Biology subjects

Charnley, M.

Publications and source records attributed to Charnley, M..

7 recordsLinked to original sources

bioRxiv2024

Cell invasive amyloid assemblies from SARS-CoV-2 peptides can form multiple polymorphs with varying neurotoxicity

The neurological symptoms of COVID-19, such as memory loss, cognitive and sensory disruption (neuro-COVID) are well reported. These neurological symptoms frequently persist for months (post-acute sequalae of COVID-19 or PASC). The molecular origins of neuro-COVID and how it contributes to PASC are unknown, however a growing body of research highlights that the self-assembly of protein fragments from SARS-CoV-2 into amyloid nanofibrils may play a causative role. Previously, we identified two fragments from the proteins Open Reading Frame 6 (ORF6) and ORF10 that self-assemble into neurotoxic amyloid assemblies. Here we further our understanding of the self-assembly mechanisms and nano-architectures formed by these fragments as well as performing a more in-depth study of the biological responses of co-cultured neurons. By solubilising the peptides in a fluorinated solvent we eliminate insoluble aggregates in the starting materials (seeds) that change the polymorphic landscape of the assemblies. The resultant assemblies are dominated by structures with higher free energies (e.g. ribbons and amorphous aggregates) that are less toxic to cultured neurons. We also show the first direct evidence of cellular uptake by viral amyloids. This work highlights the importance of understanding the polymorphic behaviour of amyloids particularly in the context of neuro-COVID and PASC. Graphical Abstract for ToCThe neurological symptoms of COVID-19 are likely to be, in part, caused by the aggregation of viral proteins into neurotoxic amyloid nanofibrils. Changes in aggregation conditions alters the balance of fibril structures formed (polymorphism), influencing their toxicity to a neuronal cell line. These findings increase our understanding of viral amyloids and highlight the importance of careful choice of experimental protocol when studying these systems. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=161 SRC="FIGDIR/small/594465v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@68f505org.highwire.dtl.DTLVardef@ae3624org.highwire.dtl.DTLVardef@164a1f1org.highwire.dtl.DTLVardef@1c3f9d5_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2022

Incorporation of bioactive peptides into peptide nanofibrillar hydrogels affects their nanostructure, mechanical properties and biocompatibility

Self-assembling peptides are promising candidates as scaffolds for 3D cell cultures. These hydrogels offer favourable biocompatibility, nanofibrillar structures that mimic native tissues, and the convenient integration of bioactive peptide sequences, such as arginine-glycine-aspartic acid (RGD), which can enable the development of therapeutically valuable cell types. In the treatment of osteoarthritis (OA) attempts have been made to combine hydrogel scaffolds with mesenchymal stem cells (MSCs) to harness their regenerative potential. This involves the deposition of extracellular matrix (ECM) components like collagen and proteoglycans. Here, we employ the hydrogel-forming peptide Fmoc-diphenylalanine (Fmoc-FF) and incorporate stoichiometric amounts of Fmoc-RGD. We investigate the impact of RGD on nanofibrillar morphologies, hydrogel stability, MSC viability, and the deposition of collagen, proteoglycans, and glycosaminoglycans. Elevating RGD content enhances cell viability and collagen deposition. However, at higher RGD concentrations, the stability of the hydrogels is compromised. To characterise collagen deposition, we introduce a non-destructive and label-free method using a plasmon-enhanced colorimetric histology technique. This innovation provides a practical means to image collagen without resorting to intricate and destructive sample processing and complex immunohistological staining procedures. This simple approach holds broad potential for routine and label-free quantification of collagen-rich biomaterials, promising widespread applications across various research and clinical settings.

bioengineering↗

bioRxiv2022

E-cadherin in developing murine T cells controls spindle alignment and differentiation during β-selection

A critical stage of T cell development is {beta}-selection; at this stage the TCR{beta} chain is generated and the developing T cell starts to acquire antigenic specificity. Progression through {beta}-selection is assisted by a low affinity interaction between the nascent TCR{beta} chain and peptide presented on stromal MHC and external cues provided by the niche, including Notch and CXCR4. In this study, we reveal the importance of a new cue within the murine developing T cell niche which is critical for T cell development. E-cadherin mediates cell-cell interactions and influences cell fate in many developmental systems. In developing T cells E-cadherin contributed to the formation of an immunological synapse and the alignment of the mitotic spindle with the polarity axis during division, which facilitated subsequent T cell development. Collectively, these data highlight a new aspect of the developing T cell niche and provide insights into the role of E-cadherin in the {beta}-selection stage of T cell development.

cell biology↗

bioRxiv2021

Neurotoxic Amyloidogenic Peptides Identified in the Proteome of SARS-COV2: Potential Implications for Neurological Symptoms in COVID-19

