Regulation of the Akt kinase by interacting proteins

Melatonin-pretreated human umbilical cord mesenchymal stem cells improved endometrium regeneration and fertility recovery through macrophage immunomodulation in rats with intrauterine adhesions†

Intrauterine adhesions (IUA) are a common gynecological problem. Stem cell therapy has been widely used in the treatment of IUA. However, due to the complex and harsh microenvironment of the uterine cavity, the effectiveness of such therapy is greatly inhibited. This study aimed to investigate whether melatonin pretreatment enhances the efficacy of human umbilical cord mesenchymal stem cells (HucMSCs) in IUA treatment in rats. First, we explored the effect of melatonin on the biological activity of HucMSCs in vitro through a macrophage co-culture system, Cell Counting Kit 8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU), flow cytometry, immunofluorescence staining, and qRT-PCR. Subsequently, we established the IUA rat model and tracked the distribution of HucMSCs in this model. In addition, we observed the number of M1 and M2 macrophages through immunofluorescence staining and detected the levels of inflammatory cytokines. Four weeks after cell transplantation, HE, Masson, and immunohistochemical staining were performed. In vitro experiments showed that melatonin pretreatment of HucMSCs promoted proliferation, reduced apoptosis, up-regulated the stemness gene, and regulated macrophage polarization. In vivo, melatonin pretreatment caused more HucMSCs to remain in the uterine cavity. Melatonin-pretreated HucMSCs recruited more macrophages, regulated macrophage polarization, and reduced inflammation. Melatonin-pretreated HucMSCs relieved fibrosis, increased endometrium thickness, and up-regulated CD34, vimentin, proliferating cell nuclear antigen (PCNA), and alpha small muscle antigen (α-SMA) expression. Fertility tests showed that melatonin-pretreated HucMSCs increased the number of embryos. In summary, pretreatment with melatonin was beneficial for HucMSC treatment because it enhanced the cell's ability to recruit macrophages and regulate macrophage polarization, which led to the regeneration of the endometrium and improved pregnancy outcomes.

DNAJB3 attenuates ER stress through direct interaction with AKT

Metabolic stress involved in several dysregulation disorders such as type 2 diabetes mellitus (T2DM) results in down regulation of several heat shock proteins (HSPs) including DNAJB3. This down regulation of HSPs is associated with insulin resistance (IR) and interventions which induce the heat shock response (HSR) help to increase the insulin sensitivity. Metabolic stress leads to changes in signaling pathways through increased activation of both c-jun N-terminal kinase-1 (JNK1) and the inhibitor of κB inflammatory kinase (IKKβ) which in turn leads to inactivation of insulin receptor substrates 1 and 2 (IRS-1 and IRS-2). DNAJB3 interacts with both JNK1 and IKKβ kinases to mitigate metabolic stress. In addition DNAJB3 also activates the PI3K-PKB/AKT pathway through increased phosphorylation of AKT1 and its substrate AS160, a Rab GTPase-activating protein, which results in mobilization of GLUT4 transporter protein and improved glucose uptake. We show through pull down that AK T1 is an interacting partner of DNAJB3, further confirmed by isothermal titration calorimetry (ITC) which quantified the avidity of AKT1 for DNAJB3. The binding interface was identified by combining protein modelling with docking of the AKT1-DNAJB3 complex. DNAJB3 is localized in the cytoplasm and ER, where it interacts directly with AKT1 and mobilizes AS160 for glucose transport. Inhibition of AKT1 resulted in loss of GLUT4 translocation activity mediated by DNAJB3 and also abolished the protective effect of DNAJB3 on tunicamycin-induced ER stress. Taken together, our findings provide evidence for a direct protein-protein interaction between DNAJB3 and AKT1 upon which DNAJB3 alleviates ER stress and promotes GLUT4 translocation.

Regeneration of Pancreatic Beta Cells by Modulation of Molecular Targets Using Plant-Derived Compounds: Pharmacological Mechanisms and Clinical Potential

Type 2 diabetes (T2D) is characterized by pancreatic beta-cell dysfunction, increased cell death and loss of beta-cell mass despite chronic treatment. Consequently, there has been growing interest in developing beta cell-centered therapies. Beta-cell regeneration is mediated by augmented beta-cell proliferation, transdifferentiation of other islet cell types to functional beta-like cells or the reprograming of beta-cell progenitors into fully differentiated beta cells. This mediation is orchestrated by beta-cell differentiation transcription factors and the regulation of the cell cycle machinery. This review investigates the beta-cell regenerative potential of antidiabetic plant extracts and phytochemicals. Various preclinical studies, including in vitro, in vivo and ex vivo studies, are highlighted. Further, the potential regenerative mechanisms and the intra and extracellular mediators that are of significance are discussed. Also, the potential of phytochemicals to translate into regenerative therapies for T2D patients is highlighted, and some suggestions regarding future perspectives are made.

A Novel FYVE Domain-Containing Protein Kinase, PsZFPK1, Plays a Critical Role in Vegetative Growth, Sporangium Formation, Oospore Production, and Virulence in Phytophthora sojae

Proteins containing both FYVE and serine/threonine kinase catalytic (STKc) domains are exclusive to protists. However, the biological function of these proteins in oomycetes has rarely been reported. In the Phytophthora sojae genome database, we identified five proteins containing FYVE and STKc domains, which we named PsZFPK1, PsZFPK2, PsZFPK3, PsZFPK4, and PsZFPK5. In this study, we characterized the biological function of PsZFPK1 using a CRISPR/Cas9-mediated gene replacement system. Compared with the wild-type strain, P6497, the PsZFPK1-knockout mutants exhibited significantly reduced growth on a nutrient-rich V8 medium, while a more pronounced defect was observed on a nutrient-poor Plich medium. The PsZFPK1-knockout mutants also showed a significant increase in sporangium production. Furthermore, PsZFPK1 was found to be essential for oospore production and complete virulence but dispensable for the stress response in P. sojae. The N-terminal region, FYVE and STKc domains, and T602 phosphorylation site were found to be vital for the function of PsZFPK1. Conversely, these domains were not required for the localization of PsZFPK1 protein in the cytoplasm. Our results demonstrate that PsZFPK1 plays a critical role in vegetative growth, sporangium formation, oospore production, and virulence in P. sojae.

Melatonin ameliorates myocardial infarction in obese diabetic individuals: The possible involvement of macrophage apoptotic factors

In recent days, the hike in obesity-mediated epidemics across the globe and the prevalence of obesity-induced cardiovascular disease has become one of the chief grounds for morbidity and mortality. This epidemic-driven detrimental events in the cardiac tissues start with the altered distribution and metabolism pattern of high-density lipoprotein and low-density lipoprotein (LDL) leading to cholesterol (oxidized LDL) deposition on the arterial wall and atherosclerotic plaque generation, followed by vascular spasms and infarction. Subsequently, obesity-triggered metabolic malfunctions induce free radical generation which may further trigger pro-inflammatory signaling and nuclear factor kappa-light-chain-enhancer of activated B cells transcriptional factor, thus inducing interferon-gamma, tumor necrosis factor-alpha, and inducible nitric oxide synthase. This terrifying cardiomyopathy can be further aggravated in type 2 diabetes mellitus, thereby making obese diabetic patients prone toward the development of myocardial infarction (MI) or stroke in comparison to their nondiabetic counterparts. The accelerated oxidative stress and pro-inflammatory response induced cardiomyocyte hypertrophy, followed by apoptosis in obese diabetic individuals, causing progression of athero-thrombotic vascular disease. Being an efficient antioxidative and anti-inflammatory indolamine, melatonin effectively inhibits lipid peroxidation, pro-inflammatory reactions, thereby resolving free radical-induced myocardial damages along with maintaining antioxidant reservoir to preserve cardiovascular integrity. Prolonged melatonin treatment maintains balanced body weight and serum total cholesterol concentration by inhibiting cholesterol synthesis and promoting cholesterol catabolism. Additionally, melatonin promotes macrophage polarization toward the anti-inflammatory state, providing a proper shield during the recovery period. Therefore, the protective role of melatonin in maintaining the lipid metabolism homeostasis and blocking the atherosclerotic plaque rupture could be targeted as the possible therapeutic strategy for the management of obesity-induced acute MI. This review aimed at orchestrating the efficacy of melatonin in ameliorating irrevocable oxidative cardiovascular damage induced by the obesity-diabetes correlation.

