Monocyte Chemoattractant Protein-induced Protein Research Articles

MCPIP1 Elicits a Therapeutic Effect on Cervical Cancer by Facilitating XIAP mRNA Decay via Its Endoribonuclease Activity.

Cervical cancer is the fourth most common malignancy in women globally. Chemotherapies, targeted therapies, and immunotherapies in the treatment of cervical cancer are usually accompanied by effective and adverse effects. Therefore, finding other efficient and accurate molecular targets remains essential to improve the treatment benefits of cervical cancer patients. MCPIP1 (monocyte chemoattractant protein-induced protein 1) is a kind of endonuclease with a CCCH zinc finger domain and a PilT-N-terminal (PIN) domain, and its function in cervical cancer is unknown. We found that MCPIP1 inhibits cell proliferation and promotes cell apoptosis of cervical cancer. Additionally, MCPIP1 suppresses mRNA and protein expression of the apoptotic inhibitor XIAP by decreasing its mRNA stability. Mechanically, MCPIP1 binds to the XIAP mRNA via its CCCH zinc finger domain and degrades the XIAP mRNA via the endonuclease activity coming from its PIN domain. Our study clarifies that MCPIP1 promotes cervical cancer cell apoptosis by suppressing the expression of XIAP, thereby impeding cervical cancer progression. Moreover, targeted delivery of MCPIP1 with engineered Salmonella typhimurium leads to tumor growth retardation in the HeLa xenograft tumor model in mice. Therefore, our study may provide a theoretical basis for formulating clinical treatment strategies for cervical cancer.

Hepatic Mcpip1 regulates adaptation to food restriction in mice.

Monocyte-chemoattractant protein-induced protein 1 (MCPIP1, or Regnase-1) is an endoribonuclease that degrades translationally active mRNA molecules. MCPIP1 is mostly known for its anti-inflammatory actions, but it is also an important regulator of adipogenesis and lipid metabolism. Its overexpression impairs adipogenesis by reducing mRNA levels of C/EBPβ and PPARγ, key transcription factors regulating this process. Although adipocytes overexpressing MCPIP1 are characterised by impaired glucose uptake, the function of MCPIP1 in hepatocyte metabolism remains unknown. In this study, conditional deletion of Zc3h12a in murine liver epithelial cells was used to characterise the role of Mcpip1 in adaptation to 24-hour food restriction. We found that Mcpip1 deficiency in liver epithelial cells (Mcpip1fl/flAlbCre mice) resulted in higher blood glucose levels in response to fasting in comparison to Mcpip1fl/fl counterparts. Hepatic proteome analysis showed 26 down-regulated and 117 up-regulated proteins in Mcpip1fl/flAlbCre animals that were involved in cellular adhesion, extracellular matrix and metabolic processes. In conclusion, our studies provide new insight into the hepatic function of Mcpip1 and its involvement in metabolic control.

MCPIP1 functions as a safeguard of early embryonic development

Monocyte chemoattractant protein-induced protein 1 (MCPIP1), also called Regnase-1, is an RNase that has been described as a key negative modulator of inflammation. MCPIP1 also controls numerous tumor-related processes, such as proliferation, apoptosis and differentiation. In this study, we utilized a zebrafish model to investigate the role of Mcpip1 during embryogenic development. Our results demonstrated that during embryogenesis, the expression of the zc3h12a gene encoding Mcpip1 undergoes dynamic changes. Its transcript levels gradually increase from the 2-cell stage to the spherical stage and then decrease rapidly. We further found that ectopic overexpression of wild-type Mcpip1 but not the catalytically inactive mutant form resulted in an embryonic lethal phenotype in zebrafish embryos (24 hpf). At the molecular level, transcriptomic profiling revealed extensive changes in the expression of genes encoding proteins important in the endoplasmic reticulum stress response and in protein folding as well as involved in the formation of primary germ layer, mesendoderm and endoderm development, heart morphogenesis and cell migration. Altogether, our results demonstrate that the expression of zc3h12a must be tightly controlled during the first cell divisions of zebrafish embryos and that a rapid decrease in its mRNA expression is an important factor promoting proper embryo development.

