Coronin 2A mediates actin-dependent de-repression of inflammatory response genes

Gut-immunity modulation in Lepidocephalichthys guntea during Aeromonas hydrophila-infection and recovery assessed with transcriptome data

The fish immune system, which consists of innate and adaptive immunologic processes, defends against viruses, bacteria, fungi, and parasites. The gut immunity is an integral part of the host immune system that controls immunological homeostasis, hosts' interactions with their microbiomes, and provides defence against a number of intestinal infections. Lepidocephalichthys guntea, a facultative air-breathing fish, was experimentally infected with Aeromonas hydrophila using intraperitoneal injection followed by bath challenge, and transcriptome data were used to examine the gut immune responses during disease progression and recovery from the diseased state without the use of medication. For the control or uninfected fish (FGC) and the infected fish that were kept for seven days (FGE1) and fifteen days (FGE2), separate water tanks were set up. Coding DNA sequences (CDS) for FGC and FGE1, FGC and FGE2, and FGE1 and FGE2 were analyzed for differential gene expression (DGE). The presence and expression of genes involved in the T cell receptor (TCR) signalling pathway, natural killer (NK) cell-mediated cytotoxicity pathway, and complement-mediated pathway, along with a large number of other immune-related proteins, and heat shock protein (HSPs) under various experimental conditions and its relationship to immune modulation of the fish gut was the primary focus of this study. Significant up-and-down regulation of these pathways shows that, in FGE1, the fish's innate immune system was engaged, whereas in FGE2, the majority of innate immune mechanisms were repressed, and adaptive immunity was activated. Expression of genes related to the immune system and heat-shock proteins was induced during this host's immunological response, and this information was then used to build a thorough network relating to immunity and the heat-shock response. This is the first study to examine the relationship between pathogenic bacterial infection, disease reversal, and modification of innate and adaptive immunity as well as heat shock response.

The intrinsically disordered region of coronins fine-tunes oligomerization and actin polymerization

Coronins play critical roles in actin network formation. The diverse functions of coronins are regulated by the structured N-terminal β propeller and the C-terminal coiled coil (CC). However, less is known about a middle "unique region" (UR), which is an intrinsically disordered region (IDR). The UR/IDR is an evolutionarily conserved signature in the coronin family. By integrating biochemical and cell biology experiments, coarse-grained simulations, and protein engineering, we find that the IDR optimizes the biochemical activities of coronins in vivo and in vitro. The budding yeast coronin IDR plays essential roles in regulating Crn1 activity by fine-tuning CC oligomerization and maintaining Crn1 as a tetramer. The IDR-guided optimization of Crn1 oligomerization is critical for F-actin cross-linking and regulation of Arp2/3-mediated actin polymerization. The final oligomerization status and homogeneity of Crn1 are contributed by three examined factors: helix packing, the energy landscape of the CC, and the length and molecular grammar of the IDR.

SENP3 deletion promotes M2 macrophage polarization and accelerates wound healing through smad6/IκB/p65 signaling pathway

Macrophages preferentially polarize to the anti-inflammatory M2 subtype in response to alterations in the wound microenvironment. SUMO-specific protease 3 (SENP3), a SUMO-specific protease, has been proven to regulate inflammation in macrophages by deSUMOylating substrate proteins, but its contribution to wound healing is poorly defined. Here, we report that SENP3 deletion promotes M2 macrophage polarization and accelerates wound healing in macrophage-specific SENP3 knockout mice. Notably, it affects wound healing through the suppression of inflammation and promotion of angiogenesis and collagen remodeling. Mechanistically, we identified that SENP3 knockout facilitates M2 polarization through the Smad6/IκB/p65 signaling pathway. SENP3 knockout elevated the expression of Smad6 and IκB. Moreover, Smad6 silencing enhanced the expression of p-p65 and proinflammatory cytokines while inhibiting the level of IκB. Our study revealed the essential role of SENP3 in M2 polarization and wound healing, which offers a theoretical basis for further research and a therapeutic strategy for wound healing.

Targeting macrophages in atherosclerosis using nanocarriers loaded with liver X receptor agonists: A narrow review

Macrophages are involved in the whole process of atherosclerosis, which is characterized by accumulation of lipid and inflammation. Presently, clinically used lipid-lowering drugs cannot completely retard the progress of atherosclerosis. Liver X receptor (LXR) plays a key role in regulation of lipid metabolism and inflammation. Accumulating evidence have demonstrated that synthetic LXR agonists can significantly retard the development of atherosclerosis. However, these agonists induce sever hypertriglyceridemia and liver steatosis. These side effects have greatly limited their potential application for therapy of atherosclerosis. The rapid development of drug delivery system makes it possible to delivery interested drugs to special organs or cells using nanocarriers. Macrophages express various receptors which can recognize and ingest specially modified nanocarriers loaded with LXR agonists. In the past decades, a great progress has been made in this field. These macrophage-targeted nanocarriers loaded with LXR agonists are found to decrease atherosclerosis by reducing cholesterol accumulation and inflammatory reactions. Of important, these nanocarriers can alleviate side effects of LXR agonists. In this article, we briefly review the roles of macrophages in atherosclerosis, mechanisms of action of LXR agonists, and focus on the advances of macrophage-targeted nanocarriers loaded with LXR agonists. This work may promote the potential clinical application of these nanocarriers.

Coronin2A links actin-based endosomal processes to the EHD1 fission machinery

Fission of transport vesicles from endosomes is a crucial step in the recycling of lipids and receptors to the plasma membrane, but this process remains poorly understood. Although key components of the fission machinery, including the actin cytoskeleton and the ATPase Eps15 homology domain protein 1 (EHD1), have been implicated in endosomal fission, how this process is coordinately regulated is not known. We have identified the actin regulatory protein Coronin2A (CORO2A) as a novel EHD1 interaction partner. CORO2A localizes to stress fibers and actin microfilaments but also can be observed in partial overlap with EHD1 on endosomal structures. siRNA knockdown of CORO2A led to enlarged lamellae-like actin-rich protrusions, consistent with a role of other Coronin family proteins in attenuating actin-branching. Moreover, CORO2A depletion also caused a marked decrease in the internalization of clathrin-dependent cargo but had little impact on the uptake of clathrin-independent cargo, highlighting key differences in the role of branched actin for different modes of endocytosis. However, CORO2A was required for recycling of clathrin-independent cargo, and its depletion led to enlarged endosomes, supporting a role for CORO2A in the fission of endosomal vesicles. Our data support a novel role for CORO2A in coordinating endosomal fission and recycling with EHD1. [Media: see text].

The untapped potential of spermidine alkaloids: Sources, structures, bioactivities and syntheses

Spermidine alkaloids are a kind of natural products possessing an aliphatic triamine structure with three or four methylene groups between two N-atoms. Spermidine alkaloids exist in plants, microorganisms, and marine organisms, which usually form amide structures with cinnamic acid or fatty acid derivatives. Their unique structures showed a wide range of biological activities such as neuroprotective, anti-aging, anti-cancer, antioxidant, anti-inflammatory, and antimicrobial. In order to better understand the research status of spermidine alkaloids and promote their applications in human health, this paper systematically reviewed the biological sources, structures, pharmacological actions, and synthetic processes of spermidine alkaloids over the past two decades. This will help to open up new pharmacological investigation fields and better drug design based on these spermidine alkaloids.