Ameliorative Effect of Citrus Lemon Peel Extract and Resveratrol on Premature Ovarian Failure Rat Model: Role of iNOS/Caspase-3 Pathway

Premature ovarian failure (POF) is described as a loss of oocytes and the absence of folliculogenesis and is considered an adverse effect of chemotherapeutic drugs, which leads to infertility. Subsequently, the existing inquiry was achieved by exploring the potential suspicious influences of lemon peel extract (LPE), and resveratrol (RES) on cyclophosphamide (CPA) induced-POF. The results showed that CPA-induced POF significantly decreased serum estradiol (E2) and progesterone levels, along with a considerable rise in serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels. Moreover, CPA administration to rats significantly increased the serum level of Malondialdehyde (MDA) and significantly lowered the levels of reduced glutathione (GSH) and superoxide dismutase (SOD); in addition, it increased nuclear factor kappa B (NF-κB) levels, tumor necrosis factor-α (TNF-α), as well as cyclooxygenase 2 (COX-2) with the spread expression of inducible nitric oxide synthase (iNOS) mRNA levels and caspase-3 (Casp3) levels in ovarian tissues versus the control rats. However, treatment with LPE and RES suppressed the triggering of NF- κB pathways, evidenced by a considerable reduction in Casp3 & iNOS mRNA expression level and significant ameliorative effects in all evaluated parameters, as confirmed by the histological and immunohistochemical investigation when comparing the model group. In overall findings, both lemon peel extract and resveratrol can mitigate the adverse effects of CPA-induced POF. Most crucially, its combination therapy is a promising pharmacological agent for this disease.

Preterm birth alters the feeding-induced activation of Akt signaling in the muscle of neonatal piglets

BACKGROUND

Postnatal lean mass accretion is commonly reduced in preterm infants. This study investigated mechanisms involved in the blunted feeding-induced activation of Akt in the skeletal muscle of preterm pigs that contributes to lower protein synthesis rates.

METHODS

On day 3 following cesarean section, preterm and term piglets were fasted or fed an enteral meal. Activation of Akt signaling pathways in skeletal muscle was determined.

RESULTS

Akt1 and Akt2, but not Akt3, phosphorylation were lower in the skeletal muscle of preterm than in term pigs (P < 0.05). Activation of Akt-positive regulators, PDK1 and mTORC2, but not FAK, were lower in preterm than in term (P < 0.05). The formation of Akt complexes with GAPDH and Hsp90 and the abundance of Ubl4A were lower in preterm than in term (P < 0.05). The abundance of Akt inhibitors, PHLPP and SHIP2, but not PTEN and IP6K1, were higher in preterm than in term pigs (P < 0.05). PP2A activation was inhibited by feeding in term but not in preterm pigs (P < 0.05).

CONCLUSIONS

Our results suggest that preterm birth impairs regulatory components involved in Akt activation, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the reduced lean accretion following preterm birth.

IMPACT

The Akt-mTORC1 pathway plays an important role in the regulation of skeletal muscle protein synthesis in neonates. This is the first evidence to demonstrate that, following preterm birth, the postprandial activation of positive regulators of Akt in the skeletal muscle is reduced, whereas the activation of negative regulators of Akt is enhanced. This anabolic resistance of Akt signaling in response to feeding likely contributes to the reduced accretion of lean mass in premature infants. These results may provide potential novel molecular targets for intervention to enhance lean growth in preterm neonates.

TSC22D4 interacts with Akt1 to regulate glucose metabolism

Maladaptive insulin signaling is a key feature in the pathogenesis of severe metabolic disorders, including obesity and diabetes. Enhancing insulin sensitivity represents a major goal in the treatment of patients affected by diabetes. Here, we identify transforming growth factor-β1 stimulated clone 22 D4 (TSC22D4) as a novel interaction partner for protein kinase B/Akt1, a critical mediator of insulin/phosphatidylinositol 3-kinase signaling pathway. While energy deprivation and oxidative stress promote the TSC22D4-Akt1 interaction, refeeding mice or exposing cells to glucose and insulin impairs this interaction, which relies on an intrinsically disordered region (D2 domain) within TSC22D4. Functionally, the interaction with TSC22D4 reduces basal phosphorylation of Akt and its downstream targets during starvation, thereby promoting insulin sensitivity. Genetic, liver-specific reconstitution experiments in mice demonstrate that the interaction between TSC22D4 and Akt1 improves glucose handling and insulin sensitivity. Overall, our findings postulate a model whereby TSC22D4 acts as an environmental sensor and interacts with Akt1 to regulate insulin signaling and glucose metabolism.

Exenatide improves hepatocyte insulin resistance induced by different regional adipose tissue

Obesity is resulted from energy surplus and is characterized by abnormal adipose tissue accumulation and/or distribution. Adipokines secreted by different regional adipose tissue can induce changes in key proteins of the insulin signaling pathway in hepatocytes and result in impaired hepatic glucose metabolism. This study aimed to investigate whether exenatide affects key proteins of IRS2/PI3K/Akt2 signaling pathway in hepatocytes altered by the different regional fat depots. Six non-obese patients without endocrine diseases were selected as the research subjects. Their subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT)were co-cultured with HepG2 cells in the transwell chamber. In the presence or absence of exenatide, adipokines content in the supernatant of each experimental group was detected by ELISA. In addition, HepG2 cells in each co-culture group with and without insulin were collected, and the expression of key proteins IRS2, p-IRS2(S731), PI3K-p85, Akt2, and p-Akt2(S473) was detected by western blotting (WB). The results showed that the adipokines IL-8, MCP-1, VEGF, and sTNFR2 in the supernatant of HepG2 cells induced by different regional adipose tissue were significantly higher than those in the HepG2 group, and VAT released more adipokines than SAT. Furthermore, these adipokines were significantly inhibited by exenatide. Importantly, the different regional fat depot affects the IRS2/PI3K/Akt2 insulin signaling pathway of hepatocytes. Exenatide can up-regulate the expression of hepatocyte proteins IRS2, PI3K-p85, p-Akt2(S731) inhibited by adipose tissue, and down-regulate the expression of hepatocyte proteins p-IRS2(S731) promoted by adipose tissue. The effect of VAT on the expression of these key proteins in hepatocytes is more significant than that of SAT. But there was no statistical difference in the expression of Akt2 protein among each experimental group, suggesting that exenatide has no influence on the expression of Akt2 protein in hepatocytes. In conclusion, exenatide may improve hepatic insulin resistance (IR) by inhibiting adipokines and regulating the expression of key proteins in the IRS2/PI3K/Akt2 pathway.

GREB1 regulates PI3K/Akt signaling to control hormone-sensitive breast cancer proliferation

Over 70% of breast cancers express the estrogen receptor (ER) and depend on ER activity for survival and proliferation. While hormone therapies that target receptor activity are initially effective, patients invariably develop resistance which is often associated with activation of the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. While the mechanism by which estrogen regulates proliferation is not fully understood, one gene target of ER, growth regulation by estrogen in breast cancer 1 (GREB1), is required for hormone-dependent proliferation. However, the molecular function by which GREB1 regulates proliferation is unknown. Herein, we validate that knockdown of GREB1 results in growth arrest and that exogenous GREB1 expression initiates senescence, suggesting that an optimal level of GREB1 expression is necessary for proliferation of breast cancer cells. Under both of these conditions, GREB1 is able to regulate signaling through the PI3K/Akt/mTOR pathway. GREB1 acts intrinsically through PI3K to regulate phosphatidylinositol (3,4,5)-triphosphate levels and Akt activity. Critically, growth suppression of estrogen-dependent breast cancer cells by GREB1 knockdown is rescued by expression of constitutively activated Akt. Together, these data identify a novel molecular function by which GREB1 regulates breast cancer proliferation through Akt activation and provides a mechanistic link between estrogen signaling and the PI3K pathway.

