Biology subjects

Gersch, M.

Publications and source records attributed to Gersch, M..

7 recordsLinked to original sources

bioRxiv2025

Targeted degradation of USP7 in solid cancer cells reveals disparate effects of deubiquitinase inhibition vs. acute protein depletion

Proteolysis-targeting chimeras (PROTACs) co-op the ubiquitin system for targeted protein degradation, creating opportunities to interrogate cellular functions of proteins through "chemical knockdown". However, matched pairs of protein degraders and inhibitors, that possess high specificity and chemical complementarity, for individual components of the ubiquitin system have remained scarce. This includes reagents to modulate activity and abundance of deubiquitinases (DUBs), which critically regulate ubiquitin-mediated signaling. Here, using an integrated chemical biology approach, we explored the cellular function of the DUB USP7 as a case study comparing inhibition and degradation of this DUB in melanoma and pancreatic cancer cells. Through the synthesis of a degrader library, we identified potent USP7 PROTACs for each cancer type, established BRET-based ternary complex formation and quantified degradation efficiency. USP7 degraders and their cognate inhibitor were subsequently employed to characterize treatment-induced phenotypic alterations. Proteomic and cellular analyses revealed that highly specific degradation of USP7 modulated both shared and distinct protein sets across cancer cell types, without impacting cell growth. Notably, cellular responses to USP7 degradation differed markedly from those to USP7 inhibition. Moreover, our data uncovered broad proteomic and metabolic changes induced by prolonged USP7 inhibitor treatment. Collectively, our work provides a chemical toolbox of comprehensively characterized reagents to distinguish on-target phenotypes which will aid the understanding of the role of USP7 in malignant diseases. More broadly, our data emphasize the importance of increased specificity via PROTAC-mediated degradation and the potential of this modality to distinguish catalytic from non-catalytic as well as cell-line specific functions of DUBs.

biochemistry↗

bioRxiv2024

Chimeric deubiquitinase engineering reveals structural basis for specific inhibition of USP30 and a framework for DUB ligandability

The mitochondrial deubiquitinase USP30 negatively regulates Pink1/Parkin-driven mitophagy. Whether enhanced mitochondrial quality control through inhibition of USP30 can protect dopaminergic neurons is currently explored in a clinical trial for Parkinsons disease. However, the molecular basis for specific inhibition of USP30 by small molecules has remained elusive. Here, we report the crystal structure of human USP30 in complex with a specific inhibitor, enabled by chimeric protein engineering. Our study uncovers how the inhibitor extends into a cryptic pocket facilitated by a compound-induced conformation of the USP30 switching loop. Our work underscores the potential of exploring induced pockets and conformational dynamics to obtain specific deubiquitinase inhibitors and identifies underlying USP30-specific residues. More broadly, we delineate a conceptual framework for specific USP deubiquitinase inhibition based on a common ligandability hotspot in the Leu73-Ubiquitin binding site and on diverse compound extensions. Collectively, our work establishes a generalizable chimeric protein engineering strategy to aid deubiquitinase crystallization and enables structure-based drug design with relevance to neurodegeneration.

biochemistry↗

bioRxiv2024

Monovalent Pseudo-Natural Product Degraders Supercharge the Native Degradation of IDO1 by KLHDC3

Targeted protein degradation (TPD) modulates protein function beyond inhibition of enzyme activity or protein-protein interactions. Most degrader drugs function by directly mediating proximity between a neosubstrate and hijacked E3 ligase. Here, we identified pseudo-natural products derived from (-)-myrtanol, termed iDegs that inhibit and induce degradation of the immunomodulatory enzyme indoleamine-2,3-dioxygenase 1 (IDO1) by a distinct mechanism. iDegs boost IDO1 ubiquitination and degradation by the cullin-RING E3 ligase CRL2KLHDC3, which we identified to natively mediate ubiquitin-mediated degradation of IDO1. Therefore, iDegs increase IDO1 turnover using the native proteolytic pathway. In contrast to clinically explored IDO1 inhibitors, iDegs reduce formation of kynurenine by both inhibition and induced degradation of the enzyme and, thus, would also modulate non-enzymatic functions of IDO1. This unique mechanism of action may open up new therapeutic opportunities for the treatment of cancer beyond classical inhibition of IDO1.

cell biology↗

bioRxiv2024

Discovery and mechanism of K63-linkage-directed deubiquitinase activity in USP53

Ubiquitin-specific proteases (USPs) are the largest class of human deubiquitinases (DUBs) and comprise its phylogenetically most distant members USP53 and USP54, which are annotated as catalytically inactive pseudo-enzymes. Conspicuously, mutations in the USP domain of USP53 cause familial intrahepatic cholestasis. Here we report the discovery that USP53 and USP54 are in fact active DUBs with high specificity for K63-linked polyubiquitin. We demonstrate how USP53 patient mutations abrogate catalytic activity, implicating loss of DUB activity in USP53-mediated pathology. Depletion of USP53 increases K63-linked ubiquitination of tricellular junction components. Assays with substrate-bound polyubiquitin reveal that USP54 cleaves within K63-linked chains, whereas USP53 can deubiquitinate a substrate in a K63-linkage-dependent manner. Biochemical and structural analyses uncover underlying K63-specific S2-ubiquitin-binding sites within their catalytic domains. Collectively, our work revises the annotation of USP53 and USP54, provides chemical reagents and a mechanistic framework to broadly investigate K63-polyubiquitin chain length decoding, and establishes K63-linkage-directed deubiquitination as novel DUB activity.

