Biology subjects

Gurung, P.

Publications and source records attributed to Gurung, P..

13 recordsLinked to original sources

bioRxiv2026

The essential function of the apical polar ring during the blood stage of Plasmodium falciparum

The apical polar ring (APR) is a defining cytoskeletal structure in apicomplexan parasites, critical for parasite morphology and host cell invasion. However, its molecular composition and function remain elusive in Plasmodium falciparum. Here, we identify and characterize PfAPR1 as an APR-resident protein. Conditional knockout of PfAPR1 reveals its essential role in asexual replication. Using iterative ultrastructure expansion microscopy (iU-ExM), we show that PfAPR1 predominantly localizes to the basal APR ring. Loss of PfAPR1 causes defects in daughter cell segmentation and subpellicular microtubules organization, while IMC formation and apical polarity are largely preserved. PfAPR1-KO parasites contact host red blood cells but fail to form a tight junction, resulting in a complete block in invasion. Using PfAPR1 as molecular bait, we identify additional APR proteins and delineate APR biogenesis with U-ExM. These findings define the molecular architecture and function of the APR in P. falciparum, highlighting it as a promising antimalarial target.

microbiology↗

bioRxiv2025

Micropropagation and Assessment of Genetic Homogeneity in Dendrobium moniliforme (L.) Sw. using Molecular Markers

Dendrobium moniliforme (L.) Sw., is a valuable medicinal orchid widely used as tonic. This study aimed to develop an effective protocol for micropropagation of D. moniliforme and to compare the genetic similarities of the micro-propagated plants to the wild plants using Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeats (ISSR) molecular markers. Healthy seeds were cultured on Murashige-Skoog (MS) medium, supplemented with various concentrations of auxins, cytokinins and coconut water for shoot and root development. Genetic homogeneity was assessed using ten primers of each RAPD and ISSR marker. MS media fortified with 10% coconut water was efficient for seed germination and protocorm development. Maximum number of shoots were produced on half strength MS (HMS) medium supplemented with 0.25 mg/L NAA and 10% coconut water (CW) i.e 22 shoots. FMS supplemented with 0.5 mg/L indole butyric acid (IBA) was found to be best as plant hormone for root induction, as it induced ten roots/shoot. RAPD and ISSR amplified a total of 15 and 5 homogeneous DNA fragments. This protocol demonstrates a reliable and efficient method for large-scale propagation and conservation of D. moniliforme, supporting its commercial and medicinal value. HighlightsDendrobium moniliforme was micro-propagated from seeds using MS medium. RAPD and ISSR markers confirmed its genetic stability. The study supports large-scale true-to-type propagation and conservation of these valuable medicinal orchids.

molecular biology↗

bioRxiv2024

An animal model for autoinflammation with infantile enterocolitis

Inflammasomes, particularly NLRC4, play a crucial role in immune responses to intracellular bacterial infections. However, gain-of-function mutations of NLRC4 are linked to severe autoinflammatory diseases, including autoinflammation with infantile enterocolitis (AIFEC). Existing mouse models do not adequately replicate the chronic, unprovoked inflammation observed in AIFEC patients. In this study, we developed a loxP-flanked NLRC4 V341A knock-in (KI) mouse model. Our global NLRC4 V341A KI mice exhibited symptoms closely mirroring those of human AIFEC. These mice demonstrated severe infantile enterocolitis, characterized by heightened intestinal inflammation, compromised intestinal barrier integrity, disrupted gut epithelium, and severe diarrhea, with high mortality within 10 days postnatally. Additionally, they displayed systemic autoinflammation marked by elevated levels of IL-1{beta}, IL-18, and IL-6, alongside cytopenia and hemophagocytosis. In contrast, adult NLRC4 conditional KI mice exhibited autoinflammation with only mild enterocolitis. Since AIFEC is characterized by life-threatening enterocolitis in infancy and recurrent severe autoinflammation throughout life, our conditional NLRC4 KI model effectively recapitulates the clinical features of human AIFEC. Moreover, the NLRC4 V341A-mediated monogenic infantile enterocolitis observed in our model resembles infantile-onset inflammatory bowel disease (IBD), positioning it as a valuable platform for research on very early-onset IBD.

immunology↗

bioRxiv2024

PfCAP-H is essential for assembly of condensin I complex and karyokinesis during asexual proliferation of Plasmodium falciparum