Distinctive Under-Expression Profile of Inflammatory and Redox Genes in the Blood of Elderly Patients with Cardiovascular Disease

Purpose

Chronic low-grade inflammation and oxidative stress are present in most of the pathologic mechanisms underlying non-communicable diseases. Inflammation and redox biomarkers might therefore have a value in disease prognosis and therapy response. In this context, we performed a case–control study for assessing in whole blood the expression profile of inflammation and redox-related genes in elderly subjects with various comorbidities.

Patients and Methods

In the blood of 130 elderly subjects with various pathologies (cardiovascular disease, hypertension, dyslipidemia including hypercholesterolemia, type 2 diabetes mellitus), kept under control by polyvalent disease-specific medication, we investigated by pathway-focused qRT-PCR a panel comprising 84 inflammation-related and 84 redox-related genes.

Results

The study highlights a distinctive expression profile of genes critically involved in NF-κB-mediated inflammation and redox signaling in the blood of patients with cardiovascular disease, characterized by significant down-regulation of the genes NFKB2, NFKBIA, RELA, RELB, AKT1, IRF1, STAT1, CD40, LTA, TRAF2, PTGS1, ALOX12, DUOX1, DUOX2, MPO, GSR, TXNRD2, HSPA1A, MSRA, and PDLIM1. This gene expression profile defines the transcriptional status of blood leukocytes in stable disease under medication control, without discriminating between disease- and therapy-related changes.

Conclusion

The study brings preliminary proof on a minimally invasive strategy for monitoring disease in patients with cardiovascular pathology, from the point of view of inflammation or redox dysregulation in whole blood.

An AKT2-specific nanobody that targets the hydrophobic motif induces cell cycle arrest, autophagy and loss of focal adhesions in MDA-MB-231 cells

The AKT kinase family is a high-profile target for cancer therapy. Despite their high degree of homology the three AKT isoforms (AKT1, AKT2 and AKT3) are non-redundant and can even have opposing functions. Small-molecule AKT inhibitors affect all three isoforms which severely limits their usefulness as research tool or therapeutic. Using AKT2-specific nanobodies we examined the function of endogenous AKT2 in breast cancer cells. Two AKT2 nanobodies (Nb8 and Nb9) modulate AKT2 and reduce MDA-MB-231 cell viability/proliferation. Nb8 binds the AKT2 hydrophobic motif and reduces IGF-1-induced phosphorylation of this site. This nanobody also affects the phosphorylation and/or expression levels of a wide range of proteins downstream of AKT, resulting in a G0/G1 cell cycle arrest, the induction of autophagy, a reduction in focal adhesion count and loss of stress fibers. While cell cycle progression is likely to be regulated by more than one isoform, our results indicate that both the effects on autophagy and the cytoskeleton are specific to AKT2. By using an isoform-specific nanobody we were able to map a part of the AKT2 pathway. Our results confirm AKT2 and the hydrophobic motif as targets for cancer therapy. Nb8 can be used as a research tool to study AKT2 signalling events and aid in the design of an AKT2-specific inhibitor.

Melatonin-stimulated MSC-derived exosomes improve diabetic wound healing through regulating macrophage M1 and M2 polarization by targeting the PTEN/AKT pathway

Background

After surgery, wound recovery in diabetic patients may be disrupted due to delayed inflammation, which can lead to undesired consequences, and there is currently a lack of effective measures to address this issue. Mesenchymal stem cell (MSC)-derived exosomes (Exo) have been proven to be appropriate candidates for diabetic wound healing through the anti-inflammatory effects. In this study, we investigated whether melatonin (MT)-pretreated MSCs-derived exosomes (MT-Exo) could exert superior effects on diabetic wound healing, and we attempted to elucidate the underlying mechanism.

Methods

For the evaluation of the anti-inflammatory effect of MT-Exo, in vitro and in vivo studies were performed. For in vitro research, we detected the secreted levels of inflammation-related factors, such as IL-1β, TNF-α and IL-10 via ELISA and the relative gene expression of the IL-1β, TNF-α, IL-10, Arg-1 and iNOS via qRT-PCR and investigated the expression of PTEN, AKT and p-AKT by Western blotting. For in vivo study, we established air pouch model and streptozotocin (STZ)-treated diabetic wound model, and evaluated the effect of MT-Exo by flow cytometry, optical imaging, H&E staining, Masson trichrome staining, immunohistochemical staining, immunofluorescence, and qRT-PCR (α-SMA, collagen I and III).

Results

MT-Exo significantly suppressed the pro-inflammatory factors IL-1β and TNF-α and reduced the relative gene expression of IL-1β, TNF-α and iNOS, while promoting the anti-inflammatory factor IL-10 along with increasing the relative expression of IL-10 and Arg-1, compared with that of the PBS, LPS and the Exo groups in vitro. This effect was mediated by the increased ratio of M2 polarization to M1 polarization through upregulating the expression of PTEN and inhibiting the phosphorylation of AKT. Similarly, MT-Exo significantly promoted the healing of diabetic wounds by inhibiting inflammation, thereby further facilitating angiogenesis and collagen synthesis in vivo.

Conclusions

MT-Exo could promote diabetic wound healing by suppressing the inflammatory response, which was achieved by increasing the ratio of M2 polarization to M1 polarization through activating the PTEN/AKT signalling pathway, and the pretreatment of MT was proved to be a promising method for treating diabetic wound healing.

Graphical abstract: MT-Exo promotes diabetic wound healing by regulating M1 and M2 macrophage polarization.

Metabolic syndrome diminishes insulin-induced Akt activation and causes a redistribution of Akt-interacting proteins in cardiomyocytes

Metabolic syndrome (MetS) is a cluster of cardiometabolic risk factors, with insulin resistance as a critical component for its development. Insulin signaling in the heart leads to Akt (also known as PKB) activation, a serine/threonine protein kinase, which regulates cardiac glucose metabolism and growth. Cardiac metabolic inflexibility, characterized by impaired insulin-induced glucose uptake and oxidation, has been reported as an early and consistent change in the heart of different models of MetS and diabetes; however, the evaluation of Akt activation has yielded variable results. Here we report in cardiomyocytes of MetS rats, diminished insulin-induced glucose uptake and Akt activation, evaluated by its impaired mobilization towards the plasma membrane and phosphorylation, and reflected in a re-distribution of its interacting proteins, assessed by label-free mass spectrometry (data are available via ProteomeXchange with identifier PXD013260). We report 45 proteins with diminished abundance in Akt complex of MetS cardiomyocytes, mainly represented by energy metabolism-related proteins, and also, 31 Akt-interacting proteins with increased abundance, which were mainly related to contraction, endoplasmic reticulum stress, and Akt negative regulation. These results emphasize the relevance of Akt in the regulation of energy metabolism in the heart and highlight Akt-interacting proteins that could be involved in the detrimental effects of MetS in the heart.

