RNA-destabilizing Factor Tristetraprolin Negatively Regulates NF-kappa B Signaling

Tristetraprolin (TTP) is a CCCH zinc finger-containing protein that destabilizes mRNA by binding to an AU-rich element. Mice deficient in TTP develop a severe inflammatory syndrome mainly because of overproduction of tumor necrosis factor alpha. We report here that TTP also negatively regulates NF-kappa B signaling at the transcriptional corepressor level, by which it may repress inflammatory gene transcription. TTP expression inhibited NF-kappa B-dependent transcription. However, overexpression of TTP did not affect reporter mRNA stability. Instead, TTP functioned as a corepressor of p65/NF-kappa B. In support of this concept, we found that TTP physically interacted with the p65 subunit of NF-kappa B and was also associated with HDAC1, -3, and -7 in vivo. Treatment with histone deacetylase inhibitors or small interfering RNA induced HDAC1 or HDAC3 knockdown completely or partly abolished the inhibitory activity of TTP on NF-kappa B reporter activation. Consistently, chromatin immuno-precipitation showed decreased recruitment of HDAC1 and increased recruitment of CREB-binding protein on the Mcp-1 promoter in TTP(-/-) cells compared with wild-type cells. Moreover, overexpression of TTP blocked CREB-binding protein-induced acetylation of p65/NF-kappa B. Taken together, these data suggest that TTP may also function in vivo as a modulator in suppressing the transcriptional activity of NF-kappa B

Regulation of CCL5 Expression in Smooth Muscle Cells Following Arterial Injury

Chemokines play a crucial role in inflammation and in the pathophysiology of atherosclerosis by recruiting inflammatory immune cells to the endothelium. Chemokine CCL5 has been shown to be involved in atherosclerosis progression. However, little is known about how CCL5 is regulated in vascular smooth muscle cells. In this study we report that CCL5 mRNA expression was induced and peaked in aorta at day 7 and then declined after balloon artery injury, whereas IP-10 and MCP-1 mRNA expression were induced and peaked at day 3 and then rapidly declined

MCP-induced protein 1 deubiquitinates TRAF proteins and negatively regulates JNK and NF-kappa B signaling

The intensity and duration of macrophage-mediated inflammatory responses are controlled by proteins that modulate inflammatory signaling pathways. MCPIP1 (monocyte chemotactic protein-induced protein 1), a recently identified CCCH Zn finger-containing protein, plays an essential role in controlling macrophage-mediated inflammatory responses. However, its mechanism of action is poorly understood. In this study, we show that MCPIP1 negatively regulates c-Jun N-terminal kinase (JNK) and NF-kappa B activity by removing ubiquitin moieties from proteins, including TRAF2, TRAF3, and TRAF6. MCPIP1-deficient mice spontaneously developed fatal inflammatory syndrome. Macrophages and splenocytes from MCPIP1(-/-) mice showed elevated expression of inflammatory gene expression, increased JNK and I. B kinase activation, and increased polyubiquitination of TNF receptor-associated factors. In vitro assays directly demonstrated the deubiquitinating activity of purified MCPIP1. Sequence analysis together with serial mutagenesis defined a deubiquitinating enzyme domain and a ubiquitin association domain in MCPIP1. Our results indicate that MCPIP1 is a critical modulator of inflammatory signaling

A novel CCCH-zinc finger protein family regulates proinflammatory activation of macrophages

Activated macrophages play an important role in many inflammatory diseases. However, the molecular mechanisms controlling macrophage activation are not completely understood. Here we report that a novel CCCH-zinc finger protein family, MCPIP1, 2, 3, and 4, encoded by four genes, Zc3h12a, Zc3h12b, Zc3h12c, and Zc3h12d, respectively, regulates macrophage activation. Northern blot analysis revealed that the expression of MCPIP1 and MCPIP3 was highly induced in macrophages in response to treatment with lipopolysaccharide (LPS). Although not affecting cell surface marker expression and phagocytotic function, overexpression of MCPIP1 significantly blunted LPS-induced inflammatory cytokine and NO(2)radical anion. production as well as their gene expression. Conversely, short interfering RNA-mediated reduction in MCPIP1 augmented LPS-induced inflammatory gene expression. Further studies demonstrated that MCPIP1 did not directly affect the mRNA stability of tumor necrosis factor alpha and monocyte chemoattractant protein 1 (MCP-1) but strongly inhibited LPS-induced tumor necrosis factor alpha and inducible nitric-oxide synthase promoter activation. Moreover, we found that forced expression of MCPIP1 significantly inhibited LPS-induced nuclear factor-kappa B activation. These results identify MCP-induced proteins, a novel CCCH-zinc finger protein family, as negative regulators in macrophage activation and may implicate them in host immunity and inflammatory diseases