Condensin I is a pentameric complex that regulates the mitotic chromosome assembly in eukaryotes. The kleisin subunit CAP-H of the condensin I complex acts as a linchpin to maintain the structural integrity and loading of this complex on mitotic chromosomes. This complex is present in all eukaryotes and has recently been identified in Plasmodium spp. However, how this complex is assembled and whether the kleisin subunit is critical for this complex in these parasites is yet to be explored. To examine the role of PfCAP-H during cell division within erythrocytes, we generated an inducible PfCAP-H knockout parasite. We find that PfCAP-H is dynamically expressed during mitosis with the peak expression at the metaphase plate. PfCAP-H interacts with PfCAP-G and is a non-SMC member of the condensin I complex. Notably, the absence of PfCAP-H does not alter the expression of PfCAP-G but affects its localization at the mitotic chromosomes. While mitotic spindle assembly is intact in PfCAP-H deficient parasites, duplicated centrosomes remain clustered over the mass of unsegmented nuclei with failed karyokinesis. This failure leads to the formation of an abnormal nuclear mass, while cytokinesis occurs normally. Altogether, our data suggest that PfCAP-H plays a crucial role in maintaining the structural integrity of the condensin I complex on the mitotic chromosomes and is essential for the asexual development of malarial parasites. ImportanceMitosis is a fundamental process for Plasmodium parasites, which plays a vital role in their survival within two distinct hosts - human and Anopheles mosquitoes. Despite its great significance, our comprehension of mitosis and its regulation remains limited. In eukaryotes, mitosis is regulated by one of the pivotal complexes known as condensin complexes. The condensin complexes are responsible for chromosome condensation, ensuring the faithful distribution of genetic material to daughter cells. While condensin complexes have recently been identified in Plasmodium spp, our understanding of how this complex is assembled and their precise functions during the blood stage development of Plasmodium falciparum remains largely unexplored. In this study, we investigate the role of a central protein, PfCAP-H, during the blood stage development of P. falciparum. Our findings reveal that PfCAP-H is essential and plays a pivotal role in upholding the structure of condensin I and facilitating karyokinesis.

cell biology↗

bioRxiv2023

LRRK2 G2019S promotes the development of colon cancer via modulating intestinal inflammation

LRRK2 G2019S is the most prevalent variant associated with Parkinsons disease (PD), found in 1-3% of sporadic and 4-8% of familial PD cases. Intriguingly, emerging clinical studies have suggested that LRRK2 G2019S carriers have an increased risk of cancers including colorectal cancer. However, the underlying mechanisms of the positive correlation between LRRK2-G2019S and colorectal cancer remain unknown. Using a mouse model of colitis-associated cancer (CAC) and LRRK2 G2019S knockin (KI) mice, here we report that LRRK2 G2019S promotes the pathogenesis of colon cancer as evidenced by increased tumor number and tumor size in LRRK2 G2019S KI mice. LRRK2 G2019S promoted intestinal epithelial cell proliferation and inflammation within the tumor microenvironment. Mechanistically, we found that LRRK2 G2019S KI mice are more susceptible to dextran sulfate sodium (DSS)-induced colitis. Suppressing the kinase activity of LRRK2 ameliorated the severity of colitis in both LRRK2 G2019S KI and WT mice. At the molecular level, our investigation unveiled that LRRK2 G2019S promotes the production of reactive oxygen species, triggers inflammasome activation, and induces cell necrosis in the gut epithelium in a mouse model of colitis. Collectively, our data provide direct evidence that gain-of-kinase activity in LRRK2 promotes colorectal tumorigenesis, implicating LRRK2 as a potential target in colon cancer patients with hyper LRRK2 kinase activity.

immunology↗

bioRxiv2023

Neuron cilia constrain glial regulators to microdomains around distal neurons

Each glia interacts with multiple neurons, but the fundamental logic of whether it interacts with all equally remains unclear. We find that a single sense-organ glia modulates different contacting neurons distinctly. To do so, it partitions regulatory cues into molecular microdomains at specific neuron contact-sites, at its delimited apical membrane. For one glial cue, K/Cl transporter KCC-3, microdomain-localization occurs through a two-step, neuron-dependent process. First, KCC-3 shuttles to glial apical membranes. Second, some contacting neuron cilia repel it, rendering it microdomain-localized around one distal neuron-ending. KCC-3 localization tracks animal aging, and while apical localization is sufficient for contacting neuron function, microdomain-restriction is required for distal neuron properties. Finally, we find the glia regulates its microdomains largely independently. Together, this uncovers that glia modulate cross-modal sensor processing by compartmentalizing regulatory cues into microdomains. Glia across species contact multiple neurons and localize disease-relevant cues like KCC-3. Thus, analogous compartmentalization may broadly drive how glia regulate information processing across neural circuits.