FGF21 protects against doxorubicin-induced cardiotoxicity by inhibiting connexin 43 ubiquitination

BackgroundFibroblast growth factor 21 (FGF21) regulates glycolipid metabolism and insulin homeostasis and acts as a cardioprotective factor by protecting against myocardial ischemia/reperfusion injury, hypertension, and vascular dysfunction. FGF21 has been reported to prevent Doxorubicin (Dox)-induced cardiotoxicity, and the related signaling pathway is worthy of further study. Connexin43 (Cx43) protein was reduced by Dox treatment, especially low phosphorylated form of Cx43. Thus the aim of study is to explore the protection effect of FGF21 on Dox induced cardiotoxicity by improving the expression of Cx43 and the involved signaling pathway. Methods and resultsFGF21 inhibited apoptosis in Dox-treated mice and cardiomyocytes. FGF21 increased the levels of connexin43 phosphorylated at serine (S) 282 (p-Cx43 S282) and total Cx43 to inhibit Dox-induced apoptosis. By RNA sequencing, we found that deubiquitinase monocyte chemoattractant protein-induced protein 1 (MCPIP1) expression was increased by FGF21. We further found that FGF21 induced the phosphorylation of fibroblast growth factor receptor 1 (FGFR1), extracellular signal-regulated kinase 1 and 2 (Erk1/2), and Elk. Phosphorylated Elk translocated to the nucleus and increased the expression of MCPIP1. Then, MCPIP1 bound neural precursor cell expressed developmentally downregulated protein 4 (Nedd4), an E3 ubiquitination ligase, as shown by co-immunoprecipitation (Co-IP), and suppressed Cx43 ubiquitination and degradation, competitively inhibiting the binding of Cx43 with Nedd4. Thus Nedd4 could not bind and ubiquitinate Cx43, leading to the up-regulation of Cx43 and phosphorylation of Cx43 at S282. ConclusionsFGF21 inhibited the effects of Dox on cardiomyocytes by elevating the phosphorylation of Cx43 at S282 and total Cx43 expression. This study suggests a previously unknown mechanism for the FGF21-mediated enhancement of cardiomyocyte survival and provides an effective approach to protect against the adverse cardiac effects of Dox.

Let-7g Upregulation Attenuated the KRAS-PI3K-Rac1-Akt Axis-Mediated Bioenergetic Functions.

The aberrant activation of signaling pathways contributes to cancer cells with metabolic reprogramming. Thus, targeting signaling modulators is considered a potential therapeutic strategy for cancer. Subcellular fractionation, coimmunoprecipitation, biochemical analysis, and gene manipulation experiments revealed that decreasing the interaction of kirsten rat sarcoma viral oncogene homolog (KRAS) with p110α in lipid rafts with the use of naringenin (NGN), a citrus flavonoid, causes lipid raft-associated phosphatidylinositol 3-kinase (PI3K)-GTP-ras-related C3 botulinum toxin substrate 1 (Rac1)-protein kinase B (Akt)-regulated metabolic dysfunction of glycolysis and mitochondrial oxidative phosphorylation (OXPHOS), leading to apoptosis in human nasopharyngeal carcinoma (NPC) cells. The use of lethal-7g (let-7g) mimic and let-7g inhibitor confirmed that elevated let-7g resulted in a decrease in KRAS expression, which attenuated the PI3K-Rac1-Akt-BCL-2/BCL-xL-modulated mitochondrial energy metabolic functions. Increased let-7g depends on the suppression of the RNA-specificity of monocyte chemoattractant protein-induced protein-1 (MCPIP1) ribonuclease since NGN specifically blocks the degradation of pre-let-7g by NPC cell-derived immunoprecipitated MCPIP1. Converging lines of evidence indicate that the inhibition of MCPIP1 by NGN leads to let-7g upregulation, suppressing oncogenic KRAS-modulated PI3K-Rac1-Akt signaling and thereby impeding the metabolic activities of aerobic glycolysis and mitochondrial OXPHOS.