The SUMO protease SENP3 regulates mitochondrial autophagy mediated by Fis1

Mitochondria are unavoidably subject to organellar stress resulting from exposure to a range of reactive molecular species. Consequently, cells operate a poorly understood quality control programme of mitophagy to facilitate elimination of dysfunctional mitochondria. Here, we used a model stressor, deferiprone (DFP), to investigate the molecular basis for stress-induced mitophagy. We show that mitochondrial fission 1 protein (Fis1) is required for DFP-induced mitophagy and that Fis1 is SUMOylated at K149, an amino acid residue critical for Fis1 mitochondrial localization. We find that DFP treatment leads to the stabilization of the SUMO protease SENP3, which is mediated by downregulation of the E3 ubiquitin (Ub) ligase CHIP. SENP3 is responsible for Fis1 deSUMOylation and depletion of SENP3 abolishes DFP-induced mitophagy. Furthermore, preventing Fis1 SUMOylation by conservative K149R mutation enhances Fis1 mitochondrial localization. Critically, expressing a Fis1 K149R mutant restores DFP-induced mitophagy in SENP3-depleted cells. Thus, we propose a model in which SENP3-mediated deSUMOylation facilitates Fis1 mitochondrial localization to underpin stress-induced mitophagy.

An in vitro chronic damage model impairs inflammatory and regenerative responses in human colonoid monolayers

Acute damage to the intestinal epithelium can be repaired via de-differentiation of mature intestinal epithelial cells (IECs) to a stem-like state, but there is a lack of knowledge on how intestinal stem cells function after chronic injury, such as in inflammatory bowel disease (IBD). We developed a chronic-injury model in human colonoid monolayers by repeated rounds of air-liquid interface and submerged culture. We use this model to understand how chronic intestinal damage affects the ability of IECs to (1) respond to microbial stimulation, using the Toll-like receptor 5 (TLR5) agonist FliC and (2) regenerate and protect the epithelium from further damage. Repeated rounds of damage impair the ability of IECs to regrow and respond to TLR stimulation. We also identify mRNA expression and DNA methylation changes in genes associated with IBD and colon cancer. This methodology results in a human model of recurrent IEC injury like that which occurs in IBD.

Retinoid X Receptor: Cellular and Biochemical Roles of Nuclear Receptor with a Focus on Neuropathological Involvement

Retinoid X receptors (RXRs) present a subgroup of the nuclear receptor superfamily with particularly high evolutionary conservation of ligand binding domain. The receptor exists in α, β, and γ isotypes that form homo-/heterodimeric complexes with other permissive and non-permissive receptors. While research has identified the biochemical roles of several nuclear receptor family members, the roles of RXRs in various neurological disorders remain relatively under-investigated. RXR acts as ligand-regulated transcription factor, modulating the expression of genes that plays a critical role in mediating several developmental, metabolic, and biochemical processes. Cumulative evidence indicates that abnormal RXR signalling affects neuronal stress and neuroinflammatory networks in several neuropathological conditions. Protective effects of targeting RXRs through pharmacological ligands have been established in various cell and animal models of neuronal injury including Alzheimer disease, Parkinson disease, glaucoma, multiple sclerosis, and stroke. This review summarises the existing knowledge about the roles of RXR, its interacting partners, and ligands in CNS disorders. Future research will determine the importance of structural and functional heterogeneity amongst various RXR isotypes as well as elucidate functional links between RXR homo- or heterodimers and specific physiological conditions to increase drug targeting efficiency in pathological conditions.

Molecular Pathogenesis of the Coronin Family: CORO2A Facilitates Migration and Invasion Abilities in Oral Squamous Cell Carcinoma

In humans, the coronin family is composed of seven proteins containing WD-repeat domains that regulate actin-based cellular processes. Some members of the coronin family are closely associated with cancer cell migration and invasion. The Cancer Genome Atlas (TCGA) analysis revealed that CORO1C, CORO2A, and CORO7 were significantly upregulated in oral squamous cell carcinoma (OSCC) tissues (p < 0.05). Moreover, the high expression of CORO2A was significantly predictive of the 5-year survival rate of patients with OSCC (p = 0.0203). Overexpression of CORO2A was detected in OSCC clinical specimens by immunostaining. siRNA-mediated knockdown of CORO2A suppressed cancer cell migration and invasion abilities. Furthermore, we investigated the involvement of microRNAs (miRNAs) in the molecular mechanism underlying CORO2A overexpression in OSCC cells. TCGA analysis confirmed that tumor-suppressive miR-125b-5p and miR-140-5p were significantly downregulated in OSCC tissues. Notably, these miRNAs bound directly to the 3'-UTR of CORO2A and controlled CORO2A expression in OSCC cells. In summary, we found that aberrant expression of CORO2A facilitates the malignant transformation of OSCC cells, and that downregulation of tumor-suppressive miRNAs is involved in CORO2A overexpression. Elucidation of the interaction between genes and miRNAs will help reveal the molecular pathogenesis of OSCC.

Deficiency of cysteinyl cathepsin K suppresses the development of experimental intimal hyperplasia in response to chronic stress

BACKGROUND

Chronic psychological stress (CPS) is linked to cardiovascular disease initiation and progression. Given that cysteinyl cathepsin K (CatK) participates in vascular remodeling and atherosclerotic plaque growth in several animal models, we investigated the role of CatK in the development of experimental neointimal hyperplasia in response to chronic stress.

METHODS AND RESULTS

At first, male wild-type (CatK) mice that underwent carotid ligation injury were subjected to chronic immobilization stress. On postoperative and stressed day 14, the results demonstrated that stress accelerated injury-induced neointima hyperplasia. On day 4, stressed mice showed following: increased levels of monocyte chemoattractant protein-1, gp91phox, toll-like receptor-2 (TLR2), TLR4, and CatK mRNAs or/and proteins, oxidative stress production, aorta-derived smooth muscle cell (SMC) migration, and macrophage infiltration as well as targeted intracellular proliferating-related molecules. Stressed mice showed increased matrix metalloproteinase-2 (MMP-2) and MMP-9 mRNA expressions and activities and elastin disruption in the injured carotid arteries. Second, CatK and CatK deficiency (CatK) mice received ligation injury and stress to explore the role of CatK. The stress-induced harmful changes were prevented by CatK. Finally, CatK mice that had undergone ligation surgery were randomly assigned to one of two groups and administered vehicle or CatK inhibitor for 14 days. Pharmacological CatK intervention produced a vascular benefit.

CONCLUSION

These data indicate that CatK deletion protects against the development of experimental neointimal hyperplasia via the attenuation of inflammatory overaction, oxidative stress production, and VSMC proliferation, suggesting that CatK is a novel therapeutic target for the management of CPS-related restenosis after intravascular intervention therapies.

