The inhibition mechanism of human 20 S proteasomes enables next-generation inhibitor design

Abstract

The proteasome is a validated target for anticancer therapy, and proteasome inhibition is employed in the clinic for the treatment of tumors and hematological malignancies. Here, we describe crystal structures of the native human 20S proteasome and its complexes with inhibitors, which either are drugs approved for cancer treatment or are in clinical trials. The structure of the native human 20S proteasome was determined at an unprecedented resolution of 1.8 angstroms. Additionally, six inhibitor-proteasome complex structures were elucidated at resolutions between 1.9 and 2.1 angstroms. Collectively, the high-resolution structures provide new insights into the catalytic mechanisms of inhibition and necessitate a revised description of the proteasome active site. Knowledge about inhibition mechanisms provides insights into peptide hydrolysis and can guide strategies for the development of next-generation proteasome-based cancer therapeutics.

Blockade of the malignant phenotype by β-subunit selective noncovalent inhibition of immuno- and constitutive proteasomes

“…Yet, it has been possible to crystallize some sulfonamide ligands at the β 1 /β 2 interface [41] related to the compounds that we identified by virtual screening [15], indicating that molecules selected by computational means can help gaining knowledge over this highly complex enzymatic system. To facilitate the reading of the structural and chemical data, we decided to present the analysis of two inhibitors that are chemically related but possess different properties and to rationalize their likely mechanism of actions in the light of the recently reported human cCP crystal structure [44] and of several other structural studies [11, 29, 45, 46]. The B1b and B1e inhibitors were docked with two different methods in all three binding centers of the constitutive human proteasome and compared with the mouse immuno- and constitutive proteasomes.…”

Activity‐based probes for the multicatalytic proteasome

“…reactive groups with catalytic Thr residues of proteasome. Epoxyketones were initially believed to form cyclic morpholine adducts with the N-terminal Thr [71], but recent high-resolution crystal structures suggest that the 1,4-oxazepane may be the preferred adduct [72].…”

Chlorocarbonylsulfenyl Chloride Cyclizations Towards Piperidin-3-yl-oxathiazol-2-ones as Potential Covalent Inhibitors of Threonine Proteases

“…5,11 Electrophilic warheads belong to structural classes of aldehydes, α',β'-epoxyketones, α-keto aldehydes, β-lactones, vinyl sulfones, Michael-acceptor systems, and boronates. 19 The active interest in this field is clearly represented by a very recent publication, 19 where a new mechanism for an existing warhead was reported, i.e. the formation of 1,4-oxazepane upon reaction of an α',β'-epoxyketone warhead with the N-terminal threonine rather than the previously reported morpholine ring.…”

“…the formation of 1,4-oxazepane upon reaction of an α',β'-epoxyketone warhead with the N-terminal threonine rather than the previously reported morpholine ring. 14,19 Such new developments provide invaluable data for the design of novel and selective irreversible inhibitors of threonine proteases.…”