Ubiquitin-like protein MNSFβ/endophilin II complex regulates Dectin-1-mediated phagocytosis and inflammatory responses in macrophages

Associations Between Diabetes Mellitus and Neurodegenerative Diseases

Diabetes mellitus (DM) and neurodegenerative diseases/disturbances are worldwide health problems. The most common chronic conditions diagnosed in persons 60 years and older are type 2 diabetes mellitus (T2DM) and cognitive impairment. It was found that diabetes mellitus is a major risk for cognitive decline, dementia, Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and other neurodegenerative disorders. Different mechanisms of associations between these diseases and diabetes mellitus have been suggested. For example, it is postulated that an impaired intracellular insulin signaling pathway, together with hyperglycemia and hyperinsulinemia, may cause pathological changes, such as dysfunction of the mitochondria, oxidative stress inflammatory responses, etc. The association between diabetes mellitus and neurodegenerative diseases, as well as the mechanisms of these associations, needs further investigation. The aim of this review is to describe the associations between diabetes mellitus, especially type 1 (T1DM) and type 2 diabetes mellitus, and selected neurodegenerative diseases, i.e., Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. Suggested mechanisms of these associations are also described.

MNSFβ promotes LPS-induced TNFα expression by increasing the localization of RC3H1 to stress granules, and the interfering peptide HEPN2 reduces TNFα production by disrupting the MNSFβ-RC3H1 interaction in macrophages

Abnormally elevated tumor necrosis factor-α (TNFα) levels at the maternal-fetal interface can lead to adverse pregnancy outcomes, including recurrent miscarriage (RM), but the mechanism underlying upregulated TNFα expression is not fully understood. We previously reported that the interaction between monoclonal nonspecific suppressor factor-β (MNSFβ) and RC3H1 upregulates TNFα expression, but the precise mechanisms are unknown. In this study, we found that MNSFβ stimulated the LPS-induced TNFα expression by inactivating the promoting effect of RC3H1 on TNFα mRNA degradation rather than directly inhibiting the expression of RC3H1 in THP1-Mϕs. Mechanistically, the 81-326 aa region of the RC3H1 protein binds to the 101-133 aa region of the MNSFβ protein, and MNSFβ facilitated stress granules (SGs) formation and the translocation of RC3H1 to SGs by interacting with RC3H1 and fragile X mental retardation 1 (FMR1) in response to LPS-induced stress. The SGs-localization of RC3H1 reduced its inhibitory effect on TNFα expression in LPS-treated THP1-Mϕs. The designed HEPN2 peptide effectively reduced the LPS-induced expression of TNFα in THP1-Mϕs by interfering with the MNSFβ-RC3H1 interaction. Treatment with the HEPN2 peptide significantly improved adverse pregnancy outcomes, including early pregnancy loss (EPL) and lower fetal weight (LFW), which are induced by LPS in mice. These data indicated that MNSFβ promoted TNFα expression at least partially by increasing the localization of RC3H1 to SGs under inflammatory stimulation and that the HEPN2 peptide improved the adverse pregnancy outcomes induced by LPS in mice, suggesting that MNSFβ is a potential pharmacological target for adverse pregnancy outcomes caused by abnormally increased inflammation at early pregnancy.

Investigating the regulatory mechanism of glucose metabolism by ubiquitin-like protein MNSFβ

BACKGROUND

Monoclonal nonspecific suppressor factor β (MNSFβ), a ubiquitously expressed member of the ubiquitin-like protein family, is associated with diverse cell regulatory functions. It has been implicated in glycolysis regulation and cell proliferation enhancement in the macrophage-like cell line Raw264.7. This study aims to show that HIF-1α regulates MNSFβ-mediated metabolic reprogramming.

METHODS AND RESULTS

In Raw264.7 cells, MNSFβ siRNA increased the oxygen consumption rate and reactive oxygen species (ROS) production but decreased ATP levels. Cells with MNSFβ knockdown showed a markedly increased ATP reduction rate upon the addition of oligomycin, a mitochondrial ATP synthase inhibitor. In addition, MNSFβ siRNA decreased the expression levels of mRNA and protein of HIF-1α-a regulator of glucose metabolism. Evaluation of the effect of MNSFβ on glucose metabolism in murine peritoneal macrophages revealed no changes in lactate production, glucose consumption, or ROS production.

CONCLUSION

MNSFβ affects both glycolysis and mitochondrial metabolism, suggesting HIF-1α involvement in the MNSFβ-regulated glucose metabolism in Raw264.7 cells.