Targeted disruption of MCPIP1/Zc3h12a results in fatal inflammatory disease

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141347/1/imcb201311.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141347/2/imcb201311-sup-0001.pd

Deletion of Mcpip1 in Mcpip1fl/flAlbCreMcpip1^{fl/fl}Alb^{Cre} mice recapitulates the phenotype of human primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune disease characterized by progressive destruction of the intrahepatic bile ducts. The immunopathology of PBC involves excessive inflammation; therefore, negative regulators of inflammatory response, such as Monocyte Chemoattractant Protein-1-Induced Protein-1 (MCPIP1) may play important roles in the development of PBC. The aim of this work was to verify whether Mcpip1 expression protects against development of PBC. Genetic deletion of Zc3h12a was used to characterize the role of Mcpip1 in the pathogenesis of PBC in 6–52-week-old mice. We found that Mcpip1 deficiency in the liver (Mcpip1fl/flAlbCre) recapitulates most of the features of human PBC, in contrast to mice with Mcpip1 deficiency in myeloid cells (Mcpip1fl/flLysMCre mice), which present with robust myeloid cell-driven systemic inflammation. In Mcpip1fl/flAlbCre livers, intrahepatic bile ducts displayed proliferative changes with inflammatory infiltration, bile duct destruction, and fibrosis leading to cholestasis. In plasma, increased concentrations of IgG, IgM, and AMA autoantibodies (anti-PDC-E2) were detected. Interestingly, the phenotype of Mcpip1fl/flAlbCre mice was robust in 6-week-old, but milder in 12–24-week-old mice. Hepatic transcriptome analysis of 6-week-old and 24-week-old Mcpip1fl/flAlbCre mice showed 812 and 8 differentially expressed genes, respectively, compared with age-matched control mice, and revealed a distinct set of genes compared to those previously associated with development of PBC. In conclusion, Mcpip1fl/flAlbCre mice display early postnatal phenotype that recapitulates most of the features of human PBC

MCP-induced protein 1 deubiquitinates TRAF proteins and negatively regulates JNK and NF-κB signaling

A previously unappreciated deubiquitinase activity of MCP-induced protein 1 contributes to its role in dampening inflammatory signaling

Role of ENPP1 on Adipocyte Maturation

BACKGROUND: It is recognized that the ability of adipose tissue to expand in response to energy excess, i.e. adipocyte maturation, is important in determining systemic abnormalities in glucose and lipid metabolism. Ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1, also known as PC-1) has been recently reported to be involved in the pathogenesis of insulin resistance and related diseases. However, its role on adipose tissue physiology as a mechanism of systemic insulin resistance is not understood. This study was performed to evaluate whether ENPP1 is regulated during adipogenesis and whether over-expression in adipocytes can affect adipocyte maturation, a potential novel mechanism of ENPP1-related insulin resistance. METHODOLOGY/PRINCIPAL FINDINGS: ENPP1 expression was found down-regulated during 3T3-L1 maturation, and over-expression of human ENPP1 in 3T3-L1 (pQCXIP-ENPP1 vector) resulted in adipocyte insulin resistance and in defective adipocyte maturation. Adipocyte maturation was more efficient in mesenchymal embryonal cells from ENPP1 knockout mice than from wild-type. CONCLUSIONS: We identify ENPP1 as a novel mechanism of defective adipocyte maturation. This mechanism could contribute to the pathogenesis of insulin resistance in absence of obesity