Biology subjects

Yadav, G.

Publications and source records attributed to Yadav, G..

At least 19 recordsLinked to original sources

bioRxiv2026

Molecular Mechanism of Lipid Recognition and Membrane-Guided Gating in Plant Minimal START Proteins

The hydrophobic nature of lipids requires specialized transport mechanisms, and one such non-vesicular transport mechanism involves START (StAR-related lipid transfer) domain proteins. START domains either occur as a part of multidomain proteins or occur solo as in minimal START proteins. Unlike well-studied multidomain variants, plant minimal START proteins remain poorly understood, leaving their ligand specificity, structural dynamics, and biological roles largely uncharacterized. Integrating structural screening with experimental validation, we analyzed representative plant minimal START proteins and confirmed their specific binding to amphipathic lipids, primarily myristic acid and lysophosphatidylcholine. The ligand binding involves a bipartite mechanism, in which basic residues within the cavity interact with polar lipid headgroups, while the hydrophobic tails are accommodated deeper within the cavity. Mechanistically, ligand binding induced closure of a lid-like gate at the cavity entrance, whereas membrane proximity promoted reopening of the gate and ligand release, collectively suggesting a membrane-guided gating mechanism for lipid exchange. Consistent with this model, localization studies show that these proteins associate with the endoplasmic reticulum, plastids, Golgi apparatus, and plasma membrane, major sites of lipid metabolism. Together, our findings establish plant minimal START proteins as bona fide lipid-binding proteins that utilize a bipartite ligand-binding mechanism coupled with membrane-responsive gating dynamics.

biochemistry↗

bioRxiv2026

Engaging working memory following skill reactivation has implications for interlimb skill generalization

Interlimb skill generalization, defined as the transfer of a newly learned skill from the trained to the untrained limb, represents a fundamental aspect of human motor behavior with significant implications for rehabilitation and athletic training. Skill generalization is influenced by processes that drive learning and interact with the newly acquired memory. For instance, in our recent work, we reported that performing a secondary, cognitively demanding task immediately after a short skill-training session impaired skill generalization when the untrained arm was tested 24-hour later. This suggests that working memory (WM) interacts with the early stage of skill memory consolidation processes and thereby impacts skill generalization. Motivated by this finding, in the current study, we investigate how WM interacts with reactivated skill memory and its subsequent impact on skill generalization, tested 24 or 48-hour post skill training. We recruited right-handed young participants (n=95) who performed a fast, accurate reaching task with their dominant right arm during a short training session (50 trials) on Day-1. After 24-hour on Day-2, depending on the group type, participants had a brief skill reactivation session (10 trials or no reactivation) and then performed the WM task (or a control task) with their right arm. Interlimb generalization to the untrained left arm was assessed either immediately after the WM/control task on Day-2 or after a 24-hour gap on Day-3. We found that, engaging in the WM task (compared to the control task) after skill reactivation on Day-2 enhanced immediate generalization. Conversely, when generalization was tested 24-hour later on Day-3, the same WM engagement impaired skill generalization. These findings demonstrate that WM engagement during the post-reactivation phase has a time-dependent influence on interlimb generalization. WM can facilitate immediate generalization, possibly by sustaining neural processes that promote skill memory generalization across effectors. However, when a 24-hours time gap is introduced, generalization is disrupted following WM engagement, possibly because of interference between underlying neural processes involved in WM and reactivation-induced (re)consolidation of the skill memory. This study highlights the delicate interplay among WM, motor memory reactivation dynamics, and skill generalization and suggests a time-dependent interplay of neural processes critical for optimizing outcomes in motor learning and clinical rehabilitation protocols. NEW & NOTEWORTHYThis study reveals that working memory engagement following skill memory reactivation exerts a time-dependent dual effect on interlimb generalization. When tested immediately, WM engagement enhances generalization by prolonging the labile state of reactivated memory, which is needed to transfer abstract/effector-independent features to the untrained arm. When tested 24-hour after a delay, the same intervention impairs generalization by possibly engaging reconsolidation processes that interfere with effector-independent features. These findings establish a unified framework in which the temporal dynamics of the reconsolidation window determine whether a cognitive intervention strengthens or weakens a motor memory, with implications for understanding memory plasticity and for designing effective rehabilitation protocols.