CaMKII oxidation is a critical performance/disease trade-off acquired at the dawn of vertebrate evolution

Antagonistic pleiotropy is a foundational theory that predicts aging-related diseases are the result of evolved genetic traits conferring advantages early in life. Here we examine CaMKII, a pluripotent signaling molecule that contributes to common aging-related diseases, and find that its activation by reactive oxygen species (ROS) was acquired more than half-a-billion years ago along the vertebrate stem lineage. Functional experiments using genetically engineered mice and flies reveal ancestral vertebrates were poised to benefit from the union of ROS and CaMKII, which conferred physiological advantage by allowing ROS to increase intracellular Ca²⁺ and activate transcriptional programs important for exercise and immunity. Enhanced sensitivity to the adverse effects of ROS in diseases and aging is thus a trade-off for positive traits that facilitated the early and continued evolutionary success of vertebrates.

Natural selection may favor traits underlying aging-related diseases if they benefit the young. Wang et al. find that oxidative activation of CaMKII provides physiological benefits critical to the initial and continued success of vertebrates but at the cost of disease, frailty, and shortened lifespan.

WNT5a in Colorectal Cancer: Research Progress and Challenges

Despite the clinical development of new adjuvant and neoadjuvant chemotherapy drugs, colorectal cancer is still one of the leading causes of cancer-related death in human beings. WNT5a, an autocrine and paracrine β-catenin independent ligand, has been shown to induce tumor inhibition and carcinogenic signals, depending on the type of cancer. In patients with colorectal cancer, WNT5a triggers a variety of downstream signaling pathways, which mainly affect the migration and invasion of tumor cells. This article reviews the mechanism and therapeutic potential of WNT5a in colorectal cancer. In short, an in-depth understanding of the role of WNT5a in colorectal cancer is very helpful to better deal with this disease.

SENP3 Suppresses Osteoclastogenesis by De-conjugating SUMO2/3 from IRF8 in Bone Marrow-Derived Monocytes

Bone metabolism depends on the balance between osteoclast-driven bone resorption and osteoblast-mediated bone formation. Diseases like osteoporosis are characterized by increased bone destruction due to partially enhanced osteoclastogenesis. Here, we report that the post-translational SUMO modification is critical for regulating osteoclastogenesis. The expression of the SUMO-specific protease SENP3 is downregulated in osteoclast precursors during osteoclast differentiation. Mice with SENP3 deficiency in bone marrow-derived monocytes (BMDMs) exhibit more severe bone loss due to over-activation of osteoclasts after ovariectomy. Deleting SENP3 in BMDMs promotes osteoclast differentiation. Mechanistically, loss of SENP3 increases interferon regulatory factor 8 (IRF8) SUMO3 modification at the K310 amino acid site, which upregulates expression of the nuclear factor of activated T cell c1 (NFATc1) and osteoclastogenesis. In summary, IRF8 de-SUMO modification mediated by SENP3 suppresses osteoclast differentiation and suggests strategies to treat bone loss diseases.

SUMOylation Connects Cell Stress Responses and Inflammatory Control: Lessons From the Gut as a Model Organ

Conjugation with the small ubiquitin-like modifier (SUMO) constitutes a key post-translational modification regulating the stability, activity, and subcellular localization of its target proteins. However, the vast numbers of identified SUMO substrates obscure a clear view on the function of SUMOylation in health and disease. This article presents a comprehensive review on the physiological relevance of SUMOylation by discussing how global SUMOylation levels—rather than specific protein SUMOylation—shapes the immune response. In particular, we highlight the growing body of work on SUMOylation in intestinal pathologies, because of the unique metabolic, infectious, and inflammatory challenges of this organ. Recent studies show that global SUMOylation can help restrain detrimental inflammation while maintaining immune defenses and tissue integrity. These results warrant further efforts to develop new therapeutic tools and strategies to control SUMOylation in infectious and inflammatory disorders.

Liver X Receptor α in Sciatic Nerve Exerts an Alleviating Effect on Neuropathic Pain Behaviors Induced by Crush Injury

Peripheral nerve injury often leads to neuropathic pain. In the present study, we assessed the role of liver x receptor alpha (LXRα), an oxysterol regulated nuclear transcription factor that promotes reverse cholesterol transport and alternative (M2) macrophage activation, in the development of neuropathic pain. We found that compared to WT mice, in LXRα knockout mice the development of mechanical allodynia following sciatic nerve crush was accelerated and the duration was prolonged. Furthermore, the expression of M1-like macrophage marker iNOS and M1-like macrophages inducer hydrogen peroxide (H2O2) was increased, whereas expression of M2 macrophage marker arginase-1 (Arg-1) and interleukin-10 (IL-10) was reduced in the sciatic nerve of LXRα knockout mice. Moreover, peri-sciatic administration of LXRs agonist GW3965, immediately after the nerve crush, into wild type mice, suppressed the mechanical allodynia induced by crush injury. GW3965 also suppressed the expression of iNOS and production of H2O2 in the injured nerve and enhanced the expression of IL-10 and Arg-1. Importantly, peri-sciatic administration of IL-10 neutralization antibody prevented the alleviating effect of GW3965 on mechanical allodynia. Altogether, these results indicates that the lack of LXRα in the sciatic nerve results in an augmented inflammatory profile of macrophages, which ultimately speed up the development of neuropathic pain and dampen its recovery following nerve injury. Activation of LXRα by its agonist might rebalance the neuroprotective and neurotoxic macrophage phenotypes, and thus alleviate the neuropathic pain behavior.

CD4+ T Cell-Specific Proteomic Pathways Identified in Progression of Hypertension Across Postmenopausal Transition

Background Menopause is associated with an increase in the prevalence and severity of hypertension in women. Although premenopausal females are protected against T cell-dependent immune activation and development of angiotensin II (Ang II) hypertension, this protection is lost in postmenopausal females. Therefore, the current study hypothesized that specific CD4+ T cell pathways are regulated by sex hormones and Ang II to mediate progression from premenopausal protection to postmenopausal hypertension. Methods and Results Menopause was induced in C57BL/6 mice via repeated 4-vinylcyclohexene diepoxide injections, while premenopausal females received sesame oil vehicle. A subset of premenopausal mice and all menopausal mice were infused with Ang II for 14 days (Control, Ang II, Meno/Ang II). Proteomic and phosphoproteomic profiles of CD4+ T cells isolated from spleens were examined. Ang II markedly increased CD4+ T cell protein abundance and phosphorylation associated with DNA and histone methylation in both premenopausal and postmenopausal females. Compared with premenopausal T cells, Ang II infusion in menopausal mice increased T cell phosphorylation of MP2K2, an upstream regulator of ERK, and was associated with upregulated phosphorylation at ERK targeted sites. Additionally, Ang II infusion in menopausal mice decreased T cell phosphorylation of TLN1, a key regulator of IL-2Rα and FOXP3 expression. Conclusions These findings identify novel, distinct T cell pathways that influence T cell-mediated inflammation during postmenopausal hypertension.