Multifunctional role of the ubiquitin proteasome pathway in phagocytosis

Phagocytosis is a specialized form of endocytosis where large cells and particles (>0.5μm) are engulfed by the phagocytic cells, and ultimately digested in the phagolysosomes. This process not only eliminates unwanted particles and pathogens from the extracellular sources, but also eliminates apoptotic cells within the body, and is critical for maintenance of tissue homeostasis. It is believed that both endocytosis and phagocytosis share common pathways after particle internalization, but specialized features and differences between these two routes of internalization are also likely. The recruitment and removal of each protein/particle during the maturation of endocytic/phagocytic vesicles has to be tightly regulated to ensure their timely action. Ubiquitin proteasome pathway (UPP), degrades unwanted proteins by post-translational modification of proteins with chains of conserved protein Ubiquitin (Ub), with subsequent recognition of Ub chains by the 26S proteasomes and substrate degradation by this protease. This pathway utilizes different Ub linkages to modify proteins to regulate protein-protein interaction, localization, and activity. Due to its vast number of targets, it is involved in many cellular pathways, including phagocytosis. This chapters describes the basic steps and signaling in phagocytosis and different roles that UPP plays at multiple steps in regulating phagocytosis directly, or through its interaction with other phagosomal proteins. How aberrations in UPP function affect phagocytosis and their association with human diseases, and how pathogens exploit this pathway for their own benefit is also discussed.

The variations of endophilin A2-FoxO3a-autophagy signal in angiotensin II-induced dopaminergic neuron injury mouse model and by biochanin A

Biochanin A (Bioch A) is a natural plant estrogen, with various biological activities such as anti-apoptosis, anti-oxidation, and suppression of inflammation. In this study, we investigated the protective effects of Bioch A on angiotensin II (AngII) - induced dopaminergic (DA) neuron damage in vivo and on molecular mechanisms. Spontaneous activity and motor ability of mice among groups was detected by open-field test and swim-test. The expression of TH, microtubule-associated proteins light chain 3B II (LC3BII)/LC3BI, beclin-1, P62, forkhead box class O3 (FoxO3), phosphorylated (p) FoxO3a/FoxO3a, FoxO3, and endophilin A2 were determined by Western blot and immunohistochemistry or immunofluorescence staining. Our results showed that AngII treatment significantly increased the behavioral dysfunction of mice and DA neuron damage. Meanwhile, AngII treatment increased the expression of LC3BII/LC3BI, beclin-1, P62, and FoxO3a and decreased the expression of endophilin A2 and p-FoxO3a/FoxO3a, however, Bioch A treatment alleviate these changes. In summary, these results suggest that Bioch A exerts protective effects on AngII-induced mouse model may be related to regulating endophilin A2, FoxO3a, and autophagy-related proteins; however, the specific mechanism is not yet clear and needs further study.

Quercetin and HSC70 coregulate the anti-inflammatory action of the ubiquitin-like protein MNSFβ

BACKGROUND

Quercetin is a flavonol that modifies many cellular processes. Monoclonal nonspecific suppressor factor β is a member of the ubiquitin-like family of proteins that are involved in various biological processes. It has been demonstrated that quercetin regulates the effect of MNSFβ on tumor necrosis factor-α secretion in lipopolysaccharide (LPS)-stimulated macrophages. This study found that quercetin and the heat shock protein HSC70 coregulate the action of MNSFβ.

METHODS AND RESULTS

Quercetin dose-dependently suppressed the LPS/interferon γ-induced nitric oxide production without cytotoxicity in the macrophage-like cell line Raw264.7. SiRNA knockdown experiments showed that quercetin inhibited the MNSFβ and HSC70 siRNA-mediated enhancement of TNFα and the production of RANTES, a member of C-C chemokine superfamily, in LPS-stimulated Raw264.7 cells. Western blot analysis showed that quercetin and HSC70 regulated ERK1/2 activation and LPS-stimulated IκBα degradation by affecting the complex formation of MNSFβ and the proapoptotic protein Bcl-G. Moreover, MNSFβ is implicated in TLR4/MyD88 signaling but not in TLR3 signaling.

CONCLUSIONS

HSC70 is an important chaperone that facilitates the stabilization of MNSFβ. Quercetin may negatively control the function of MNSFβ by regulating the action of the molecular chaperone HSC70. MNSFβ mediates TLR4/Myd88 signaling but not TLR3 signaling.

