-responsive systems engaged in stress vulnerability. Antioxid. Redox Signal. 28, 760-772.

miR-6743-5p, as a direct upstream regulator of GRIM-19, enhances proliferation and suppresses apoptosis in glioma cells

Gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) has been recognized as a tumor suppressor protein, which regulates cell growth, apoptosis, and migration by signal transducer and activator of transcription 3 (STAT3) signaling pathway and non-STAT3 pathway in glioma cells. Here, we investigated the molecular mechanisms that regulated GRIM-19 expression in glioma cells. By the TargetScan algorithm, four miRNAs, hsa-miR-17-3p, hsa-miR-423-5p, hsa-miR-3184-5p, and hsa-miR-6743-5p, were identified with the potential to bind with 3′-UTR of GRIM-19. Further miRNA inhibitor transfection and luciferase assays revealed that miR-6743-5p was able to directly target the 3′-UTR of GRIM-19. Additionally, miR-6743-5p expression was inversely related with GRIM-19 expression in glioma specimens and cell lines. Moreover, the inhibition of miR-6743-5p caused a significant inhibition of cell proliferation and a marked promotion of cell apoptosis in glioma cells, and this phenotype was rescued by GRIM-19 knockdown. Finally, the inhibition of miR-6743-5p expression suppressed the phosphorylation of STAT3, and the mRNA expression of CyclinD1 and Bcl-2, two target genes of STAT3, while miR-6743-5p mimic had the inversed effects. Treatment with STAT3 inhibitor AG490 partially rescued the proliferation-promoting and anti-apoptosis effects of miR-6743-5p overexpression or GRIM-19 knockdown. Collectively, miR-6743-5p may act as an oncomiRNA in glioma by targetting GRIM-19 and STAT3.

Prognostic value of GRIM-19, NF-κB and IKK2 in patients with high-grade serous ovarian cancer

AIMS

High grade serous carcinoma (HGSC) is an aggressive tumour, and most patients relapse after treatment, acquiring resistance to platinum-based chemotherapy. One of the resistance mechanisms proposed is apoptosis evasion triggered by drug-related cytotoxic effect in the cell. In this context, this study aims to evaluate the protein expression of GRIM-19, NF-κB and IKK2, their association with chemotherapy response and to determine their prognostic values in HGSC.

METHODS

GRIM-19, NF-κB and IKK2 expression was evaluated by immunohistochemistry (IHC) in 71 patients with HGSC selected between 2003 and 2013, whose underwent primary debulking surgery with complete cytoreduction. Protein expression was analyzed in relation to platinum response groups, tumour progression, clinicopathological data and survival.

RESULTS

Positive IKK2 expression was related to resistance (p = 0.011), shorter disease-free survival (p = 0.001) and overall survival (p = 0.026) and was also a risk factor for relapse (p = 0.002) and death (p = 0.032). The association between IKK2 and NF-κB positivity predicted a subgroup with shorter overall survival (p = 0.004), disease-free survival (p = 0.003) and resistance to platinum-based chemotherapy (p = 0.036). NF-κB positivity was associated with worse overall survival (p = 0.005) and disease-free survival (p = 0.027) and was a positive predictor for relapse (p = 0.032) and death (p = 0.008). Higher expression of GRIM-19 was associated with higher disease-free survival (p = 0.039) and was a negative predictor for relapse (p = 0.046).

CONCLUSIONS

GRIM-19 is a potential predictor of prognosis and disease recurrence in HGSC. IKK2 and NF-κB are related to poor prognosis and are potential predictors of response to platinum-based chemotherapy in HGSC. IHC analyses of GRIM19, IKK2 and NF-κB may be important in the attempt to provide prognostic values for relapse and response to treatment in patients with HGSC.