Suppression of the TGF-β pathway by a macrolide antibiotic decreases fibrotic responses by ocular fibroblasts in vitro

To elucidate and to inhibit post-surgical fibrotic processes after trabeculectomy in glaucoma therapy, we measured gene expression in a fibrotic cell culture model, based on transforming growth factor TGF-β induction in primary human tenon fibroblasts (hTFs), and used Connectivity Map (CMap) data for drug repositioning. We found that specific molecular mechanisms behind fibrosis are the upregulation of actins, the downregulation of CD34, and the upregulation of inflammatory cytokines such as IL6, IL11 and BMP6. The macrolide antibiotic Josamycin (JM) reverses these molecular mechanisms according to data from the CMap, and we thus tested JM as an inhibitor of fibrosis. JM was first tested for its toxic effects on hTFs, where it showed no influence on cell viability, but inhibited hTF proliferation in a concentration-dependent manner. We then demonstrated that JM suppresses the synthesis of extracellular matrix (ECM) components. In hTFs stimulated with TGF-β1, JM specifically inhibited α-smooth muslce actin expression, suggesting that it inhibits the transformation of fibroblasts into fibrotic myofibroblasts. In addition, a decrease of components of the ECM such as fibronectin, which is involved in in vivo scarring, was observed. We conclude that JM may be a promising candidate for the treatment of fibrosis after glaucoma filtration surgery or drainage device implantation in vivo.

LXRα Phosphorylation in Cardiometabolic Disease: Insight From Mouse Models

Posttranslational modifications, such as phosphorylation, are a powerful means by which the activity and function of nuclear receptors such as LXRα can be altered. However, despite the established importance of nuclear receptors in maintaining metabolic homeostasis, our understanding of how phosphorylation affects metabolic diseases is limited. The physiological consequences of LXRα phosphorylation have, until recently, been studied only in vitro or nonspecifically in animal models by pharmacologically or genetically altering the enzymes enhancing or inhibiting these modifications. Here we review recent reports on the physiological consequences of modifying LXRα phosphorylation at serine 196 (S196) in cardiometabolic disease, including nonalcoholic fatty liver disease, atherosclerosis, and obesity. A unifying theme from these studies is that LXRα S196 phosphorylation rewires the LXR-modulated transcriptome, which in turn alters physiological response to environmental signals, and that this is largely distinct from the LXR-ligand-dependent action.

Integrating the roles of liver X receptors in inflammation and infection: mechanisms and outcomes

Liver X receptors (LXRs) are transcription factors from the nuclear receptor family that can be pharmacologically activated by high-affinity agonists. LXR activation exerts a combination of metabolic and anti-inflammatory actions that result in the modulation of immune responses and in the amelioration of inflammatory disorders. In addition, LXR agonists modulate the metabolism of infected cells and limit the infectivity and/or growth of several pathogens. This review gives an overview of the recent advances in understanding the complexity of the mechanisms through which the LXR pathway controls inflammation and host-cell pathogen interaction.

Effects of CORO2A on Cell Migration and Proliferation and Its Potential Regulatory Network in Breast Cancer

Coronin 2A (CORO2A) is a novel component of the N-CoR (nuclear receptor co-repressor) complex. Abnormal CORO2A expression is associated with carcinogenesis. We used databases from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO), and analyzed CORO2A expression and gene regulation networks in breast cancer. Expression was analyzed using GEO and TCGA database and further validated in breast cancer samples collected in our clinic. The prognostic value of CORO2A was explored by using the Kaplan–Meier survival analysis and Cox proportional hazards regression analysis. LinkedOmics was used to identify coexpressed genes associated with CORO2A. After analyzing the intersection of coexpressed genes correlated with CORO2A and differentially expressed genes after CORO2A silencing, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of the intersecting genes were conducted by using FunRich software. Transwell assays were performed in breast cancer cells to determine the effect of CORO2A on cell migration. MTS, colony formation, and cell cycle distribution assays were performed in breast cancer cells to determine the effect of CORO2A on cell proliferation. Gene enrichment analysis was employed to explore the target networks of transcription factors and miRNAs. We found that CORO2A was upregulated and that the elevated expression of CORO2A was associated with poor overall survival (OS) and relapse-free survival (RFS) in TNBC patients. Further bioinformatics analysis of public sequencing data and our own RNA-Seq data revealed that CORO2A was probably involved in the epithelial-to-mesenchymal transition process and might have a significant effect on the migration of breast cancer cells, which might be mediated via pathways involving several miRNAs and MYC transcription factors. Functionally, the knockdown of CORO2A inhibited cell migration, decreased viability, and colony formation and induced cell cycle arrest in the G0/G1 phase in breast cancer cells. These results demonstrate that bioinformatics-based analysis efficiently reveals information about CORO2A expression and its potential regulatory networks in breast cancer, laying a foundation for further mechanistic research on the role of CORO2A in carcinogenesis. Moreover, CORO2A promotes the migration and proliferation of breast cancer cells and may have an important function in breast cancer progression. CORO2A is a potential prognostic predictor for TNBC patients. Targeting CORO2A may provide promising therapy strategies for breast cancer treatment.

LXRα Regulates ChREBPα Transactivity in a Target Gene-Specific Manner through an Agonist-Modulated LBD-LID Interaction

The cholesterol-sensing nuclear receptor liver X receptor (LXR) and the glucose-sensing transcription factor carbohydrate responsive element-binding protein (ChREBP) are central players in regulating glucose and lipid metabolism in the liver. More knowledge of their mechanistic interplay is needed to understand their role in pathological conditions like fatty liver disease and insulin resistance. In the current study, LXR and ChREBP co-occupancy was examined by analyzing ChIP-seq datasets from mice livers. LXR and ChREBP interaction was determined by Co-immunoprecipitation (CoIP) and their transactivity was assessed by real-time quantitative polymerase chain reaction (qPCR) of target genes and gene reporter assays. Chromatin binding capacity was determined by ChIP-qPCR assays. Our data show that LXRα and ChREBPα interact physically and show a high co-occupancy at regulatory regions in the mouse genome. LXRα co-activates ChREBPα and regulates ChREBP-specific target genes in vitro and in vivo. This co-activation is dependent on functional recognition elements for ChREBP but not for LXR, indicating that ChREBPα recruits LXRα to chromatin in trans. The two factors interact via their key activation domains; the low glucose inhibitory domain (LID) of ChREBPα and the ligand-binding domain (LBD) of LXRα. While unliganded LXRα co-activates ChREBPα, ligand-bound LXRα surprisingly represses ChREBPα activity on ChREBP-specific target genes. Mechanistically, this is due to a destabilized LXRα:ChREBPα interaction, leading to reduced ChREBP-binding to chromatin and restricted activation of glycolytic and lipogenic target genes. This ligand-driven molecular switch highlights an unappreciated role of LXRα in responding to nutritional cues that was overlooked due to LXR lipogenesis-promoting function.

