Biology subjects

Datta, R.

Publications and source records attributed to Datta, R..

At least 19 recordsLinked to original sources

bioRxiv2026

Functional characterization of a cytosolic malic enzyme crucial for pyridine nucleotide homeostasis, redox balance, and virulence in Leishmania major

Malic enzymes (MEs) occupy a central node in metabolism, by catalyzing the reversible oxidative decarboxylation of malate to pyruvate, thereby contributing to maintenance of NADPH homeostasis. Leishmania spp. are known to encode two ME isoforms, however only one from Leishmania major has been functionally characterised till date to be a mitochondrial enzyme, playing critical role in gluconeogenesis. Here, we cloned and functionally characterized the second isoform, LmME2. Colocalization and subcellular fractionation analysis established that LmME2 localizes to the cytosol. Kinetic analyses of purified LmME2 revealed comparable rates of malate decarboxylation and pyruvate carboxylation, however, pyruvate carboxylation predominated in parasite cell lysates, indicating that the directionality of the reaction is metabolically regulated in cellular environment. Consistent with this, we identified oxaloacetate, ATP and fumarate as allosteric modulators of LmME2 activity. To dissect its physiological role, we generated CRISPR-Cas9-mediated LmME2 knockout parasites (LmME2-/-). Interestingly, LmME2 deletion did not alter NADPH levels but depleted both NADP+ and NAD+ pools, with reduction in NAD+ being more pronounced. This disruption of pyridine nucleotide homeostasis resulted in elevated intracellular ROS levels. Furthermore, inhibition of the pentose phosphate pathway, the alternative cytosolic source of NADPH, severely impaired the growth of LmME2-/- strain, highlighting the role of LmME2 in maintaining parasite fitness. These metabolic defects translated into markedly diminished intracellular survival of LmME2-/- parasites and its attenuated virulence in mice. Collectively, our findings identify LmME2 as the first functionally characterized cytosolic malic enzyme in Leishmania and establish it as a redox-associated virulence factor. These results further highlight LmME2 as a promising antileishmanial drug target.

cell biology↗

bioRxiv2026

Leishmania major targets macrophage Syntaxin-2 to impair phagolysosome biogenesis and promote intracellular survival

Macrophages destroy pathogens by engulfing them into phagosomes that mature into degradative phagolysosomes via lysosome fusion. Leishmania parasites subvert this antimicrobial pathway to establish intracellular infection and cause leishmaniasis. We previously identified the SNARE protein syntaxin-2 (Stx2) as a promoter of phagolysosome biogenesis that simultaneously limits particle binding and uptake. Consistent with this dual role, Stx2-depleted macrophages (Stx2-KD) show enhanced binding and internalization of Leishmania major. Stx2-KD macrophages also sustain higher intracellular parasite loads. We find that L. major actively targets macrophage Stx2 by selectively depleting Stx2 from phagosomes through its virulence metalloprotease GP63. Phagosomes containing GP63-deficient L. major retain Stx2 and acquire increased levels of lysosomal hydrolases and v-ATPase, restoring degradative capacity. In BALB/c mice, L. major infection markedly reduces Stx2 in infected tissues in a GP63-dependent manner. Collectively, our findings identify GP63-mediated Stx2 depletion as a key virulence strategy of L. major, positioning the GP63-Stx2 axis as a promising therapeutic target for leishmaniasis.

Cell Biology↗

bioRxiv2026

Single-Nuclei Transcriptomic Characterization of APOE4-Associated Alzheimer's Disease

