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

Abstract

A structure-based virtual screening of over 400,000 small molecules against the constitutive proteasome activity followed by in vitro assays led to the discovery of a family of proteasome inhibitors with a sulfonyl piperazine scaffold. Some members of this family of small non-peptidic inhibitors were found to act selectively on the β2 trypsin-like catalytic site with a preference for the immunoproteasome β2i over the constitutive proteasome β2c, while some act on the β5 site and post-acid site β1 of both, the immunoproteasome and the constitutive proteasome. Anti-proliferative and anti-invasive effects on tumor cells were investigated and observed for two compounds. We report novel chemical inhibitors able to interfere with the three types of active centers of both, the immuno- and constitutive proteasomes. Identifying and analyzing a novel scaffold with decorations able to shift the binders’ active site selectivity is essential to design a future generation of proteasome inhibitors able to distinguish the immunoproteasome from the constitutive proteasome.

Conversion of Isatins to Tryptanthrins, Heterocycles Endowed with a Myriad of Bioactivities

“…It was analyzed by Lineweawer–Burk plots that showed a mixed inhibition mechanism (Figure c.). Such an allosteric modulation of the proteasome activity, already observed with non‐peptide inhibitors[42b], and also peptide inhibitors, indicated that binding occurred at a site other than the ChT‐L active site, while resulting in inhibition of enzyme activity.…”

“…Three peptide proteasome inhibitors bearing an electrophilic warhead are currently marketed for the treatment of multiple myeloma, a blood cancer . In order to circumvent peptide limitations in therapy, the development of non‐peptide inhibitors, especially heterocyclic compounds, is growing ,. [51a], [51b], [51c], [51d], The heterocyclic structure of the prepared tryptanthrins 1‐R and their described cytotoxicity prompted us to test their ability to inhibit purified human constitutive 20S proteasome in vitro.…”

“…This result prompted us to extend the reaction to substituted isatins 1‐R (Table ; R = substituent), and to assess some of their biological properties. Particularly, in the course of our search for new non‐peptide proteasome inhibitors, we evaluated their ability to inhibit human 20S proteasome.…”

Furin Prodomain Ppfurin Enhances Soce Through trpc6 Activation in Breast Cancer Cells

“…The cell viability was evaluated using the MTT assay, as previously described [45]. Control and MDA-MB-231 ppFurin cells were plated in 96-well microtiter plates respectively at a density of (1 × 10 4 /ml) cells/well.…”

Structure-based design of human immuno- and constitutive proteasomes inhibitors

“…3-4) [18][19][20][21][22][23][24], and pseudopeptides [25][26][27] (Figure 2). Nonpeptidic noncovalent inhibitors have also been described (e. g. sulfonamides [28][29][30][31], hydroxyurea [32], 1,2,4-oxadiazoles [33], pyrazoles [34], phakellins [35], quinolines [36], psoralene [37]). The three approved covalent drugs inhibit mainly the β5 activity of the M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 catalytic core of the constitutive proteasome (cCP) but also that of the inducible immunoproteasome (iCP).…”