MCPIP-1 knockdown enhances endothelial colony-forming cell angiogenesis via the TFRC/AKT/mTOR signaling pathway in the ischemic penumbra of MCAO mice

Cerebral ischemia is a serious disease characterized by brain tissue ischemia and hypoxic necrosis caused by the blockage of blood vessels within the central nervous system. Although stem cell therapy is a promising approach for treating ischemic stroke, the inflammatory, oxidative, and hypoxic environment generated by cerebral ischemia greatly reduces the survival and therapeutic effects of transplanted stem cells. Endothelial colony-forming cells (ECFCs) are a class of precursor cells with strong proliferative potential that can migrate and differentiate directly into mature vascular endothelial cells. Consequently, ECFCs can exert significant therapeutic and reparative effects in diseases associated with vascular injury. Monocyte chemoattractant protein-induced protein 1 (MCPIP-1) exerts multiple biological effects; however, no studies have yet reported its role in the angiogenic function of ECFCs. In this study, we performed Proteome Profiler™ Human Angiogenesis Antibody arrays and tandem mass tag protein profiling to investigate the effect of MCPIP-1 on ECFCs. We demonstrated that MCPIP-1 knockdown enhanced the proliferation, migration, and in vivo and in vitro angiogenic capacity of ECFCs by upregulating the transferrin receptor-activated AKT/m-TOR signaling pathway to promote cellular trophic factor secretion. Furthermore, we found that the lateral ventricular transplantation of ECFCs with lentiviral MCPIP-1 knockdown into mice with middle cerebral artery occlusion increased serum vacular endothelial growth factor(VEGF), angiopoietin-1, and HIF-1a levels, enhanced neovascularization and neurogenesis in the ischemic penumbra, reduced the size of cerebral infarcts, and promoted neurological recovery. Together, these findings suggest new avenues for enhancing the therapeutic efficacy of ECFCs.

The role of Monocyte Chemoattractant Protein-Induced Protein-1 in the regulation of the immune responses to mycobacterial infection

Abstract Mycobacterium tuberculosis (Mtb) infection is mainly controlled by protective cell-mediated immunity. TNFα and other mediators, such as nitric oxide (NO), are crucial to the macrophage’s antimicrobial activity. The RNA-binding protein MCPIP1 is a zinc-finger protein with RNase activity that targets the 3’UTR region of cytokine’s mRNA for degradation like IL-6, IL-1β, and IL-12. Here, we aim to investigate the role of MCPIP1 during infection and its contribution to Mtb’s immune evasion. Our observations show that MCPIP1 increases after Mtb infection, correlating with disease progression. Similarly, global MCPIP1 KO (MCPIP1 −/−) mice showed lower lung bacterial burden than WT mice after 30 days. To address wheater the reduced number of bacteria was due to the macrophage’s absent MCPIP1 expression, we generated myeloid-specific MCPIP1 KO mice (M-MCPIP1 −/−). M-MCPIP1 −/−mice showed a similar reduction of bacterial growth as the MCPIP1 −/−mice compared with their WT littermates. Infection of bone marrow-derived macrophages confirmed that myeloid-MCPIP1 deficient cells had improved control of bacterial growth with increased IL-1β, IL-6, IL-12, iNOS, and TNFα. To evidence the mechanism by which M-MCPIP1 −/−macrophages contribute to Mtb growth control, we blocked TNFα and iNOS activity. Results showed that protection in M-MCPIP1 −/−is partly due to these molecule’s high expression, as the blockade of these mediators increased the bacterial burden. Our preliminary data suggest that the induction of MCPIP1 contributes to the bacteria’s immune evasion by targeting critical anti-TB molecules. Further experiments are needed to understand the mechanisms involved and consider MCPIP1 as a target for host-directed therapy for TB. R21AI151936 R21AI171734

Localization and expression profiles of gingival monocyte chemoattractant protein-1-induced protein-1 (MCPIP-1) and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT-1)