Apolipoprotein E (APOE) genotype contributes significantly to Alzheimers disease (AD) risk and pathogenesis. Cell-type specific effects of APOE alleles have been studied. However, due to the variable prevalence of APOE genotypes within human populations, characterization of cell-type specific transcriptomes across APOE genotypes has been challenging. Here, we integrated previous and newly generated single-nuclei sequencing (snRNA-seq) data in the prefrontal cortex (PFC) from individuals across APOE genotypes (2/2, 2/3, 3/3, 3/4, 4/4). Clustering analysis revealed distinct excitatory and microglial subpopulations that were uniquely enriched or depleted for APOE4/4 AD. Notably, an excitatory neuronal cluster exhibited neurofibrillary tangle (NFT) signatures and was selectively depleted in APOE4/4 AD cases. In addition, several microglial subpopulations were influenced by both APOE4 dosage and disease status. Among these, the putative AD risk gene FRMD4A emerged as APOE4 dose and AD-dependent. These findings were validated by RNAscope in an extended cohort. Together, our findings provide insights into how APOE4 reshapes cellular states and contributes to cell-type-specific vulnerability in AD.

neuroscience↗

bioRxiv2025

Trehalose-mediated activation of Mitf corrects autophagy defects and ameliorates neurodegeneration in MPS VII

Mucopolysaccharidosis type VII (MPS VII) is a progressive lysosomal storage disorder caused by {beta}-glucuronidase ({beta}-GUS) deficiency, featuring pronounced neurodegeneration. The Drosophila model of MPS VII, generated by deleting the fly {beta}-GUS ortholog CG2135, exhibits hallmark neuropathological features, including dopaminergic neuron loss, brain vacuolisation, and impaired locomotor performance. Using this CG2135-/- fly, we recently showed that impaired autophagosome formation and their turnover led to abnormal accumulation of damaged mitochondria and lipofuscins in the brain. In this study, we investigated the molecular basis of this autophagy defect and found that Mitf (the TFEB homolog), the transcriptional regulator of autophagy, is markedly downregulated in CG2135-/- fly brains, accompanied by reduced expression of its target genes, including LAMP1, CLN3, and v-ATPase subunits. Guided by these observations, we assessed whether boosting Mitf activity could ameliorate neuropathology. Interestingly, oral trehalose treatment reactivated Mitf and its downstream autophagy gene network in CG2135-/- fly brains, restoring autophagosome biogenesis, reducing lipofuscin accumulation, and alleviating apoptosis. Trehalose treatment also improved locomotor performance, indicating a clear mitigation of neurodegeneration. These findings demonstrate that Mitf dysregulation drives autophagy impairment in MPS VII fly brain and highlight Mitf activation as a promising therapeutic strategy to alleviate neurological pathology.

cell biology↗

bioRxiv2025

Muscle Energy Crisis is the Initial Driver of Locomotor Dysfunction in β-glucuronidase-Deficient Drosophila

Mucopolysaccharidosis type VII (MPS VII) is characterised by progressive locomotor decline, attributed to musculoskeletal and neurological defects. However, the severity varies according to the extent of {beta}-glucuronidase ({beta}-GUS) deficiency, with musculoskeletal deformities typically preceding neurological manifestations. To investigate the underlying cause of neuromuscular pathology, we employed {beta}-GUS-deficient Drosophila models. In Drosophila, {beta}-GUS is encoded by two genes, CG2135 and CG15117. Previously generated CG2135-/- flies recapitulated several hallmark features of MPS VII, despite retaining approximately 30% residual {beta}-GUS activity contributed by CG15117. To assess the consequences of complete loss of {beta}-GUS, we now generated CG15117-/- flies using CRISPR/Cas9 and subsequently established CG15117-/-;CG2135-/- double knockout (DKO) flies. Phenotypic assessment revealed differences in susceptibility to starvation, lifespan, and locomotor function, with DKO flies exhibiting more severe impairments than either single knockout flies. Notably, CG15117-/- did not show any significant defect in lifespan or locomotion, except under starvation conditions. Consistent with our earlier finding in CG2135-/- fly brains, ATP depletion in DKO fly brains became evident only after 45 days of age, failing to explain the locomotory defects observed in earlier ages. Interestingly, analysis of muscles of 30-day-old CG2135-/- and DKO flies revealed abnormal mitochondrial accumulation with autophagy defect and severe ATP depletion. Consequently, these defects led to locomotor impairment driven by apoptotic muscle degeneration. Collectively, this work provides the first evidence of tissue-specific vulnerability in MPS VII models, identifying muscle as an early pathological target and offering new insights into disease progression.

