Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

Background Cystic echinococcosis is a parasitic zoonotic disease, which poses a threat to public health and animal husbandry, and causes significant economic losses. Annexins are a family of phospholipid-binding proteins with calcium ion-binding activity, which have many functions. Methods Two annexin protein family genes [Echinococcus granulosus annexin B3 (EgAnxB3) and EgAnxB38] were cloned and molecularly characterized using bioinformatic analysis. The immunoreactivity of recombinant EgAnxB3 (rEgAnxB3) and rEgAnxB38 was investigated using western blotting. The distribution of EgAnxB3 and EgAnxB38 in protoscoleces (PSCs), the germinal layer, 18-day strobilated worms and 45-day adult worms was analyzed by immunofluorescence localization, and their secretory characteristics were analyzed preliminarily; in addition, quantitative real-time reverse transcription polymerase chain reaction was used to analyze their transcript levels in PSCs and 28-day strobilated worms stages. The phospholipid-binding activities of rEgAnxB3 and rEgAnxB38 were also analyzed. Results EgAnxB3 and EgAnxB38 are conserved and contain calcium-binding sites. Both rEgAnxB3 and rEgAnxB38 could be specifically recognized by the serum samples from E. granulosus-infected sheep, indicating that they had strong immunoreactivity. EgAnxB3 and EgAnxB38 were distributed in all stages of E. granulosus, and their transcript levels were high in the 28-day strobilated worms. They were found in liver tissues near the cysts. In addition, rEgAnxB3 has Ca2+-dependent phospholipid-binding properties. Conclusions EgAnxB3 and EgAnxB38 contain calcium-binding sites, and rEgAnxB3 has Ca2+-dependent phospholipid-binding properties. EgAnxB3 and EgAnxB38 were transcribed in PSCs and 28-day strobilated worms. They were expressed in all stages of E. granulosus, and distributed in the liver tissues near the hydatid cyst, indicating that they are secreted proteins that play a crucial role in the development of E. granulosus.

Background Scabies is caused by burrowing of the mite Sarcoptes scabiei into the stratum corneum. Currently, diagnosis via routine skin scraping is very difficult, and information on the allergenic identification of S. scabiei remains limited. Methods We performed comparative analysis of the serological diagnostic potential of recombinant S. scabiei chitinase-like protein-5 (rSsCLP5) and recombinant S. scabiei chitinase-like protein-12 (rSsCLP12) by measuring the levels of serum-specific IgG and IgE antibodies (Abs) as diagnostic markers. In addition, the allergenic characteristics of rSsCLP5 and rSsCLP12 were evaluated using IgE-binding experiments and skin tests. Results The IgE Abs-based indirect enzyme-linked immunosorbent assay (ELISA) methods showed high sensitivity and specificity: the rSsCLP5-based assay had 93.5% sensitivity and 94.4% specificity; the rSsCLP12-based assay had 100% sensitivity and 98.1% specificity. The specific IgE Abs in infested mouse sera could bind rSsCLP5 and rSsCLP12. In skin tests, rabbits in the rSsCLP5 and rSsCLP12 groups and positive control (histamine) groups exhibited allergic reactions. Most test sites in the rSsCLP12 group had edema, bleeding spots, and even ulcers or scabs, but such allergy symptoms were rare in the rSsCLP5 group. Moreover, the allergic history rabbit group had more severe allergic reactions and lower levels of IgE Abs compared to the healthy rabbit group in the same protein group. Conclusions These findings validate the use of IgE Abs to rSsCLP5 and rSsCLP12 as potentially useful markers for diagnosing scabies. Moreover, both rSsCLP5 and rSsCLP12 have allergenic properties, and the potential allergen rSsCLP12 is a stronger allergen than rSsCLP5.

Cystic echinococcosis (CE) is a neglected tropical zoonosis caused by Echinococcus granulosus sensu lato (s.l.) and remains a major public health concern globally. Here, CE isolates (n = 3310) with clearly defined genotypes and geographical origins in China were retrieved through our epidemiological survey (2016-2020) and systematic review . Existing known genotypes of Echinococcus granulosus sensu lato (E. granulosus s.l.) except for G4 have been found in China, particularly on the Tibetan Plateau, where their genetic diversity is unique to that part of the world. According to the systematic review, genetic compositions of E. granulosus s.l. in China were as follows: E. granulosus (G1, G3), 98.3%; Echinococcus ortleppi (G5), 0.1%; Echinococcus intermedius (G6, G7), 1.4%; and Echinococcus canadensis (G8, G10), 0.2%. Specifically, G1 was responsible for 97.7% of infections and characterized by the broadest host ranges and geographic distributions. Our epidemiological results showed a relatively stable genetic composition of E. granulosus s.l. in sheep and yaks from three CE hyperendemic provinces (Xinjiang, Sichuan, Qinghai). A higher proportion of fertile cysts were found in sheep (287/406, 70.7%) than in yaks (28/184, 15.2%). During the past 29 years, 51 cox1 haplotypes of E. granulosus s.l. were endemic in China. The ancestral haplotype (Hap_2) remained the most common haplotype, 12 relatively common haplotypes were endemic and nine newly reported haplotypes were found during the survey. Overall, our results demonstrate that the compulsory immunization of sheep and the pilot EG95 vaccination campaign in yaks are well matched with the current genotypic situation. In addition to yaks, we advocate for more surveillance of CE isolates from pigs, cattle, goats and camels, since their roles in the transmission and reservation of E. granulosus s.l. have been largely ignored in China.

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