neuroscience↗

bioRxiv2022

Biomechanical origins of proprioceptive maps in the Drosophila leg

Our ability to sense and move our bodies relies on proprioceptors, sensory neurons that detect mechanical forces within the body. Proprioceptors are diverse: different subtypes detect different features of joint kinematics, such as position, directional movement, and vibration. However, because they are located within complex and dynamic peripheral tissues, the underlying mechanisms of proprioceptor feature selectivity remain poorly understood. Here, we investigate molecular and biomechanical contributions to proprioceptor diversity in the Drosophila leg. Using single-nucleus RNA sequencing, we found that different proprioceptor subtypes express similar complements of mechanosensory and other ion channels. However, anatomical reconstruction of the proprioceptive organ and connected tendons revealed major biomechanical differences between proprioceptor subtypes. We constructed a computational model of the proprioceptors and tendons, which identified a putative biomechanical mechanism for joint angle selectivity. The model also predicted the existence of a goniotopic map of joint angle among position-tuned proprioceptors, which we confirmed using calcium imaging. Our findings suggest that biomechanical specialization is a key determinant of proprioceptor feature selectivity in Drosophila. More broadly, our discovery of proprioceptive maps in the fly leg reveals common organizational principles between proprioception and other topographically organized sensory systems.

neuroscience↗

bioRxiv2021

Epigenetic Programming during thymic development sets the stage for optimal function in effector T cells via DNA demethylation

The repressive effect of DNA methylation at promoters is well-known. However, its role within conserved sequences in intragenic and intergenic regions is less clear. Using Cd4 as a model gene, here we show that DNA methylation regulates the function of stimulus-responsive regulatory elements in effector T cells. Two cis-elements orchestrate intra-and intergenic DNA demethylation of the Cd4 gene during thymic development, which in turn licenses a stimulus-responsive element, E4a, for its later function in effector cells. Deficiency in DNA demethylation leads to impaired E4a function, reduced H3K4me3 promoter levels and an inability to repel de novo DNA methylation during replication, ultimately leading to gene silencing. This physiological reduction in CD4 expression leads to a defect in Th1 polarization during cutaneous Leishmaniasis. Similar patterns of regulation were observed in a broad number of genes, highlighting an essential role for DNA demethylation during thymic development in modulating the function of stimulus-responsive elements.

immunology↗

bioRxiv2021

Altered cleavage of Caspase-1 in hepatocytes limits control of malaria in the liver

Malaria, caused by Plasmodium parasites, is a devastating disease that kills over half a million people each year1. Plasmodium sporozoites inoculated by mosquitoes into mammalian hosts undergo a clinically silent phase of obligatory development and replication in hepatocytes before initiating the life-threatening blood-stage of malaria2. Thus, understanding the immune responses elicited by Plasmodium infection in the liver is key to controlling clinical malaria and transmission3,4. Here, we show that Plasmodium DNA can be detected by AIM2 (absent in melanoma 2) sensors in the infected hepatocytes, resulting in Caspase-1 activation and pyroptotic cell-death. However, Caspase-1 was observed to undergo only partial cleavage in hepatocytes, limiting pyroptosis, and the maturation of pro-inflammatory cytokines classically associated with Caspase-1 activation. We discovered that the extent of Caspase-1 cleavage in cells is determined by the expression of ASC (apoptosis-associated speck-like protein containing a CARD). ASC expression is inherently low in hepatocytes, and transgenically enhancing it in the hepatocytes induced complete processing of Caspase-1, efficient secretion of pro-inflammatory cytokines, enhanced pyroptotic cell-death, and markedly improved control of malaria infection in the liver. In addition to describing a novel pathway of natural immunity to malaria, our findings uncover a key aspect of liver biology that may have been exploited during evolution by successful hepatotropic pathogens.

immunology↗

bioRxiv2020

Central processing of leg proprioception in Drosophila

Proprioception, the sense of self-movement and position, is mediated by mechanosensory neurons that detect diverse features of body kinematics. Although proprioceptive feedback is crucial for accurate motor control, little is known about how downstream circuits transform limb sensory information to guide motor output. Here, we investigate neural circuits in Drosophila that process proprioceptive information from the fly leg. We identify three cell-types from distinct developmental lineages that are positioned to receive input from proprioceptor subtypes encoding tibia position, movement, and vibration. 13B neurons encode femur-tibia joint angle and mediate postural changes in tibia position. 9A neurons also drive changes in leg posture, but encode a combination of directional movement, high frequency vibration, and joint angle. Activating 10B neurons, which encode tibia vibration at specific joint angles, elicits pausing in walking flies. Altogether, our results reveal that central circuits integrate information across proprioceptor subtypes to construct complex sensorimotor representations that mediate diverse behaviors, including reflexive control of limb posture and detection of leg vibration.

