Biology subjects

Jordan-Sciutto, K. L.

Publications and source records attributed to Jordan-Sciutto, K. L..

6 recordsLinked to original sources

bioRxiv2026

The lysosomal cation channel TRPML1 regulates the oligodendrocyte cytoskeleton

Differentiating oligodendrocytes undergo dramatic morphologic alterations to transition from progenitors to mature oligodendrocytes that synthesize myelin, the lipid-rich membrane coating axons which strengthens saltatory conduction and provides metabolic support. Actin dynamics, which are often regulated by membrane bound nucleators associated with organelles, underpin the morphologic shifts in oligodendrocyte maturation; however, the origin of such regulation during oligodendrocyte differentiation remains unknown. Here, we demonstrate that the lysosomal non-selective cation channel, transient potential mucolipin 1 (TRPML1), is a critical regulator of oligodendrocyte morphology during differentiation and initial myelination. Lysosomes move into oligodendrocyte processes during differentiation. While manipulation of TRPML1 did not change the expression of oligodendrocyte lineage markers, activation of TRPML1 resulted in altered oligodendrocyte morphology and an increase in actin filament content driven by the small GTPase Rac1 and subsequent disinhibition of PAK1 via phosphorylation. Actin associated changes in morphology are accompanied by the presence of lysosomal-derived calcium transients in nascent oligodendrocyte processes, potentially revealing a link between localized calcium signaling and actin polymerization. Lastly, adolescent mice (Mcoln1-/-), in which TRPML1 had been deleted, had significantly impaired myelination and decreased numbers of mature oligodendrocyte, which was associated with a reduction in staining for the phosphorylated form of the actin regulator, PAK1, in the motor cortex and corpus callosum as evidence of decreased TRPML1/Rac1/PAK1 signaling. Together, our work reveals lysosomal TRPML1 activity as a central regulator of oligodendrocyte morphology independent of myelin protein expression and may provide mechanistic insight into the distinct but coordinated pathways that lead to oligodendrocyte differentiation and how lysosomal dysfunction impacts these processes in diseased states.

neuroscience↗

bioRxiv2025

Neuroinflammatory crosstalk between microglia and astrocytes increases viral replication in an iPSC-derived model of CNS HIV infection

People living with HIV suffer multiple comorbid conditions related to chronic inflammation at increased rates compared to the general population, even when on effective antiretroviral therapy. In particular, current data indicate that the increased incidence and severity of neurocognitive impairment (NCI) are associated with unresolved neuroinflammation. Attempts to treat NCI in people living with HIV by reducing inflammation have thus far been unsuccessful, suggesting that a more mechanistic understanding of inflammatory processes in the CNS during HIV is necessary. Here, we use iPSC-derived microglia (iMg) and astrocytes (iAst) to model HIV infection in the CNS. We show that our iMg robustly express markers associated with microglial identity and are susceptible to HIV infection, but exhibit lower HIV replication rates and weaker immune response to HIV challenge compared to monocyte-derived macrophages. Coculture of iAst with iMg leads to a much stronger pro-inflammatory immune response, and, surprisingly, a robust increase in rates of HIV replication. Increased replication in iMg/iAst cocultures is associated with higher levels of multiple pro-inflammatory cytokines, including TNF, which is produced by iAst upon exposure to HIV-infected iMg. Addition of exogenous TNF to iMg during HIV infection is also sufficient to increase rates of replication, and neutralization of TNF via adalimumab/Humira treatment in iMg/iAst cocultures reduces replication. Blocking NF-kB signaling with iKK inhibitor Bay-11-7082 (Bay-11) demonstrates that increased HIV replication in iMg/iAst cocultures is due to increased NF-kB activity. Finally, we show that in HIV-infected iMg there is movement of lysosomes to the periphery of the cell membrane and release of lysosomal content into the extracellular space, suggesting that this dysregulated lysosomal flux could further contribute to the pro-inflammatory microenvironment. We propose that this altered lysosomal trafficking and increased cytokine production drives a pro-inflammatory phenotype in glia and represents a potential source of unresolved neuroinflammation in people living with HIV.

immunology↗

bioRxiv2022

Copper as a Novel Regulator of PERK

PERK is a kinase that, in response to ER stress, mediates duplicitous homeostatic and pro-apoptotic signaling. Thus, intricate regulation is required for physiologic function. Attempts to modulate PERK activity have shown that the determinants of adaptive vs. mal-adaptive signaling remain ambiguous. Here, with purified protein, we provide direct evidence that PERK binds copper, identify the residues that coordinate binding, and demonstrate that binding is necessary for kinase activity. Furthermore cellular PERK activity can be modulated via copper availability, and this regulatory relationship can be manipulated to dictate ER stress tolerance. Critically, these phenomenon translate to phenotypes in vivo, as C. elegans harboring a "copper-binding mutant" of PERK exhibit enhanced ER-stress sensitivity. The copper-PERK paradigm adds onto a new class of dynamic copper-binding enzymes and implicates that copper homeostasis, as a regulator of PERK, may constitute a previously unknown variable to resolve long-standing ambiguity in endeavors to therapeutically target PERK.