Interactome and F-Actin Interaction Analysis of Dictyostelium discoideum Coronin A

Coronin proteins are evolutionary conserved WD repeat containing proteins that have been proposed to carry out different functions. In Dictyostelium, the short coronin isoform, coronin A, has been implicated in cytoskeletal reorganization, chemotaxis, phagocytosis and the initiation of multicellular development. Generally thought of as modulators of F-actin, coronin A and its mammalian homologs have also been shown to mediate cellular processes in an F-actin-independent manner. Therefore, it remains unclear whether or not coronin A carries out its functions through its capacity to interact with F-actin. Moreover, the interacting partners of coronin A are not known. Here, we analyzed the interactome of coronin A as well as its interaction with F-actin within cells and in vitro. Interactome analysis showed the association with a diverse set of interaction partners, including fimbrin, talin and myosin subunits, with only a transient interaction with the minor actin10 isoform, but not the major form of actin, actin8, which was consistent with the absence of a coronin A-actin interaction as analyzed by co-sedimentation from cells and lysates. In vitro, however, purified coronin A co-precipitated with rabbit muscle F-actin in a coiled-coil-dependent manner. Our results suggest that an in vitro interaction of coronin A and rabbit muscle actin may not reflect the cellular interaction state of coronin A with actin, and that coronin A interacts with diverse proteins in a time-dependent manner.

LXR Suppresses Inflammatory Gene Expression and Neutrophil Migration through cis-Repression and Cholesterol Efflux

The activation of liver X receptor (LXR) promotes cholesterol efflux and repression of inflammatory genes with anti-atherogenic consequences. The mechanisms underlying the repressive activity of LXR are controversial and have been attributed to cholesterol efflux or to transrepression of activator protein-1 (AP-1) activity. Here, we find that cholesterol efflux contributes to LXR repression, while the direct repressive functions of LXR also play a key role but are independent of AP-1. We use assay for transposase-accessible chromatin using sequencing (ATAC-seq) to show that LXR reduces chromatin accessibility in cis at inflammatory gene enhancers containing LXR binding sites. Targets of this repressive activity are associated with leukocyte adhesion and neutrophil migration, and LXR agonist treatment suppresses neutrophil recruitment in a mouse model of sterile peritonitis. These studies suggest a model of repression in which liganded LXR binds in cis to canonical nuclear receptor binding sites and represses pro-atherogenic leukocyte functions in tandem with the induction of LXR targets mediating cholesterol efflux.

Thomas et al. show the roles of cholesterol efflux and direct repression in anti-inflammatory effects of LXR and establish the mechanism of LXR cis-repression using ATAC-seq. LXR agonists suppress neutrophil migration genes and neutrophil recruitment during inflammation, highlighting a potential role for these compounds in the control of neutrophil-predominant inflammatory conditions.

Localization Analysis of Seven De-sumoylation Enzymes (SENPs) in Ocular Cell Lines

PURPOSE

It is now well established that protein sumoylation acts as an important regulatory mechanism modulating functions over three thousand proteins. In the vision system, protein conjugation with SUMO peptides can regulate differentiation of multiple ocular tissues. Such regulation is often explored through analysis of biochemical and physiological changes with various cell lines in vitro. We have recently analyzed the expression levels of both mRNAs and proteins for seven de-sumoylation enzymes (SENPs) in five major ocular cell lines. In continuing the previous study, here we have determined their cellular localization of the seven de-sumoylation enzymes (SENP1, 2, 3, 5, 6, 7 and 8) in the above 5 major ocular cell lines using immunocytochemistry.

METHODS

The 5 major ocular cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS) or rabbit serum (RBS) and 1% Penicillin- Streptomycin. The localization of the 7 major de-sumoylation enzymes (SENPs) in the 5 major ocular cell lines were determined with immunohistochemistry. The images were captured with a Zeiss LSM 880 confocal microscope.

RESULTS

1) The SENP1 was localized in both cytoplasm and nucleus of 3 human ocular cell lines, FHL124, HLE and ARPE-19; In N/N1003A and αTN4-1, SENP 1 was more concentrated in the cytoplasm. SENP1 appears in patches; 2) SENP2 was distributed in both cytoplasm and nucleus of all ocular cell lines in patches. In HLE and ARPE-19 cells, SENP2 level was higher in nucleus than in cytoplasm; 3) SENP3 was almost exclusively concentrated in the nuclei in all ocular cells except for N/N1003A cells. In the later cells, a substantial amount of SENP3 was also detected in the cytoplasm although nuclear SENP3 level was higher than the cytoplasmic SENP3 level. SENP3 appeared in obvious patches in the nuclei; 4) SENP5 was dominantly localized in the cytoplasm (cellular organelles) near nuclear membrane or cytoplasmic membrane ; 5) SENP6 was largely concentrated in the nuclei of all cell lines except for αTN4-1 cells. In the later cells, a substantial amount of SENP6 was also detected in the cytoplasm although nuclear SENP6 level was higher than the cytoplasmic SENP6 level. 6) SENP7 has an opposite localization pattern between human and animal cell lines. In human cell lines, a majority of SENP7 was localized in nuclei whereas in mouse and rabbit lens epithelial cells, most SENP7 was distributed in the cytoplasm. SENP8 was found present in human cell lines. The 3 human ocular cell lines had relatively similar distribution pattern. In FHL124 and ARPE-19 cells, SENP8 was detected only in the cytoplasm, but in HLE cells, patches of SENP8 in small amount was also detected in the nuclei.

CONCLUSIONS

Our results for the first time defined the differential distribution patterns of seven desumoylation enzymes (SENPs) in 5 major ocular cell lines. These results help to understand the different functions of various SENPs in maintaining the homeostasis of protein sumoylation patterns during their functioning processes.

Changes in the intestinal mucosal proteome of turkeys (Meleagris gallopavo) infected with haemorrhagic enteritis virus

Haemorrhagic enteritis (HE) is a viral disease affecting intestinal integrity and barrier function in turkey (Meleagris gallopavo) and resulting in a significant economic loss. Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH-MS) was applied to identify crucial proteins involved in HE infection. A total of 938 proteins were identified and used to generate a reference library for SWATH-MS analysis. In total, 523 proteins were reliably quantified, and 64 proteins were found to be differentially expressed, including 49 up-regulated and 15 down-regulated proteins between healthy and HE-affected intestinal mucosa. Functional analysis suggested that these proteins were involved in the following categories of cellular pathways and metabolisms: 1) energy pathways; 2) intestine lipid and amino acid metabolism; 3) oxidative stress; 4) intestinal immune response. Major findings of this study demonstrated that natural HE infection is related to the changes in abundance of several proteins involved in cell-intrinsic immune defense against viral invasion, systemic inflammation, modulation of excessive inflammation, B and T cell development and function and antigen presentation. mRNA quantitative expression demonstrated that most of the proteins involved in innate immunity that were found to be differentially abundant were produced by intestinal mucosa, suggesting its direct involvement in immune defences against HE infection.

Exome sequencing in multiple sclerosis families identifies 12 candidate genes and nominates biological pathways for the genesis of disease

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system characterized by myelin loss and neuronal dysfunction. Although the majority of patients do not present familial aggregation, Mendelian forms have been described. We performed whole-exome sequencing analysis in 132 patients from 34 multi-incident families, which nominated likely pathogenic variants for MS in 12 genes of the innate immune system that regulate the transcription and activation of inflammatory mediators. Rare missense or nonsense variants were identified in genes of the fibrinolysis and complement pathways (PLAU, MASP1, C2), inflammasome assembly (NLRP12), Wnt signaling (UBR2, CTNNA3, NFATC2, RNF213), nuclear receptor complexes (NCOA3), and cation channels and exchangers (KCNG4, SLC24A6, SLC8B1). These genes suggest a disruption of interconnected immunological and pro-inflammatory pathways as the initial event in the pathophysiology of familial MS, and provide the molecular and biological rationale for the chronic inflammation, demyelination and neurodegeneration observed in MS patients.