cell biology↗

bioRxiv2025

FLIM Playground: An interactive, end-to-end graphical user interface for analyzing single-cell fluorescence lifetime data

Fluorescence lifetime imaging microscopy (FLIM) is a cellular-resolution molecular imaging technique. Yet, the journey from raw photon decays to biological insight remains fragmented by multi-step data extraction and siloed analyses. This work presents FLIM Playground, the first interactive graphical platform that unifies single-cell FLIM workflows, embeds user checks at each stage, and offers diverse user options. Built in Python and available open-source, FLIM Playground runs on major operating systems as a ready-to-run application and is web deployable. Its Data Extraction section collects and checks field-of-view metadata, calibrates via instrument response function shift or fluorescence lifetime standard, and extracts single-cell fluorescence lifetime features, along with morphology and texture features across channels. Multiple datasets can be merged through an interface that assigns categorical labels. The Data Analysis section provides real-time visual analytic modules for outputs from Data Extraction or user-provided datasets. Lifetime extraction by fitting and phasor were validated by comparison with a commercial software and published results, respectively, and both sections were demonstrated on a FLIM dataset of cancer cell lines to obtain biological insights. By adopting best practices and offering interactivity, FLIM Playground accelerates hypothesis-driven discovery and promotes reproducibility, and its modular design can incorporate new imaging modalities, extraction methods, and analysis modules.

bioengineering↗

bioRxiv2025

Segmentation-guided photon pooling enables robust single cell analysis and fast fluorescence lifetime imaging microscopy

Fluorescence lifetime imaging microscopy (FLIM) can probe the metabolic environment of living cells in a label-free and non-invasive manner. However, endogenous fluorophores have low absorption and quantum yields, which necessitates long integration times to acquire the high photon counts needed for accurate pixel-wise multi-exponential decay fitting. Here, we present a region-of-interest photon pooling technique to expedite label-free, single cell FLIM acquisition and analysis. As a result, we achieved single-cell metabolic information at intervals as low as one second and acquired large FLIM mosaics 15 times faster than would be possible with conventional pixel-level analysis. This technique is computationally light, does not require machine learning algorithms, and has been integrated with commonly used analysis software and file types.

cell biology↗

bioRxiv2025

Identification of a novel bicarbonate transporter critical for Leishmania virulence

Leishmania parasites survive and proliferate within the acidic phagolysosomes of host macrophages while maintaining a near-neutral cytosolic pH, a process essential for intracellular survival and virulence. Although our prior work implicated a bicarbonate-based buffering mechanism, the absence of any annotated bicarbonate transporter in the parasite genome has hindered its identification. Using an isotope ratio mass spectrometry-based assay, we first confirmed the presence of a functional bicarbonate transport system in the parasite. Guided by this, a noncanonical homology search identified an uncharacterized protein, hereafter designated LmSLC26A, with similarity to metazoan SLC26 family of multi-anion transporters. LmSLC26A localized to the parasite plasma membrane and, under acidic conditions, was found to associate with the membrane carbonic anhydrase LmCA2. Disruption of a single LmSLC26A allele significantly reduced bicarbonate uptake, leading to intracellular acidification that was reversible upon exogenous bicarbonate supplementation. LmSLC26A-deficient parasites exhibited sluggish growth, increased apoptosis, reduced production of virulence associated cAMP and impaired exosome release. Consequently, these mutant parasites showed diminished survival within host macrophages and markedly attenuated virulence in mice. Intriguingly, LmSLC26A harbours a unique histidine ecto-phosphatase domain, revealing an unprecedented functional coupling between bicarbonate transport and enzymatic activity. Together, these findings establish LmSLC26A as the first identified bicarbonate transporter not only in Leishmania but also across the broader trypanosomatid and protozoan lineages, and define bicarbonate transport as a critical determinant of pH homeostasis and pathogenicity in the parasite. Significance StatementLeishmania parasites proliferate within the acidic phagolysosomes of host macrophages, yet the mechanism by which they maintain intracellular pH homeostasis has remained incompletely understood. Here, we identify LmSLC26A as the first bicarbonate transporter discovered in Leishmania and, more broadly, in protozoan parasites and demonstrate its essential role in bicarbonate uptake and maintenance of cytosolic pH homeostasis. LmSLC26A-deficient parasites exhibited impaired growth, increased apoptosis, reduced virulence-associated cAMP production and exosome release, resulting in compromised intracellular survival and attenuated virulence in mice. Intriguingly, LmSLC26A harbours a unique histidine ecto-phosphatase domain, revealing a previously unrecognized functional coupling between bicarbonate transport and enzymatic activity. Collectively, these findings establish LmSLC26A as a central regulator of parasite physiology and virulence.

