Potential allosteric modulators of the proteasome activity

Abstract

Proteasome, consisting of a tube-shaped proteolytic core particle and attached to it regulatory modules, is a multifunctional enzymatic complex essential for the ubiquitin-proteasome metabolic pathway. Due to its immense involvement in regulation of cellular physiology, the proteasome is an acknowledged anti-cancer drug target and potential target to treat inflammatory or degenerative diseases. So far, competitive inhibitors of the core particle gain most consideration as drugs. We postulate that noncompetitively-acting small-molecule compounds would provide excellent means to precisely regulate actions of the proteasome. In this study we evaluated five short peptides based on sequences of two proteins known to interact with the core proteasome: HIV-1 Tat and PA28/REG activator. We performed CD, FT-IR and NMR analysis, supplemented by MD simulations, and tested influence of the peptides on performance of the core particle active sites and functioning of regulatory modules. We found that PP2-containing Tat peptides are noncompetitive inhibitors of the core, interfering with the actions of PA28αβ activator. In addition, at low concentrations the turn-prone Tat2 is able to activate the latent core. The random coil-structured PA28-derived peptides display only weak or nondetectable direct effects on the core activities, exhibiting, however, a positive cooperation with activity-enhancing actions of PA28αβ.

Rapamycin Allosterically Inhibits the Proteasome

“…The diversity of effects exerted on the peptidase activities (i.e., pure noncompetitive inhibition, mixed-type inhibition, or moderate activation) provides the first culprit. We noted similarly diverse effects before with allosteric ligands of the 20S core: PR peptides and peptide fragments of proteins binding to the proteasome (Gaczynska et al, 2003;Jankowska et al, 2010). The AFM-detected rapamycin-induced changes in the dynamics of the gate offer an additional line of evidence for the allosteric nature of rapamycin actions.…”

“…4B). Similar to certain other small noncompetitive ligands of the proteasome, the actions of rapamycin were not restricted to inhibition of the peptidases (Jankowska et al, 2010). The T-L peptidase was moderately activated by rapamycin.…”

“…A straightforward case of such interference is provided by short peptide sequences derived from C termini of the modules, blocking the grooves and mimicking some allosteric effects of their parent proteins (Jankowska et al, 2010). The anchor peptide fragments of selected regulatory particle ATPases (Rpt) subunits of the 19S, and of PA200 activator, are equipped with the Hb-Y-X motif (hydrophobic amino acid-Tyr-any amino acid) (Ortega et al, 2005;Rabl et al, 2008).…”

Oligomers and peptidomimetics consisting of methyl 3-amino-2,3-dideoxyhexopyranosiduronic acids

“…The peptide Tat1, comprising residues 48e59 of its parental protein, was proved to be a quite potent noncompetive inhibitor of the human 20S proteasome (h20S). 37 To continue the studies, we synthesized a peptide 16, which was very basic in its character since it consisted mainly of lysine residues, and its mimetic 17 with 3-amino-2,3-dideoxy-a-D-arabino-hexopyranosiduronic acid incorporated in the middle of the sequence (Fig. 10).…”

Harnessing Proteasome Dynamics and Allostery in Drug Design

“…The two 12-residue fragments (Fig. 4C) containing the RTP site and carved out of the basic domain (Tat1), as well as the basic and Gln-rich domains (Tat2) of HIV-1Tat noncompetitively inhibit the ChT-L and PGPH peptidases of the activated human 20S core at high nanomolar concentrations, and also efficiently compete with the core activation by PA28ab complex (65). The Tat1 peptide is better characterized to date than Tat2.…”