Immunoproteasome is a special form of proteasome, which is a multicatalytic enzyme that acts via the ubiquitin protease system. The enzyme ensures homeostasis of cells by proteolysing of incorrectly formed and senescent proteins. The inhibition of this enzyme may lead to cell death. It has been demonstrated that increased quantities of immunoproteasome occur in certain pathological conditions, such as autoimmune diseases and cancer. For this reason, the inhibition of immunoproteasome activity has become an interesting modern approach to development of new selective agents aimed for the treatment of various diseases.We have successfully synthesized six new potential inhibitors of the chymotrypsin-like subunit of immunoproteasome. All new compounds contain psoralene moiety as a polycyclic system to which methyl groups are bound at the positions 4 and 8. The synthesis of compounds was carried out in several stages. Firstly, we formed the basic sceleton for all molecules by reacting 2-methylresorcinol and diethyl 2-acetoglutarate. Properly substituted 2-bromoacetophenone, with diverse functional groups at the positions 3 or 4 in the aromatic ring were used for preparation of corresponding ethers. Some of the reagents used were prepared in situ. In the next stage, we performed condensation, which resulted in the formation of a psoralene ring. One of the synthesized compounds was activated in the form of N-hydroxysuccinimide ester in order to achieve a stronger interaction with amino acid residues in the active site of immunoproteasome. Finally a biochemical evaluation of synthesized compounds was carried out at the Department of Clinical Biochemistry, in which the residual activity of chymotrypsin-like immunoproteasome subunit was determined following the addition of selected compounds. The compound 18 showed the most pronounced inhibitory activity. In order to achieve a better inhibitory activity, the formation of activated esters is required to enable the formation of covalent bonds with amino acid residues present in the active site of immunoproteasome. The addition of an additional methyl group at the position 8 of the psoralene ring and different by substituted phenyl fragments on the furan part of the psoralene molecule however do not improve the affinity of new compounds for their binding to immunoproteasome.
|
