Alteration of alpha-spectrin ubiquitination after hemorrhagic shock

Background

RBC deformability after trauma and hemorrhagic shock (T/HS) leads to the microcirculatory dysfunction and clinical manifestations of organ failure. However, the cellular mechanism of this phenomenon remains unknown. Spectrins are important for the shape and physical properties of erythrocytes, such as deformability and resistance to mechanical stress. Previous studies have shown that erythrocyte α-spectrin is ubiquitinated. Studies of sickled cells and aged erythrocytes, 2 conditions known to have decreased RBC deformability, have shown decreased α-spectrin ubiquitination, which may contribute to the inability of these cells to change shape. It was hypothesized that decreased α-spectrin ubiquitination could participate in the mechanism(s) whereby T/HS erythrocytes become less deformable.

Methods

The level of α-spectrin ubiquitination in erythrocytes isolated from T/HS rats was determined and compared with erythrocytes from control sham-shocked (T/SS) animals. After T/SS (n = 4) or T/HS (n = 7), α- and β-spectrin subunits were isolated using a low ionic-strength buffer at 37°C for 30 minutes. The relative amount of ubiquitinated α-spectrin was evaluated by Western blotting using a monoclonal antibody to ubiquitin.

Results

The relative level of α-spectrin ubiquitination (normalized to total α-spectrin in the same preparation) was found to be significantly decreased after T/HS (.319 ± .03) compared with T/SS control erythrocytes (.485 ± .06, P < .05). To evaluate the content and relative amounts of the other membrane proteins, the profiles of T/HS and T/SS erythrocytes were compared by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. This did not reveal any significant quantitative differences between T/SS and T/HS spectrin or other membrane proteins.

Conclusions

The finding of decreased α-spectrin ubiquitination after T/HS suggests that this mechanism could contribute to increased rigidity of the erythrocyte membrane.     

黑色素瘤抗原泛素连接酶的研究进展

黑色素瘤抗原（melanoma-associated antigen gene, MAGE）被视为一种肿瘤标志物和免疫治疗的热门对象。研究发现MAGE联合E3-RING泛素连接酶形成MAGE-RING连接酶复合体（MAGE-RING ligases, MRLs）,成为泛素化的调控因子,从而调控连接酶的活性、底物的特异性和亚细胞定位。该文就MRLs的结构、活化机制和转录功能作一综述。     

蛋白酶体活性抑制对大鼠海马tau蛋白的泛素化影响

目的:探讨蛋白酶体活性抑制对大鼠海马tau蛋白的泛素化影响.方法:利用双侧海马注射蛋白酶体的特异性抑制剂--乳胞素分别进行蛋白酶体活性检测、免疫印迹、免疫共沉淀,以检测大鼠海马内tau蛋白的泛素化改变情况.结果:(1)乳胞素引起蛋白酶体活性在24和48 h较对照组明显下降;(2)免疫共沉淀结果显示,蛋白酶体活性抑制使t...     

卵巢相关F-box蛋白的功能及研究进展

F-box蛋白广泛存在于真核生物和原核生物中,可以通过泛素-蛋白酶体途径参与调控细胞周期、细胞凋亡、细胞信号转导和肿瘤发生等多种生物学过程。近年来研究提示卵巢中存在多种F-box蛋白的表达,F-box蛋白功能紊乱可导致卵巢生殖和内分泌功能发生障碍及卵巢疾病,出现卵泡发育不良、卵巢早衰（POF）及卵巢癌等病理反应。随着对细胞内泛素化作用研究的不断深入,越来越多F-box蛋白通过调控细胞周期和信号传导通路等途径影响卵巢功能的作用机制逐渐被揭示,这也为相关卵巢疾病的临床诊治提供了理论基础和新思路。现就与卵巢相关的F-box蛋白的功能及研究进展进行综述。     

c‐IAP ubiquitin protein ligase activity is required for 4‐1BB signaling and CD8+ memory T‐cell survival

Cellular inhibitor of apoptosis proteins (c‐IAP) 1 and 2 are widely expressed ubiquitin protein ligases that regulate a variety of cellular functions, including the sensitivity of T cells to costimulation. 4‐1BB is a TNF receptor family member that signals via a complex that includes TRAF family members and the c‐IAPs to upregulate NF‐κB and ERK, and has been implicated in memory T‐cell survival. Here, we show that effector and memory T cells from mice expressing a dominant negative E3‐inactive c‐IAP2 (c‐IAP2^H570A) have impaired signaling downstream of 4‐1BB. When infected with lymphocytic choriomeningitis virus, unlike mice in which c‐IAPs were acutely downregulated by c‐IAP antagonists, the primary response of c‐IAP2^H570A mice was normal. However, the number of antigen‐specific CD8⁺ but not CD4⁺ T cells declined more rapidly and to a greater extent in c‐IAP2^H570A mice than in WT controls. Studies with T‐cell adoptive transfer demonstrated that the enhanced decay of memory cells was T‐cell intrinsic. Thus, c‐IAP E3 activity is required for 4‐1BB coreceptor signaling and maintenance of CD8⁺ T‐cell memory.     

Tripartite Motif-Containing 46 Promotes Viability and Inhibits Apoptosis of Osteosarcoma Cells by Activating NF-kB Signaling Through Ubiquitination of PPARα

Osteosarcoma (OS), the most common bone cancer, causes high morbidity in children and young adults. TRIM46 is a member of the family of tripartite motif (TRIM)-containing proteins that serve as important regulators of tumorigenesis. Here we investigate the possible role of TRIM46 in OS and the underlying molecular mechanism. We report an increase in the expression of TRIM46 in OS and its association with tumor size, Enneking’s stage, and patient prognosis. TRIM46 knockdown inhibits OS cell viability and cell cycle progression and induces apoptosis, while TRIM46 overexpression exerts inverse effects, which are inhibited by peroxisome proliferator-activated receptor alpha (PPAR ) overexpression and the nuclear factor kappa B (NF- B) inhibitor, pyrrolidine dithiocarbamate (PDTC). Furthermore, TRIM46 negatively regulates PPAR expression via ubiquitination-mediated protein degradation and modification. PPAR overexpression also inactivates NF- B signaling and NF- B promoter activity in OS cells overexpressing TRIM46. Moreover, TRIM46 knockdown inhibits tumor growth and induces apoptosis of OS cells in vivo. TRIM46 acts as an oncogene in OS by interacting with and ubiquitinating PPAR , resulting in the activation of NF- B signaling pathway. Thus, TRIM46 may be a potential biomarker of carcinogenesis. Key words: Osteosarcoma (OS); TRIM46; Ubiquitination; NF     

The deubiquitinating enzyme 13 retards non-alcoholic steatohepatitis via blocking inactive rhomboid protein 2-dependent pathway

Nowadays potential preclinical drugs for the treatment of nonalcoholic steatohepatitis(NASH) have failed to achieve expected therapeutic efficacy because the pathogenic mechanisms are underestimated.Inactive rhomboid protein 2(IRHOM2),a promising target for treatment of inflammationrelated diseases,contributes to deregulated hepatocyte metabolism-associated nonalcoholic steatohepatitis(NASH) progression.However,the molecular mechanism underlying Irhom2 regulation is still not completely understo...