Myofibrillar proteolysis in chick muscle cell cultures during heat stress

The effect of heat stress on protein oxidation and myofibrillar proteolysis in chick myotubes was investigated. Myotubes were incubated at 37 or 41°C for 6 and 24 h. Protein carbonyl content, as an index of protein oxidation, increased more at 41°C than at 37°C for 6 and 24 h incubations. N^τ‐methylhistidine release as an index of myofibrillar proteolysis also increased more at 41°C than at 37°C for 6 and 24 h incubations. Proteasome activity also increased more under those same conditions. Calpain and cathepsin D but not B + L activities showed a greater increase at 41°C than at 37°C for 24 but not the 6 h incubation. These results indicate that heat stress increases protein oxidation and proteasome activity, resulting in an increase in myofibrillar proteolysis for short‐term incubation and, for long‐term incubation, it increases calpain, proteasome and cathepsin D activities, finally accelerating myofibrillar proteolysis in chick myotubes.     

泛素/26S蛋白酶体途径调节作物种子大小的研究进展

泛素/26S蛋白酶体系统（ubiquitin/26S proteasome system, UPS）是蛋白质泛素化的重要途径,作为蛋白质翻译后重要的修饰系统,在作物生长发育的各个阶段发挥重要作用。大量研究表明,UPS中泛素受体蛋白、E3泛素连接酶、去泛素化酶等能相互协调,通过在目标蛋白上连接或去除不同数量的泛素来介导目标蛋白的降解、改变亚细胞定位、蛋白活性等,从而调控种子的大小。对不同作物中泛素/26S蛋白酶体系统调节种子大小方面的研究进展进行了综述,并对其未来的发展进行了展望,为研究种子大小的调控机制及育种改良提供参考。     

Dietary intake of probiotics and maslinic acid in juvenile dentex (Dentex dentex L.): effects on growth performance, survival and liver proteolytic activities

Two feeding trials were carried out to evaluate the efficiency of probiotics and maslinic acid, on growth and survival of juvenile dentex; liver proteolytic activities were also investigated in the second trial. For experiment 1, triplicate groups were fed six diets with two probiotics (Bacillus toyoi, T, and B. cereus, E) at increasing levels (0.5, 1 and 2 g kg^?1 diet) and a control diet. Growth and feed conversion were not significantly influenced by the probiotics. The diet T1 produced the lower mortality, whereas diet E1 rendered the higher mortality. It was concluded that no significant effects on growth and survival were found following the addition of two kinds of probiotics to dentex diets. However, the diet E0.5 showed a tendency to ameliorate the growth and feed utilization of the diet. In a second trial, triplicate groups were fed four diets with increasing levels of maslinic acid (0, 20, 40 and 80 mg kg^?1 diet). Growth of fish given diets with the highest level of maslinic acid (D80) was slightly but not significantly lower than those from the other groups. Furthemore, mortality of fish fed diet D40 was the lowest. Changes in liver proteasome and endoprotease activities measured on sodium dodecyl sulphate (SDS)/gelatin gels were also detected in a dose‐dependent manner. It was concluded that a dietary maslinic acid at a level of 80 mg kg^?1 diet seems to be too high for juvenile dentex to maintain a maximal growth and survival rate.     