cell biology↗

bioRxiv2025

Leishmania secretory factor GP63 targets the DICER1/miR-122/hepcidin axis in host macrophages to deplete Nramp1

Micronutrient sequestration is a powerful host defence mechanism against intracellular pathogens. Central to this is the iron transporter Nramp1, which actively effluxes iron from phagolysosomes, depriving the engulfed pathogens of this essential element. Leishmania have evolved a clever strategy to counteract this by triggering hepcidin-mediated proteasomal degradation of Nramp1. Interestingly, treatment with Leishmania major conditioned media induced hepcidin upregulation and Nramp1 degradation even in uninfected macrophages, with simultaneous increase in endo/lysosomal iron content. This suggested the involvement of a parasite-derived secretory factor, ultimately leading to the identification of the metalloprotease GP63 as the effector responsible for Nramp1 degradation. Conditioned medium from the GP63 knockout strain (LmGP63-/-) failed to upregulate hepcidin expression or promote Nramp1 degradation. Further, we show that GP63 depletes DICER1 in macrophages, blocking maturation of miR-122, a known negative regulator of hepcidin. These in vitro findings were validated in a mouse model, where the wild type L. major, but not the LmGP63-/- strain, could deplete DICER1, induce hepcidin expression and reduce Nramp1 levels in the infected tissue. Collectively, we uncover a novel role for Leishmania GP63 in targeting the DICER1/miR-122 axis in host macrophages to trigger hepcidin expression and Nramp1 degradation, thereby facilitating iron acquisition by the parasite.

cell biology↗

bioRxiv2025

Mitochondrial metabolism is rapidly re-activated in mature neutrophils to support stimulation-induced response

Neutrophils are highly abundant innate immune cells that are constantly produced from myeloid progenitors in the bone marrow. Differentiated neutrophils can perform an arsenal of effector functions critical for host defense. This study aims to quantitatively understand neutrophil mitochondrial metabolism throughout differentiation and activation, and to elucidate the impact of mitochondrial metabolism on neutrophil functions. To study metabolic remodeling throughout neutrophil differentiation, murine ER-Hoxb8 myeloid progenitor-derived neutrophils and human induced pluripotent stem cell-derived neutrophils were assessed as models. To study the metabolic remodeling upon neutrophil activation, differentiated ER-Hoxb8 neutrophils and primary human neutrophils were activated with various stimuli, including ionomycin, MSU crystals, and PMA. Characterization of cellular metabolism by isotopic tracing, extracellular flux analysis, metabolomics, and fluorescence-lifetime imaging microscopy revealed dynamic changes in mitochondrial metabolism. As neutrophils mature, mitochondrial metabolism decreases drastically, energy production is fully offloaded from oxidative phosphorylation, and glucose oxidation through TCA cycle is substantially reduced. Nonetheless, mature neutrophils retain the capacity for mitochondrial metabolism. Upon stimulation with certain stimuli, TCA cycle is rapidly activated. Mitochondrial pyruvate carrier inhibitors reduce this re-activation of the TCA cycle and inhibit the release of neutrophil extracellular traps. Mitochondrial metabolism also impacts neutrophil redox status, migration, and apoptosis without significantly changing overall bioenergetics. Together, these results demonstrate that mitochondrial metabolism is dynamically remodeled and plays a significant role in neutrophil function and fate. Furthermore, these findings point to the therapeutic potential of mitochondrial pyruvate carrier inhibitors in a range of conditions where dysregulated neutrophil response drives inflammation and contributes to pathology.

