ИСТИНА

Proteasome is a ubiquitous cell nanofactory for waste disposal. The 26S proteasome is a 2.5-MDa molecular machine built from ~31 different subunits, which catalyzes protein degradation. It has cylinder-shaped body and one or two caps with overall diameter around 20 nm and height around 60 nm. The size of this multifunctional protease complex is huge compared to usual enzymes and is close to ribosome. Because of its enormous size and complex architecture the compartmentalization of the proteolysis is achieved, and this vitally important process normally proceeds only in special places for specially marked proteins. Proteasome plays an essential role not only in continual turnover of intracellular proteins but also in antigen processing. Autoimmune diseases such as multiple sclerosis and its murine model, EAE, are believed to rise from a breakdown of tolerance and a deregulation of the immune system to discriminate effectively between “self” and “non-self”. As it was showed that proteasome change its subunit composition (forming immunoproteasome) during inflammation under the influence of cytokines, such as interferon gamma, it could be assumed that immunoproteasome could play an important role in autoimmune diseases. 2. Results and discussion Up-to-date several classes of chemicals proved to be inhibitors of proteins degradation by proteasome. Among them boronate peptide derivatives was FDA approved as anti-cancer drugs for multiple myeloma. These inhibitors, however, affected any cell, malignant or healthy, and result in full stop of intracellular protein turnover and cell death via apoptosis. Another class of inhibitors, peptide epoxy ketones, was shown to be more selective for immunoproteasome and could be used not for full stop of proteasome function, but for fine tuning of altered, invalid proteasome functioning. We examined properties of several inhibitors of four different classes, namely peptide boronate bortezomib, peptide aldehyde MG132, natural lactam lactacystin, and peptide epoxyketones epoxomicin, MG132ek, LMP2-specific and LMP7-specific inhibitors. For inhibition experiments we used proteasome isolated from eukaryotic cell lines CHO and NSO, treated and non-treated with interferon gamma, and from murine brains of BALB/c mouse and SJL mouse developed EAE, murine model of MS. The upregulation of proteasome immunosubunits was revealed in SJL-EAE brains and in CHO and NSO cells treated with interferon gamma. The IC50 values for all studied inhibitors were obtained, and Ki in some cases were calculated. The epoxyketones were shown to selectively inhibit in submicromolar concentrations the proteasome sample from murine SJL-EAE brains which contain high amount of immunosubunits.