Acupuncture Reduces Apoptosis of Granulosa Cells in Rats with Premature Ovarian Failure Via Restoring the PI3K/Akt Signaling Pathway

Acupuncture is widely recognized as an effective therapy for premature ovarian failure (POF) in clinical, but information about its potential mechanisms is rarely explored. To investigate the mechanism, fifty SD female rats were randomly divided into normal group, POF group, POF+estradiol-valerate group (abbreviated as estradiol group), and POF+acupuncture group (abbreviated as acupuncture group). The estrous cycle of the rats was tracked by vaginal smears. Their ovaries morphology was observed by hematoxylin-eosin staining. The apoptotic level of granulosa cells was detected by in situ TUNEL fluorescence staining assay. Serum follicle-stimulating hormone (FSH) and estrogen (E2) levels were measured by enzyme-linked-immunosorbent-assay (ELISA). Protein and gene expression of PI3K, Akt, bcl-2, and bax were detected by Western blotting and qPCR. In the acupuncture and estradiol groups, compared with the POF group as controls, the apoptosis number of granulosa cells was significantly decreased (p < 0.05). FSH levels were decreased, while E2 levels were increased (p > 0.05). The gene and protein expression levels of PI3K, Akt, and bcl-2 were increased, while the expression levels of bax were decreased (p < 0.05), and the protein expression level of p-Akt increased. There was no significant difference between the acupuncture group and the estradiol group (p > 0.05). Acupuncture was able to regulate hormone levels in POF rats, up-regulate PI3K/Akt signaling pathway, and reduce the apoptosis of granulosa cells. This may be one of the mechanisms of acupuncture treating premature ovarian failure.

Role of Tim-3 in Decidual Macrophage Functional Polarization During Abnormal Pregnancy With Toxoplasma gondii Infection

Vertical transmission of the intracellular parasite Toxoplasma gondii (T. gondii) can lead to devastating consequences during gestation. Tim-3, a negative immune regulator, is constitutively expressed on decidual macrophages, but its specific role during T. gondii infection has not yet been explored. In the present study, we discovered that Tim-3 plays an important role in the abnormal pregnancy due to T. gondii infection using Tim-3^−/− pregnant mice and anti-Tim-3 neutralizing antibody treated human decidual macrophages. The results showed that abnormal pregnancy outcomes were more prevalent in Tim-3^−/− infected pregnant mice than in wild-type infected pregnant mice. Tim-3 expression in decidual macrophages was significantly down-regulated after T. gondii infection both in vitro and in vivo. Tim-3 down-regulation by T.gondii infection could strengthen M1 activation and weaken M2 tolerance by changing the M1 and M2 membrane molecule expression, arginine metabolic enzymes synthesis, and cytokine secretion profiles of decidual macrophages. Moreover, Tim-3 down-regulation by T.gondii infection led to PI3K-AKT phosphorylation inhibition, downstream transcription factor C/EBPβ expression, and SOCS1 activation, which resulted in enzymes synthesis regulation and cytokines secretion. Our study demonstrates that Tim-3 plays an indispensable role in the adverse pregnancy outcomes caused by T. gondii infection.

MERTK mediated novel site Akt phosphorylation alleviates SAV1 suppression

Akt plays indispensable roles in cell proliferation, survival and metabolism. Mechanisms underlying posttranslational modification-mediated Akt activation have been extensively studied yet the Akt interactome is less understood. Here, we report that SAV1, a Hippo signaling component, inhibits Akt, a function independent of its role in Hippo signaling. Binding to a proline-tyrosine motif in the Akt-PH domain, SAV1 suppresses Akt activation by blocking Akt’s movement to plasma membrane. We further identify cancer-associated SAV1 mutations with impaired ability to bind Akt, leading to Akt hyperactivation. We also determine that MERTK phosphorylates Akt1-Y26, releasing SAV1 binding and allowing Akt responsiveness to canonical PI-3K pathway activation. This work provides a mechanism underlying MERTK-mediated Akt activation and survival signaling in kidney cancer. Akt activation drives oncogenesis and therapeutic resistance; this mechanism of Akt regulation by MERTK/SAV1 provides yet another complexity in an extensively studied pathway, and may yield prognostic information and therapeutic targets.

Hyperactivation of Akt promotes tumorigenesis. Here, the authors show that SAV1, a member of Hippo signalling, interacts with Akt to suppress Akt activity and MERTK-mediated Akt phosphorylation relieves this suppression to facilitate Akt oncogenic activity in clear cell renal carcinomas.

PI3K/Akt signaling transduction pathway, erythropoiesis and glycolysis in hypoxia (Review)

The purpose of this review is to summarize the research progress of PI3K/Akt signaling pathway in erythropoiesis and glycolysis. Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) is activated by numerous genes and leads to protein kinase B (Akt) binding to the cell membrane, with the help of phosphoinositide-dependent kinase, in the PI3K/Akt signal transduction pathway. Threonine and serine phosphorylation contribute to Akt translocation from the cytoplasm to the nucleus and further mediates enzymatic biological effects, including those involved in cell proliferation, apoptosis inhibition, cell migration, vesicle transport and cell cancerous transformation. As a key downstream protein of the PI3K/Akt signaling pathway, hypoxia-inducible factor (HIF)-1 is closely associated with the concentration of oxygen in the environment. Maintaining stable levels of HIF-1 protein is critical under normoxic conditions; however, HIF-1 levels quickly increase under hypoxic conditions. HIF-1α is involved in the acute hypoxic response associated with erythropoietin, whereas HIF-2α is associated with the response to chronic hypoxia. Furthermore, PI3K/Akt can reduce the synthesis of glycogen and increase glycolysis. Inhibition of glycogen synthase kinase 3β activity by phosphorylation of its N-terminal serine increases accumulation of cyclin D1, which promotes the cell cycle and improves cell proliferation through the PI3K/Akt signaling pathway. The PI3K/Akt signaling pathway is closely associated with a variety of enzymatic biological effects and glucose metabolism.

Relationship between tumour PTEN/Akt/COX-2 expression, inflammatory response and survival in patients with colorectal cancer

In patients with colorectal cancer (CRC), local and systemic inflammatory responses have been extensively reported to associate with cancer survival. However, the specific signalling pathways responsible for inflammatory responses are not clear. The PTEN/Akt pathway is a plausible candidate as it may play a role in mediating inflammation via COX-2, and has been associated with cancer progression. This study therefore examined the relationship between tumour PTEN/Akt/COX-2 expression, inflammatory responses and survival in CRC patients using a tissue microarray.

In 201 CRC patients, activation of tumour-specific PTEN/Akt significantly associated with poorer CSS (12.0yrs v 7.3yrs, P=0.032), poorer differentiation (P=0.032), venous invasion (P=0.008) and peritoneal involvement (P=0.004). Patients were stratified for peri-nuclear expression of COX-2 to examine associations with inflammatory responses. In patients with absent peri-nuclear COX-2 expression, activation of tumour-specific PTEN/Akt significantly associated with poorer CSS (11.9yrs v 5.4yrs, P=0.001), poorer differentiation (P=0.018), venous invasion (P=0.003) and peritoneal involvement (P=0.001). However, no associations were seen with either the local or systemic inflammatory responses.

In CRC patients, tumour-specific PTEN/Akt pathway activation was significantly associated with poorer CSS, particularly when peri-nuclear COX-2 expression was absent. However, activation of the PTEN/Akt pathway appears not to be responsible for the regulation of inflammatory responses.

AKT1 distinctively suppresses MyD88-depenedent and TRIF-dependent Toll-like receptor signaling in a kinase activity-independent manner

We found that AKT1, a primary effector molecule of PI3K-AKT signaling, distinctively suppressed Toll-like receptor (TLR)-mediated MyD88-dependent and Toll/IL-1R domain-containing adaptor inducing IFN-β (TRIF)-dependent signaling by inhibiting NF-κB activation and IRF3 activity independently of its kinase activity. In AKT1 knockout RAW264.7 cells, lipopolysaccharide (LPS)-induced transcription and protein production of cytokines including IL-1β and TNF-α (regulated by the MyD88-dependent pathway), as well as IFN-β and RANTES (C-C motif chemokine ligand 5: CCL-5; regulated by the TRIF-dependent pathways) was enhanced compared to wild type cells. In response to LPS stimulation, AKT1 knockout cells also exhibited enhanced NF-κB and IFN-β promoter activities, which were reduced to a level comparable to that in wild type cells by complementation with either AKT1 or its kinase-dead mutant (AKT1-KD). Expression of AKT1 or AKT1-KD similarly suppressed NF-κB and IFN-β promoter activities induced by LPS and other TLR ligands in wild type cells. Analysis of NF-κB activation caused by transient expression of proteins involved in the MyD88-dependent pathway in TLR signaling revealed that AKT1 suppressed signaling that occurs between activation of IKKβ and that of NF-κB. In contrast, AKT1 appeared to suppress the IFN-β promoter through inhibition of IRF3 activity itself. These results demonstrate a novel, non-kinase function of AKT1 that inhibits TLR signaling, and suggest the multifunctional nature of AKT1.

