Progettazione, sintesi ed attività di inibitori del Proteasoma a base peptidica

The ubiquitin-proteasome pathway represents an attractive target in the development of new drug therapies. In particular, the proteasome 26S, a multicatalytic threonine protease complex, is involved in intracellular ubiquitinated-protein degradation and many biological processes, such as cell cycle control and differentiation, apoptosis and generation of antigenic peptides presented by major histocompatibility complex class I (MHC I) molecules. The activity of 26S proteasome is located in a central 20S core, the proteoliytic chamber is composed of four stacked rings capped by two 19S regulatory complexes. Each ring is composed for seven b subunits with three different active sites: in particular, the b1 subunit contains a peptidyl-glutamyl peptide hydrolizing active site (PGPH), the b2 subunit expresses tryptic-like (T-L) activity, and b5 contains a chimotryptic-like (ChT-L) activity. Modulation of the proteasome activity by specific inhibitors may represent an useful tool for the treatment of tumors, metabolic and autoimmune disorders. The aim of this PhD work is the design, sythesis and evaluation of the biological activity of several classes peptide-based proteasome inhibitors, containing different pharmacophoric moieties at the C-terminal position as a potential substrate for Michael addiction by the catalytic threonine through a mechanism similar to that of the well-known inhibitors. Herein we reported studies of the molecules bearing as pharmacophoric Cterminal function: N-allyl vinil ester, a,b-unsaturated N-acylpyrrole, vinyl ketone, butadienyl vinyl ester, divinyl ketone and isoxazolin vinyl ester groups. In accordance with the results obtained in previous series, the pharmacophoric units are linked to oligopeptidic sequences functionalized at the N-terminal by appropriated groups. Biological evaluation of the all new compounds was carried out to assess their inhibition of the trypsin-like, chymotrypsin-like and post-acidic activities of proteasome using the isolated enzyme purified from lymphoblastoid cell lines. Some compounds as a,b-unsaturated N-acylpyrrole and vinyl ketone analogs showed selective inhibition of the proteasome subunits in a mM range, while other derivatives bearing different pharmacophoric units don’t provide a favorable biological response.