Recent findings indicate that the ubiquitin‐proteasome system is involved in the pathogenesis of cancer as well as autoimmune and several neurodegenerative diseases, and is thus a target for novel therapeutics. One disease that is related to aberrant protein degradation is multiple sclerosis, an autoimmune disorder involving the processing and presentation of myelin autoantigens that leads to the destruction of axons. Here, we show that brain‐derived proteasomes from SJL mice with experimental autoimmune encephalomyelitis (EAE) in an ubiquitin‐independent manner generate significantly increased amounts of myelin basic protein peptides that induces cytotoxic lymphocytes to target mature oligodendrocytes ex vivo. Ten times enhanced release of immunogenic peptides by cerebral proteasomes from EAE‐SJL mice is caused by a dramatic shift in the balance between constitutive and β1i ^high immunoproteasomes in the CNS of SJL mice with EAE. We found that during EAE, β1i is increased in resident CNS cells, whereas β5i is imported by infiltrating lymphocytes through the blood‐brain barrier. Peptidyl epoxyketone specifically inhibits brain‐derived β1i ^high immunoproteasomes in vitro (k _obs /[I] = 240 M ^‐1 s ^‐1 ), and at a dose of 0.5 mg/kg, it ameliorates ongoing EAE in vivo . Therefore, our findings provide novel insights into myelin metabolism in pathophysiologic conditions and reveal that the β1i subunit of the immunoproteasome is a potential target to treat autoimmune neurologic diseases.—Belogurov Jr., A., Kuzina, E., Kudriaeva, A., Kononikhin, A., Kovalchuk, S., Surina, Y., Smirnov, I., Lomakin, Y., Bacheva, A., Stepanov, A., Karpova, Y., Lyupina, Y., Kharybin, O., Melamed, D., Ponomarenko, N., Sharova, N., Nikolaev, E., Gabibov, A. Ubiquitin‐independent proteosomal degradation of myelin basic protein contributes to development of neurodegenerative autoimmunity. FASEB J. 29, 1901‐1913 (2015). www.fasebj.org

This review provides information on the structure of estrogen receptors (ERs), their localization and functions in mammalian cells. Additionally, the structure of proteasomes and mechanisms of protein ubiquitination and cleavage are described. According to the modern concept, the ubiquitin proteasome system (UPS) is involved in the regulation of the activity of ERs in several ways. First, UPS performs the ubiquitination of ERs with a change in their functional activity. Second, UPS degrades ERs and their transcriptional regulators. Third, UPS affects the expression of ER genes. In addition, the opportunity of the regulation of proteasome functioning by ERs—in particular, the expression of immune proteasomes—is discussed. Understanding the complex mechanisms underlying the regulation of ERs and proteasomes has great prospects for the development of new therapeutic agents that can make a significant contribution to the treatment of diseases associated with the impaired function of these biomolecules.

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.

Mammalian and human cells contain multiple forms of proteasomes different in their structure and functions. 26S-proteasome pool regulates most cellular processes through ATP- and ubiquitin-dependent hydrolysis of proteins participating in these processes. This function is possible due to 19S-subparticle capable to recognize ubiquitinated proteins, unfold and direct them into the proteolytic chamber. 20S-proteasome pool is capable to degrade some damaged and foreign proteins in an ATP- and ubiquitin-independent manner. Among both proteasome pools, the immune proteasomes effectively produce antigen epitopes for MHC class I molecules and play a crucial role in the antitumor immunity. Excluding the immune proteasomes from their cells, numerous tumors avoid the immune system. On the contrary, tumor cells enhance the expression of the housekeeping proteasomes and 19S-subparticle. At this time, bortezomib, a patented proteasome inhibitor, is used as an anticancer therapy. This drug induces the cell cycle arrest and apoptosis of dividing tumor cells. However, bortezomib causes, firstly, deviations in immune functions, secondly, the increase of the housekeeping proteasome expression by a feedback mechanism. Taking into account the recent patents, we consider prospects of the development of new drugs directed to the regulation of the expression of the immune and housekeeping proteasomes and 19S-subparticle in tumor cells.

Tumor growth is associated with elevated proteasome expression and activity. This makes proteasomes a promising target for antitumor drugs. Current antitumor drugs such as bortezomib that inhibit proteasome activity have significant side effects. The purpose of the present study was to develop effective low-toxic antitumor compositions with combined effects on proteasomes. For compositions, we used bortezomib in amounts four and ten times lower than its clinical dose, and chose menadione sodium bisulfite (MSB) as the second component. MSB is known to promote oxidation of NADH, generate superoxide radicals, and as a result damage proteasome function in cells that ensure the relevance of MSB use for the composition development. The proteasome pool was investigated by the original native gel electrophoresis method, proteasome chymotrypsin-like activity—by Suc-LLVY-AMC-hydrolysis. For the compositions, we detected 10 and 20 μM MSB doses showing stronger proteasome-suppressing and cytotoxic in cellulo effects on malignant cells than on normal ones. MSB indirectly suppressed 26S-proteasome activity in cellulo, but not in vitro. At the same time, MSB together with bortezomib displayed synergetic action on the activity of all proteasome forms in vitro as well as synergetic antitumor effects in cellulo. These findings determine the properties of the developed compositions in vivo: antitumor efficiency, higher (against hepatocellular carcinoma and mammary adenocarcinoma) or comparable to bortezomib (against Lewis lung carcinoma), and drastically reduced toxicity (LD50) relative to bortezomib. Thus, the developed compositions represent a novel generation of bortezomib-based anticancer drugs combining high efficiency, low general toxicity, and a potentially expanded range of target tumors.