Deficiency of BPOZ2 Decreases Liver Fibrosis After Chronic Carbon Tetrachloride Administration in Mice

2015 ◽  
Vol 34 (2) ◽  
pp. 204-210
Author(s):  
Feng Zhang ◽  
Suying Dang ◽  
Runzhe Shu ◽  
Yougui Xiang ◽  
Ying Kuang ◽  
...  
Keyword(s):  
Carbon Tetrachloride ◽  
Liver Fibrosis ◽  
Ubiquitin Ligase ◽  
Adaptor Protein ◽  
Matrix Metalloprotease ◽  
Carbon Tetrachloride Administration ◽  
Broad Complex ◽  
Sustained Activation

Bood POZ containing gene type 2 (BPOZ2), a Broad-Complex, Tramtrack, and Bric a brac domain containing protein, is an adaptor protein for the E3 ubiquitin ligase scaffold protein CUL3. It plays an important role in acute carbon tetrachloride (CCl4)-induced liver injury and regeneration in mice. In this study, we investigated the role of BPOZ2 in the process of liver fibrosis induced by chronic CCl4 treatment. The results indicate that BPOZ2 deficiency decreases sustained activation of hepatic stellate cells, attenuates collagen αI(I) and tissue inhibitor of matrix metalloprotease 1 expression, and decreases liver fibrosis after repeated CCl4 administration. These findings suggest BPOZ2 as a new therapeutic target for the prevention and treatment of hepatic fibrosis in chronic liver disease.

scholarly journals SPOP mutation induces replication over-firing by impairing Geminin ubiquitination and triggers replication catastrophe upon ATR inhibition

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jian Ma ◽  
Qing Shi ◽  
Gaofeng Cui ◽  
Haoyue Sheng ◽  
Maria Victoria Botuyan ◽  
...  
Keyword(s):  
Dna Replication ◽  
Ubiquitin Ligase ◽  
Genome Instability ◽  
Human Cancer ◽  
Adaptor Protein ◽  
Dna Unwinding ◽  
Binding Partner ◽  
Lysine Residues ◽  
Cancer Types

AbstractGeminin and its binding partner Cdt1 are essential for the regulation of DNA replication. Here we show that the CULLIN3 E3 ubiquitin ligase adaptor protein SPOP binds Geminin at endogenous level and regulates DNA replication. SPOP promotes K27-linked non-degradative poly-ubiquitination of Geminin at lysine residues 100 and 127. This poly-ubiquitination of Geminin prevents DNA replication over-firing by indirectly blocking the association of Cdt1 with the MCM protein complex, an interaction required for DNA unwinding and replication. SPOP is frequently mutated in certain human cancer types and implicated in tumorigenesis. We show that cancer-associated SPOP mutations impair Geminin K27-linked poly-ubiquitination and induce replication origin over-firing and re-replication. The replication stress caused by SPOP mutations triggers replication catastrophe and cell death upon ATR inhibition. Our results reveal a tumor suppressor role of SPOP in preventing DNA replication over-firing and genome instability and suggest that SPOP-mutated tumors may be susceptible to ATR inhibitor therapy.

scholarly journals The E3 Ubiquitin Ligase TBK1 Mediates the Degradation of Multiple Picornavirus VP3 Proteins by Phosphorylation and Ubiquitination

2019 ◽  
Vol 93 (23) ◽  
Author(s):  
Dan Li ◽  
Wenping Yang ◽  
Jingjing Ren ◽  
Yi Ru ◽  
Keshan Zhang ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Molecular Mechanisms ◽  
E3 Ubiquitin Ligase ◽  
Adaptor Protein ◽  
Ubiquitin Ligase Activity ◽  
Lysine Residues ◽  
Innate Antiviral Immunity

ABSTRACT TANK-binding kinase 1 (TBK1) is essential for interferon beta (IFN-β) production and innate antiviral immunity. However, other, additional functions of TBK1 have remained elusive. Here, we showed that TBK1 is an E3 ubiquitin ligase that undergoes self-ubiquitylation in vitro in the presence of the E2 enzyme UbcH5c. Further evidence showed that TBK1 could also be self-ubiquitylated in vivo. Importantly, multiple picornavirus VP3 proteins were degraded by TBK1 through its kinase and E3 ubiquitin ligase activity. Mechanistically, TBK1 phosphorylated multiple picornavirus VP3 proteins at serine residues and ubiquitinated them via K63-linked ubiquitination at lysine residues. In addition, the C426 and C605 residues of TBK1 were not essential for TBK1 innate immunity activity; however, these residues were required for degradation of multiple picornavirus VP3 proteins and for its E3 ubiquitin ligase activity. Hence, our findings identified a novel role of TBK1 in regulating the virus life cycle and provided new insights into the molecular mechanisms of TBK1-mediated antiviral response. IMPORTANCE TBK1 is an important adaptor protein required for innate immune response to viruses, but its other functions were unknown. In this study, we found that TBK1 is an E3 ubiquitin ligase that undergoes self-ubiquitylation in vitro in the presence of the E2 enzyme UbcH5c. In addition, multiple picornavirus VP3 proteins were degraded by TBK1 through its kinase and E3 ubiquitin ligase activity. Our report provides evidence that TBK1 plays a role in viral protein degradation.

