Biology subjects

Stroebel, D.

Publications and source records attributed to Stroebel, D..

5 recordsLinked to original sources

bioRxiv2026

Distribution, assembly and mechanism of GluN1/GluN3A excitatory glycine receptors

NMDA receptors play key roles in brain development, plasticity and diseases. While glutamate and glycine co-gated GluN2-containing NMDARs have been extensively characterized, little is known regarding GluN3A-containing NMDARs that form receptors gated by glycine only. Here, combining native purification, mass spectrometry, cryo-EM and electrophysiology, we provide key insights on the molecular logic of GluN3A-NMDARs. We demonstrate that native GluN3A receptors account for a sizeable fraction of total NMDARs, are enriched at extrasynaptic compartments in the adult brain, and assemble specifically as diheteromeric GluN1/GluN3A excitatory glycine receptors (eGlyRs) rather than as triheteromeric GluN1/GluN2/GluN3A receptors. The architecture of eGlyRs reveal splayed and loosely packed extracellular domains, strikingly different from conventional GluN1/GluN2 receptors. Through back-and- forth structural and functional validations, we demonstrate how the combined effects of a weak ligand-binding domain (LBD) dimer interface and high intrinsic mobility of the N-terminal domains (NTDs) shape the atypical gating of eGlyRs. These findings illuminate GluN3A-NMDAR physiology and mechanism, with implications for neuronal signaling and pharmacology.

neuroscience↗

bioRxiv2024

Key roles of the zona pellucida and perivitelline space in promoting gamete fusion and fast block to polyspermy inferred from the choreography of spermatozoa in mice oocytes

Mammalian fertilization is still lacking a comprehensive understanding of gamete fusion and block to polyspermy mechanisms. One reason is that they are highly dynamic processes involving transient events that can only be revealed and characterized by direct observation. To extend while challenging existing knowledge, this study applies real time brightfield and confocal imaging to inseminated ZP-intact mouse oocytes and statistical analyses to establish an accurate dynamic picture of the cascade of events leading to fusion and prevention of polyspermy in conditions as close to physiology as possible. These observations allow to characterize the roles of the different components of the oocyte (i.e. zona pellucida (ZP), perivitelline space (PVS), oocyte plasma membrane (OPM)) and the spermatozoon (i.e. head, flagellum) in promoting fertilization and preventing polyspermy. The kinetics we have determined challenge dogmas by showing that: (i) the first sperm is not necessarily the one that fertilizes in mice pointing to the existence of other post-penetration fertilization factors, (ii) the ZP block resulting from the cortical reaction is too slow to contribute to the prevention of polyspermy in mice. On the other hand, it evidences that the ZP directly contributes to polyspermy block in two other ways: (a) as a naturally effective entry barrier for the spermatozoon (independent of any block caused by fertilization), (b) as an effective exit barrier for components released by the OPM, which may contribute to a fast PVS block to polyspermy through the neutralizing of unwanted spermatozoa in the PVS. Moreover, our observations reveal that the ZP plays a key role in fertilization itself by channeling the flagellar oscillations of spermatozoa in the PVS to make them conducive to fusion.

cell biology↗

bioRxiv2022

Evolution is not uniform along protein sequences

Amino acids evolve at different speeds within protein sequences, because their functional and structural roles are different. However, the position of an amino-acid within the sequence is not known to influence this evolutionary speed. Here we discovered that amino-acid evolve almost twice faster at protein termini than in their centre, hinting at a strong topological bias along the sequence length. We further show that the distribution of functional domains and of solvent-accessible residues in proteins readily explain how functional constrains are weaker at their termini, leading to the observed excess of amino-acid substitutions. Finally, we show that methods inferring sites under positive selection are strongly biased towards protein termini, suggesting that they may confound positive selection with weak negative selection. These results suggest that accounting for positional information should improve evolutionary models.

evolutionary biology↗

bioRxiv2019

Arabidopsis S2Lb links AtCOMPASS-like and SDG2 activity in histone H3 Lys-4 trimethylation independently from histone H2B monoubiquitination

The functional determinants of histone H3 Lys-4 trimethylation (H3K4me3), their potential dependency on histone H2B monoubiquitination (H2Bub) and their contribution to defining transcriptional regimes are poorly defined in plant systems. Unlike in S. cerevisiae, where a single SET1 protein catalyzes H3 Lys-4 trimethylation as part of COMPASS (COMPlex of proteins ASsociated with Set1), in Arabidopsis thaliana this activity involves multiple histone methyltransferases (HMTs). Among these, the plant-specific SDG2 (SET DOMAIN GROUP2) has a prominent role. We report that SDG2 co-regulates hundreds of genes with SWD2-like b (S2Lb), a plant ortholog of the Swd2 axillary subunit of yeast COMPASS. S2Lb co-purifies with the AtCOMPASS core subunit WDR5 from a high-molecular weight complex, and both S2Lb and SDG2 directly influence H3K4me3 enrichment over highly transcribed genes. S2Lb knockout triggers pleiotropic developmental phenotypes at the vegetative and reproductive stages, including reduced fertility and seed dormancy. Notwithstanding, s2lb seedlings display little transcriptomic defects as compared to the large repertoire of genes targeted by S2Lb, SDG2 or H3 Lys-4 trimethylation, suggesting that H3K4me3 enrichment is important for optimal gene induction during cellular transitions rather than for determining on/off transcriptional status. Moreover, unlike in budding yeast, most of the S2Lb and H3K4me3 genomic distribution does not rely on a trans-histone crosstalk with histone H2B monoubiquitination. Collectively, this study unveils that the evolutionarily conserved COMPASS-like complex has been coopted by the plant-specific SDG2 HMT and mediates H3K4me3 deposition through an H2Bub-independent pathway in Arabidopsis.

plant biology↗

bioRxiv2018

DET1-mediated degradation of a SAGA-like deubiquitination module controls H2Bub homeostasis

DE-ETIOLATED 1 (DET1) is an evolutionarily conserved component of the ubiquitination machinery that mediates the destabilization of key regulators of cell differentiation and proliferation in multicellular organisms. In this study, we provide evidence from Arabidopsis that DET1 is essential for the regulation of histone H2B monoubiquitination (H2Bub) over most genes by controlling the stability of a plant deubiquitination module (DUBm). In contrast with yeast and metazoan DUB modules that are associated with the large SAGA complex, the Arabidopsis DUBm only comprises three proteins (hereafter named SGF11, ENY2 and UBP22) and appears to act independently as a major H2Bub deubiquitinase activity. Our study further unveils that DET1-DDB1-Associated-1 (DDA1) protein interacts with SGF11 in vivo, linking the DET1 complex to light-dependent ubiquitin-mediated proteolytic degradation of the DUBm. Collectively, these findings uncover a signaling path controlling DUBm availability, potentially adjusting H2Bub turnover capacity to the cell transcriptional status.

plant biology↗