The complex roles of STAT3 and STAT5 in maintaining redox balance: Lessons from STAT-mediated xCT expression in cancer cells

STAT3 and STAT5 mediate diverse cellular processes, transcriptionally regulating gene expression and interacting with cytoplasmic proteins. Their canonical activity is stimulated by cytokines/growth factors through JAK-STAT signaling. As targets of oncogenes with intrinsic tyrosine kinase activity, STAT3 and STAT5 become constitutively active in hematologic neoplasms and solid tumors, promoting cell proliferation and survival and modulating redox homeostasis. This review summarizes reactive oxygen species (ROS)-regulated STAT activation and how STATs influence ROS production. ROS-induced effects on post-translational modifications are presented, and STAT3/5-mediated regulation of xCT, a redox-sensitive target up-regulated in numerous cancers, is discussed with regard to transcriptional cross-talk.

Mitochondrial Metabolism in Aging Heart

Altered mitochondrial metabolism is the underlying basis for the increased sensitivity in the aged heart to stress. The aged heart exhibits impaired metabolic flexibility, with a decreased capacity to oxidize fatty acids and enhanced dependence on glucose metabolism. Aging impairs mitochondrial oxidative phosphorylation, with a greater role played by the mitochondria located between the myofibrils, the interfibrillar mitochondria. With aging, there is a decrease in activity of complexes III and IV, which account for the decrease in respiration. Furthermore, aging decreases mitochondrial content among the myofibrils. The end result is that in the interfibrillar area, there is ≈50% decrease in mitochondrial function, affecting all substrates. The defective mitochondria persist in the aged heart, leading to enhanced oxidant production and oxidative injury and the activation of oxidant signaling for cell death. Aging defects in mitochondria represent new therapeutic targets, whether by manipulation of the mitochondrial proteome, modulation of electron transport, activation of biogenesis or mitophagy, or the regulation of mitochondrial fission and fusion. These mechanisms provide new ways to attenuate cardiac disease in elders by preemptive treatment of age-related defects, in contrast to the treatment of disease-induced dysfunction.

Signal Transducers and Activators of Transcription: Insights into the Molecular Basis of Oral Cancer

Recent efforts on developing more direct and effective targets for cancer therapy have revolved around a family of transcription factors known as STATs (signal transducers and activators of transcription). STAT proteins are latent cytoplasmic transcription factors that become activated in response to extracellular signaling proteins. STAT proteins have been convincingly reported to possess oncogenic properties in a plethora of human cancers, including oral and oropharyngeal cancer. Signal transduction pathways mediated by these oncogenic transcription factors and their regulation in oral cancer are the focus of this review.

GRIM-19: A master regulator of cytokine induced tumor suppression, metastasis and energy metabolism

Cytokines induce cell proliferation or growth suppression depending on the context. It is increasingly becoming clear that success of standard radiotherapy and/or chemotherapeutics to eradicate solid tumors is dependent on IFN signaling. In this review we discuss the molecular mechanisms of tumor growth suppression by a gene product isolated in our laboratory using a genome-wide expression knock-down strategy. Gene associated with retinoid-IFN-induced mortality -19 (GRIM-19) functions as non-canonical tumor suppressor by antagonizing oncoproteins. As a component of mitochondrial respiratory chain, GRIM-19 influences the degree of "Warburg effect" in cancer cells as many advanced and/or aggressive tumors show severely down-regulated GRIM-19 levels. In addition, GRIM-19 appears to regulate innate and acquired immune responses in mouse models. Thus, GRIM-19 is positioned at nodes that favor cell protection and/or prevent aberrant cell growth.

GRIM19 ameliorates acute graft-versus-host disease (GVHD) by modulating Th17 and Treg cell balance through down-regulation of STAT3 and NF-AT activation

BACKGROUND

T helper (Th) 17 cells are a subset of T helper cells that express interleukin (IL)-17 and initiate the inflammatory response in autoimmune diseases. Regulatory T cells (Tregs) are a subpopulation of T cells that produce forkhead box P3 (FOXP3) and inhibit the immune response. Graft versus host disease (GVHD) is a complication of allogeneic tissue transplantation, and Th17 cells and their proinflammatory activity play a central role in the pathogenesis of GVHD. Gene associated with retinoid-interferon-induced mortality (GRIM) 19, originally identified as a nuclear protein, is expressed ubiquitously in various human tissues and regulate signal transducer and activator of transcription (STAT)3 activity.