An Akt3 Splice Variant Lacking the Serine 472 Phosphorylation Site Promotes Apoptosis and Suppresses Mammary Tumorigenesis

The Akt pathway is a well-known promoter of tumor malignancy. Akt3 is expressed as two alternatively spliced variants, one of which lacks the key regulatory serine 472 phosphorylation site. Whereas the function of full-length Akt3 isoform (Akt3/+S472) is well-characterized, that of Akt3/-S472 isoform remains unknown. Despite being expressed at a substantially lower level than Akt3/+S472 in triple-negative breast cancer cells, specific ablation of Akt3/-S472 enhanced, whereas overexpression, suppressed mammary tumor growth, consistent with a significant association with patient survival duration relative to Akt3/+S472. These effects were due to striking induction of apoptosis, which was mediated by Bim upregulation, leading to conformational activation of Bax and caspase-3 processing. Bim accumulation was caused by marked endocytosis of EGF receptors with concomitant ERK attenuation, which stabilizes BIM. These findings demonstrate an unexpected function of an endogenously expressed Akt isoform in promoting, as opposed to suppressing, apoptosis, underscoring that Akt isoforms may exert dissonant functions in malignancy.Significance: These results illuminate an unexpected function for an endogenously expressed Akt isoform in promoting apoptosis, underscoring the likelihood that different Akt isoforms exert distinct functions in human cancer. Cancer Res; 78(1); 103-14. ©2017 AACR.

Akt/mTOR mediated induction of bystander effect signaling in a nucleus independent manner in irradiated human lung adenocarcinoma epithelial cells

Cytoplasm is an important target for the radiation-induced bystander effect (RIBE). In the present work, the critical role of protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway in the generation of RIBE signaling after X-ray irradiation and the rapid phosphorylation of Akt and mTOR was observed in the cytoplasm of irradiated human lung adenocarcinoma epithelial (A549) cells. Targeting A549 cytoplasts with individual protons from a microbeam showed that RIBE signal(s) mediated by the Akt/mTOR pathway were generated even in the absence of a cell nucleus. These results provide a new insight into the mechanisms driving the cytoplasmic response to irradiation and their impact on the production of RIBE signal(s).

Akt Signaling Pathway in Macrophage Activation and M1/M2 Polarization

Macrophages become activated initiating innate immune responses. Depending on the signals, macrophages obtain an array of activation phenotypes, described by the broad terms of M1 or M2 phenotype. The PI3K/Akt/mTOR pathway mediates signals from multiple receptors including insulin receptors, pathogen-associated molecular pattern receptors, cytokine receptors, adipokine receptors, and hormones. As a result, the Akt pathway converges inflammatory and metabolic signals to regulate macrophage responses modulating their activation phenotype. Akt is a family of three serine-threonine kinases, Akt1, Akt2, and Akt3. Generation of mice lacking individual Akt, PI3K, or mTOR isoforms and utilization of RNA interference technology have revealed that Akt signaling pathway components have distinct and isoform-specific roles in macrophage biology and inflammatory disease regulation, by controlling inflammatory cytokines, miRNAs, and functions including phagocytosis, autophagy, and cell metabolism. Herein, we review the current knowledge on the role of the Akt signaling pathway in macrophages, focusing on M1/M2 polarization and highlighting Akt isoform-specific functions.

Attractor landscape analysis of colorectal tumorigenesis and its reversion

Background

Colorectal cancer arises from the accumulation of genetic mutations that induce dysfunction of intracellular signaling. However, the underlying mechanism of colorectal tumorigenesis driven by genetic mutations remains yet to be elucidated.

Results

To investigate colorectal tumorigenesis at a system-level, we have reconstructed a large-scale Boolean network model of the human signaling network by integrating previous experimental results on canonical signaling pathways related to proliferation, metastasis, and apoptosis. Throughout an extensive simulation analysis of the attractor landscape of the signaling network model, we found that the attractor landscape changes its shape by expanding the basin of attractors for abnormal proliferation and metastasis along with the accumulation of driver mutations. A further hypothetical study shows that restoration of a normal phenotype might be possible by reversely controlling the attractor landscape. Interestingly, the targets of approved anti-cancer drugs were highly enriched in the identified molecular targets for the reverse control.

Conclusions

Our results show that the dynamical analysis of a signaling network based on attractor landscape is useful in acquiring a system-level understanding of tumorigenesis and developing a new therapeutic strategy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-016-0341-9) contains supplementary material, which is available to authorized users.

Gamma-synuclein binds to AKT and promotes cancer cell survival and proliferation

Hyperactivation of AKT plays a critical role in the survival and proliferation of cancer cells. However, the molecular mechanisms underlying AKT activation remain elusive. Here, we tested the effect of γ-synuclein, a member of the synuclein family of proteins, on the activation of AKT. We show that the expression level of γ-synuclein is increased in non-small cell lung cancer (NSCLC) tissues. γ-Synuclein binds to the protein kinase domain of AKT and promotes its phosphorylation. Overexpression of γ-synuclein in H157 cells enhances cell proliferation and protects the cells from staurosporine-induced cytotoxicity. Knockdown of γ-synuclein attenuates AKT activation and cell proliferation induced by epidermal growth factor. The effect of γ-synuclein is abolished when AKT is depleted. Thus, γ-synuclein promotes cell survival and proliferation via activating AKT and may play a causal role in the pathogenesis of NSCLC.

Nuclear EGFR impairs ASPP2-p53 complex-induced apoptosis by inducing SOS1 expression in hepatocellular carcinoma

ASPP2 can bind to p53 and enhance the apoptotic capabilities of p53 by guiding it to the promoters of pro-apoptotic genes. Here, ASPP2 overexpression for 24 hours transiently induced apoptosis in hepatoma cells by enhancing the transactivation of p53 on pro-apoptotic gene promoters. However, long-term ASPP2 overexpression (more than 48 hours) failed to induce apoptosis because p53 was released from the pro-apoptotic gene promoters. In non-apoptotic cells, nuclear EGFR induced SOS1 expression by directly binding to the SOS1 promoter. SOS1 activated the HRAS/PI3K/AKT pathway and resulted in nuclear translocation of p-AKT and Bcl-2. The interaction between p-AKT and ASPP2 facilitates Bcl-2 binding to p53, which releases p53 from the pro-apoptotic gene promoters. The in vivo assay demonstrated that EGFR/SOS1-promoted growth of nuclear p-AKT⁺, Bcl-2⁺ cells results in the resistance of hepatoma cells to ASPP2-p53 complex-induced apoptosis and that blocking nuclear translocation of EGFR dramatically improves and enhances the pro-apoptotic function of ASPP2. Finally, the activation of the HRAS/PI3K/AKT pathway by EGFR-induced SOS1 also inhibits cisplatin-induced apoptosis, suggesting a common apoptosis-evasion mechanism in hepatoma cells. Because evasion of apoptosis contributes to treatment resistance in hepatoma, our results also support further investigation of combined therapeutic blockade of EGFR and SOS1.

