Synthesis and Application of a Caged Bioluminescent Probe for the Immunoproteasome.

Monitoring the catalytic activity of the proteasome and its various isoforms has become increasingly important with the continued development of core particle inhibitors and targeted protein degraders as potential therapies for diseases with high protein accumulation. The immunoproteasome (iCP) is expressed in a variety of diseases due to inflammatory signals, such as interferon-gamma, that alert the cell to begin generating iCP preferentially over the standard proteasome. There is a need to understand iCP activity and expression both in cells and in vivo because it is becoming a widely targeted isoform in a variety of diseases.

A Phenotypic High-Throughput Screen Identifies Small Molecule Modulators of Endogenous RGS10 in BV-2 Cells.

Chronic dysregulation of microglial phenotypic balance contributes to prolonged neuroinflammation and neurotoxicity, which is a hallmark of neurodegenerative diseases. Thus, targeting microglial inflammatory signaling represents a promising therapeutic strategy for neurodegenerative diseases. Regulator of G protein Signaling 10 (RGS10) is highly expressed in microglia, where it suppresses pro-inflammatory signaling.

Methylarginine targeting chimeras for lysosomal degradation of intracellular proteins.

A paradigm shift in drug development is the discovery of small molecules that harness the ubiquitin-proteasomal pathway to eliminate pathogenic proteins. Here we provide a modality for targeted protein degradation in lysosomes. We exploit an endogenous lysosomal pathway whereby protein arginine methyltransferases (PRMTs) initiate substrate degradation via arginine methylation.

Synthesis and Application of a Versatile Immunoproteasome Activity Probe.

The immunoproteasome (iCP) has gained significant interest in recent years as it has been discovered to be significantly expressed under inflammatory conditions, as well as playing significant roles in several diseases, such as autoimmune disorders, viral infection, and cancer. Selective inhibitors have been generated as a method to overcome the off-target effects of current proteasome inhibitor therapeutics. However, selective probes that allow for monitoring this protein complex remain limited, hindering our understanding of the iCP.

Caged aminoluciferin probe for bioluminescent immunoproteasome activity analysis.

The immunoproteasome (iCP) can be expressed under inflammatory conditions, such as exposure to interferon-gamma (IFN-γ), that alerts the cell to begin generating iCP preferentially over the standard proteasome (sCP). With the iCP becoming a widely targeted isoform in a variety of diseases, there is a need to understand its activity and expression in cells and Activity-based probes for the iCP have been developed but their application has been limited due to their difficult synthesis and cannot be used in tissues or whole animals. Our lab has previously demonstrated we can monitor iCP activity using a 4-mer peptide linked to a fluorophore and a peptoid.

Primed for Interactions: Investigating the Primed Substrate Channel of the Proteasome for Improved Molecular Engagement.

Protein homeostasis is a tightly conserved process that is regulated through the ubiquitin proteasome system (UPS) in a ubiquitin-independent or ubiquitin-dependent manner. Over the past two decades, the proteasome has become an excellent therapeutic target through inhibition of the catalytic core particle, inhibition of subunits responsible for recognizing and binding ubiquitinated proteins, and more recently, through targeted protein degradation using proteolysis targeting chimeras (PROTACs). The majority of the developed inhibitors of the proteasome's core particle rely on gaining selectivity through binding interactions within the unprimed substrate channel.

ByeTAC: Bypassing an E3 Ligase for Targeted Protein Degradation.

Targeted protein degradation utilizing a bifunctional molecule to initiate ubiquitination and subsequent degradation by the 26S proteasome has been shown to be a powerful therapeutic intervention. Many bifunctional molecules, including covalent and non-covalent ligands to proteins of interest, have been developed. The traditional target protein degradation methodology targets the protein of interest in both healthy and diseased cell populations, and a therapeutic window is obtained based on the overexpression of the targeted protein.

Discovery of a non-covalent ligand for Rpn-13, a therapeutic target for hematological cancers.

The ubiquitin-proteasome system serves as the major proteolytic degradation pathway in eukaryotic cells. Many inhibitors that covalently bind to the proteasome's active sites have been developed for hematological cancers, but resistance can arise in patients. To overcome limitations of active-site proteasome inhibitors, we and others have focused on developing ligands that target subunits on the 19S regulatory particle (19S RP).