METHODS

Splenoytes and bone marrow cells were transplanted into mice with GVHD. The alloresponse of T cells and GVHD clinical score was measured. Realtime-polymerase chain reaction (realtime-PCR) was used to examine mRNA level. Flow cytometry and enzyme linked immunosorbent assay (ELISA) was used to evaluate protein expression.

RESULTS

A GRIM19 transgenic cell transplant inhibited Th17 cell differentiation, alloreactive T cell responses, and STAT3 expression in mice with GVHD. On the other hand, the differentiation of Tregs and STAT5 production were enhanced by GRIM19. Overall, the severity of GVHD was decreased in mice that had received GRIM19 transgenic bone marrow and spleen transplants. Transplantation from GRIM19-overexpressing cells downregulated the expression of nuclear factor of activated T cells (NFATc1) but promoted the expression of regulator of calcineurin (RCAN)3 while downregulating NFAT-dependent cytokine gene expression. This complex mechanism underlies the therapeutic effect of GRIM19.

CONCLUSIONS

We observed that GRIM19 can reduce Th17 cell differentiation and alloreactive T cell responses in vitro and in vivo. Additionally, GRIM19 suppressed the severity of GVHD by modulating STAT3 activity and controlling Th17 and Treg cell differentiation. These results suggest that GRIM19 attenuates acute GVHD through the inhibition of the excessive inflammatory response mediated by T cell activation.

Mitochondrial GRIM-19 as a potential therapeutic target for STAT3-dependent carcinogenesis of gastric cancer

Aberrant STAT3 activation occurs in most human gastric cancers (GCs) and contributes to the malignant progression of GC, but mechanism(s) underlying aberrant STAT3 remain largely unknown. Here we demonstrated that the gene associated with retinoid interferon-induced mortality 19 (GRIM-19) was severely depressed or lost in GC and chronic atrophic gastritis (CAG) tissues and its loss contributed to GC tumorigenesis partly by activating STAT3 signaling. In primary human GC tissues, GRIM-19 was frequently depressed or lost and this loss correlated with advanced clinical stage, lymph node metastasis, H. pylori infection and poor overall survival of GC patients. In CAG tissues, GRIM-19 was progressively decreased along with its malignant transformation. Functionally, we indentified an oncogenic role of GRIM-19 loss in promoting GC tumorigenesis. Ectopic GRIM-19 expression suppressed GC tumor formation in vitro and in vivo by inducing cell cycle arrest and apoptosis. Moreover, we revealed that GRIM-19 inhibited STAT3 transcriptional activation and its downstream targets by reducing STAT3 nuclear distribution. Conversely, knockdown of GRIM-19 induced aberrant STAT3 activation and accelerated GC cell growth in vitro and in vivo, and this could be partly attenuated by the blockage of STAT3 activation. In addition, we observed subcellular redistributions of GRIM-19 characterized by peri-nuclear aggregates, non-mitochondria cytoplasmic distribution and nuclear invasion, which should be responsible for reduced STAT3 nuclear distribution. Our studies suggest that mitochondrial GRIM-19 could not only serve as an valuable prognostic biomarker for GC development, but also as a potential therapeutic target for STAT3-dependent carcinogenesis of GC.

Grim19 Attenuates DSS Induced Colitis in an Animal Model

DSS induced colitis is a chronic inflammatory disease characterized by inflammation in the gastrointestinal tract, which destabilizes the gut and induces an uncontrolled immune response. Although DSS induced colitis is generally thought to develop as a result of an abnormally active intestinal immune system, its pathogenesis remains unclear. Gene associated with retinoid interferon induced mortality (Grim) 19 is an endogenous specific inhibitor of STAT3, which regulates the expression of proinflammatory cytokines. In this study, we investigated the influence of GRIM19 in a DSS induced colitis mouse model. We hypothesized that Grim19 would ameliorate DSS induced colitis by altering STAT3 activity and intestinal inflammation. Grim19 ameliorated DSS induced colitis severity and protected intestinal tissue. The expression of STAT3 and proinflammatory cytokines such as IL-1β and TNF-α in colon and lymph nodes was decreased significantly by Grim19. Moreover, DSS induced colitis progression in a Grim19 transgenic mouse line was inhibited in association with a reduction in STAT3 and IL-17 expression. These results suggest that Grim19 attenuates DSS induced colitis by suppressing the excessive inflammatory response mediated by STAT3 activation.

