Structure of Neuroglobin from Cold-Water Sponge Halisarca dujardinii

Molecular Biology - The iron-containing protein neuroglobin (Ngb) involved in the transport of oxygen is generally considered the precursor of all animal globins. In this report, we studied the...     

Role of proteasomes in non-specific immune response of marine annelids

We investigated functioning of proteasomes and chaperones in Arenicola marina coelomocytes in conditions of lipopolysaccharide-induced inflammation. We observed the increase of chymotrypsin-like proteasome activity in coelomocytes 1 h after induction. Amount of proteasome subunits alpha- and beta-5 types increased as well. We also detected appearance of a new form of Hsp70 chaperone in infected coelomocytes. Our results allow us to consider the changes in proteasome structure and induction of chaperones as principle mechanisms in stress adaptation and defensive reactions development in annelids.     

Proteasome Expression in Ovarian Heterotopic Allografts of Wistar and August Rats under Induction of Donor-Specific Tolerance

Russian Journal of Developmental Biology - The aim of this work is to investigate the dynamics for the ovarian tissue engraftment of inbred August rats transplanted to outbred Wistar rats and vice...     

Native structure of rat liver immune proteasomes

Native structure of active forms of rat liver immune proteasomes has been studied by two-dimensional electrophoresis method modified for analysis of unpurified protein fractions. The developed method allowed revealing the proteasome immune subunits LMP7 and LMP2 in 20S subparticles and in the structures bound to one or two PA28αβ activators, but not to the PA700 activator, which is involved in the hydrolysis of ubiquitinated proteins. The results obtained indicate the participation of the immune proteasomes in delicate regulatory mechanisms based on the production of biologically active peptides and exclude their participation in processes of crude degradation of “rotated” ubiquitinated proteins.     

Proteasome Functioning in Breast Cancer: Connection with Clinical-Pathological Factors

Breast cancer is one of four oncology diseases that are most widespread in the world. Moreover, breast cancer is one of leading causes of cancer-related deaths in female population within economically developed regions of the world. So far, detection of new mechanisms of breast cancer development is very important for discovery of novel areas in which therapy approaches may be elaborated. The objective of the present study is to investigate involvement of proteasomes, which cleave up to 90% of cellular proteins and regulate numerous cellular processes, in mechanisms of breast cancer development. Proteasome characteristics in 106 patient breast carcinomas and adjacent tissues, as well as relationships of detected proteasome parameters with clinical-pathological factors, were investigated. Proteasome chymotrypsin-like activity was evaluated by hydrolysis of fluorogenic peptide Suc-LLVY-AMC. The expression of proteasome subunits was studied by Western-blotting and immunohistochemistry. The wide range of chymotrypsin-like activity in tumors was detected. Activity in tumors was higher if compared to adjacent tissues in 76 from 106 patients. Multiple analysis of generalized linear models discovered that in estrogen α-receptor absence, tumor growth was connected with the enhanced expression of proteasome immune subunit LMP2 and proteasome activator PA700 in tumor (at 95% confidence interval). Besides, by this analysis we detected some phenomena in adjacent tissue, which are important for tumor growth and progression of lymph node metastasis in estrogen α-receptor absence. These phenomena are related to the enhanced expression of activator PA700 and immune subunit LMP7. Thus, breast cancer development is connected with functioning of immune proteasome forms and activator PA700 in patients without estrogen α-receptors in tumor cells. These results could indicate a field for search of new therapy approaches for this category of patients, which has the worst prognosis of health recovery.     

Proteasomes on thyroid tissue allotransplantation under induction of donor-specific tolerance in rats

Proteasomes in the liver of August rats (RT1^c) were investigated 30 days after allotransplantation of Wistar rat (RT1^u) thyroid tissue under renal capsule with/without induction of donor-specific tolerance by donor splenocyte intraportal administration. The levels of total proteasome pool, immune proteasomes containing subunits LMP2 and/or LMP7, and proteasome regulators 19S and 11S were defined. Intact and sham-operated August rats were used as control groups. The level of all immune proteasome forms and 11S regulator increased while the level of the total proteasome pool and 19S regulator decreased in the liver of experimental animals compared to the control groups, which indicated changes of liver functional state after transplantation. The 19S/11S ratio increased in the liver of nontolerant rats compared to tolerant animals. In the liver of tolerant rats with accepted grafts, the number of mononuclear cells expressing the immune subunit LMP2 greatly increased in comparison with control and nontolerant animals. Study of accepted grafts showed an increase in the ratio of LMP2/LMP7 immune subunits and 19S/11S regulators in them, compared to the tissue replacing the rejected grafts. Immune proteasomes were almost completely absent from the control intact thyroid tissue, while 19S/11S ratio was maximal in it. Thus, the development of the immune reaction or its suppression are accompanied by a change in the balance between different proteasome forms. Immune subunit LMP7 and 11S regulator are associated with the response against donor tissue. On the contrary, immune subunit LMP2 and 19S regulator are likely to be important for the development of immune tolerance and surviving tissue functioning. Immunofluorescence assay revealed a low content of the immune proteasomes in the follicle cells. Probably, formation of antigens for the major histocompatibility complex class I molecules was impaired by the low content of immune proteasomes, which led to immunological tolerance of hormone-producing follicle cells.     