Nuclear Actin: From Discovery to Function

While actin was discovered in the nucleus over 50 years ago, research lagged for decades due to strong skepticism. The revitalization of research into nuclear actin occurred after it was found that cellular stresses induce the nuclear localization and alter the structure of actin. These studies provided the first hints that actin has a nuclear function. Subsequently, it was established that the nuclear import and export of actin is highly regulated. While the structures of nuclear actin remain unclear, it can function as monomers, polymers, and even rods. Furthermore, even within a given structure, distinct pools of nuclear actin that can be differentially labeled have been identified. Numerous mechanistic studies have uncovered an array of functions for nuclear actin. It regulates the activity of RNA polymerases, as well as specific transcription factors. Actin also modulates the activity of several chromatin remodeling complexes and histone deacetylases, to ultimately impinge on transcriptional programing and DNA damage repair. Further, nuclear actin mediates chromatin movement and organization. It has roles in meiosis and mitosis, and these functions may be functionally conserved from ancient bacterial actin homologs. The structure and integrity of the nuclear envelope and sub-nuclear compartments are also regulated by nuclear actin. Furthermore, nuclear actin contributes to human diseases like cancer, neurodegeneration, and myopathies. Here, we explore the early discovery of actin in the nucleus and discuss the forms and functions of nuclear actin in both normal and disease contexts. Anat Rec, 301:1999-2013, 2018. © 2018 Wiley Periodicals, Inc.

Retinal Vascular Abnormalities and Microglia Activation in Mice with Deficiency in Cytochrome P450 46A1-Mediated Cholesterol Removal

CYP46A1 is the cytochrome P450 enzyme that converts cholesterol to 24-hydroxycholesterol, a cholesterol elimination product and a potent liver X receptor (LXR) ligand. We conducted retinal characterizations of Cyp46a1^-/- mice that had normal fasting blood glucose levels but up to a 1.8-fold increase in retinal cholesterol. The retina of Cyp46a1^-/- mice exhibited venous beading and tortuosity, microglia/macrophage activation, and increased vascular permeability, features commonly associated with diabetic retinopathy. The expression of Lxrα and Lxrβ was increased in both the whole Cyp46a1^-/- retina and retinal macroglia/macrophages. The LXR-target genes were affected as well, primarily in activated microglial cells and macrophages. In the latter, the LXR-transactivated genes (Abca1, Abcg1, Apod, Apoe, Mylip, and Arg2) were up-regulated; similarly, there was an up-regulation of the LXR-transrepressed genes (Ccl2, Ptgs2, Cxcl1, Il1b, Il6, Nos2, and Tnfa). For comparison, gene expression was investigated in bone marrow-derived macrophages from Cyp46a1^-/- mice as well as retinal and bone marrow-derived macrophages from Cyp27a1^-/- and Cyp27a1^-/-Cyp46a1^-/- mice. CYP46A1 expression was detected in retinal endothelial cells, and this expression was increased in the proinflammatory environment. Retinal Cyp46a1^-/- phosphoproteome revealed altered phosphorylation of 30 different proteins, including tight junction protein zonula occludens 1 and aquaporin 4. Collectively, the data obtained establish metabolic and regulatory significance of CYP46A1 for the retina and suggest pharmacologic activation of CYP46A1 as a potential therapeutic approach to dyslipidemia-induced retinal damage.

SUMOylation pathway alteration coupled with downregulation of SUMO E2 enzyme at mucosal epithelium modulates inflammation in inflammatory bowel disease

Post-translational modification pathways such as SUMOylation are integral to all cellular processes and tissue homeostasis. We investigated the possible involvement of SUMOylation in the epithelial signalling in Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of inflammatory bowel disease (IBD). Initially in a murine model of IBD, induced by dextran–sulfate–sodium (DSS mice), we observed inflammation accompanied by a lowering of global SUMOylation of colonic epithelium. The observed SUMOylation alteration was due to a decrease in the sole SUMO E2 enzyme (Ubc9). Mass-spectrometric analysis revealed the existence of a distinct SUMOylome (SUMO-conjugated proteome) in DSS mice with alteration of key cellular regulators, including master kinase Akt1. Knocking-down of Ubc9 in epithelial cells resulted in dramatic activation of inflammatory gene expression, a phenomenon that acted via reduction in Akt1 and its SUMOylated form. Importantly, a strong decrease in Ubc9 and Akt1 was also seen in endoscopic biopsy samples (N = 66) of human CD and UC patients. Furthermore, patients with maximum disease indices were always accompanied by severely lowered Ubc9 or SUMOylated-Akt1. Mucosal tissues with severely compromised Ubc9 function displayed higher levels of pro-inflammatory cytokines and compromised wound-healing markers. Thus, our results reveal an important and previously undescribed role for the SUMOylation pathway involving Ubc9 and Akt1 in modulation of epithelial inflammatory signalling in IBD.

Cholesterol metabolism in innate and adaptive response

It has been long recognized that cholesterol is a critical molecule in mammalian cell biology, primarily for its contribution to the plasma membrane's composition and its role in assuring proper transmembrane receptor signaling as part of lipid rafts. Efforts have also been made to characterize the cholesterol biosynthetic pathway, cholesterol homeostasis, and cholesterol-derived metabolites in order to gain insights into their dysregulation during metabolic diseases. Despite the central role cholesterol metabolism plays in shaping human health, its regulation during immune activation, such as immune response to pathogens or autoimmune/autoinflammatory diseases, is poorly understood. The immune system is composed of several type of cells with distinct developmental origin, life span, molecular requirements, and gene expressions. It is unclear whether the same array of cholesterol metabolism regulators are equally employed by different immune cells and whether distinct cholesterol metabolites have similar biological consequences in different immune cells. In this review, we will describe how cholesterol metabolism is controlled during the adaptive and the innate immune response and the role for intracellular and extracellular receptors for cholesterol and its derivatives.

TGF-β-mediated enhancement of TH17 cell generation is inhibited by bone morphogenetic protein receptor 1α signaling

The cytokines of the transforming growth factor-β (TGF-β) family promote the growth and differentiation of multiple tissues, but the role of only the founding member, TGF-β, in regulating the immune responses has been extensively studied. TGF-β is critical to prevent the spontaneous activation of self-reactive T cells and sustain immune homeostasis. In contrast, in the presence of proinflammatory cytokines, TGF-β promotes the differentiation of effector T helper 17 (TH17) cells. Abrogating TGF-β receptor signaling prevents the development of interleukin-17 (IL-17)-secreting cells and protects mice from TH17 cell-mediated autoimmunity. We found that the receptor of another member of TGF-β family, bone morphogenetic protein receptor 1α (BMPR1α), regulates T helper cell activation. We found that the differentiation of TH17 cells from naive CD4+ T cells was inhibited in the presence of BMPs. Abrogation of BMPR1α signaling during CD4+ T cell activation induced a developmental program that led to the generation of inflammatory effector cells expressing large amounts of IL-17, IFN-γ, and TNF family cytokines and transcription factors defining the TH17 cell lineage. We found that TGF-β and BMPs cooperated to establish effector cell functions and the cytokine profile of activated CD4+ T cells. Together, our data provide insight into the immunoregulatory function of BMPs.