Acidosis promotes invasiveness of breast cancer cells through ROS-AKT-NF-κB pathway

It is well known that acidic microenvironment promotes tumorigenesis, however, the underlying mechanism remains largely unknown. In the present study, we show that acidosis promotes invasiveness of breast cancer cells through a series of signaling events. First, our study indicates that NF-κB is a key factor for acidosis-induced cell invasion. Acidosis activates NF-κB without affecting STAT3 activity; knockdown of NF-κB p65 abrogates the acidosis-induced invasion activity. Next, we show that the activation of NF-κB is mediated through phosphorylation and degradation of IκBα; and phosphorylation and nuclear translocation of p65. Upstream to NF-κB signaling, AKT is activated under acidic conditions. Moreover, acidosis induces generation of reactive oxygen species (ROS) which can be suppressed by ROS scavengers, reversing the acidosis-induced activation of AKT and NF-κB, and invasiveness. As a negative regulator of AKT, PTEN is oxidized and inactivated by the acidosis-induced ROS. Finally, inhibition of NADPH oxidase (NOX) suppresses acidosis-induced ROS production, suggesting involvement of NOX in acidosis-induced signaling cascade. Of considerable interest, acidosis-induced ROS production and activation of AKT and NF-κB can be only detected in cancer cells, but not in non-malignant cells. Together, these results demonstrate a cancer specific acidosis-induced signaling cascade in breast cancer cells, leading to cell invasion.

The Role of Soy Phytoestrogens on Genetic and Epigenetic Mechanisms of Prostate Cancer

Soy phytoestrogens are dietary components with considerable effects on reducing the incidence of prostate cancer. Epidemiological studies demonstrated that occurrence of prostate cancer is relatively low in Asia and Southern Europe, a status associated with consuming of soy isoflavones, such as genistein, daidzein, and glycitein. Soy phytoestrogens exert their activity on molecular mechanisms, including cell-cycle control, induction of apoptosis, inhibition of angiogenesis, and metastasis. In addition, they have antioxidant activity and show regulatory effect on the expression of genes involved in DNA damage and repair. Furthermore, the epigenetic regulation of gene expression can be modified by soy phytoestrogens. They show regulatory effects on gene activity by altering DNA methylation and/or histone modification patterns. In this chapter, we discuss the role of soy phytoestrogens on the genetic and epigenetic mechanisms of prostate cancer. We attempt to provide further insight in order to understand the underlying mechanisms of protective effects of soy phytoestrogens in preventing prostate cancer.

Constitutive control of AKT1 gene expression by JUNB/CJUN in ALK+ anaplastic large-cell lymphoma: a novel crosstalk mechanism

Anaplastic lymphoma kinase-positive (ALK+) anaplastic large-cell lymphoma (ALCL) is an aggressive T-cell non-Hodgkin lymphoma characterized by the t(2;5), resulting in the overexpression of nucleophosmin (NPM)-ALK, which is known to activate the phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, resulting in cell cycle and apoptosis deregulation. ALK+ ALCL is also characterized by strong activator protein-1 (AP-1) activity and overexpression of two AP-1 transcription factors, CJUN and JUNB. Here, we hypothesized that a biologic link between AP-1 and AKT kinase may exist, thus contributing to ALCL oncogenesis. We show that JUNB and CJUN bind directly to the AKT1 promoter, inducing AKT1 transcription in ALK+ ALCL. Knockdown of JUNB and CJUN in ALK+ ALCL cell lines downregulated AKT1 mRNA and promoter activity and was associated with lower AKT1 protein expression and activation. We provide evidence that this is a transcriptional control mechanism shared by other cell types even though it may operate in a way that is cell context-specific. In addition, STAT3 (signal transducer and activator of transcription 3)-induced control of AKT1 transcription was functional in ALK+ ALCL and blocking of STAT3 and AP-1 signaling synergistically affected cell proliferation and colony formation. Our findings uncover a novel transcriptional crosstalk mechanism that links AP-1 and AKT kinase, which coordinate uncontrolled cell proliferation and survival in ALK+ ALCL.

Genome-wide identification and comprehensive analyses of the kinomes in four pathogenic microsporidia species

Microsporidia have attracted considerable attention because they infect a wide range of hosts, from invertebrates to vertebrates, and cause serious human diseases and major economic losses in the livestock industry. There are no prospective drugs to counteract this pathogen. Eukaryotic protein kinases (ePKs) play a central role in regulating many essential cellular processes and are therefore potential drug targets. In this study, a comprehensive summary and comparative analysis of the protein kinases in four microsporidia–Enterocytozoon bieneusi, Encephalitozoon cuniculi, Nosema bombycis and Nosema ceranae–was performed. The results show that there are 34 ePKs and 4 atypical protein kinases (aPKs) in E. bieneusi, 29 ePKs and 6 aPKs in E. cuniculi, 41 ePKs and 5 aPKs in N. bombycis, and 27 ePKs and 4 aPKs in N. ceranae. These data support the previous conclusion that the microsporidian kinome is the smallest eukaryotic kinome. Microsporidian kinomes contain only serine-threonine kinases and do not contain receptor-like and tyrosine kinases. Many of the kinases related to nutrient and energy signaling and the stress response have been lost in microsporidian kinomes. However, cell cycle-, development- and growth-related kinases, which are important to parasites, are well conserved. This reduction of the microsporidian kinome is in good agreement with genome compaction, but kinome density is negatively correlated with proteome size. Furthermore, the protein kinases in each microsporidian genome are under strong purifying selection pressure. No remarkable differences in kinase family classification, domain features, gain and/or loss, and selective pressure were observed in these four species. Although microsporidia adapt to different host types, the coevolution of microsporidia and their hosts was not clearly reflected in the protein kinases. Overall, this study enriches and updates the microsporidian protein kinase database and may provide valuable information and candidate targets for the design of treatments for pathogenic diseases.

The MT2 receptor stimulates axonogenesis and enhances synaptic transmission by activating Akt signaling

The MT2 receptor is a principal type of G protein-coupled receptor that mainly mediates the effects of melatonin. Deficits of melatonin/MT2 signaling have been found in many neurological disorders, including Alzheimer's disease, the most common cause of dementia in the elderly, suggesting that preservation of the MT2 receptor may be beneficial to these neurological disorders. However, direct evidence linking the MT2 receptor to cognition-related synaptic plasticity remains to be established. Here, we report that the MT2 receptor, but not the MT1 receptor, is essential for axonogenesis both in vitro and in vivo. We find that axon formation is retarded in MT2 receptor knockout mice, MT2-shRNA electroporated brain slices or primary neurons treated with an MT2 receptor selective antagonist. Activation of the MT2 receptor promotes axonogenesis that is associated with an enhancement in excitatory synaptic transmission in central neurons. The signaling components downstream of the MT2 receptor consist of the Akt/GSK-3β/CRMP-2 cascade. The MT2 receptor C-terminal motif binds to Akt directly. Either inhibition of the MT2 receptor or disruption of MT2 receptor-Akt binding reduces axonogenesis and synaptic transmission. Our data suggest that the MT2 receptor activates Akt/GSK-3β/CRMP-2 signaling and is necessary and sufficient to mediate functional axonogenesis and synaptic formation in central neurons.

Imidazo[1,2-a]pyridine-based peptidomimetics as inhibitors of Akt

We report the design, synthesis, and biological evaluation of imidazopyridine-based peptidomimetics based on the substrate consensus sequence of Akt, an AGC family serine/threonine kinase hyperactivated in over 50% of human tumors. Our ligand-based approach led to the identification of novel substrate mimetic inhibitors of Akt1 featuring an unnatural extended dipeptide surrogate. Compound 11 inhibits Akt isoforms in the sub-micromolar range and exhibits improved proteolytic stability relative to a parent pentapeptide.