Potential new therapeutic target for Alzheimer's disease: Glucagon-like peptide-1

Increasing evidence shows a close relationship between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). Recently, glucagon-like peptide-1 (GLP-1), a gut incretin hormone, has become a well-established treatment for T2DM and is likely to be involved in treating cognitive impairment. In this mini review, the similarities between AD and T2DM are summarised with the main focus on GLP-1-based therapeutics in AD.

MNSFβ regulates placental development by conjugating IGF2BP2 to enhance trophoblast cell invasiveness

Objectives

Success in pregnancy in mammals predominantly depends on a well‐developed placenta. The differentiation of invasive trophoblasts is a fundamental process of placentation, the abnormalities of which are tightly associated with pregnancy disorders including preeclampsia (PE). Monoclonal nonspecific suppressor factor beta (MNSFβ) is an immunosuppressive factor. Its conventional knockout in mice induced embryonic lethality, whereas the underlying mechanism of MNSFβ in regulating placentation and pregnancy maintenance remains to be elucidated.

Methods

Trophoblast‐specific knockout of MNSFβ was generated using Cyp19‐Cre mice. In situ hybridization (ISH), haematoxylin and eosin (HE), immunohistochemistry (IHC) and immunofluorescence (IF) were performed to examine the distribution of MNSFβ and insulin‐like growth factor 2 mRNA‐binding protein 2 (IGF2BP2) at the foeto‐maternal interface. The interaction and expression of MNSFβ, IGF2BP2 and invasion‐related molecules were detected by immunoprecipitation (IP), immunoblotting and quantitative real‐time polymerase chain reaction (qRT‐PCR). The cell invasion ability was measured by the Transwell insert assay.

Results

We found that deficiency of MNSFβ in trophoblasts led to embryonic growth retardation by mid‐gestation and subsequent foetal loss, primarily shown as apparently limited trophoblast invasion. In vitro experiments in human trophoblasts demonstrated that the conjugation of MNSFβ with IGF2BP2 and thus the stabilization of IGF2BP2 essentially mediated the invasion‐promoting effect of MNSFβ. In the placentas from MNSFβ‐deficient mice and severe preeclamptic (PE) patients, downregulation of MNSFβ was evidently associated with the repressed IGF2BP2 expression.

Conclusions

The findings reveal the crucial role of MNSFβ in governing the trophoblast invasion and therefore foetal development, and add novel hints to reveal the placental pathology of PE.

MNSFβ Regulates TNFα Production by Interacting with RC3H1 in Human Macrophages, and Dysfunction of MNSFβ in Decidual Macrophages Is Associated With Recurrent Pregnancy Loss

Decidual macrophages (dMϕ) are the second largest population of leukocytes at the maternal–fetal interface and play critical roles in maintaining pregnancy. Our previous studies demonstrated the active involvement of monoclonal nonspecific suppressor factor-β (MNSFβ) in embryonic implantation and pregnancy success. MNSFβ is a ubiquitously expressed ubiquitin-like protein that also exhibits immune regulatory potential, but its function in human dMϕ remains unknown. Here, we observed that the proportion of CD11c^high (CD11cHI) dMϕ was significantly increased in dMϕ derived from patients with recurrent pregnancy loss (RPL dMϕ) compared to those derived from normal pregnant women (Control dMϕ). The production of MNSFβ and TNFα by RPL dMϕ was also significantly increased compared to that by Control dMϕ. Conditioned medium from RPL dMϕ exerted an inhibitory effect on the invasiveness of human trophoblastic HTR8/SVneo cells, and this effect could be partially reversed by a neutralizing antibody against TNFα. Bioinformatics analysis indicated a potential interaction between MNSFβ and RC3H1, a suppressor of TNFα transcription. Immunoprecipitation experiments with human Mϕ differentiated from the human monocyte cell line Thp1 (Thp1-derived Mϕ) proved the binding of MNSFβ to RC3H1. Specific knockdown of MNSFβ in Thp1-derived Mϕ led to a marked decrease in TNFα production, which could be reversed by inhibiting RC3H1 expression. Interestingly, a significant decrease in the protein level of RC3H1 was observed in RPL dMϕ. Together, our findings indicate that aberrantly increased MNSFβ expression in dMϕ may promote TNFα production via its interaction with RC3H1, and these phenomena could result in the disruption of the immune balance at the maternal–fetal interface and thus pregnancy loss.