Differential effects of and mechanisms underlying the protection of cardiomyocytes by liver-X-receptor subtypes against high glucose stress-induced injury

Liver-X-receptors (LXRs) are ligand-activated transcription factors belonging to the nuclear receptor superfamily. The two popular homologous receptor subtypes, LXRα and LXRβ, exhibit differential expression patterns, thereby probably playing different roles in different contexts. This study aimed to evaluate the different roles of the two LXR subtypes and the mechanisms underlying their protection of cardiomyocytes against high-glucose stress. Silencing of LXRα, but not LXRβ impaired normal LXR-mediated cardioprotective effects against high glucose-induced oxidative stress, apoptosis, and inflammation. Mechanistically, silencing of small ubiquitin-like modifier (SUMO)1 or SUMO2/3 did not affect LXR-mediated cardioprotective effects; however, these were impaired in response to nuclear receptor corepressor (NCoR) silencing. Together, these findings indicate that LXRα, but not LXRβ, protects against high glucose-induced cardiomyocyte injury, probably via the NCoR-dependent transrepression of downstream target genes.

Regulation of cytochrome P450 gene expression by ketamine: a review

INTRODUCTION

Although used as an anesthetic drug for decades, ketamine appears to have garnered renewed interest due to its potential therapeutic uses in pain therapy, neurology, and psychiatry. Ketamine undergoes extensive oxidative metabolism by cytochrome P450 (CYP) enzymes. Considerable efforts have been expended to elucidate the ketamine-induced regulation of CYP gene expression. The safety profile of chronic ketamine administration is still unclear. Understanding how ketamine regulates CYP gene expression is clinically meaningful. Areas covered: In this article, the authors provide a brief review of clinical applications of ketamine and its metabolism by CYP enzymes. We discuss the effects of ketamine on the regulation of CYP gene expression, exploring aspects of cytoskeletal remodeling, mitochondrial functions, and calcium homeostasis. Expert opinion: Ketamine may inhibit CYP gene expression through inhibiting calcium signaling, decreasing ATP levels, producing excessive reactive oxygen species, and subsequently perturbing cytoskeletal dynamics. Further research is still needed to avoid possible ketamine-drug interactions during long-term use in the clinic.

SUMO-specific proteases and isopeptidases of the SENP family at a glance

The ubiquitin-related SUMO system controls many cellular signaling networks. In mammalian cells, three SUMO forms (SUMO1, SUMO2 and SUMO3) act as covalent modifiers of up to thousands of cellular proteins. SUMO conjugation affects cell function mainly by regulating the plasticity of protein networks. Importantly, the modification is reversible and highly dynamic. Cysteine proteases of the sentrin-specific protease (SENP) family reverse SUMO conjugation in mammalian cells. In this Cell Science at a Glance article and the accompanying poster, we will summarize how the six members of the mammalian SENP family orchestrate multifaceted deconjugation events to coordinate cell processes, such as gene expression, the DNA damage response and inflammation.

DeSUMOylation of MKK7 kinase by the SUMO2/3 protease SENP3 potentiates lipopolysaccharide-induced inflammatory signaling in macrophages

Protein SUMOylation has been reported to play a role in innate immune response, but the enzymes, substrates, and consequences of the specific inflammatory signaling events are largely unknown. Reactive oxygen species (ROS) are abundantly produced during macrophage activation and required for Toll-like receptor 4 (TLR4)-mediated inflammatory signaling. Previously, we demonstrated that SENP3 is a redox-sensitive SUMO2/3 protease. To explore any links between reversible SUMOylation and ROS-related inflammatory signaling in macrophage activation, we generated mice with Senp3 conditional knock-out in myeloid cells. In bacterial lipopolysaccharide (LPS)-induced in vitro and in vivo inflammation models, we found that SENP3 deficiency markedly compromises the activation of TLR4 inflammatory signaling and the production of proinflammatory cytokines in macrophages exposed to LPS. Moreover, Senp3 conditional knock-out mice were significantly less susceptible to septic shock. Of note, SENP3 deficiency was associated with impairment in JNK phosphorylation. We found that MKK7, which selectively phosphorylates JNK, is a SENP3 substrate and that SENP3-mediated deSUMOylation of MKK7 may favor its binding to JNK. Importantly, ROS-dependent SENP3 accumulation and MKK7 deSUMOylation rapidly occurred after LPS stimulation. In conclusion, our findings indicate that SENP3 potentiates LPS-induced TLR4 signaling via deSUMOylation of MKK7 leading to enhancement in JNK phosphorylation and the downstream events. Therefore this work provides novel mechanistic insights into redox regulation of innate immune responses.

Immunometabolic Signaling Pathways Contribute to Macrophage and Dendritic Cell Function

Understanding of antigen-presenting cell (APC) participation in tissue inflammation and metabolism has advanced through numerous studies using systems biology approaches. Previously unrecognized connections between these research areas have been elucidated in the context of inflammatory disease involving innate and adaptive immune responses. A new conceptual framework bridges APC biology, metabolism, and cytokines in the generation of effective T-cell responses. Exploring these connections is paramount to addressing the rising tide of multi-organ system diseases, particularly chronic diseases associated with metabolic syndrome, infection, and cancer. Focused research in these areas will aid the development of strategies to harness and manipulate innate immunology to improve vaccine development, anti-viral, anti-inflammatory, and anti-tumor therapies. This review highlights recent advances in APC "immunometabolism" specifically related to chronic viral and metabolic disease in humans. The goal of this review is to develop an abridged and consolidated outlook on recent thematic updates to APC immunometabolism in the areas of regulation and crosstalk between metabolic and inflammatory signaling and the integrated stress response and how these signals dictate APC function in providing T-cell activation Signal 3.

Ubiquitin specific protease 19 involved in transcriptional repression of retinoic acid receptor by stabilizing CORO2A

Deubiquitination via deubiquitinating enzymes (DUBs) has been emerged as one of the important post-translational modifications, resulting in the regulation of numerous target proteins. In this study, we screened new protein biomarkers for adipogenesis, and related studies showed that ubiquitin specific protease 19 (USP19) as a DUB is gradually decreased during adipogenesis and it regulates coronin 2A (CORO2A) as one of the components for the nuclear receptor co-repressor (NCoR) complex in some studies. The regulation of CORO2A through the deubiquitinating activity of USP19 affected the transcriptional repression activity of the retinoic acid receptor (RAR), suggesting that USP19 may be involved in the regulation of RAR-mediated adipogenesis.