biochemistry↗

bioRxiv2022

Antiretroviral treatment reveals a novel role for lysosomes in oligodendrocyte maturation

White matter deficits are a common neuropathologic finding in neurologic disorders, including HIV-associated neurocognitive disorders (HAND). In HAND, the persistence of white matter alterations despite suppressive antiretroviral (ARV) therapy suggests that ARVs may be directly contributing to these impairments. Here, we report that a frontline ARV, bictegravir (BIC), significantly attenuates remyelination following cuprizone-mediated demyelination, a model that recapitulates acute demyelination, but has no impact on already formed mature myelin. Mechanistic studies in vitro revealed that treatment with BIC leads to significant decrease in mature oligodendrocytes accompanied by lysosomal de-acidification and impairment of lysosomal degradative capacity with no alterations in lysosomal membrane permeability or total lysosome number. Activation of the endolysosomal cation channel TRPML1 prevents both lysosomal de-acidification and impairment of oligodendrocyte differentiation by BIC. Lastly, we show that de-acidification of lysosomes by compounds that raise lysosomal pH is sufficient to prevent maturation of oligodendrocytes. Overall, this study has uncovered a critical role for lysosomal acidification in modulating oligodendrocyte function and has implications for neurologic diseases characterized by lysosomal dysfunction and white matter abnormalities. Table of ContentsO_ST_ABSMain PointsC_ST_ABSO_LIThe antiretroviral, bictegravir, inhibited remyelination through OPC differentiation blockade and had no effect on mature myelin C_LIO_LIBictegravir inhibits oligodendrocyte differentiation through de-acidification of lysosomes and this was prevented via activation of the lysosomal channel TRPML1 C_LIO_LIDe-acidification of lysosomes by other drugs (e.g. bafilomycin A) is sufficient to inhibit oligodendrocyte maturation C_LI Table of Contents Image O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC="FIGDIR/small/502855v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@12f4d8borg.highwire.dtl.DTLVardef@8be876org.highwire.dtl.DTLVardef@14ad1a0org.highwire.dtl.DTLVardef@108631d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

HIV antiretrovirals have differential effects on viability and function in human iPSC-derived neurons and neural precursor cells

Despite viral suppression due to combination antiretroviral therapy (cART), HIV-associated neurocognitive disorders (HAND) continue to affect half of people with HIV, suggesting that certain antiretrovirals (ARVs) may contribute to HAND. We examined the effects of nucleoside/nucleotide reverse transcriptase inhibitors tenofovir disproxil fumarate (TDF) and emtricitabine (FTC) and the integrase inhibitors dolutegravir (DTG) and elvitegravir (EVG) on viability, structure, and function of glutamatergic neurons (a subtype of CNS neuron involved in cognition) derived from human induced pluripotent stem cells (hiPSC-neurons), and primary human neural precursor cells (hNPCs), which are responsible for neurogenesis. Using automated digital microscopy and image analysis (high content analysis, HCA), we found that DTG, EVG, and TDF decreased hiPSC-neuron viability, neurites, and synapses after seven days of treatment. Analysis of hiPSC-neuron calcium activity using Kinetic Image Cytometry (KIC) demonstrated that DTG and EVG also decreased the frequency and magnitude of intracellular calcium transients. Longer ARV exposures and simultaneous exposure to multiple ARVs increased the magnitude of these neurotoxic effects. Using the Microscopic Imaging of Epigenetic Landscapes (MIEL) assay, we found that TDF decreased hNPC viability and changed the distribution of histone modifications that regulate chromatin packing, suggesting that TDF may reduce neuroprogenitor pools important for CNS development and maintenance of cognition in adults. This study establishes human preclinical assays that can screen potential ARVs for CNS toxicity to develop safer cART regimens and HAND therapeutics.

neuroscience↗

bioRxiv2019

Neuroinflammation and EIF2 signaling persist in an HiPSC tri-culture model of HIV infection despite antiretroviral treatment

HIV-Associated Neurocognitive Disorders (HAND) affect over half of HIV-infected individuals worldwide, despite antiretroviral therapy (ART). Therapeutically targetable mechanisms underlying HAND remain elusive. We developed a human-induced pluripotent stem cell (HiPSC) based model; whereby, we independently differentiate HiPSCs into neurons, astrocytes, and microglia and systematically combine to generate a tri-culture with or without HIV-infection and ART. scRNAseq analysis on tri-cultures including HIV-infected microglia revealed inflammatory signatures in the microglia and EIF2 signaling in all three cell types. Remarkably, EFZ alone induced a similar response to infection. Treatment with the antiretroviral compound Efavirenz (EFZ) mostly resolved these signatures; However, EFZ increased RhoGDI and CD40 signaling in the HIV-infected microglia. This activation was associated with a persistent increase in TNFa expression. This work establishes a tri-culture that recapitulates key features of HIV infection in the CNS and provides a new model to examine the effects of HIV infection and its treatment with antiretrovirals.

pathology↗