The carpase-like sites of proteasomes: substrate specificity, new inhibitors and substrates, and allosteric interactions with the trypsin-like sites

Bio-Organische synthes

The novel beta 2-selective proteasome inhibitor LU-102 decreases phosphorylation of I kappa B and induces highly synergistic cytotoxicity in combination with ibrutinib in multiple myeloma cells

Bio-organic Synthesi

An inhibitor of proteasome beta 2 sites sensitizes myeloma cells to immunoproteasome inhibitors

Bio-organic Synthesi

The novel beta 2-selective proteasome inhibitor LU-102 synergizes with bortezomib and carfilzomib to overcome proteasome inhibitor resistance of myeloma cells

Bio-organic Synthesi

Use of proteasome inhibitors

Proteasome inhibitors are indispensable research tools in immunology and cell biology. With numerous proteasome inhibitors available commercially, choosing the appropriate compound for a biological experiment may be challenging, especially for a novice. This unit provides an overview of the proteasome inhibitors commonly used in research. It discusses how to select an appropriate highly specific inhibitor, its concentration, and length of exposure for mammalian cell culture experiments. In addition, assays that can be used to confirm proteasome inhibition are discussed. © 2015 by John Wiley & Sons, Inc.Bio-organic Synthesi

Structure-based design of fluorogenic substrates selective for human proteasome subunits

Proteasomes are established therapeutic targets for hematological cancers and promising targets for autoimmune diseases. In the past we designed and synthesized mechanism-based proteasome inhibitors selective for individual catalytic activities of human constitutive proteasomes and immunoproteasomes: β1c, β1i, β2c, β2i, β5c and β5i. We show here that by taking the oligopeptide recognition element and substituting the electrophile for a fluorogenic leaving group fluorogenic substrates are obtained that report on the proteasome catalytic activity also targeted by the parent inhibitor. Though not generally applicable (β5c and β2i substrates showing low activity), effective fluorogenic substrates reporting on the individual activity of β1c, β1i, β2c and β5i subunits in Raji (human B cell) lysates and purified 20S proteasome were identified in this manner. Our work thus adds to the expanding proteasome research toolbox through the identification of new and/or more effective subunit-selective fluorogenic substrates.Bio-organic Synthesi

Inhibition of the Proteasome beta 2 Site Sensitizes Triple-Negative Breast Cancer Cells to beta 5 Inhibitors and Suppresses Nrf1 Activation

The proteasome inhibitors carfilzomib (Cfz) and bortezomib (Btz) are used successfully to treat multiple myeloma, but have not shown clinical efficacy in solid tumors. Here we show that clinically achievable inhibition of the β5 site of the proteasome by Cfz and Btz does not result in loss of viability of triple-negative breast cancer cell lines. We use site-specific inhibitors and CRISPR-mediated genetic inactivation of β1 and β2 to demonstrate that inhibiting a second site of the proteasome, particularly the β2 site, sensitizes cell lines to Btz and Cfz in vitro and in vivo. Inhibiting both β5 and β2 suppresses production of the soluble, active form of the transcription factor Nrf1 and prevents the recovery of proteasome activity through induction of new proteasomes. These findings provide a strong rationale for the development of dual β5 and β2 inhibitors for the treatment of solid tumors.Bio-organic Synthesi

A Set of Activity-Based Probes to Visualize Human (Immuno)proteasome Activities

Bio-organic Synthesi

Asymmetric synthesis of lysine analogues with reduced basicity, and their incorporation into proteasome inhibitors

Molecular PhysiologyBio-organic Synthesi