泛素蛋白酶体途径及其在体外受精中的作用研究进展

泛素蛋白酶体途径（ubiquitin proteasome pathway,UPP）是生物体内最主要的蛋白质降解途径,与多种疾病有关,在生物体内具有十分重要的作用,主要降解错误折叠的、多余的蛋白质。UPP是一个循环途径,其主要作用起始于泛素（ubiquitin,Ub）的激活,是受泛素激活酶（ubiquitin-activating enzyme,E1,酵母菌中是UbE1）、泛素结合酶（ubiquitin-conjugating enzyme,E2,UbE2）、泛素连接酶（ubiquitin-protein ligase,E3,UbE3）和去泛素化酶（deubiquitinating enzymes,DUBs）调控的级联过程,最终使被多聚泛素化（polyubiquitination,polyubiquitination,Poly-Ub）标记的蛋白底物在UPP的蛋白水解核心--26S蛋白酶体内被降解成寡肽,寡肽可以进入新的蛋白循环,Ub则由DUBs去除进入下一个UPP循环。UPP在海鞘类和一些哺乳类体外受精（in vitro fertilization,IVF）过程中具有十分重要的作用,能够参与精子获能和顶体反应（acrosomal reaction,AR）,促进精子顶体胞吐,在精卵结合时降解透明带（zona pellucida,ZP）蛋白,辅助精子穿透卵母细胞ZP,促进精子与卵母细胞ZP的融合,从而促使IVF的成功。通过在IVF液中添加一些UPP相关的抗体或抑制剂能够抑制IVF过程中的多精入卵,提高IVF率。作者综述了UPP的主要组成成分及其对IVF的辅助作用及相关抗体的研究进展,以期为今后研究UPP循环在生物体内的作用机制、与生物体内各种疾病的关系、在IVF过程中的作用机制及抑制多精入卵等提供一定的理论依据。     

Pathophysiological significance of ubiquition-proteasome system in myocardial infarction

Degradation of most proteins in eukaryotic cells is through the ubiquition-proteasome system (UPS). Recently, it demonstrated that UPS regulates cell apoptosis and cardiac hypertrophy. The differences of UPS regulation lie in E3 ligases, which specifically recognize targets and direct the ubiquitination process. Recent evidence suggests that atrogin-1/muscle atrophy F-box (Mafbx) and muscle RING finger 1 (MuRF1) may be critical mediators of the heart and muscle atrophy and hypertrophy. This review summarizes the possible relationship between UPS and cardiac dysfunction after myocardial infarction in order to inhibit cardiac dysfunction after myocardial infarction.     

Relationship between UPS-E3 ubiquitin ligase ITCH and insulin resistance

Insulin resistance is a typical manifestation of type 2 diabetes mellitus. ITCH belongs to HECT family E3 ubiquitin ligase, and mediates substrate ubiquitination and degradation to participate in the regulation of multiple signaling pathways. Recent studies found that the abnormal expression of ITCH is closely related to the occurrence and development of insulin resistance. This review focuses on the E3 ubiquitin ligase ITCH that is involved in insulin resistance based on its biological characteristics, including the effects on the molecules of insulin signaling pathway and the products of metabolism in the body.     

Secomycalolide A: A New Proteasome Inhibitor Isolated from a Marine Sponge of the Genus Mycale

A new oxazole-containing proteasome inhibitor, secomycalolide A, together with known mycalolide A and 30-hydroxymycalolide A, was isolated from a marine sponge of the genus Mycale. They showed proteasome inhibitory activities with IC₅₀ values of 11–45 μg/mL.     

拟南芥Rad23原核重组蛋白构建和活性检测

在拟南芥中,Rad23基因通过参与泛素/26S蛋白酶体途径调节植物生长发育和激素应答.为进一步研究该基因编码蛋白的分子作用机制及其生物学功能,构建了pCold-Rad23融合蛋白重组表达载体,将该载体转化到大肠杆菌BL21中诱导表达目的蛋白.SDS聚丙烯酰胺凝胶电泳检测结果表明,分子质量为94 ku左右的融合重组蛋白在大肠杆菌中获得高效表达.采用纯化的重组蛋白多次免疫昆明小白鼠的方法,获得了特异性强并且效价高的多克隆抗体,经蛋白印迹检测,在分子质量40 ku左右处出现特异的蛋白质条带,证明所制备的抗血清可以与拟南芥Rad23蛋白特异性结合.     

Total Synthesis of Fellutamide B and Deoxy-Fellutamides B,C, and D

The total syntheses of the marine-derived lipopeptide natural product fellutamide B and deoxy-fellutamides B, C, and D are reported. These compounds were accessed through a novel solid-phase synthetic strategy using Weinreb amide-derived resin. As part of the synthesis, a new enantioselective route to (3R)-hydroxy lauric acid was developed utilizing a Brown allylation reaction followed by an oxidative cleavage-oxidation sequence as the key steps. The activity of these natural products, and natural product analogues was also assessed against Mycobacterium tuberculosis in vitro.