ObjectivesThe purposes of this study were to localize monocyte chemoattractant protein-1-induced protein-1 (MCPIP-1) and its suppressor mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT-1) in gingival tissues and to profile their protein expression levels in relation to the clinical inflammation, Porphyromonas gingivalis colonization, and interleukin (IL)-8 levels.Materials and methodsStudy samples were collected from two independent study populations: (1) Gingival tissues were collected from eight periodontally healthy individuals and eight periodontitis patients to localize MCPIP-1 and MALT-1 immunohistochemically, and (2) forty-one gingival tissue samples with marginal, mild, or moderate to severe inflammation were collected from 20 periodontitis patients to determine MCPIP-1 and MALT-1 levels using immunoblots, P. gingivalis levels with qPCR, P. gingivalis gingipain activities with fluorogenic substrates, and IL-8 levels with multiplex technique.ResultsMCPIP-1 was detectable in the epithelium and in connective tissue, being especially prominent around the blood vessel walls in healthy periodontal tissues. MALT-1 was observed at all layers of gingival epithelium and especially around the accumulated inflammatory cells in connective tissue. No difference in gingival tissue MCPIP-1 and MALT-1 levels was observed in relation to the severity of gingival inflammation. MALT-1 levels were elevated (p = 0.023) with the increase in tissue P. gingivalis levels, and there was an association between MALT-1 and IL-8 levels (β = 0.054, p = 0.001).ConclusionsInteractions of MALT-1 levels with gingival tissue P. gingivalis counts and IL-8 levels suggest that activation of MALT-1 can take part in P. gingivalis-regulated host immune responses.Clinical relevancePharmacological targeting the crosstalk between immune response and MCPIP-1/MALT-1 may have benefits in periodontal treatment.

Hepatic MCPIP1 protein levels are reduced in NAFLD patients and are predominantly expressed in cholangiocytes and liver endothelium

NAFLD is characterized by the excessive accumulation of fat in hepatocytes. NAFLD can range from simple steatosis to the aggressive form called NASH, which is characterized by both fatty liver and liver inflammation. Without proper treatment, NAFLD may further progress to life-threatening complications, such as fibrosis, cirrhosis, or liver failure. Monocyte chemoattractant protein-induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through the cleavage of transcripts coding for proinflammatory cytokines and the inhibition of NF-κB activity. In this study, we investigated MCPIP1 expression in the liver and peripheral blood mononuclear cells (PBMCs) collected from a cohort of 36 control and NAFLD patients hospitalized due to bariatric surgery or primary inguinal hernia laparoscopic repair. Based on liver histology data (hematoxylin and eosin and Oil Red-O staining), 12 patients were classified into the NAFL group, 19 into the NASH group, and 5 into the control (non-NAFLD) group. Biochemical characterization of patient plasma was followed by expression analysis of genes regulating inflammation and lipid metabolism. The MCPIP1 protein level was reduced in the livers of NAFL and NASH patients in comparison to non-NAFLD control individuals. In addition, in all groups of patients, immunohistochemical staining showed that the expression of MCPIP1 was higher in the portal fields and bile ducts in comparison to the liver parenchyma and central vein. The liver MCPIP1 protein level negatively correlated with hepatic steatosis but not with patient body mass index or any other analyte. The MCPIP1 level in PBMCs did not differ between NAFLD patients and control patients. Similarly, in patients' PBMCs there were no differences in the expression of genes regulating β-oxidation (ACOX1, CPT1A, and ACC1) and inflammation (TNF, IL1B, IL6, IL8, IL10, and CCL2), or transcription factors controlling metabolism (FAS, LCN2, CEBPB, SREBP1, PPARA, and PPARG). We have demonstrated that MCPIP1 protein levels are reduced in NAFLD patients, but further research is needed to investigate the specific role of MCPIP1 in NAFL initiation and the transition to NASH.

MCPIP1 alleviates inflammatory response through inducing autophagy in Aspergillus fumigatus keratitis