Mitochondrial Stat3, the Need for Design Thinking

Stat3 has been studied extensively as a transcription factor, however the finding that Stat3 also localizes to mitochondria has opened a new area to discover non-classical functions. Here we review the current knowledge of mitochondrial Stat3 as a regulator of the electron transport chain (ETC) and its impact on mitochondrial production of ATP and ROS. We also describe recent findings identifying Stat3 as a regulator of mitochondrial Ca(2+) homeostasis through its effect on the ETC. It is becoming evident that these non-classical functions of Stat3 can have a major impact on cancer progression, cardiovascular diseases, and inflammatory diseases. Therefore, mitochondrial Stat3 functions challenge the current design of therapies that solely target Stat3 as a transcription factor and suggest the need for "design thinking," which leads to the development of novel strategies, to intervene the Stat3 pathway.

The GRIM-19 plays a vital role in shrimps' responses to Vibrio alginolyticus

GRIM-19 (gene associated with retinoid-interferon-induced mortality 19), a novel cell death regulatory gene, plays important roles in cell apoptosis, mitochondrial respiratory chain and immune response. It has been reported to interact physically with STAT3 and inhibit STAT3-dependent signal transduction. In this study, a new GRIM-19 gene, which is a 789-bp gene encoding a 149 amino acids protein, is identified and characterized from Litopenaeus vannamei. The tissue distribution patterns showed that LvGRIM-19 was widely expressed in all examined tissues, with the highest expression in muscle. Quantitative real-time PCR revealed that LvGRIM-19 was down-regulated in hepatopancreas after infection with the Vibrio alginolyticus. Knockdown of LvGRIM-19 by RNA interference resulted in a lower mortality of L. vannamei under V. alginolyticus infection, as well as an enhancement in the protein expression of STAT gene and JAK gene. V. alginolyticus infection caused an increase apoptotic cell ratio and ROS production of L. vannamei, while LvGRIM-19 silenced shrimps showed significantly lower than GFP group. Our results suggest that the GRIM-19 plays a vital role in shrimps' responses to V. alginolyticus. Interferenced LvGRIM-19 treatment during V. alginolyticus infection could increase 12 h survival rate, which might indicated that LvGRIM-19 is closely related to death of shrimps.

Thyroid Hürthle cell tumors: research of potential markers of malignancy

INTRODUCTION

Hurthle cell tumors (HCTs) are rare thyroid neoplasia. To date, capsular and/or vascular invasion are the only findings predicting malignancy. Recently, mutation of 19p13, encoding two proteins involved in cell proliferation and apoptosis (GRIM-19 and p19), has been described. The aim of our study is to evaluate the cellular proliferation index (Ki67), GRIM-19 and p19 expression as diagnostic markers of malignancy in HCT.

MATERIALS AND METHODS

Eighty patients with HCT (32 carcinomas, 48 adenomas) whom underwent surgery in our center were included. Samples of both neoplastic lesions and adjacent normal thyroid tissue were analyzed by means of tissue micro-arrays. Correlations between expressions of Ki67, GRIM-19 and p19 and final histology were analyzed.

RESULTS

Mean size of the lesion was higher in carcinomas than in adenomas (p = 0.01). GRIM-19 and p19 were significantly underexpressed in Hurthle cells tumors compared to normal tissue (p = 0.0004 and p = 0.0001, respectively). Ki67 and GRIM-19 were, respectively, higher and down-expressed in carcinomas compared to adenomas (p = 0.0004 and p = 0.005, respectively). On multivariate analysis, size correlates with carcinoma diagnosis. Neither GRIM-19 nor Ki67 index was related to size. The expression of p19 was reduced in both adenoma and carcinoma but differences were not statistically significant (p = 0.13).

CONCLUSIONS

Our study suggest that Ki67 and GRIM-19 correlate with malignancy in HCT. The expression of p19 is down-regulated in HCT, but it is not diagnostic of carcinoma. Ki67 and GRIM-19 may potentially help as cytological markers of malignancy in HCT.