scholarly journals Serum Cytokine Dependent Hematopoietic Cell Linker (CLNK) as a Predictor for the Duration of Illness in Type 2 Diabetes Mellitus

2020 ◽  
Author(s):  
Suhaer Zeki Al-Fadhel ◽  
Nibras H. Abdulsada Al-Ghuraibawi ◽  
Dunia M. Mohammed Ali ◽  
Hussein Kadhem Al-Hakeim
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Cell Function ◽  
Adaptor Protein ◽  
Correlation Study ◽  
Hematopoietic Cell ◽  
Receptor Signaling

Type 2 diabetes mellitus (T2DM) is an endocrine illness associate with various changes in the immune system and adaptor protein levels. Cytokine dependent hematopoietic cell linker (CLNK) is an adapter protein that regulates immune receptor signaling and acts as a regulator of the receptor signaling of T-cells and natural killer T-cell. The role of CLNK in T2DM is not studied previously. In the present study, serum CLNK level was measured and correlated with some sociodemographic and insulin resistance (IR) parameters. This is achieved by performing measurement of CLNK and insulin parameters (glucose, insulin, and HbA1c in addition to the calculation of the functions of IR (HOMA2IR), insulin sensitivity (HOMA%S), and beta-cell function (HOMA%B)) in 60 T2DM patients and 30 controls. The results indicated a significant increase (p=0.025) in serum CLNK in patients group in comparison with the controls. Multivariate generalized linear model (GLM) analysis revealed no significant effect of age, BMI, and sex on the CLNK level. The results of tests for between-subjects showed that the CLNK affects diagnosis significantly (F=7.445, p=0.008, partial η2 =0.081) and its effect is approximately the same as the effect of insulin (F=8.107, p=0.006, partial η2 =0.087). The correlation study showed a highly significant positive correlation between CLNK and the duration of disease (rho=0.420, p<0.001). It can be concluded that the increase CLNK in T2DM revealing the role of the adaptor proteins level in the nature of disease. Elevation of CLNK level may be used as a predictor for diabetes complications, which needs more investigations.

Loss of Gab1 adaptor protein in hepatocytes aggravates experimental liver fibrosis in mice

2015 ◽  
Vol 308 (7) ◽  
pp. G613-G624 ◽  
Author(s):  
Takashi Kizu ◽  
Yuichi Yoshida ◽  
Kunimaro Furuta ◽  
Satoshi Ogura ◽  
Mayumi Egawa ◽  
...  
Keyword(s):  
Liver Fibrosis ◽  
Tyrosine Kinases ◽  
Molecular Mechanisms ◽  
Adaptor Protein ◽  
Conditional Knockout ◽  
Hepatocyte Proliferation ◽  
Duct Ligation ◽  
Liver Fibrogenesis

Grb2-associated binder 1 (Gab1) adaptor protein amplifies signals downstream of a broad range of growth factors/receptor tyrosine kinases. Although these signals are implicated in liver fibrogenesis, the role of Gab1 remains unclear. To elucidate the role of Gab1, liver fibrosis was examined in hepatocyte-specific Gab1-conditional knockout (Gab1CKO) mice upon bile duct ligation (BDL). Gab1CKO mice developed exacerbated liver fibrosis with activation of hepatic myofibroblasts after BDL compared with control mice. The antifibrotic role of hepatocyte Gab1 was further confirmed by another well-established mouse model of liver fibrosis using chronic injections of carbon tetrachloride. After BDL, Gab1CKO mice also displayed exacerbated liver injury, decreased hepatocyte proliferation, and enhanced liver inflammation. Furthermore, cDNA microarray analysis was used to investigate the potential molecular mechanisms of the Gab1-mediated signal in liver fibrosis, and the fibrosis-promoting factor chemokine (C-C motif) ligand 5 ( Ccl5) was identified as upregulated in the livers of Gab1CKO mice following BDL. Interestingly, in vitro studies using primary hepatocytes isolated from control and Gab1CKO mice revealed that the loss of Gab1 resulted in increased hepatocyte CCL5 synthesis upon lipopolysaccharide stimulation. Finally, pharmacological antagonism of CCL5 reduced BDL-induced liver fibrosis in Gab1CKO mice. In conclusion, our results demonstrate that hepatocyte Gab1 is required for liver fibrosis and that hepatocyte CCL5 could be an important contributor to this process. Thus, we present a novel antifibrotic function of hepatocyte Gab1 in liver fibrogenesis.

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