Initiation of DNA replication requires actin dynamics and formin activity

Nuclear actin regulates transcriptional programmes in a manner dependent on its levels and polymerisation state. This dynamics is determined by the balance of nucleocytoplasmic shuttling, formin- and redox-dependent filament polymerisation. Here, using Xenopus egg extracts and human somatic cells, we show that actin dynamics and formins are essential for DNA replication. In proliferating cells, formin inhibition abolishes nuclear transport and initiation of DNA replication, as well as general transcription. In replicating nuclei from transcriptionally silent Xenopus egg extracts, we identified numerous actin regulators, and disruption of actin dynamics abrogates nuclear transport, preventing NLS (nuclear localisation signal)-cargo release from RanGTP-importin complexes. Nuclear formin activity is further required to promote loading of cyclin-dependent kinase (CDK) and proliferating cell nuclear antigen (PCNA) onto chromatin, as well as initiation and elongation of DNA replication. Therefore, actin dynamics and formins control DNA replication by multiple direct and indirect mechanisms.

CAMKIIγ suppresses an efferocytosis pathway in macrophages and promotes atherosclerotic plaque necrosis

Atherosclerosis is the underlying etiology of cardiovascular disease, the leading cause of death worldwide. Atherosclerosis is a heterogeneous disease in which only a small fraction of lesions lead to heart attack, stroke, or sudden cardiac death. A distinct type of plaque containing large necrotic cores with thin fibrous caps often precipitates these acute events. Here, we show that Ca2+/calmodulin-dependent protein kinase γ (CaMKIIγ) in macrophages plays a major role in the development of necrotic, thin-capped plaques. Macrophages in necrotic and symptomatic atherosclerotic plaques in humans as well as advanced atherosclerotic lesions in mice demonstrated activation of CaMKII. Western diet-fed LDL receptor-deficient (Ldlr-/-) mice with myeloid-specific deletion of CaMKII had smaller necrotic cores with concomitantly thicker collagen caps. These lesions demonstrated evidence of enhanced efferocytosis, which was associated with increased expression of the macrophage efferocytosis receptor MerTK. Mechanistic studies revealed that CaMKIIγ-deficient macrophages and atherosclerotic lesions lacking myeloid CaMKIIγ had increased expression of the transcription factor ATF6. We determined that ATF6 induces liver X receptor-α (LXRα), an Mertk-inducing transcription factor, and that increased MerTK expression and efferocytosis in CaMKIIγ-deficient macrophages is dependent on LXRα. These findings identify a macrophage CaMKIIγ/ATF6/LXRα/MerTK pathway as a key factor in the development of necrotic atherosclerotic plaques.

The Roles of SUMO in Metabolic Regulation

Protein modification with the small ubiquitin-related modifier (SUMO) can affect protein function, enzyme activity, protein-protein interactions, protein stability, protein targeting and cellular localization. SUMO influences the function and regulation of metabolic enzymes within pathways, and in some cases targets entire metabolic pathways by affecting the activity of transcription factors or by facilitating the translocation of entire metabolic pathways to subcellular compartments. SUMO modification is also a key component of nutrient- and metabolic-sensing mechanisms that regulate cellular metabolism. In addition to its established roles in maintaining metabolic homeostasis, there is increasing evidence that SUMO is a key factor in facilitating cellular stress responses through the regulation and/or adaptation of the most fundamental metabolic processes, including energy and nucleotide metabolism. This review focuses on the role of SUMO in cellular metabolism and metabolic disease.

Selenoprotein MsrB1 promotes anti-inflammatory cytokine gene expression in macrophages and controls immune response in vivo

Post-translational redox modification of methionine residues often triggers a change in protein function. Emerging evidence points to this reversible protein modification being an important regulatory mechanism under various physiological conditions. Reduction of oxidized methionine residues is catalyzed by methionine sulfoxide reductases (Msrs). Here, we show that one of these enzymes, a selenium-containing MsrB1, is highly expressed in immune-activated macrophages and contributes to shaping cellular and organismal immune responses. In particular, lipopolysaccharide (LPS) induces expression of MsrB1, but not other Msrs. Genetic ablation of MsrB1 did not preclude LPS-induced intracellular signaling in macrophages, but resulted in attenuated induction of anti-inflammatory cytokines, such as interleukin (IL)-10 and the IL-1 receptor antagonist. This anomaly was associated with excessive pro-inflammatory cytokine production as well as an increase in acute tissue inflammation in mice. Together, our findings suggest that MsrB1 controls immune responses by promoting anti-inflammatory cytokine expression in macrophages. MsrB1-dependent reduction of oxidized methionine in proteins may be a heretofore unrecognized regulatory event underlying immunity and inflammatory disease, and a novel target for clinical applications.

The Mechanism of Diabetic Retinopathy Pathogenesis Unifying Key Lipid Regulators, Sirtuin 1 and Liver X Receptor

Diabetic retinopathy (DR) is a complication secondary to diabetes and is the number one cause of blindness among working age individuals worldwide. Despite recent therapeutic breakthroughs using pharmacotherapy, a cure for DR has yet to be realized. Several clinical trials have highlighted the vital role dyslipidemia plays in the progression of DR. Additionally, it has recently been shown that activation of Liver X receptor (LXRα/LXRβ) prevents DR in diabetic animal models. LXRs are nuclear receptors that play key roles in regulating cholesterol metabolism, fatty acid metabolism and inflammation. In this manuscript, we show insight into DR pathogenesis by demonstrating an innovative signaling axis that unifies key metabolic regulators, Sirtuin 1 and LXR, in modulating retinal cholesterol metabolism and inflammation in the diabetic retina. Expression of both regulators, Sirtuin 1 and LXR, are significantly decreased in diabetic human retinal samples and in a type 2 diabetic animal model. Additionally, activation of LXR restores reverse cholesterol transport, prevents inflammation, reduces pro-inflammatory macrophages activity and prevents the formation of diabetes-induced acellular capillaries. Taken together, the work presented in this manuscript highlights the important role lipid dysregulation plays in DR progression and offers a novel potential therapeutic target for the treatment of DR.

•

Diabetes affects retinal Liver X Receptor and Sirtuin 1 expression levels.

•

Liver X Receptor normalized reverse cholesterol transport and prevented diabetes-induced inflammation in retinal cells.

•

Liver X Receptor activation reduced the number of pro-inflammatory macrophages and prevented DR-like pathology.

Results of recent clinical trials demonstrate strong association between lipid abnormalities and progression of diabetic retinopathy (DR), the sight-threatening secondary complication of diabetes. This study addresses the role of key metabolic lipid regulators, SIRT1 and LXR in the progression of DR. All the components of SIRT1-LXR axis were downregulated in retinal cells isolated from human donor tissue or a DR animal model. Activation of LXR normalized reverse cholesterol transport, prevented diabetes-induced inflammation, reduced the number of pro-inflammatory macrophages and prevented DR-like pathology, suggesting that control of SIRT1-LXR axis could be a promising therapeutic target for treatment of DR.

Liver X receptors link lipid metabolism and inflammation

The response of immune cells to pathogens is often associated with changes in the flux through basic metabolic pathways. Indeed, in many cases changes in metabolism appear to be necessary for a robust immune response. The Liver X receptors (LXRs) are members of the nuclear hormone receptor superfamily that regulate gene networks controlling cholesterol and lipid metabolism. In immune cells, particularly in macrophages, LXRs also inhibit proinflammatory gene expression. This Review will highlight recent studies that connect LXR-dependent control of lipid metabolism to regulation of the immune response.