GRIM-19 inhibition induced autophagy through activation of ERK and HIF-1α not STAT3 in Hela cells

Gene associated with retinoid-interferon-induced mortality (GRIM-19), an important subunit of mitochondrial complex I, has been identified as a tumor suppressor, and its reduced expression has been reported to be associated with tumorigenesis and metastasis. Autophagy has been proposed as a protective mechanism for cell survival under various stresses, including chemotherapy. However, it remains unknown whether GRIM-19 is linked to autophagy and chemotherapy resistance. Here, we showed that suppression of GRIM-19 by shRNA enhanced cell-type-dependent autophagy by activating extracellular regulated protein kinase (ERK) and hypoxia inducible factor-1a (HIF-1a) in a reactive oxygen species (ROS)-mediated manner, and thereby conferred resistance to paclitaxel. Besides, the antioxidant N-acetyl-L-cysteine (NAC) and autophagy inhibitor 3-MA could in part overcome this resistance. We also found that GRIM-19 expression was significantly correlated with clinical stage and grade in patients with cervical cancers. Taken together, our results indicated that GRIM-19 inhibition induced autophagy and chemotherapy resistance, which could affect prognosis of cervical cancers. Our study has identified new function of GRIM-19 and its underlying mechanism, and it will provide possible avenues for therapeutic targeting in cervical cancers.

Expression of GRIM-19 in adenomyosis and its possible role in pathogenesis

OBJECTIVE

To study the expression of the gene associated with retinoid-interferon (IFN)-induced mortality 19 (GRIM-19) in the endometrial tissue of patients with adenomyosis and to describe the possible pathogenic mechanisms of this phenomenon.

DESIGN

Experimental study using human samples and cell lines.

SETTING

University-affiliated hospital.

PATIENT(S)

Ectopic and eutopic endometrial tissues were obtained from 30 patients with adenomyosis, whereas normal endometrial specimens were obtained from 10 control patients without adenomyosis.

INTERVENTION(S)

Patients with rapid pathology report-confirmed adenomyosis were recruited, and eutopic and ectopic endometrial tissue samples were collected from patients who had undergone hysterectomies by either the transabdominal or laparoscopic method at Qilu Hospital. Normal endometrial tissue was collected from a group of control patients without adenomyosis.

MAIN OUTCOME MEASURE(S)

Immunohistochemistry (IHC) was performed to evaluate the expression of GRIM-19, phospho-signal transducer and activator of transcription 3 (Y705) (Y705) (pSTAT3(Y705)), and vascular endothelial growth factor (VEGF) in endometrial tissue samples. The protein levels of GRIM-19, pSTAT3(Y705), STAT3, and VEGF were detected by Western blot. Apoptosis in endometrial specimens was assayed by TUNEL. Immunohistochemistry with an antibody directed against CD34 was performed to detect new blood vessels in the endometrial tissue. GRIM-19 small interfering RNA and a recombinant plasmid carrying GRIM-19 were constructed to evaluate the effects of GRIM-19 on the downstream factors pSTAT3(Y705), STAT3, and VEGF in Ishikawa cells.

RESULT(S)

The expression of GRIM-19 was down-regulated in the eutopic endometria of patients with adenomyosis compared with the endometria of patients in the control group, and it was further reduced in the endometrial glandular epithelial cells of adenomyotic lesions. Apoptosis was reduced in the eutopic endometrium compared with the control group, and it was significantly reduced in ectopic endometrial tissues. In addition, the ectopic and eutopic endometria of patients with adenomyosis displayed a much higher microvessel density. In the eutopic and ectopic endometria of patients with adenomyosis, the expression levels of pSTAT3(Y705) and VEGF were significantly higher than in the controls. Furthermore, down-regulation of GRIM-19 in Ishikawa cells significantly promoted the activation of both pSTAT3(Y705) and its dependent gene VEGF.

CONCLUSION(S)

Aberrant expression of GRIM-19 may be associated with adenomyosis through the regulation of apoptosis and angiogenesis.