Obesity and Diabetes Mediated Chronic Inflammation: A Potential Biomarker in Alzheimer's Disease

Alzheimer’s disease (AD) is the sixth leading cause of death and is correlated with obesity, which is the second leading cause of preventable diseases in the United States. Obesity, diabetes, and AD share several common features, and inflammation emerges as the central link. High-calorie intake, elevated free fatty acids, and impaired endocrine function leads to insulin resistance and systemic inflammation. Systemic inflammation triggers neuro-inflammation, which eventually hinders the metabolic and regulatory function of the brain mitochondria leading to neuronal damage and subsequent AD-related cognitive decline. As an early event in the pathogenesis of AD, chronic inflammation could be considered as a potential biomarker in the treatment strategies for AD.

Biochanin A protects against angiotensin II-induced damage of dopaminergic neurons in rats associated with the increased endophilin A2 expression

The brain renin-angiotensin system plays a vital role in the modulation of the neuroinflammatory responses and the progression of dopaminergic (DA) degeneration. Angiotensin II (Ang II) induces microglia activation via angiotensin II type 1 receptor (AT1R), which in turn affects the function of DA neurons. Endophilin A2 (EPA2) is involved in fast endophilin-mediated endocytosis and quickly endocytoses several G-protein-coupled receptor (GPCR), while AT1R belongs to GPCR family. Therefore, we speculated that EPA2 may modulate microglia activation via endocytosing AT1R. Biochanin A is an O-methylated isoflavone, classified as a kind of phytoestrogen due to its chemical structure that is similar to mammalian estrogens. In this study, we investigated the protective effects of biochanin A on Ang II-induced DA neurons damage in vivo, and molecular mechanisms. The results showed that biochanin A treatment for 7 days attenuated the behavioral dysfunction, inhibited the microglial activation, and prevented DA neuron damage in Ang II-induced rats. Furthermore, biochanin A increased EPA2 expression and decreased the expression of AT1R, gp91phox, p22 phox, NLRP3, ASC, Caspase-1, IL-1β, IL-6, IL-18, and TNF-α. In summary, these results suggest that biochanin A exerts protective effects in Ang II-induced model rats, and the mechanisms may involve inhibition of inflammatory responses, an increase in EPA2 expression and a decrease in AT1R expression.

Type 2 Diabetes Mellitus and Alzheimer's Disease: Role of Insulin Signalling and Therapeutic Implications

In the last two decades, numerous in vitro studies demonstrated that insulin receptors and theirs downstream pathways are widely distributed throughout the brain. This evidence has proven that; at variance with previous believes; insulin/insulin-like-growth-factor (IGF) signalling plays a crucial role in the regulation of different central nervous system (CNS) tasks. The most important of these functions include: synaptic formation; neuronal plasticity; learning; memory; neuronal stem cell activation; neurite growth and repair. Therefore; dysfunction at different levels of insulin signalling and metabolism can contribute to the development of a number of brain disorders. Growing evidences demonstrate a close relationship between Type 2 Diabetes Mellitus (T2DM) and neurodegenerative disorders such as Alzheimer’s disease. They, in fact, share many pathophysiological characteristics comprising impaired insulin sensitivity, amyloid β accumulation, tau hyper-phosphorylation, brain vasculopathy, inflammation and oxidative stress. In this article, we will review the clinical and experimental evidences linking insulin resistance, T2DM and neurodegeneration, with the objective to specifically focus on insulin signalling-related mechanisms. We will also evaluate the pharmacological strategies targeting T2DM as potential therapeutic tools in patients with cognitive impairment.

Ubiquitin-like protein MNSFβ noncovalently binds to molecular chaperone HSPA8 and regulates osteoclastogenesis

MNSFβ, a ubiquitin-like protein, covalently binds to various target proteins including proapoptotic Bcl-G. During the course of isolation of MNSFβ-conjugating enzyme(s), we identified a novel target protein for MNSFβ. MALDI-TOF MS fingerprinting revealed that the MNSFβ-interacting protein is HSPA8 (heat shock 70-kDa protein 8). We observed that MNSFβ noncovalently binds to HSPA8 in the presence of ATP in vitro. Double knockdown of MNSFβ and HSPA8 strongly inhibited RANKL-induced osteoclastogenesis from Raw264.7 macrophage-like cells. The same treatment inhibited RANKL-induced ERK1/2 and p38 phosphorylation and TNFα production, suggesting that the association of MNSFβ with HSPA8 may promote RANKL-induced osteoclastogenesis. This is the first report that MNSFβ binds to a protein substrate via the noncovalent association and exerts biological effects.

