Biology subjects

Bryan, L.

Publications and source records attributed to Bryan, L..

3 recordsLinked to original sources

bioRxiv2026

Sex-Specific Stress Outcomes Following Acute and Chronic Social Defeat Stress

Stressful experiences are a major risk factor for the development of neuropsychiatric disorders in vulnerable individuals. Identifying features that can distinguish stress-susceptible from resilient individuals remains a central goal in stress neurobiology. Due to the routine exclusion of female subjects from stress research or the use of male-defined criteria in behavioral characterization of subjects post-stress, female stress responses and vulnerability profiles remain poorly understood. This work aimed to gain a better understanding of sex-specific stress responses to social defeat stress. Here, we used a novel paired male-female social defeat paradigm and tracked subjects longitudinally in a ''two-hit'' design to evaluate responses to both acute social defeat stress (ASDS) and chronic social defeat stress (CSDS), and to determine how prior stress exposure influences subsequent vulnerability. We found that both ASDS and CSDS induces changes in social avoidance/approach behavior in males but not females, as measured by a classic social interaction ratio. Prior ASDS exposure enhanced susceptibility to subsequent CSDS most clearly in males, with females displaying specific changes in corner zone occupancy. Furthermore, we observed divergent anxiety profiles between males and females in a post-stress behavioral battery. Finally, females exhibited specific stress-related locomotor responses following ASDS. Together, these findings suggest that females may adopt distinct behavioral strategies following social defeat stress.

neuroscience↗

bioRxiv2022

Site-specific C-terminal fluorescent labeling of Tau protein

Formation of Tau protein aggregates in neurons is a pathological hallmark of several neurodegenerative diseases, including Alzheimers disease. Fluorescently-labeled Tau protein is therefore useful to study the aggregation of these pathological proteins and to identify potential therapeutic targets. Conventionally, cysteine residues are used for labeling Tau proteins, however, the full-length Tau isoform contains two cysteine residues in the microtubule-binding region, which are implicated in Tau aggregation by forming intermolecular disulfide bonds. In order to prevent the fluorescent label from disturbing the microtubule binding region, we developed a strategy to fluorescently label Tau at its C-terminus while leaving cysteine residues unperturbed. We took advantage of a Sortase A-mediated transpeptidation approach to bind a short peptide (GGGH6-Alexa647) with a His-tag and a covalently attached Alexa 647 fluorophore to the C-terminus of Tau. This reaction relies on the presence of a Sortase recognition motif (LPXTG), which we attached to the C-terminus of recombinantly expressed Tau. We determined the possible effects of the resulting C-terminal modification on the secondary structure of Tau protein, its aggregation kinetics, and fibril morphology compared to the unlabeled native Tau protein in vitro. The results showed no significant differences between the native and C-terminally labeled Tau monomer with regard to aggregation kinetics, secondary structure, and morphology.

biophysics↗

bioRxiv2019

KAP1 is an antiparallel dimer with a natively functional asymmetry

KAP1 (KRAB-domain associated protein 1) plays a fundamental role in regulating gene expression in mammalian cells by recruiting different transcription factors and altering the chromatin state. In doing so, KAP1 acts both as a platform for macromolecular interactions and as an E3 SUMO ligase. This work sheds light on the overall organization of the full-length protein combining solution scattering diffraction data, integrative modeling and single-molecule experiments. We show that KAP1 is an elongated antiparallel dimer with a native asymmetry at the C-terminal domain. This conformation supports our finding that the RING domain contributes to KAP1 auto-SUMOylation. Importantly, this intrinsic asymmetry has key functional implications for the KAP1 network of interactions, as the heterochromatin protein 1 (HP1) occupies only one of the two putative HP1 binding sites on the KAP1 dimer, resulting in an unexpected stoichiometry, even in the context of chromatin fibers.

biophysics↗