COVID-19 is primarily known as a respiratory disease caused by the virus SARS-CoV-2. However, neurological symptoms such as memory loss, sensory confusion, cognitive and psychiatric issues, severe headaches, and even stroke are reported in as many as 30% of cases and can persist even after the infection is over (so-called long COVID). These neurological symptoms are thought to be caused by brain inflammation, triggered by the virus infecting the central nervous system of COVID-19 patients, however we still dont fully understand the mechanisms for these symptoms. The neurological effects of COVID-19 share many similarities to neurodegenerative diseases such as Alzheimers and Parkinsons in which the presence of cytotoxic protein-based amyloid aggregates is a common etiological feature. Following the hypothesis that some neurological symptoms of COVID-19 may also follow an amyloid etiology we performed a bioinformatic scan of the SARS-CoV-2 proteome, detecting peptide fragments that were predicted to be highly amyloidogenic. We selected two of these peptides and discovered that they do rapidly self-assemble into amyloid. Furthermore, these amyloid assemblies were shown to be highly toxic to a neuronal cell line. We introduce and support the idea that cytotoxic amyloid aggregates of SARS-CoV-2 proteins are causing some of the neurological symptoms commonly found in COVID-19 and contributing to long COVID, especially those symptoms which are novel to long COVID in contrast to other post-viral syndromes.

biochemistry↗

bioRxiv2021

Stepwise progression of β-selection during T cell development as revealed by histone deacetylation inhibition

During T cell development, the first step in creating a unique T Cell Receptor (TCR) is the genetic recombination of the TCR{beta} chain. The quality of the newly recombined TCR{beta} is assessed at the {beta}-selection checkpoint. Most cells fail this checkpoint and die, but the coordination of the complex events that control fate at the {beta}-selection checkpoint is not yet understood. We shed new light on fate determination during {beta}-selection using a selective inhibitor of histone deacetylase 6, ACY1215. ACY1215 disrupted the {beta}-selection checkpoint. Characterising the basis for this disruption revealed a new, pivotal stage in {beta}-selection, bookended by upregulation of the TCR co-receptors, CD28 and CD2 respectively. Within this DN3bPre stage, CD5 and Lef1 are upregulated to reflect pre-TCR signalling and their expression correlates with proliferation. During this phase, ACY1215-mediated disruption of the organisation of the {beta}-selection immunological synapse is associated with a breakdown in connectivity of expression of pre-TCR, CD5 and Lef1. Subsequent deregulation of pre-TCR-induced proliferation leads to bypass of the {beta}-selection checkpoint and subsequent failure to progress. We propose that the progressive expression of CD28, CD5 and Lef1, then CD2 reports and modulates the pre-TCR signal to orchestrate passage through the {beta}-selection checkpoint. These findings suggest a refined model of {beta}-selection in which a coordinated increase in expression of pre-TCR, CD28, CD5 and Lef1 allows for modulating TCR signalling strength, and culminates in the expression of CD2 to enable exit from the {beta}-selection checkpoint.

developmental biology↗

bioRxiv2019

Developing T cells form an immunological synapse for passage through the β-selection checkpoint

The {beta}-selection checkpoint of T cell development tests whether the cell has recombined its genomic DNA to produce a functional T Cell Receptor {beta} (TCR{beta}) receptor. Passage through the {beta}-selection checkpoint requires the nascent TCR{beta} protein to mediate signaling through a pre-TCR complex. In this study, we show that developing T cells at the {beta}-selection checkpoint establish an immunological synapse in in vitro & in situ, resembling that of the mature T cell. The immunological synapse is dependent on two key signaling pathways known to be critical for the transition beyond the {beta}-selection checkpoint, Notch and CXCR4 signaling. In vitro and in situ analyses indicate that the immunological synapse promotes passage through the {beta}-selection checkpoint. Collectively, these data indicate that developing T cells regulate pre-TCR signaling through the formation of an immunological synapse. This signaling platform integrates cues from Notch, CXCR4, and MHC on the thymic stromal cell, to allow transition beyond the {beta}-selection checkpoint.\n\nSummaryT cell development requires testing whether genomic rearrangement has produced a T cell receptor capable of transmitting signals. Most T cells fail this test. Here, we show that passage through the {beta}-selection checkpoint requires assembly of a platform to support TCR signaling.

immunology↗

bioRxiv2019

A new role for Notch in control of polarity and asymmetric cell division of developing T cells

A fundamental question in biology is how single cells can reliably produce progeny of different cell types. Notch signalling frequently facilitates fate determination. Asymmetric cell division (ACD) often controls segregation of Notch signalling by imposing unequal inheritance of regulators of Notch. Here, we assessed the functional relationship between Notch and ACD in mouse T cell development. To attain immunological specificity, developing T cells must pass through a pivotal stage termed {beta}-selection, which involves Notch signalling and ACD. We assessed functional interactions between Notch and ACD during {beta}-selection using direct presentation of Notch ligands, DL1 and DL4, and pharmacological inhibition of Notch signalling. Contrary to prevailing models, we find Notch controls distribution of Notch1 itself and cell fate determinants, -Adaptin and Numb. Notch and CXCR4 signalling cooperated to drive polarity during division. Thus, Notch signalling directly orchestrates ACD, and Notch1 is differentially inherited by sibling cells.

cell biology↗