Taphonomic experiments imply a possible link between the evolution of multicellularity and the fossilization potential of soft‐bodied organisms

The reliability of evolutionary reconstructions based on the fossil record critically depends on our knowledge of the factors affecting the fossilization of soft‐bodied organisms. Despite considerable research effort, these factors are still poorly understood. In order to elucidate the main prerequisites for the preservation of soft‐bodied organisms, we conducted long‐term (1–5 years) taphonomic experiments with the model crustacean Artemia salina buried in five different sediments. The subsequent analysis of the carcasses and sediments revealed that, in our experimental settings, better preservation was associated with the fast deposition of aluminum and silicon on organic tissues. Other elements such as calcium, magnesium, and iron, which can also accumulate quickly on the carcasses, appear to be much less efficient in preventing decay. Next, we asked if the carcasses of uni‐ and multicellular organisms differ in their ability to accumulate aluminum ions on their surface. The experiments with the flagellate Euglena gracilis and the sponge Spongilla lacustris showed that aluminum ions are more readily deposited onto a multicellular body. This was further confirmed by the experiments with uni‐ and multicellular stages of the social ameba Dictyostelium discoideum. The results lead us to speculate that the evolution of cell adhesion molecules, which provide efficient cell–cell and cell–substrate binding, probably can explain the rich fossil record of soft‐bodied animals, the comparatively poor fossil record of nonskeletal unicellular eukaryotes, and the explosive emergence of the Cambrian diversity of soft‐bodied fossils.     

Changes in the proteasome function after induction of donor-specific tolerance in rats with ovarian allograft

Induction of donor-specific tolerance in a recipient is one of the methods for enhancing acceptance of the grafts of endocrine glands in the absence of immunodepressants, which interfere with hormone production. This paper describes changes in the proteasome pool in the rat liver, spleen, and graft during the development of donor-specific tolerance after intraportally infusing the recipient with donor splenocytes with subsequent allografting of ovarian tissue into the renal capsule. It has been demonstrated that the shift in the balance in the liver and graft proteasome pools towards the variants with the LMP2 subunit determines the development of immunological tolerance and graft retention. On the contrary, an increase in the forms with the LMP7 subunit induces the immune response and graft rejection.     

Immune proteasomes in the development of the rat immune system

The dynamics of the expression of LMP7 and LMP2 proteasome subunits during embryonic and early postnatal development of rat spleen and liver was studied in comparison with the dynamics of chymotrypsin-like and caspase-like proteasome activities and expression of MHC (major histocompatibility complex) class I molecules. The distribution of LMP7 and LMP2 immune subunits in spleen and liver cells was also evaluated throughout development. The common tendency of both organs to increase the expression of both LMP7 and LMP2 subunits on the 21st postnatal day (P21) was found. However, the total proteasome level was shown to be constant. At certain developmental stages, the dynamics of immune subunits expression in the spleen and liver was different. While the gradual enhancement of both immune subunits was observed on P1, P18 and P21 in the spleen, the periods of gradual increase observed on E16 (the 16th embryonic day) and E18 gave way to a period of decrease in immune subunits on P5 in the liver. This level did not reliably change until P18 and increased on P21. The revealed changes were accompanied by an increase in chymotrypsin-like activity and a decrease in caspase-like activity in the spleen at P21 compared to the embryonic period. This indicates the increase in proteasome ability to form antigenic epitopes for MHC class I molecules. In the liver, both activities increased compared to the embryonic period by P21. The dynamics of caspase-like activity can be explained not only by the change of proteolytic constitutive and immune subunits, but also by additional regulatory mechanisms. Moreover, it was discovered that the increase in the expression of immune subunits during early spleen development is associated with the process of formation of white pulp by B- and T-lymphocytes enriched with immune subunits. In the liver, the increase in the level of immune subunits by P21 was also accompanied by an increase of their expression in hepatocytes. While the decrease of their level by P5 may be associated with the fact that the liver has lost its function as the primary lymphoid organ in the immune system by this time, as well as with the disappearance of B-lymphocytes enriched with immune proteasomes. In the spleen and the liver, MHC class I molecules were found during the periods of increased levels of proteasome immune subunits. On E21, the liver was enriched with neuronal nitric oxide synthase (nNOS); the level of nNOS decreased after birth and then increased by P18. This fact indicates the possibility of the induction of expression of the LMP7 and LMP2 immune subunits in hepatocytes via a signaling pathway involving nNOS. These results indicate that compared to the rat liver cells, splenic T cell immune response develops in rats starting around P19–P21. First, a T-area of white pulp is formed in the spleen during this period. Second, an increased level of immune proteasomes and MHC class I molecules in hepatocytes can ensure the formation of antigenic epitopes from foreign proteins and their delivery to the cell surface for subsequent presentation to cytotoxic T-lymphocytes.