Pivotal Importance of STAT3 in Protecting the Heart from Acute and Chronic Stress: New Advancement and Unresolved Issues

The transcription factor, signal transducer and activator of transcription 3 (STAT3), has been implicated in protecting the heart from acute ischemic injury under both basal conditions and as a crucial component of pre- and post-conditioning protocols. A number of anti-oxidant and antiapoptotic genes are upregulated by STAT3 via canonical means involving phosphorylation on Y705 and S727, although other incompletely defined posttranslational modifications are involved. In addition, STAT3 is now known to be present in cardiac mitochondria and to exert actions that regulate the electron transport chain, reactive oxygen species production, and mitochondrial permeability transition pore opening. These non-canonical actions of STAT3 are enhanced by S727 phosphorylation. The molecular basis for the mitochondrial actions of STAT3 is poorly understood, but STAT3 is known to interact with a critical subunit of complex I and to regulate complex I function. Dysfunctional complex I has been implicated in ischemic injury, heart failure, and the aging process. Evidence also indicates that STAT3 is protective to the heart under chronic stress conditions, including hypertension, pregnancy, and advanced age. Paradoxically, the accumulation of unphosphorylated STAT3 (U-STAT3) in the nucleus has been suggested to drive pathological cardiac hypertrophy and inflammation via non-canonical gene expression, perhaps involving a distinct acetylation profile. U-STAT3 may also regulate chromatin stability. Our understanding of how the non-canonical genomic and mitochondrial actions of STAT3 in the heart are regulated and coordinated with the canonical actions of STAT3 is rudimentary. Here, we present an overview of what is currently known about the pleotropic actions of STAT3 in the heart in order to highlight controversies and unresolved issues.

DAB2IP loss confers the resistance of prostate cancer to androgen deprivation therapy through activating STAT3 and inhibiting apoptosis

Loss of DAB2IP, a novel tumor suppressor gene, is associated with the high risk of aggressive prostate cancer (PCa). Previously, we reported that DAB2IP modulated androgen receptor activation in the development of castration-resistant PCa; however, its direct action on the failure of androgen deprivation therapy (ADT) remains largely unknown. In this study, we showed that DAB2IP knockdown could significantly enhance in vitro growth and colony formation of PCa cells following ADT as well as tumorigenicity in pre-castrated nude mice. In addition, DAB2IP loss stabilized mitochondrial transmembrane potential, prevented release of cytochrome c, Omi/HtrA2 and Smac from the mitochondria to the cytoplasm and inhibited intrinsic apoptosis induced by ADT. Mechanistically, DAB2IP could interact with the signal transducer and activator of transcription 3 (STAT3) via its unique PR domain and suppress STAT3 phosphorylation and transactivation, leading to the inhibition of survivin expression in PCa cells. Moreover, the luminal epithelia in DAB2IP^−/− mice with more activated STAT3 and survivin expression were resistant to castration-induced apoptosis. Consistently, DAB2IP expression inversely correlated with STAT3 phosphorylation and survivin expression in PCa patients. Together, our data indicate that DAB2IP loss reprograms intracellular signal transduction and anti-apoptotic gene expression, which potentiates PCa cell survival from ADT-induced cell death.

Mitochondrial STAT3 and reactive oxygen species: A fulcrum of adipogenesis?

The balance between cellular lineages can be controlled by reactive oxygen species (ROS). Cellular differentiation into adipocytes is highly dependent on the production of ROS to initiate the process through activation of multiple interlinked factors that stimulate mitotic clonal expansion and cellular maturation. The signal transducer and activator of transcription family of signaling proteins have accepted roles in adipogenesis and associated lipogenesis. Non-canonical mitochondrial localization of STAT3 and other members of the STAT family however opens up new avenues for investigation of its role in the aforementioned processes. Following recent observations of differences in mitochondrially localized serine 727 phosphorylated STAT3 (mtSTAT3-pS727) in preadipocytes and adipocytes, here, we hypothesize and speculate further on the role of mitochondrial STAT3 in adipogenesis.