immunology↗

bioRxiv2025

Positive allosteric modulation of emodepside sensitive Brugia malayi SLO-1F and Onchocerca volvulus SLO-1A potassium channels by GoSlo-SR-5-69

Human lymphatic filariasis and onchocerciasis are Neglected Tropical Diseases (NTDs), of major public health concern. Prophylaxis and treatment rely on anthelmintics that effectively eliminate migrating microfilariae but lack efficacy against adult filarial worms. To expedite the elimination of both diseases, the introduction of drugs with adulticidal activity is paramount. The broad-spectrum anthelmintic emodepside, a nematode selective SLO-1 K channel activator, has been considered a promising candidate for the treatment of onchocerciasis due to its macrofilaricidal activity against Onchocerca volvulus. Nevertheless, it is less effective against adult Brugia malayi, one of the causative agents of human lymphatic filariasis. Characterizing molecular and pharmacological disparities between highly conserved splice variant isoforms of B. malayi and O. volvulus SLO-1 K channels and identifying allosteric modulators that can increase emodepside potency on B. malayi SLO-1 K channels is necessary for therapeutic advance. In this study, we tested the effects of emodepside and the mammalian BK channel activator, GoSlo-SR-5-69 alone and in combination on Xenopus expressed B. malayi SLO-1F and O. volvulus SLO-1A channels. Additionally, binding poses of emodepside, and GoSlo-SR-5-69 were predicted on both channels using molecular docking. Ovo-SLO-1A was more sensitive to emodepside than Bma-SLO-1F. GoSlo-SR- 5-69 was a positive allosteric modulator, potentiating the effects of emodepside. Emodepside was docked at the S6 pocket below the selectivity filter for Bma-SLO-1F and Ovo-SLO-1A. The binding of emodepside in the S6 pocket indicated a stabilizing{pi} -{pi} interaction between F342 and the phenyl rings of emodepside which may contribute to the potency of emodepside on these filaria channels. Molecular docking suggested that GoSlo-SR-5-69 binds at the RCK1 pocket. This study reveals for the first time, allosteric modulation of filarial nematode SLO-1 K channels by a mammalian BK channel activator and highlights its ability to increase emodepside potency on the B. malayi SLO-1 K channel. Author SummaryB. malayi is one of the causative agents of lymphatic filariasis, while O. volvulus causes onchocerciasis. Elimination of adult B. malayi and O. volvulus is impeded by anthelmintics lacking adequate macrofilaricidal activity. The anthelmintic emodepside has microfilaricidal and macrofilaricidal activity. However, it exhibits poor efficacy against adult B. malayi in vivo. Here, we conducted a comparative pharmacological characterization of two closely related splice variants SLO-1 K channels of B. malayi and O. volvulus. Using voltage clamp, we tested the effects of emodepside and GoSlo-SR-5-69 independently and in combination on Xenopus expressed B. malayi SLO-1F and O. volvulus SLO-1A channels. Binding poses of emodepside, and GoSlo-SR-5-69 were predicted on both channels using molecular docking. We demonstrate that the O. volvulus SLO-1A receptor is more sensitive to emodepside than the B. malayi SLO-1F receptor. GoSlo-SR-5-69 is also a potentiator of emodepside responses. Homology modelling revealed that emodepside probably binds in the pore region of the B. malayi SLO-1F and O. volvulus SLO-1A channels, while GoSlo-SR-5-69 probably binds to the RCK1 domain of the channels. Our study provides new insights into similarities and differences shared between SLO-1 K channels of each species and reveals positive allosteric modulation by a mammalian SLO-1 K activator.