Fungal keratitis (FK) is a serious corneal infection caused by pathogenic fungi. Monocyte chemoattractant protein-induced protein 1 (MCPIP1) plays an important role in restricting the inflammatory response in various immune disorders. However, the function of MCPIP1 in Aspergillus fumigatus (A. fumigatus) keratitis is unclear. In the present study, we found that A. fumigatus infection promotes the expression of MCPIP1 in human corneal epithelial cells (HCECs) and in mouse corneas. Overexpression of MCPIP1 decreased the production of inflammatory cytokines, including TNF-α, IL-6, and IL-1β, while knockdown of MCPIP1 increased the expression of these cytokines. MCPIP1 enhanced autophagy flux by inhibiting the mTOR signaling in HCECs with A. fumigatus infection. Further study showed that inhibition of autophagy using chloroquine reverses the anti-inflammatory effect of MCPIP1 in HCECs infected with A. fumigatus. Moreover, MCPIP1 alleviated the severity of keratitis and inhibited the expression of inflammatory cytokines by activating autophagy in an FK mouse model. In conclusion, our study demonstrated that MCPIP1 alleviates the severity of A. fumigatus keratitis by inducing mTOR-mediated autophagy in HCECs and in a mouse model. Exogenous use of MCPIP1 protein may have potential applications in FK clinical therapy.

SAT179 - Role of Monocyte chemoattractant protein-induced protein 1 in liver fibrosis and activation of hepatic stellate cells

SAT179 - Role of Monocyte chemoattractant protein-induced protein 1 in liver fibrosis and activation of hepatic stellate cells

Macrophage-Specific MCPIP1/Regnase-1 Attenuates Kidney Ischemia-Reperfusion Injury by Shaping the Local Inflammatory Response and Tissue Regeneration.

Sterile inflammation either resolves the initial insult or leads to tissue damage. Kidney ischemia/reperfusion injury (IRI) is associated with neutrophilic infiltration, enhanced production of inflammatory mediators, accumulation of necrotic cells and tissue remodeling. Macrophage-dependent microenvironmental changes orchestrate many features of the immune response and tissue regeneration. The activation status of macrophages is influenced by extracellular signals, the duration and intensity of the stimulation, as well as various regulatory molecules. The role of macrophage-derived monocyte chemoattractant protein-induced protein 1 (MCPIP1), also known as Regnase-1, in kidney ischemia-reperfusion injury (IRI) and recovery from sterile inflammation remains unresolved. In this study, we showed that macrophage-specific Mcpip1 deletion significantly affects the kidney phenotype. Macrophage-specific Mcpip1 transgenic mice displayed enhanced inflammation and loss of the tubular compartment upon IRI. We showed that MCPIP1 modulates sterile inflammation by negative regulation of Irf4 expression and accumulation of IRF4+ cells in the tissue and, consequently, suppresses the post-ischemic kidney immune response. Thus, we identified MCPIP1 as an important molecular sentinel of immune homeostasis in experimental acute kidney injury (AKI) and renal fibrosis.

Monocyte Chemotactic Protein-Induced Protein 1 (MCPIP-1): A Key Player of Host Defense and Immune Regulation

Inflammatory response is a host-protective mechanism against tissue injury or infections, but also has the potential to cause extensive immunopathology and tissue damage, as seen in many diseases, such as cardiovascular diseases, neurodegenerative diseases, metabolic syndrome and many other infectious diseases with public health concerns, such as Coronavirus Disease 2019 (COVID-19), if failure to resolve in a timely manner. Recent studies have uncovered a superfamily of endogenous chemical molecules that tend to resolve inflammatory responses and re-establish homeostasis without causing excessive damage to healthy cells and tissues. Among these, the monocyte chemoattractant protein-induced protein (MCPIP) family consisting of four members (MCPIP-1, -2, -3, and -4) has emerged as a group of evolutionarily conserved molecules participating in the resolution of inflammation. The focus of this review highlights the biological functions of MCPIP-1 (also known as Regnase-1), the best-studied member of this family, in the resolution of inflammatory response. As outlined in this review, MCPIP-1 acts on specific signaling pathways, in particular NFκB, to blunt production of inflammatory mediators, while also acts as an endonuclease controlling the stability of mRNA and microRNA (miRNA), leading to the resolution of inflammation, clearance of virus and dead cells, and promotion of tissue regeneration via its pleiotropic effects. Evidence from transgenic and knock-out mouse models revealed an involvement of MCPIP-1 expression in immune functions and in the physiology of the cardiovascular system, indicating that MCPIP-1 is a key endogenous molecule that governs normal resolution of acute inflammation and infection. In this review, we also discuss the current evidence underlying the roles of other members of the MCPIP family in the regulation of inflammatory processes. Further understanding of the proteins from this family will provide new insights into the identification of novel targets for both host effectors and microbial factors and will lead to new therapeutic treatments for infections and other inflammatory diseases.