The links between AKT and two intracellular proteolytic cascades: ubiquitination and autophagy

The serine threonine kinase AKT plays a central role in the regulation of cell survival in a variety of human neoplastic diseases. A series of studies have revealed a connection between AKT signaling and two important protein degradation pathways in mammalian cells: the ubiquitin-proteasome system and autophagy. Two distinct ubiquitination systems have been reported to regulate AKT signaling: K63-linked ubiquitination, which promotes the oncogenic activation of AKT, and K48-linked ubiquitination, which triggers the proteasomal degradation of phosphorylated AKT. Autophagy is an evolutionarily conserved mechanism for the gross disposal and recycling of intracellular proteins in mammalian cells. AKT signaling may play a regulatory role in autophagy; however, the underlying mechanisms have not been fully clarified. Recently, AKT was shown to phosphorylate key molecules involved in the regulation of autophagy. Furthermore, lysosomal co-localization of the AKT-Phafin2 complex is reportedly critical for the induction of autophagy. In this review, we will discuss the connection between AKT, a core intracellular survival regulator, and two major intracellular proteolytic signaling pathways in mammalian cells.

microRNA and non-canonical TGF-β signalling: implications for prostate cancer therapy

The incidence of prostate cancer is increasing worldwide and marks a significant health issue. Paired with this, current therapeutic options for advanced prostate cancer, notably androgen deprivation therapy (ADT), fail to provide a consistent level of efficacy throughout the treatment period, highlighting the need for new robust therapies. Growth factors, such as Transforming Growth Factor-beta (TGF-β), possess the ability to impede cancer development in the early stages, via alterations in either apoptosis, cell proliferation, or the promotion of cellular senescence. However, later in the pathogenesis, advanced prostate cancer cells become insensitive to the previously beneficial effects of TGF-β. The molecular mechanisms behind this acquired insensitivity are not well understood. Thus, the aim of this review is to examine the effects of a class of small non-coding RNA, microRNA (miRNA), on TGF-β signalling. The impact of miRNA on the canonical TGF-β Smad signalling pathway has been well investigated, hence, in this review, we will examine whether miRNA targeting members of non-canonical TGF-β signalling members, such as, Erk, RhoA, PI3K/Akt and JNK/p38 could provide alternate therapeutic options for advanced prostate cancer.

Follicular thyroid cancers demonstrate dual activation of PKA and mTOR as modeled by thyroid-specific deletion of Prkar1a and Pten in mice

CONTEXT

Thyroid cancer is the most common form of endocrine cancer, and it is a disease whose incidence is rapidly rising. Well-differentiated epithelial thyroid cancer can be divided into papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC). Although FTC is less common, patients with this condition have more frequent metastasis and a poorer prognosis than those with PTC.

OBJECTIVE

The objective of this study was to characterize the molecular mechanisms contributing to the development and metastasis of FTC.

DESIGN

We developed and characterized mice carrying thyroid-specific double knockout of the Prkar1a and Pten tumor suppressor genes and compared signaling alterations observed in the mouse FTC to the corresponding human tumors.

SETTING

The study was conducted at an academic research laboratory. Human samples were obtained from academic hospitals.

PATIENTS

Deidentified, formalin-fixed, paraffin-embedded (FFPE) samples were analyzed from 10 control thyroids, 30 PTC cases, five follicular variant PTC cases, and 10 FTC cases.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Mouse and patient samples were analyzed for expression of activated cAMP response element binding protein, AKT, ERK, and mammalian target of rapamycin (mTOR). Murine FTCs were analyzed for differential gene expression to identify genes associated with metastatic progression.

RESULTS

Double Prkar1a-Pten thyroid knockout mice develop FTC and recapitulate the histology and metastatic phenotype of the human disease. Analysis of signaling pathways in FTC showed that both human and mouse tumors exhibited strong activation of protein kinase A and mTOR. The development of metastatic disease was associated with the overexpression of genes required for cell movement.

CONCLUSIONS

These data imply that the protein kinase A and mTOR signaling cascades are important for the development of follicular thyroid carcinogenesis and may suggest new targets for therapeutic intervention. Mouse models paralleling the development of the stages of human FTC should provide important new tools for understanding the mechanisms of FTC development and progression and for evaluating new therapeutics.

Signaling steps in the induction of genomic damage by insulin in colon and kidney cells

Diabetes mellitus (DM), a disease with almost 350 million people affected worldwide, will be the seventh leading cause of death by 2030. Diabetic patients develop various types of complications, among them an increased rate of malignancies. Studies reported the strong correlation between DM and several cancer types, of which colon and kidney cancers are the most common. Hyperinsulinemia, the high insulin blood level characteristic of early diabetes type 2, was identified as a risk factor for cancer development. In previous studies, we showed that an elevated insulin level can induce oxidative stress, resulting in DNA damage in colon cells in vitro and in kidney cells in vitro and in vivo. In the present study, we elucidate the signaling pathway of insulin-mediated genotoxicity, which is effective through oxidative stress induction in colon and kidney. The signaling mechanism is starting by phosphorylation of the insulin and insulin-like growth factor-1 receptors, followed by activation of phosphatidylinositide 3-kinase (PI3K), which in turn activates AKT. Subsequently, mitochondria and nicotinamide adenine dinucleotide phosphate oxidase (NADPH) isoforms (Nox1 and Nox4 in colon and kidney, respectively) are activated for reactive oxygen species (ROS) production, and the resulting excess ROS can attack the DNA, causing DNA oxidation. We conclude that hyperinsulinemia represents an important risk factor for cancer initiation or progression as well as a target for cancer prevention in diabetic patients.

Control of oncogenesis by eIF2α phosphorylation: implications in PTEN and PI3K-Akt signaling and tumor treatment

mRNA translation plays an important role in tumor development and represents a valid target of pharmaceutical intervention in cancer. A key step in mRNA translation involves the regulation of initiation by the eukaryotic initiation factor eIF2. Eukaryotic cells respond to various forms of stress by inducing the phosphorylation of the α-subunit of eIF2 at S51, a modification that leads to protein synthesis inhibition. Phosphorylated eIF2α can act either as a promoter of cell survival or an inducer of cell death in response to distinct stimuli. Increased eIF2α phosphorylation has a cytoprotective function in response to genetic or pharmacological inhibition of the PI3K-Akt pathway but also exhibits a proapoptotic function downstream of the PTEN tumor suppressor, independent of PI3K-Akt signaling inhibition. The functional interplay between the PI3K-Akt and eIF2α phosphorylation pathways may have important implications in the design of anti-tumor therapies that depend on the cell fate decisions of phosphorylated eIF2α.

Phospholipase D2 mediates survival signaling through direct regulation of Akt in glioblastoma cells

The lack of innovative drug targets for glioblastoma multiforme (GBM) limits patient survival to approximately 1 year following diagnosis. The pro-survival kinase Akt provides an ideal target for the treatment of GBM as Akt signaling is frequently activated in this cancer type. However, the central role of Akt in physiological processes limits its potential as a therapeutic target. In this report, we show that the lipid-metabolizing enzyme phospholipaseD(PLD) is a novel regulator of Akt inGBM.Studies using a combination of small molecule PLD inhibitors and siRNA knockdowns establish phosphatidic acid, the product of the PLD reaction, as an essential component for the membrane recruitment and activation of Akt. Inhibition of PLD enzymatic activity and subsequent Akt activation decreases GBM cell viability by specifically inhibiting autophagic flux. We propose a mechanism whereby phosphorylation of beclin1 by Akt prevents binding of Rubicon (RUN domain cysteine-rich domain containing beclin1-interacting protein), an interaction known to inhibit autophagic flux. These findings provide a novel framework through which Akt inhibition can be achieved without directly targeting the kinase.

