Biology subjects

Dragon, J. A.

Publications and source records attributed to Dragon, J. A..

5 recordsLinked to original sources

bioRxiv2026

Giant spider neurons uncover a myelin-derived waste-internalizing canal system that fails in neurodegeneration

The underlying causes for Alzheimer disease are presumed to lie in failed waste removal from the brain. However, the mechanisms by which waste is cleared from neurons, and how this system fails in neurodegeneration are poorly understood. A novel glial-canal-hypothesis postulates that myelin-forming macroglia give rise to waste internalizing canals that project into neuronal somata and remove cellular debris in an aquaporin4-dependent manner. We postulate that abnormal swelling of the aquaporin4-expressing glial cells leads to spongiform abnormalities, gradual depletion, and death of associated neurons. Due to the novelty of this postulation little is known about the cellular architecture of this canal system that was first discovered in giant neurons of the wandering spider Cupiennius salei. Here we have utilized histological, ultrastructural and immunohistochemical methods to describe the structural foundation of this glial canal system in giant spider neurons in which waste-internalizing canals and associated structures are clearly visible. Sequencing the spider genome, we show compelling homologies of key proteins that are implicated in neurodegeneration between phylogenetically distant species. Based on this work, we provide a testable functional hypothesis regarding waste removal from neuronal somata and how this system fails in neurodegeneration. We highlight structural similarities of this system in rodent and human brain. Supported by the findings presented here we postulate that (i) neurodegeneration in C. salei may be caused by hypertrophic swelling of myelin-forming waste-internalizing macroglia, and (ii) that a similar canal system, although structurally modified, is likely highly conserved in the mammalian brain.

neuroscience↗

bioRxiv2022

The Fatty Acid Binding Protein Family Represents a Novel Target in Multiple Myeloma

BackgroundMultiple myeloma is an incurable plasma cell malignancy with only a 53% 5-year survival rate, highlighting a critical need for new multiple myeloma vulnerabilities and therapeutic avenues. Herein, we explored a novel multiple myeloma target: the fatty acid binding protein (FABP) family. MethodsMyeloma cells treated with FABP inhibitors (BMS3094013 and SBFI-26) were examined in vivo and in vitro for cell cycle, proliferation, apoptosis, mitochondrial membrane potential, cellular metabolism (oxygen consumption rates and fatty acid oxidation), and DNA methylation. Myeloma cell responses to BMS309403 and/or SBFI-26 were assessed with RNA-sequencing and proteomic analysis, and confirmed with western blotting and qRT-PCR. Myeloma cell dependency on FABPs was assessed using DepMap. Finally, MM patient datasets (CoMMpass and GEO) were mined for FABP expression correlations with clinical outcomes. ResultsMyeloma cells treated with FABPi or with FABP5 knockout (generated via CRISPR/Cas9 editing) exhibited diminished proliferation in vitro. FABPi had potent anti- tumor effects both in vitro and in vivo in two pre-clinical MM mouse models where increased mouse survival was observed. FABPi negatively impacted mitochondrial respiration and reduced expression of MYC and other key signaling pathways in MM cells. Clinical data demonstrated worse overall and progression-free survival in patients with high FABP5. ConclusionsThis study establishes the FABP family as a therapeutically actionable dependency in multiple myeloma with a multitude of actions and cellular roles that result in the support of myeloma progression. Statement of translational relevanceMultiple myeloma (MM) is an incurable disease of the plasma cell and MM patients require better treatments as soon as possible. The fatty acid binding protein (FABP) family plays a number of roles in cells, including supporting fatty acid oxidation, lipid shuttling and signal transduction. Here, we demonstrate with CoMMpass and other clinical data that FABPs represent a biomarker for aggressive disease in MM, and are a novel, targetable protein family expressed by myeloma cells. Pharmacologically inhibiting FABPs kills tumor cells and induces cell cycle arrest in vitro and in pre-clinical models. Mechanisms of action are multitudinous, as we discovered with RNA-sequencing, proteomic analysis, and phenotyping assays. Cell metabolism, cell signaling, cell stress, and epigenetic signatures were altered in MM cells when FABPs were inhibited. In summary, targeting FABP5 holds great therapeutic potential for killing diseased cells, with few negative off-target effects on healthy cells.