MCPIP1 Enhances TNF-α-Mediated Apoptosis through Downregulation of the NF-κB/cFLIP Axis

Simple SummaryTNF-α is considered to be a potential therapeutic drug for cancer, but the systemic toxicity problem still exists in clinical use. MCPIP1 plays a crucial role in anti-inflammatory and anti-viral contexts, as well as in the inhibition of cell growth. This study aims to investigate the roles of MCPIP1 in TNF-α-treated cells and their underlying molecular mechanisms. MCPIP1 was found to enhance TNF-α-induced apoptosis by activating the caspase cascade, and pan-caspase inhibitor and the caspase-1/-4 inhibitor could reverse TNF-α/MCPIP1-mediated apoptosis. MCPIP1 was first identified with cleavage site of caspase-1/-4 and could be cleaved during apoptosis. Downregulation of NF-κB activation and a caspase-8 inhibitor, cFLIP, were associated with TNF-α/MCPIP1-mediated apoptosis.Monocyte chemoattractant protein-1-induced protein 1 (MCPIP1) is rapidly produced under proinflammatory stimuli, thereby feeding back to downregulate excessive inflammation. In this study, we used the stable, inducible expressions of wild-type (WT) MCPIP1 and an MCPIP1-D141N mutant in T-REx-293 cells by means of a tetracycline on (Tet-on) system. We found that WT MCPIP1 but not MCPIP1-D141N mutant expression dramatically increased apoptosis, caspase-3, -7, -8, and -9 activation, and c-Jun N-terminal kinase (JNK) phosphorylation in TNF-α-treated cells. The pan-caspase inhibitor, z-VAD-fmk, and the caspase-1 inhibitor, z-YVAD-fmk, but not the JNK inhibitor, SP600125, significantly reversed apoptosis and caspase activation in TNF-α/MCPIP1-treated cells. Surprisingly, MCPIP1 itself was also cleaved, and the cleavage was suppressed by treatment with the pan-caspase inhibitor and caspase-1 inhibitor. Moreover, MCPIP1 was found to contain a caspase-1/-4 consensus recognition sequence located in residues 234~238. As expected, the WT MCPIP1 but not the MCPIP1-D141N mutant suppressed NF-κB activation, as evidenced by inhibition of IκB kinase (IKK) phosphorylation and IκB degradation using Western blotting, IKK activity using in vitro kinase activity, and NF-κB translocation to nuclei using an immunofluorescence assay. Interestingly, MCPIP1 also significantly inhibited importin α3 and importin α4 expressions, which are major nuclear transporter receptors for NF-κB. Inhibition of NF-κB activation further downregulated expression of the caspase-8 inhibitor, cFLIP. In summary, the results suggest that MCPIP1 could enhance the TNF-α-induced apoptotic pathway through decreasing NF-κB activation and cFLIP expression.

Subversion of Lipopolysaccharide Signaling in Gingival Keratinocytes via MCPIP-1 Degradation as a Novel Pathogenic Strategy of Inflammophilic Pathobionts.

ABSTRACTPeriodontal disease (PD) is an inflammatory disease of the supporting tissues of the teeth that develops in response to formation of a dysbiotic biofilm on the subgingival tooth surface. Although exacerbated inflammation leads to alveolar bone destruction and may cause tooth loss, the molecular basis of PD initiation and progression remains elusive. Control over the inflammatory reaction and return to homeostasis can be efficiently restored by negative regulators of Toll-like receptor (TLR) signaling pathways such as monocyte chemoattractant protein-induced protein 1 (MCPIP-1), which is constitutively expressed in gingival keratinocytes and prevents hyperresponsiveness in the gingiva. Here, we found that inflammophilic periodontal species influence the stability of MCPIP-1, leading to an aggravated response of the epithelium to proinflammatory stimulation. Among enzymes secreted by periodontal species, gingipains—cysteine proteases from Porphyromonas gingivalis—are considered major contributors to the pathogenic potential of bacteria, strongly influencing the components of the innate and adaptive immune system. Gingipain proteolytic activity leads to a rapid degradation of MCPIP-1, exacerbating the inflammatory response induced by endotoxin. Collectively, these results establish a novel mechanism of corruption of inflammatory signaling by periodontal pathogens, indicating new possibilities for treatment of this chronic disease.