Preclinical trial of a new dual mTOR inhibitor, MLN0128, using renal cell carcinoma tumorgrafts

mTOR is a rational target in renal cell carcinoma (RCC) because of its role in disease progression. However, the effects of temsirolimus, the only first-generation mTOR inhibitor approved by the FDA for first-line treatment of metastatic RCC, on tumor reduction and progression-free survival are minimal. Second-generation mTOR inhibitors have not been evaluated on RCC. We compared the effects of temsirolimus and MLN0128, a potent second-generation mTOR inhibitor, on RCC growth and metastasis using a realistic patient-derived tissue slice graft (TSG) model. TSGs were derived from three fresh primary RCC specimens by subrenal implantation of precision-cut tissue slices into immunodeficient mice that were randomized and treated with MLN0128, temsirolimus, or placebo. MLN0128 consistently suppressed primary RCC growth, monitored by magnetic resonance imaging (MRI), in three TSG cohorts for up to 2 months. Temsirolimus, in contrast, only transiently inhibited the growth of TSGs in one of two cohorts before resistance developed. In addition, MLN0128 reduced liver metastases, determined by human-specific quantitative polymerase chain reaction, in two TSG cohorts, whereas temsirolimus failed to have any significant impact. Moreover, MLN0128 decreased levels of key components of the two mTOR subpathways including TORC1 targets 4EBP1, p-S6K1, HIF1α and MTA1 and the TORC2 target c-Myc, consistent with dual inhibition. Our results demonstrated that MLN0128 is superior to temsirolimus in inhibiting primary RCC growth as well as metastases, lending strong support for further clinical development of dual mTOR inhibitors for RCC treatment.

2,3,7,8-Tetrachlorodibenzo-p-dioxin stimulates proliferation of HAPI microglia by affecting the Akt/GSK-3β/cyclin D1 signaling pathway

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental toxin that induces apoptosis of neurons and a pro-inflammatory response in microglial cells. First, we found that TCDD induced proliferation of HAPI microglial cells in a dose- and time-dependent manner. Flow cytometry analysis showed that this proliferation by TCDD was due to mainly enhancing the G1 to S phase transition. Next, it was found that TCDD treatment led to up-regulation of cyclin D1, which induces cell cycle progression from G1 to S phase, in a time-dependent manner. As for molecular mechanism, we revealed that TCDD was capable of inducing Akt phosphorylation and activation, resulting in phosphorylation and inactivation of glycogen synthase kinase-3β (GSK-3β). Inactivated GSK-3β attenuated proteasomal degradation of cyclin D1 by reducing Thr(286)-phosphorylated cyclin D1 levels. Moreover, inactivated GSK-3β increased cyclin D1 gene transcription by increasing its transcription factor β-catenin in the nucleus. Further, blockage of phosphoinositide 3-kinase/Akt kinase with their specific inhibitors, LY294002 and Akt 1/2 kinase inhibitor, significantly reduced TCDD-enhanced proliferation of HAPI microglial cells. In conclusion, TCDD stimulates proliferation of HAPI microglial cells by affecting the Akt/GSK-3β/cyclin D1 signaling pathway.

Carboxyl-terminal modulator protein positively regulates Akt phosphorylation and acts as an oncogenic driver in breast cancer

Akt activation has been implicated broadly in tumorigenesis, but the basis for its dysregulation in cancer cells is incompletely understood. In this study, we sought to clarify a regulatory role for the Akt-binding carboxy-terminal modulator protein (CTMP), which has been controversial. In evaluating CTMP expression in paired normal-tumor specimens of 198 patients with breast cancer, we found that CTMP was upregulated in breast tumors, where it was associated with poor patient survival. Notably, CTMP expression also correlated positively with Akt phosphorylation in breast cancer clinical specimens and cell lines. Furthermore, ectopic expression of CTMP promoted cell proliferation and enhanced the tumorigenic properties of estrogen-dependent breast cancer cells. This effect was correlated with increased sensitivity to insulin-induced Akt phosphorylation, which is mediated primarily by the phosphoinositide 3-kinase-Akt pathway. In contrast, short hairpin RNA-mediated silencing of endogenous CTMP decreased the proliferation of estrogen-dependent or estrogen-independent breast cancer cells. Mechanistic investigations defined the N-terminal domain of CTMP at amino acids 1 to 64 as responsible for Akt binding. Taken together, our results firmly corroborate the concept that CTMP promotes Akt phosphorylation and functions as an oncogenic molecule in breast cancer.

Distinct responses of protein turnover regulatory pathways in hypoxia- and semistarvation-induced muscle atrophy

The balance of muscle protein synthesis and degradation determines skeletal muscle mass. We hypothesized that hypoxia-induced muscle atrophy and alterations in the regulation of muscle protein turnover include a hypoxia-specific component, in addition to the observed effects of reduction in food intake in response to hypoxia. Mice were subjected to normoxic, hypoxic (8% oxygen), or pair-fed conditions for 2, 4, and 21 days. Cell-autonomous effects of hypoxia on skeletal muscle were also assessed in differentiated C2C12 myotubes. Hypoxia induced an initial rapid loss of body and muscle weight, which remained decreased during chronic hypoxia and could only in part be explained by the hypoxia-induced reduction of food intake (semistarvation). Regulatory steps of protein synthesis (unfolded protein response and mammal target of rapamycin signaling) remained active in response to acute and sustained hypoxia but not to semistarvation. Activation of regulatory signals for protein degradation, including increased expression of Murf1, Atrogin-1, Bnip3, and Map1lc3b mRNAs, was observed in response to acute hypoxia and to a lesser extent following semistarvation. Conversely, the sustained elevation of Atrogin-1, Bnip3, and Map1lc3b mRNAs and the increased activity of their upstream transcriptional regulator Forkhead box O1 were specific to chronic hypoxia because they were not observed in response to reduced food intake. In conclusion, altered regulation of protein turnover during hypoxia-induced muscle atrophy resulted from an interaction of semistarvation and a hypoxia-specific component. The finding that food restriction but not hypoxia-induced semistarvation inhibited regulatory steps in protein synthesis suggests a hypoxia-specific impairment of the coordination between protein-synthesis signaling and protein-degradation signaling in skeletal muscle.

Effective identification of Akt interacting proteins by two-step chemical crosslinking, co-immunoprecipitation and mass spectrometry

Akt is a critical protein for cell survival and known to interact with various proteins. However, Akt binding partners that modulate or regulate Akt activation have not been fully elucidated. Identification of Akt-interacting proteins has been customarily achieved by co-immunoprecipitation combined with western blot and/or MS analysis. An intrinsic problem of the method is loss of interacting proteins during procedures to remove non-specific proteins. Moreover, antibody contamination often interferes with the detection of less abundant proteins. Here, we developed a novel two-step chemical crosslinking strategy to overcome these problems which resulted in a dramatic improvement in identifying Akt interacting partners. Akt antibody was first immobilized on protein A/G beads using disuccinimidyl suberate and allowed to bind to cellular Akt along with its interacting proteins. Subsequently, dithiobis[succinimidylpropionate], a cleavable crosslinker, was introduced to produce stable complexes between Akt and binding partners prior to the SDS-PAGE and nanoLC-MS/MS analysis. This approach enabled identification of ten Akt partners from cell lysates containing as low as 1.5 mg proteins, including two new potential Akt interacting partners. None of these but one protein was detectable without crosslinking procedures. The present method provides a sensitive and effective tool to probe Akt-interacting proteins. This strategy should also prove useful for other protein interactions, particularly those involving less abundant or weakly associating partners.

TRIP6 regulates p27 KIP1 to promote tumorigenesis

TRIP6 is an adaptor protein that regulates cell motility and antiapoptotic signaling. Although it has been implicated in tumorigenesis, the underlying mechanism remains largely unknown. Here we provide evidence that TRIP6 promotes tumorigenesis by serving as a bridge to promote the recruitment of p27(KIP1) to AKT in the cytosol. TRIP6 regulates the membrane translocation and activation of AKT and facilitates AKT-mediated recognition and phosphorylation of p27(KIP1) specifically at T157, thereby promoting the cytosolic mislocalization of p27(KIP1). This is required for p27(KIP1) to enhance lysophosphatidic acid (LPA)-induced ovarian cancer cell migration. TRIP6 also promotes serum-induced reduction of nuclear p27(KIP1) expression levels through Skp2-dependent and -independent mechanisms. Consequently, knockdown of TRIP6 in glioblastoma or ovarian cancer xenografts restores nuclear p27(KIP1) expression and impairs tumor proliferation. As TRIP6 is upregulated in gliomas and its levels correlate with poor clinical outcomes in a dose-dependent manner, it may represent a novel prognostic marker and therapeutic target in gliomas.