neuroscience↗

bioRxiv2019

A size principle for leg motor control in Drosophila

To move the body, the brain must precisely coordinate patterns of activity among diverse populations of motor neurons. In many species, including vertebrates, the motor neurons innervating a given muscle fire in a specific order that is determined by a gradient of cellular size and electrical excitability. This hierarchy allows premotor circuits to recruit motor neurons of increasing force capacity in a task-dependent manner. However, it remains unclear whether such a size principle also applies to species with more compact motor systems, such as the fruit fly, Drosophila melanogaster, which has just 53 motor neurons per leg. Using in vivo calcium imaging and electrophysiology, we found that genetically-identified motor neurons controlling flexion of the fly tibia exhibit a gradient of anatomical, physiological, and functional properties consistent with the size principle. Large, fast motor neurons control high force, ballistic movements while small, slow motor neurons control low force, postural movements. Intermediate neurons fall between these two extremes. In behaving flies, motor neurons are recruited in order from slow to fast. This hierarchical organization suggests that slow and fast motor neurons control distinct motor regimes. Indeed, we find that optogenetic manipulation of each motor neuron type has distinct effects on the behavior of walking flies.

neuroscience↗

bioRxiv2019

Leishmania major degrades murine CXCL1 - an immune evasion strategy

Leishmaniasis is a global health problem with an estimated report of 2 million new cases every year and more than 1 billion people at risk of contracting this disease in endemic areas. The innate immune system plays a central role in controlling L. major infection by initiating a signaling cascade that results in production of pro-inflammatory cytokines and recruitment of both innate and adaptive immune cells. Upon infection with L. major, CXCL1 is produced locally and plays an important role in the recruitment of neutrophils to the site of infection. Herein, we report that L. major specifically targets murine CXCL1 for degradation. The degradation of CXCL1 is not dependent on host factors as L. major can directly degrade recombinant CXCL1 in a cell-free system. Using mass spectrometry, we discovered that the L. major protease cleaves at the C-terminal end of murine CXCL1. Finally, our data suggest that L. major metalloproteases are involved in the direct cleavage and degradation of CXCL1, and a synthetic peptide spanning the CXCL1 cleavage site can be used to inhibit L. major metalloprotease activity. In conclusion, our study has identified an immune evasion strategy employed by L. major to evade innate immune responses in mice, likely reservoirs in the endemic areas, and further highlights that targeting these L. major metalloproteases may be important in controlling infection within the reservoir population and transmittance of the disease.\n\nAuthors summaryOur study discovered a highly specific role for L. major metalloprotease in cleaving and degrading murine CXCL1. Indeed, L. major metalloprotease did not cleave murine CXCL2 or human CXCL1, CXCL2 and CXCL8. CXCL1 is a critical chemokine required for neutrophil recruitment to the site of infection; thus, we propose that this metalloprotease may have evolved to evade immune responses specifically in the murine host. We have further identified that the C-terminal end on CXCL1 is targeted for cleavage by the L. major metalloprotease. Finally, this cleavage site information was used to design peptides that are able to inhibit CXCL1 degradation by L. major. Our study highlights an immune evasion strategy utilized by L. major to establish infection within a murine host.

microbiology↗

bioRxiv2018

Neural coding of leg proprioception in Drosophila

Animals rely on an internal sense of body position and movement to effectively control motor behavior. This sense of proprioception relies on diverse populations of mechanosensory neurons distributed throughout the body. However, little is known about how proprioceptor neurons collectively encode sensory stimuli. Here, we investigate neural coding of leg proprioception in Drosophila, using in vivo two-photon calcium imaging of proprioceptors during controlled movements of the fly tibia. We found that the axons of leg proprioceptors are organized into distinct functional projections that contain topographic representations of specific kinematic features. Using subtype-specific genetic driver lines, we show that one group of axons encodes tibia position (flexion/extension), another encodes movement direction, and a third encodes bidirectional movement and vibration frequency. Thus, proprioceptive sensing of a single leg joint is mediated by multiple subtypes of specialized sensory neurons. This architecture may help to maximize information transmission, processing speed, and robustness, which are critical for feedback control of the limbs during locomotion.

neuroscience↗