Biology subjects

Curth, U.

Publications and source records attributed to Curth, U..

3 recordsLinked to original sources

bioRxiv2026

Conserved tyrosine Y16 acts as a phosphorylation switch controlling Ena/VASP recruitment to sites of actin assembly

Ena/VASP proteins are powerful actin polymerases that accumulate at sites of active actin assembly, including lamellipodial and microspike tips, focal adhesions and pathogen surfaces, where they drive processive filament elongation. However, the mechanisms controlling their recruitment remain elusive. Here, we used cells lacking all Ena/VASP-family members to systematically test phosphomimetic and nonphosphorylatable substitutions at conserved tyrosine and serine residues implicated in subcellular targeting. Combining cell-based reconstitution with biochemical assays, we identify phosphorylation of Y16 in vertebrate Ena/VASP proteins as the decisive inhibitory modification controlling subcellular Ena/VASP recruitment, in contrast to previously proposed roles for Y39 and S157. Corresponding phosphomimetic substitutions in the C. elegans orthologue UNC-34 phenocopied uncoordinated locomotion of UNC-34 null worms, supporting the evolutionary conservation of this regulatory mechanism. Thus, our findings identify a conserved phosphorylation-sensitive switch at the EVH1-FP4 ligand interface that links EVH1-dependent targeting to dynamic control of actin assembly in adhesion, migration and pathogenesis.

cell biology↗

bioRxiv2025

The SH3BGRL protein family nucleates and caps actin filaments via its conserved thioredoxin fold

Cellular actin polymerization is a tightly regulated process, typically controlled by proteins with specialized domains such as the Wiskott-Aldrich syndrome protein homology 2 (WH2) domain. Here, we identify SH3BGRL family proteins as modulators of actin dynamics, uniquely characterized by their thioredoxin (Trx) fold structure and the absence of the canonical CXXC enzymatic site essential for redox activity. The Trx fold is generally associated with enzymatic activity; however, in this context, it functions non-enzymatically to enhance actin filament nucleation and inhibit depolymerization. The family member SH3BGRL-2 was previously identified as part of the spectrin-actin complex in porcine erythrocytes. Further structural analysis reveals that human SH3BGRL proteins share structural homology with the C-terminal region of Saccharomyces cerevisiae YFR016c/Aip5, a known actin nucleation factor reported to bind G-actin. Notably, our results show that human SH3BGRL proteins do not bind G-actin directly. While they do not interact with G-actin, SH3BGRL proteins significantly increase actin assembly rates by accelerating filament nucleation without affecting barbed end elongation, as demonstrated in pyrene-actin bulk-polymerization assays and total internal reflection fluorescence microscopy (TIRFM) based single-filament studies. Furthermore, using all-atom molecular dynamics (MD) simulations and in vitro assays that directly probe the pointed end of the actin filament, we show that SH3BGRL proteins inhibit the depolymerization of existing filaments by interacting with the pointed end of the actin filament, also in the presence of the well-characterized pointed end capping protein tropomodulin. Our results indicate that all SH3BGRL family proteins promote actin nucleation by stabilizing energetically unstable actin dimers and trimers and inhibit depolymerization by direct association with the pointed end, suggesting a direct role for the Trx fold in actin dynamics.

biochemistry↗

bioRxiv2022

Redox regulation of the SARS-CoV-2 main protease provides new opportunities for drug design

AO_SCPLOWBSTRACTC_SCPLOWBesides vaccines, the development of antiviral drugs targeting SARS-CoV-2 is critical for stopping the current COVID-19 pandemic and preventing future outbreaks. The SARS-CoV-2 main protease (Mpro), a cysteine protease with essential functions in viral replication, has been validated as an effective drug target. Here, we show that Mpro is subject to redox regulation and reversibly switches between the enzymatically active dimer and the functionally dormant monomer through redox modifications of cysteine residues. These include sulfenylation, disulfide formation between the catalytic cysteine and a proximal cysteine, and generation of an allosteric lysine-cysteine SONOS bridge that is required for structural stability under oxidative stress conditions, such as those exerted by the innate immune system. We identify homo- and heterobifunctional reagents that mimic the redox switching and possess antiviral activity. The discovered redox switches are conserved in main proteases from other coronaviruses, e.g. MERS and SARS-CoV, indicating their potential as common druggable sites.

biochemistry↗