pathology↗

bioRxiv2024

Epithelium Stratifies via Nucleation and Growth Induced by Foam-Geometric Instability

The epithelium undergoes stratification, transitioning from a monolayer to a multilayer structure, across broad phenomena. Recent studies have identified several cell behaviors as triggers, including junctional tension, cell density and geometry, and topological defects. However, how these factors drive stratification throughout the entire epithelium remains poorly understood. Here, we report a mechanism underlying epithelial stratification that mirrors the physics of phase transition. Combining cell culture with three-dimensional vertex modeling, we demonstrate that epithelial stratification is analogous to a structural phase transition driven by the nucleation-growth process, i.e., multilayer origins dispersedly appear and expand across the epithelium via unordered intermediate states. This transition is induced by a mechanical instability inherent in the foam-like geometry of the epithelium. Moreover, the nucleation-growth concept applies to embryonic skin development and intestinal cancer transformation. These findings conceptualize epithelial stratification as a form of a phase transition governed by foam mechanics, offering a physical perspective on various epithelial developments.

biophysics↗

bioRxiv2024

In vivo changes in zebrafish anesthetic sensitivity in response to the loss of kif5Aa are associated with the alteration of mitochondrial motility

Anesthetic and sedative drugs are small compounds known to bind to hundreds of proteins. One intriguing binding partner of propofol is the kinesin motor domain, kif5A, a neuronal mitochondrial transport protein. Here, we used zebrafish WT and kif5Aa KO larval behavioral assays to assess anesthetic sensitivity and combined that with zebrafish primary neuronal cell culture to probe for alteration in mitochondrial motility. We found that the loss of kif5Aa increases behavioral sensitivity to propofol and etomidate, with etomidate hypersensitivity greater than propofol. In contrast, kif5Aa KO animals were resistant to the behavioral effects of dexmedetomidine. Finally, WT and kif5Aa KO larvae responded similarly to the behavioral effects of ketamine. Propofol inhibited the anterograde motility of mitochondria in WT zebrafish neurons, while etomidate inhibited mitochondrial motility in both anterograde and retrograde directions; neither drug altered mitochondrial motility in the kif5Aa knockout (KO) neurons. In contrast, dexmedetomidine enhanced retrograde mitochondrial motility in both WT and kif5Aa KO animals. Finally, ketamine had little significant effect on mitochondrial motility in either mutant or WT animals. These data demonstrate that each anesthetic/sedative drug affects the motor protein machinery uniquely and is associated with unique changes in behavior. Understanding how different anesthetic compounds alter neuron motor proteins will be important in defining how anesthetics alter neuronal signaling and energetic dynamics.

neuroscience↗

bioRxiv2024

GATA1-deficient human pluripotent stem cells generate neutrophils with improved antifungal immunity that is mediated by the integrin CD18

Neutrophils are critical for host defense against fungi. However, the short life span and lack of genetic tractability of primary human neutrophils has limited in vitro analysis of neutrophil-fungal interactions. Human induced pluripotent stem cell (iPSC)-derived neutrophils (iNeutrophils) are a genetically tractable alternative to primary human neutrophils. Here, we show that deletion of the transcription factor GATA1 from human iPSCs results in iNeutrophils with improved antifungal activity against Aspergillus fumigatus. GATA1 knockout (KO) iNeutrophils have increased maturation, antifungal pattern recognition receptor expression and more readily execute neutrophil effector functions compared to wild-type iNeutrophils. iNeutrophils also show a shift in their metabolism following stimulation with fungal {beta}-glucan, including an upregulation of the pentose phosphate pathway (PPP), similar to primary human neutrophils in vitro. Furthermore, we show that deletion of the integrin CD18 attenuates the ability of GATA1-KO iNeutrophils to kill A. fumigatus but is not necessary for the upregulation of PPP. Collectively, these findings support iNeutrophils as a robust system to study human neutrophil antifungal immunity and has identified specific roles for CD18 in the defense response. Author SummaryNeutrophils are important first responders to fungal infections, and understanding their antifungal functions is essential to better elucidating disease dynamics. Primary human neutrophils are short lived and do not permit genetic manipulation, limiting their use to study neutrophil-fungal interactions in vitro. Human induced pluripotent stem cell (iPSC)-derived neutrophils (iNeutrophils) are a genetically tractable alternative to primary human neutrophils for in vitro analyses. In this report we show that GATA1-deficient iPSCs generate neutrophils (iNeutrophils) that are more mature than wild-type iNeutrophils and display increased antifungal activity against the human fungal pathogen Aspergillus fumigatus. We also show that GATA1-deficient iNeutrophils have increased expression of antifungal receptors than wild-type cells and shift their metabolism and execute neutrophil antifungal functions at levels comparable to primary human neutrophils. Deletion of the integrin CD18 blocks the ability of GATA1-deficient iNeutrophils to kill and control the growth of A. fumigatus, demonstrating an important role for this integrin in iNeutrophil antifungal activity. Collectively, these findings support the use of iNeutrophils as a model to study neutrophil antifungal immunity.

