Biology subjects

Hirschi, M.

Publications and source records attributed to Hirschi, M..

4 recordsLinked to original sources

bioRxiv2025

Human SerRS/SIRT2 complex structure reveals cross regulation between translation and NAD+ metabolism

Life at the cellular level depends on effective coordination between diverse processes. Here we uncover a novel cross-regulation between metabolism and translation through a 3.2 [A] cryo-EM structure of human cytosolic seryl-tRNA synthetase (SerRS) bound to sirtuin-2 (SIRT2), an NAD+-dependent deacetylase. This interaction, naturally triggered by the NAD+ metabolite ADP-ribose (ADPR), resembles substrate binding and block SIRT2s active site. Interestingly, SerRS acetylation is not required for this interaction. SIRT2 binding sterically and allosterically impedes tRNA binding to SerRS, lowering charged tRNASer level and protein synthesis activity. Key interaction residues in both proteins emerged simultaneously in vertebrates, suggesting co-evolution for cross-regulation. Given ADPRs accumulation under stress, the ADPR-induced SerRS/SIRT2 interaction likely serves as a cell-protective response.

molecular biology↗

bioRxiv2024

Expanding the ligandable proteome by paralog hopping with covalent probes

More than half of the [~]20,000 protein-encoding human genes have at least one paralog. Chemical proteomics has uncovered many electrophile-sensitive cysteines that are exclusive to a subset of paralogous proteins. Here, we explore whether such covalent compound-cysteine interactions can be used to discover ligandable pockets in paralogs that lack the cysteine. Leveraging the covalent ligandability of C109 in the cyclin CCNE2, we mutated the corresponding residue in paralog CCNE1 to cysteine (N112C) and found through activity-based protein profiling (ABPP) that this mutant reacts stereoselectively and site-specifically with tryptoline acrylamides. We then converted the tryptoline acrylamide-N112C-CCNE1 interaction into a NanoBRET-ABPP assay capable of identifying compounds that reversibly inhibit both N112C- and WT-CCNE1:CDK2 complexes. X-ray crystallography revealed a cryptic allosteric pocket at the CCNE1:CDK2 interface adjacent to N112 that binds the reversible inhibitors. Our findings thus provide a roadmap for leveraging electrophile-cysteine interactions to extend the ligandability of the proteome beyond covalent chemistry.

biochemistry↗

bioRxiv2021

A case for glycerol as an acceptable additive to cryoEM samples

Buffer composition and sample preparation guidelines for cryo-electron microscopy are geared toward maximizing imaging contrast and reducing electron beam-induced motion. These pursuits often involve the minimization or complete removal of additives that are commonly used to facilitate proper protein folding and minimize aggregation. Among these admonished additives is glycerol, a widely used osmolyte that aids protein stability. In this work, we show that inclusion of glycerol does not preclude high-resolution structure determination by cryoEM, as demonstrated by a [~]2.3 [A] reconstruction of mouse apoferritin ([~]500 kDa) and a [~]3.3 [A] reconstruction of rabbit muscle aldolase ([~]160 kDa) in presence of 20% v/v glycerol. While we found that generating thin ice that is amenable for high-resolution imaging requires long blot times, the addition of glycerol did not result in increased beam-induced motion nor an inability to pick particles. Overall, our findings indicate glycerol should not be discounted as a cryoEM sample buffer additive, particularly for large, fragile complexes that are prone to disassembly or aggregation upon its removal.

biophysics↗

bioRxiv2018

Conformational ensemble of the human TRPV3 ion channel

Transient receptor potential vanilloid channel 3 (TRPV3), a member of the thermosensitive TRP (thermoTRPV) channels, is activated by warm temperatures and serves as a key regulator of normal skin physiology through the release of pro-inflammatory messengers. Mutations in trpv3 have been identified as the cause of the congenital skin disorder, Olmsted syndrome. Unlike other members of the thermoTRPV channel family, TRPV3 sensitizes upon repeated simulation, yet a lack of structural information about the channel precludes a molecular-level understanding of TRPV3 sensitization and gating. Here, we present the cryo-electron microscopy structures of apo and sensitized human TRPV3, as well as several structures of TRPV3 in the presence of the common thermoTRPV agonist 2-aminoethoxydiphenyl borate (2-APB). Our results show -to-{pi}-helix transitions in the S6 during sensitization, and suggest a critical role for the S4-S5 linker {pi}-helix during ligand gating.

biochemistry↗