cancer biology↗

bioRxiv2021

Caught in Motion: Human NTHL1 Undergoes Interdomain Rearrangement Necessary for Catalysis

Base excision repair (BER) is the main pathway protecting cells from the continuous damage to DNA inflicted by reactive oxygen species. BER is initiated by DNA glycosylases, each of which repairs a particular class of base damage. NTHL1, a bifunctional DNA glycosylase, possesses both glycolytic and {beta}-lytic activities with a preference for oxidized pyrimidine substrates. Defects in human NTLH1 drive a class of polyposis colorectal cancer. We report the first X-ray crystal structure of hNTHL1, revealing an open conformation not previously observed in the bacterial orthologs. In this conformation, the six-helical barrel domain comprising the helix-hairpin-helix (HhH) DNA binding motif is tipped away from the iron sulphur cluster-containing domain, requiring a conformational change to assemble a catalytic site upon DNA binding. We found that the flexibility of hNTHL1 and its ability to adopt an open configuration can be attributed to an interdomain linker. Swapping the human linker sequence for that of Escherichia coli yielded a protein chimera that crystallized in a closed conformation and had a lower binding affinity for lesion-containing DNA. This large scale interdomain rearrangement during catalysis is unprecedented for a HhH superfamily DNA glycosylase and provides important insight into the molecular mechanism of hNTHL1.

biochemistry↗

bioRxiv2020

Unique structural features of mammalian NEIL2 DNA glycosylase prime its activity for diverse DNA substrates and environments

Oxidative damage on DNA arising from both endogenous and exogenous sources can result in base modifications that promote errors in replication as well as generate sites of base loss (abasic sites) that present unique challenges to maintaining genomic integrity. These lesions are excised by DNA glycosylases in the first step of the base excision repair pathway. Here we present the first crystal structure of a NEIL2 glycosylase, an enzyme active on cytosine oxidation products and abasic sites. The structure reveals an unusual "open" conformation not seen in NEIL1 or NEIL3 orthologs. NEIL2 is predicted to adopt a "closed" conformation when bound to its substrate. Combined crystallographic and solution scattering studies show the enzyme to be conformationally dynamic in a manner distinct among the NEIL glycosylases and provide insight into the unique substrate preference of the enzyme. Additionally, we characterized three cancer variants of human NEIL2, namely S140N, G230W, and G303R.

biochemistry↗

bioRxiv2019

Critical role for Slam/SAP signaling in the thymic developmental programming of IL-17- and IFN-γ-producing γδ T cells

During thymic development, {gamma}{delta} T cells commit to either an IFN-{gamma}- or an IL-17-producing phenotype through mechanisms that remain unclear. Here, we investigated whether the SLAM/SAP signaling pathway played a role in the functional programming of thymic {gamma}{delta} T cells. Characterization of SLAM family receptor expression revealed that thymic {gamma}{delta} T cell subsets were each marked by distinct co-expression profiles of SLAMF1, SLAMF4, and SLAMF6. In the thymus, immature CD24hi V{gamma}1 and V{gamma}4 {gamma}{delta} T cells were largely contained within a SLAMF1+SLAMF6+ double positive (DP) population, while mature CD24low subsets were either SLAMF1+ or SLAMF6+ single positive (SP) cells. In the periphery, SLAMF1 and SLAMF6 expression on V{gamma}1, V{gamma}4, and V{gamma}6 T cells distinguished IL-17- and IFN-{gamma}-producing subsets, respectively. Disruption of SLAM family receptor signaling through deletion of SAP resulted in impaired thymic {gamma}{delta} T cell maturation at the CD24hiSLAMF1+SLAMF6+ DP stage that was associated with a decreased frequency of CD44+ROR{gamma}t+ {gamma}{delta} T cells. These defects were in turn associated with impaired {gamma}{delta} T cell IL-17 and IFN-{gamma} production in both the thymus as well as in peripheral tissues. The role for SAP was subset-specific, as V{gamma}1, V{gamma}4, V{gamma}5, but not V{gamma}6 subsets were SAP-dependent. Together, these data suggest that the SLAM/SAP signaling pathway regulates a critical checkpoint in the functional programming of IL-17 and IFN-{gamma}-producing {gamma}{delta} T cell subsets during thymic development.

immunology↗