Mitochondrial STAT3 contributes to transformation of Barrett's epithelial cells that express oncogenic Ras in a p53-independent fashion

Metaplastic epithelial cells of Barrett's esophagus transformed by the combination of p53-knockdown and oncogenic Ras expression are known to activate signal transducer and activator of transcription 3 (STAT3). When phosphorylated at tyrosine 705 (Tyr705), STAT3 functions as a nuclear transcription factor that can contribute to oncogenesis. STAT3 phosphorylated at serine 727 (Ser727) localizes in mitochondria, but little is known about mitochondrial STAT3's contribution to carcinogenesis in Barrett's esophagus, which is the focus of this study. We introduced a constitutively active variant of human STAT3 (STAT3CA) into the following: 1) non-neoplastic Barrett's (BAR-T) cells; 2) BAR-T cells with p53 knockdown; and 3) BAR-T cells that express oncogenic H-Ras(G12V). STAT3CA transformed only the H-Ras(G12V)-expressing BAR-T cells (evidenced by loss of contact inhibition, formation of colonies in soft agar, and generation of tumors in immunodeficient mice), and did so in a p53-independent fashion. The transformed cells had elevated levels of both mitochondrial (Ser727) and nuclear (Tyr705) phospho-STAT3. Introduction of a STAT3CA construct with a mutated tyrosine phosphorylation site into H-Ras(G12V)-expressing Barrett's cells resulted in high levels of mitochondrial phospho-STAT3 (Ser727) with little or no nuclear phospho-STAT3 (Tyr705), and the cells still formed tumors in immunodeficient mice. Thus tyrosine phosphorylation of STAT3 is not required for tumor formation in Ras-expressing Barrett's cells. We conclude that mitochondrial STAT3 (Ser727) can contribute to oncogenesis in Barrett's cells that express oncogenic Ras. These findings suggest that agents targeting STAT3 might be useful for chemoprevention in patients with Barrett's esophagus.

STAT3-Mediated Metabolic Reprograming in Cellular Transformation and Implications for Drug Resistance

Signal transducer and activator of transcription (STAT)3 mediates the signaling downstream of cytokine and growth factor receptors, regulating the expression of target genes. It is constitutively phosphorylated on tyrosine (Y-P) in many tumors, where its transcriptional activity can induce a metabolic switch toward aerobic glycolysis and down-regulate mitochondrial activity, a prominent metabolic feature of most cancer cells, correlating with reduced production of ROS, delayed senescence, and protection from apoptosis. STAT3 can, however, also localize to mitochondria, where its serine-phosphorylated (S-P) form preserves mitochondrial oxidative phosphorylation and controls the opening of the mitochondrial permeability transition pore, also promoting survival and resistance to apoptosis in response to specific signals/oncogenes such as RAS. Thus, downstream of different signals, both nuclear, Y-P STAT3, and mitochondrial, S-P STAT3, can act by promoting cell survival and reducing ROS production. Here, we discuss these properties in the light of potential connections between STAT3-driven alterations of mitochondrial metabolism and the development of drug resistance in cancer patients.

Mutation in NDUFA13/GRIM19 leads to early onset hypotonia, dyskinesia and sensorial deficiencies, and mitochondrial complex I instability

Mitochondrial complex I (CI) deficiencies are causing debilitating neurological diseases, among which, the Leber Hereditary Optic Neuropathy and Leigh Syndrome are the most frequent. Here, we describe the first germinal pathogenic mutation in the NDUFA13/GRIM19 gene encoding a CI subunit, in two sisters with early onset hypotonia, dyskinesia and sensorial deficiencies, including a severe optic neuropathy. Biochemical analysis revealed a drastic decrease in CI enzymatic activity in patient muscle biopsies, and reduction of CI-driven respiration in fibroblasts, while the activities of complex II, III and IV were hardly affected. Western blots disclosed that the abundances of NDUFA13 protein, CI holoenzyme and super complexes were drastically reduced in mitochondrial fractions, a situation that was reproduced by silencing NDUFA13 in control cells. Thus, we established here a correlation between the first mutation yet identified in the NDUFA13 gene, which induces CI instability and a severe but slowly evolving clinical presentation affecting the central nervous system.