Role of Mcpip1 in obesity-induced hepatic steatosis as determined by myeloid and liver-specific conditional knockouts.

Monocyte chemoattractant protein‐induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through cleavage of transcripts coding for proinflammatory cytokines and by inhibition of NFκB activity. Moreover, it was demonstrated that MCPIP1 regulates lipid metabolism both in adipose tissue and in hepatocytes. In this study, we investigated the effects of tissue‐specific Mcpip1 deletion on the regulation of hepatic metabolism and development of nonalcoholic fatty liver disease (NAFLD). We used control Mcpip1fl/fl mice and animals with deletion of Mcpip1 in myeloid leukocytes (Mcpip1fl/flLysMCre) and in hepatocytes (Mcpip1fl/flAlbCre), which were fed chow or a high‐fat diet (HFD) for 12 weeks. Mcpip1fl/flLysMCre mice fed a chow diet were characterized by a significantly reduced hepatic expression of genes regulating lipid and glucose metabolism, which subsequently resulted in low plasma glucose level and dyslipidemia. These animals also displayed systemic inflammation, demonstrated by increased concentrations of cytokines in the plasma and high Tnfa, Il6, IL1b mRNA levels in the liver and brown adipose tissue (BAT). Proinflammatory leukocyte infiltration into BAT, together with low expression of Ucp1 and Ppargc1a, resulted in hypothermia of 22‐week‐old Mcpip1fl/flLysMCre mice. On the other hand, there were no significant changes in phenotype in Mcpip1fl/flAlbCre mice. Although we detected a reduced hepatic expression of genes regulating glucose metabolism and β‐oxidation in these mice, they remained asymptomatic. Upon feeding with a HFD, Mcpip1fl/flLysMCre mice did not develop obesity, glucose intolerance, nor hepatic steatosis, but were characterized by low plasma glucose level and dyslipidemia, along with proinflammatory phenotype. Mcpip1fl/flAlbCre animals, following a HFD, became hypercholesterolemic, but accumulated lipids in the liver at the same level as Mcpip1fl/fl mice, and no changes in the level of soluble factors tested in the plasma were detected. We have demonstrated that Mcpip1 protein plays an important role in the liver homeostasis. Depletion of Mcpip1 in myeloid leukocytes, followed by systemic inflammation, has a more pronounced effect on controlling liver metabolism and homeostasis than the depletion of Mcpip1 in hepatocytes.

Multifunctional RNase MCPIP1 and its Role in Cardiovascular Diseases.

Monocyte chemoattractant protein-1 induced protein 1 (MCPIP1), one of the MCPIP family members, is characterized by the presence of both C-x8-C-x5-C-x3-H (CCCH)- type zinc finger and PilT-N-terminal domains. As a potent regulator of innate immunity, MCPIP1 exerts anti-inflammatory effects through its ribonuclease (RNase) and deubiquitinating enzyme activities to degrade cytokine mRNAs and inhibit nuclear factor- kappa B (NF-κB), respectively. MCPIP1 is expressed not only in immune cells but also in many other cell types, including cardiomyocytes, vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Increasing evidence indicates that MCPIP1 plays a role in the regulation of cardiac functions and is involved in the processes of vascular diseases, such as ischemia-reperfusion (I/R) and atherosclerosis. To better understand the emerging roles of MCPIP1 in the cardiovascular system, we reviewed the current literature with respect to MCPIP1 functions and discussed its association with the pathogenesis of cardiovascular diseases and the implication as a therapeutic target.

Monocyte chemoattractant protein-induced protein 1 directly degrades viral miRNAs with a specific motif and inhibits KSHV infection.