microbiology↗

bioRxiv2024

Identification of a novel basal body-localized epsilon-tubulin in Leishmania

Epsilon-tubulins are unconventional isoforms of the tubulin family, found in only a few organisms so far. We identified a novel epsilon-tubulin in Leishmania major (Lme-tubulin) that exhibits significant sequence similarity and conservation of functional domains with its known counterparts. Lme-tubulin was found to be constitutively expressed in both the extracellular promastigote form of the parasite and the amastigotes residing within infected macrophages. For localization studies, we generated a Leishmania strain expressing mNeonGreen-tagged Lme-tubulin using CRISPR-Cas9-mediated endogenous protein tagging method. Imaging studies with this strain revealed Lme-tubulin to be localized near the kinetoplast and at the flagellar base, indicating a basal body localization. That Lme-tubulin is indeed localized at the basal body and not a part of the microtubular network was confirmed when its localization was found to remain unaltered upon treatment with nocodazole, a microtubule disruptor. This is the first experimental finding of an e-tubulin not only in the genus Leishmania but in the entire Trypanosomatidae family and is likely to incite further research to uncover the physiological role of this intriguing tubulin in this group of protozoan parasites. Summary StatementWe report for the first time an epsilon-tubulin in Leishmania parasite. This nocodazole-insensitive unconventional tubulin is expressed constitutively and found to be localized in the basal body.

cell biology↗

bioRxiv2024

Unravelling a mechanistic link between mitophagy defect, mitochondrial malfunction, and apoptotic neurodegeneration in MPS VII

Progressive neurodegeneration and cognitive disability are prominent symptoms of MPS VII, a lysosomal storage disorder caused by {beta}-glucuronidase enzyme deficiency. Yet, the mechanism of neurodegeneration in MPS VII remains elusive thereby limiting the scope of targeted intervention. To address this, we recently developed a {beta}-glucuronidase-deficient (CG2135-/-) Drosophila model of MPS VII. The CG2135-/- flies exhibited signs of neuromuscular degeneration, including loss of dopaminergic neurons, and accumulated engorged lysosomes, ubiquitinated proteins and mitochondria in their brains. These observations, coupled with our current finding that the CG2135-/- flies were highly susceptible to starvation, prompted us to investigate potential defects in the autophagy-lysosomal clearance machinery in the brain. We found that both autophagy induction and lysosome-mediated autophagosomal turnover were impaired in the CG2135-/- fly brain. This was evidenced by lower Atg8a-II levels, reduced Atg1 and Ref(2)P expression along with accumulation of lipofuscin-like inclusions and multilamellar bodies. Interestingly, mitophagy was also found to be defective in their brain, causing buildup of enlarged mitochondria with distorted cristae and reduced membrane potential. This, in turn, affected mitochondrial function as reflected by drastically reduced brain ATP levels. Energy depletion triggered apoptosis in neuronal as well as non-neuronal cells of the CG2135-/- fly brain, where we also detected apoptotic dopaminergic neurons. Resveratrol treatment, previously found to protect against loss of dopaminergic neurons in the CG2135-/- flies, has now been shown act by correcting the mitophagy defect and preventing ATP depletion. Collectively, our study establishes a causal link between mitophagy defect, mitochondrial malfunction, and apoptotic neurodegeneration in MPS VII.