biochemistry↗

bioRxiv2023

Surprising variety in the USP deubiquitinase catalytic mechanism

The USP family of deubiquitinases (DUBs) controls many ubiquitin-dependent signaling events. This generates therapeutic potential, with active-site inhibitors in preclinical and clinical studies. Understanding of the USP active site was so far primarily guided by USP7 data, where the catalytic triad consists of cysteine, histidine and a third residue (first critical residue), which polarizes the histidine through a hydrogen bond. A conserved aspartate (second critical residue) is directly adjacent to this first critical residue. Here we study the roles of these critical residues in a subset of USPs and reveal a remarkable variety in function. While USP7 relies on the first critical residue for catalysis, this residue is dispensable in USP1, USP15, USP40 and USP48. Instead, their second critical residue is vital for catalysis. Interestingly, without their respective vital residue USP7, USP15 and USP40 can still perform nucleophilic attack. The diverging catalytic mechanisms of USP1 and USP7 are independent of substrate and retained in cells for USP1. The unexpected variety of catalytic mechanisms in this well-conserved protein family may generate opportunities for selective targeting of individual USPs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/550302v2_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1f3fdbeorg.highwire.dtl.DTLVardef@197f836org.highwire.dtl.DTLVardef@28b588org.highwire.dtl.DTLVardef@a62a2b_HPS_FORMAT_FIGEXP M_FIG C_FIG SynopsisO_LIThe roles of the highly conserved critical residues in USP active sites are poorly understood. Here we show that these two residues have varying importance for catalysis between different USPs. C_LIO_LIExcept for USP7, the majority of USPs does not rely on the canonical third catalytic residue (first critical residue). Instead, the USPs tested rely primarily on the highly conserved second critical residue. C_LIO_LIIn some USPs, either critical residues can accommodate nucleophilic attack (USP7, USP40, USP15). USP1 and USP48 are unable to perform the nucleophilic attack without the second critical residue. C_LI

biochemistry↗

bioRxiv2020

USP28 deletion and small molecule inhibition destabilises c-Myc and elicitsregression of squamous cell lung carcinoma

Lung squamous cell carcinoma (LSCC) is a considerable global health burden, with an incidence of over 600,000 cases per year. Treatment options are limited, and patient 5-year survival rate is less than 5%. The ubiquitin specific protease 28 (USP28) has been implicated in tumorigenesis through its stabilization of the oncoprotein c-MYC. Here, we show that genetic inactivation of Usp28 induced regression of established murine LSCC lung tumors. We developed a small molecule that inhibits USP28 activity in the low nanomole range. While displaying cross-reactivity against the closest homologue USP25, this inhibitor showed a high degree of selectivity over other deubiquitinases. USP28 inhibitor treatment resulted in a dramatic decrease in c-Myc proteins levels and consequently induced substantial regression of autochthonous murine LSCC tumors and human LSCC xenografts, thereby phenocopying the effect observed by genetic deletion. Thus, USP28 may represent a promising therapeutic target for the treatment of squamous cell lung carcinoma.

cancer biology↗

bioRxiv2020

A novel USP30 inhibitor recapitulates genetic loss of USP30 and sets the trigger for PINK1-PARKIN amplification of mitochondrial ubiquitylation.

The mitochondrial deubiquitylase USP30 negatively regulates the selective autophagy of damaged mitochondria. It has been proposed as an actionable target to alleviate the loss of function of the mitophagy pathway governed by the Parkinsons Disease associated genes PINK1 and PRKN. We present the characterisation of a N-cyano pyrrolidine derived compound, FT3967385, with high selectivity for USP30. The compound is well tolerated with no loss of total mitochondrial mass. We demonstrate that ubiquitylation of TOM20, a component of the outer mitochondrial membrane import machinery that directly interacts with USP30, represents a robust biomarker for both USP30 loss and inhibition. We have conducted proteomics analyses on a SHSY5Y neuroblastoma cell line model to directly compare the effects of genetic loss of USP30 with selective inhibition in an unbiased fashion. We have thereby identified a subset of ubiquitylation events consequent to mitochondrial depolarisation that are USP30 sensitive. Within responsive elements of the ubiquitylome, several components of the outer mitochondrial membrane transport (TOM) complex are most prominent. Thus, our data support a model whereby USP30 can regulate the availability of ubiquitin at the specific site of mitochondrial PINK1 accumulation following membrane depolarisation. In this model, USP30 deubiquitylation of TOM complex components dampens the trigger for the Parkin-dependent amplification of mitochondrial ubiquitylation leading to mitophagy. Accordingly, PINK1 generation of phospho-Ser65 Ubiquitin proceeds more rapidly and to a greater extent in cells either lacking USP30 or subject to USP30 inhibition.

cell biology↗