The role of type 2 diabetes in neurodegeneration

A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseases such as Alzheimer's disease (AD). AD is the most common form of dementia and is characterised neuropathologically by the accumulation of extracellular beta amyloid (Aβ) peptide aggregates and intracellular hyper-phosphorylated tau protein, which are thought to drive and/or accelerate inflammatory and oxidative stress processes leading to neurodegeneration. Although the precise mechanism remains unclear, T2D can exacerbate these neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism and CNS insulin resistance are features of both AD and T2D. Cell culture and animal studies have indicated that the early accumulation of Aβ may play a role in CNS insulin resistance and impaired insulin signalling. From the viewpoint of insulin resistance and impaired insulin signalling in the brain, these are also believed to initiate other aspects of brain injury, including inflammatory and oxidative stress processes. Here we review the clinical and experimental pieces of evidence that link these two chronic diseases of ageing, and discuss underlying mechanisms. The evaluation of treatments for the management of diabetes in preclinical, and clinical studies and trials for AD will also be discussed.

Ubiquitin-like protein MNSFβ covalently binds to Bcl-G and enhances lipopolysaccharide/interferon γ-induced apoptosis in macrophages

Monoclonal non-specific suppressor factor β (MNSFβ) is a ubiquitously expressed member of the ubiquitin-like family that is involved in various biological functions. Previous studies have demonstrated that MNSFβ covalently binds to intracellular pro-apoptotic protein Bcl-G and regulates the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) cascade in the mouse macrophage cell line Raw264.7. In this study, we demonstrate that MNSFβ promotes lipopolysaccharide (LPS)/interferon γ (IFNγ)-induced apoptosis of Raw264.7 macrophages. In Raw264.7 cells treated with MNSFβ small interfering RNA (siRNA), LPS/IFNγ- or NO donor S-nitrosoglutathione-induced apoptosis was inhibited. siRNA-mediated knockdown of MNSFβ did not affect inducible nitric-oxide synthase (iNOS) expression in LPS/IFNγ-stimulated Raw264.7 cells. Conversely, co-transfection with MNSFβ and Bcl-G greatly enhanced LPS/IFNγ- induced apoptosis in Raw264.7 cells, accompanied by increased expression of p53 and decreased Cox-2 activity. Unlike co-transfection with wild-type MNSFβ, co-transfection of a mutant MNSFβ (G74A) and Bcl-G did not result in enhancement of LPS/IFNγ-induced apoptosis. Co-over-expression of MNSFβ and Bcl-G reduced S-nitrosoglutathione-induced ERK1/2 phosphorylation. Furthermore, electrophoretic mobility shift assay experiments revealed that MNSFβ down-regulates the ERK/activator protein 1 (AP-1) signaling cascade which leads to Cox-2 activation. We also observed that MNSFβ-Bcl-G promotes LPS/IFNγ-induced apoptosis of mouse peritoneal macrophages, together with a decrease in Cox-2 expression. Taken together, our data indicate an apoptosis-enhancing effect of MNSFβ-Bcl-G is due in part to down-regulation of Cox-2 activation in macrophages.

Ubiquitin-like protein MNSFβ regulates TLR-2-mediated signal transduction

Post-translational modification by monoclonal nonspecific suppressor factor β (MNSFβ) has been involved in the regulation of a variety of cellular processes. Previous studies have demonstrated that MNSFβ covalently binds to the intracellular pro-apoptotic protein Bcl-G and regulates TLR-4-mediated signal transduction. Recently, we found that MNSFβ also covalently conjugates to endophilin II, a member of the endophilin A family, and inhibits the signal pathway upstream of IKK activation, but not downstream of TLR-2 signaling. In this study, we further examined the mechanism of action of MNSFβ in TLR-2-mediated signal transduction in macrophage-like cell line Raw264.7 cells. Although MNSFβ siRNA enhanced Pam(3)CDK(4) (TLR-2-specific ligand)-stimulated TNFα production, Bcl-G siRNA did not affect. MNSFβ cDNA inhibited the Pam(3)CDK(4)-stimulated TNFα production. High-molecular weight (130 kDa) MNSFβ-adduct was induced in Pam(3)CDK(4)-stimulated Raw264.7 cells. This MNSFβ-adduct was not induced by LPS, indicative of the specificity of TLR-2-mediated signal transduction. Similar observations were seen in BALB/c peritoneal macrophages. Interestingly, 40-kDa MNSFβ-adduct was tyrosine phosphorylated by Pam(3)CDK(4) stimulation. Collectively, novel MNSFβ-adducts may regulate TLR-2 signaling pathway in macrophages.