cell biology↗

bioRxiv2024

Single cell autofluorescence imaging reveals immediate metabolic shifts of neutrophils with activation across biological systems

Neutrophils, the most abundant leukocytes in human peripheral circulation, are crucial for the innate immune response. They are typically quiescent but rapidly activate in response to infection and inflammation, performing diverse functions such as oxidative burst, phagocytosis, and NETosis, which require significant metabolic adaptation. Deeper insights into such metabolic changes will help identify regulation of neutrophil functions in health and diseases. Due to their short lifespan and associated technical challenges, the metabolic processes of neutrophils are not completely understood. This study uses optical metabolic imaging (OMI), which entails optical redox ratio and fluorescence lifetime imaging microscopy of intrinsic metabolic coenzymes NAD(P)H and FAD to assess the metabolic state of single neutrophils. Primary human neutrophils were imaged in vitro under a variety of activation conditions and metabolic pathway inhibitors, while metabolic and functional changes were confirmed with mass spectrometry, oxidative burst, and NETosis measurements. Our findings show that neutrophils undergo rapid metabolic remodeling to a reduced redox state indicated by changes in NAD(P)H lifetime and optical redox ratio, with a shift to an oxidized redox state during activation. Additionally, single cell OMI analysis reveals a heterogeneous metabolic response across neutrophils and human donors to live pathogen infection (Pseudomonas aeruginosa and Toxoplasma gondii). Finally, consistent OMI changes with activation were confirmed between in vitro human and in vivo zebrafish larvae neutrophils. This study demonstrates the potential of OMI as a versatile tool for studying neutrophil metabolism and underscores its use across different biological systems, offering insights into neutrophil metabolic activity and function at a single cell level.

immunology↗

bioRxiv2024

Syntaxin-2 inhibits phagocytic uptake but promotes phagolysosome formation in macrophages

Phagocytosis engulfs receptor-bound particles by structuring phagocytic cups that expand to form phagosome vesicles. Phagosomes fuse with endosomes and lysosomes to gradually mature into acidic, hydrolase-enriched phagolysosomes for content degradation. While an essential cellular process for eliminating unwanted substances to secure host defense and organismal homeostasis, defective or uncontrolled phagocytosis can be detrimental. Here, we report syntaxin-2 (Stx2), a poorly characterized SNARE in phagocytes, defines the course of macrophage phagocytosis by coordinating cell surface receptor density, phagocytic cup expansion, and phagosome maturation. Stx2 is expressed on the plasma membrane, phagosomes, early endosomes, and to some extent on recycling endosomes, late endosomes and VAMP4-positive compartments. Stx2 knockdown (Stx2-KD) augments engagement and uptake of IgG-opsonized particles by enhanced surface expression of Fc receptors (FcR) and efficient expansion of phagocytic cups. These events are driven by increased recycling of FcR, and enhanced delivery of early endosomes and VAMP4-positive post-Golgi compartments to phagocytic cups. Interestingly, Stx2-KD macrophages exhibit reduced secretion of pro-cathepsins with concomitant increase in lysosome content. However, Stx2 depletion prevents phagosome coalescence with late endosomes and lysosomes to impair maturation by depleted acquisition of cathepsins and reduced acidification. Consequently, macrophages depleted of Stx2 manifest uncontrolled uptake of IgG-opsonized Escherichia coli and impaired digestion resulting in increased bacterial load. Collectively, we uncovered a previously unknown role of Stx2 as a critical balancer of phagocytic uptake and phagolysosomal clearance in macrophages, suggesting that it could be an attractive target for modulation of phagocytosis plasticity and to control aberrant phagocytosis.

cell biology↗