Kaposi's sarcoma-associated herpesvirus (KSHV) expresses miRNAs during latency. However, regulation of viral miRNAs remains largely unknown. Our prior studies demonstrated that MCPIP1 regulates KSHV miRNA biogenesis by degrading most KSHV pre-miRNAs through its RNase activity. Some viral pre-miRNAs are partially resistant to degradation by MCPIP1. Here, we further characterized MCPIP1 substrate specificity and its antiviral potential against KSHV infection. In vitro cleavage assays and binding assays showed that MCPIP1 cleavage efficiency is related to binding affinity. Motif-based sequence analysis identified that KSHV pre-miRNAs that are well degraded by MCPIP1 have a 5-base motif (M5 base motif) within their terminal loops and this motif region consists of multiple pyrimidine-purine-pyrimidine (YRY) motifs. We further demonstrated that mutation of this M5 base motif within terminal loop of pre-miRNAs inhibited MCPIP1-mediated RNA degradation. We also revealed that MCPIP1 has an antiviral effect against KSHV infection. MCPIP1 can reduce the expression of Dicer, which in turn restricts KSHV infection. Conclusively, our findings demonstrated that MCPIP1 inhibited KSHV infection and suppressed viral miRNA biogenesis by directly degrading KSHV pre-miRNAs and altering the expression of miRNA biogenesis factors.

MCPIP-1 Restricts Inflammation via Promoting Apoptosis of Neutrophils.

Monocyte chemoattractant protein-induced protein-1 (MCPIP-1) is a potent inhibitor of inflammatory response to pathogens. Acting as endonuclease against transcripts of inflammatory cytokines or transcription factors MCPIP-1 can significantly reduce the cytokine storm, thus limiting the tissue damage. As the adequate resolution of inflammation depends also on the efficient clearance of accumulated neutrophils, we focused on the role of MCPIP-1 in apoptosis and retention of neutrophils. We used peritoneal neutrophils from cell-specific MCPIP-1 knockout mice and showed prolonged survival of these cells. Moreover, we confirmed that MCPIP-1-dependent degradation of transcripts of antiapoptotic genes, including BCL3, BCL2A1, BCL2L1, and for the first time MCL-1, serves as an early event in spontaneous apoptosis of primary neutrophils. Additionally, we identified previously unknown miRNAs as potential binding partners to the MCPIP-1 transcript and their regulation suggest a role in MCPIP-1 half-life and translation. These phenomena may play a role as a molecular switch that balances the MCPIP-1-dependent apoptosis. Besides that, we determined these particular miRNAs as integral components of the GM-CSF-MCPIP-1 axis. Taken together, we identified the novel anti-inflammatory role of MCPIP-1 as a regulator of accumulation and survival of neutrophils that simultaneously promotes an adequate resolution of inflammation.

MCPIP1 expression positively correlates with melanoma-specific survival of patients, and its overexpression affects vital intracellular pathways of human melanoma cells.

The suppressive activity of monocyte chemoattractant protein 1-induced protein 1 (MCPIP1) an inflammation-related ribonuclease, has been described in a few cancer types but has yet to be assessed in the most common subtype of skin cancer: melanoma. Here, we have evaluated the MCPIP1 expression in melanoma tissues by reanalysis of publicly available transcriptome data from 89 melanoma samples, and immunohistochemical staining of 21 primary and 81 metastatic melanomas. Our data implicated decreased MCPIP1 expression in melanoma tumors compared to normal tissues, and positive correlation between high ribonuclease expression and melanoma-specific survival of patients. To investigate the ribonuclease activity in melanoma cells, MCPIP1 was ectopically expressed in the MV3 human melanoma cell line. Following the transcriptome, proteome, and intracellular signaling of MCPIP1-overexpressing MV3 cells was assessed via real-time quantitative polymerase chain reaction, Western blot analysis, and RNAseq. MV3 cells overexpressing MCPIP1 exhibited a broad range of alterations in the transcriptome and proteome, as well as in the phosphorylation status of a number of proteins, strongly indicating MCPIP1-dependent cell cycle arrest and inhibition of Akt/mTOR signaling in these cells. Moreover, we have shown, that MCPIP1 overexpression downregulates miRNA-193a-3p expression in MV3 cells. Furthermore, the majority of the described effects were dependent on the ribonucleolytic activity of the protein. The presented body of data strongly suggests a potential tumor suppressor role and possible future application as a positive prognostic marker of MCPIP1 protein in melanoma.