neuroscience↗

bioRxiv2026

Genome-wide architecture of prolonged starvation adaptation in experimentally evolved Drosophila and comparative enrichment in human orthologs

Long-term starvation stress represents a strong evolutionary constraint across taxa, yet the genetic architecture underlying adaptation to sustained nutrient deprivation remains poorly resolved. We experimentally evolved Drosophila melanogaster under starvation stress for 60 generations, maintaining four starvation-selected populations and four matched controls, and then performed whole-genome resequencing. Starvation-selected populations exhibited extended survival and pronounced genome-wide restructuring, including the expansion of low-heterozygosity regions, reduced nucleotide diversity, and recurrent sweep signatures across replicates. Drift-aware allele-frequency modeling identified 3,578 single-nucleotide polymorphisms (SNPs) whose shifts exceeded neutral expectations, indicating widespread, parallel responses to sustained starvation. Mitochondrial pathways emerged as prominent targets: nuclear-encoded mitochondrial genes were significantly enriched among low-diversity, sweep-associated, and drift-exceeding loci, and the mitochondrial origin of replication harbored a sharply differentiated variant, suggesting a mito-nuclear component of starvation adaptation. Comparative analyses further showed that human orthologs of starvation-responsive fly genes were enriched for highly differentiated variants in selected 1000 Genomes populations, with regulators of TOR/S6K signaling recurring among loci in the extreme tails of population differentiation. Together, these results define a replicate-convergent and functionally coherent genomic response to prolonged starvation in Drosophila, comprising regional signatures of linked selection and distributed allele-frequency shifts exceeding neutral expectations, and connect laboratory selection in flies to population differentiation in human orthologs.

evolutionary biology↗

bioRxiv2025

Non-invasive Stimulation of Contralateral Primary Motor Cortex Reduces the Amount of Skill Generalization to the Untrained Arm

Successfully learned motor skills can generalize or transfer to the untrained arm. The neural substrate underlying such intermanual/interlimb generalization of newly acquired skill memory is unclear. Here, we focused on contralateral primary motor cortex (cM1) which is considered a key brain area for skill learning and memory consolidation. We probed the causal role of cM1 in intermanual skill generalization in a two-day study involving right-handed young individuals (n=31) who learned a novel motor skill reaching task. Immediately following (right-arm) learning, we delivered low-frequency (1Hz, 1800 pulses) repetitive transcranial magnetic stimulation (rTMS) to target left cM1 in one group of individuals (n=15), while another group (n=16) served as an active control in which ipsilateral M1 (iM1) was targeted. On the same day we measured corticospinal excitability (CSE) to assess learning-induced and rTMS-induced neuroplastic changes occurring in the targeted M1s. Next day after 24-hours, both groups were tested for intermanual skill generalization (left-arm), followed by a brief test of intralimb retention (right-arm). Our results show that stimulating cM1, versus iM1, reduced the amount of generalization to the untrained arm on the next day, without affecting its (re)learning ability or the follow-up retention performance of the trained arm. Further, rTMS stimulation induced a net facilitation in CSE- with higher facilitation tending to correlate to lower generalization in a subset of high learners in cM1 group. Taken together, this study highlights the role of cM1 in skill generalization such that it seems to mediate the early transfer of learning to the untrained arm. NEW AND NOTEWORTHYIntermanual skill generalization from trained to the untrained arm is causally mediated by the contralateral (trained) primary motor cortex (cM1) as opposed to the ipsilateral (untrained) motor cortex. Low-frequency stimulation of M1 in our study led to a facilitation of corticospinal excitability, while impairing the amount of skill generalization in the cM1 group. This highlights a rather paradoxical and opposite effect of non-invasive brain stimulation, such as rTMS, on motor behavior and associated motor excitability. Our data also suggest involvement of additional brain areas for such motor skill behavior that were rendered unperturbed by rTMS in this case and, thus, contributed to an overall positive skill performance achieved by both arms the next day.

neuroscience↗

bioRxiv2025

Molecular basis for the activation of Pseudomonas aeruginosa MsbA by Zn2+

Proteins involved in the biogenesis of lipopolysaccharide (LPS), a lipid exclusive to Gram-negative bacteria, are promising candidates for drug discovery. Specifically, the ABC transporter MsbA plays a crucial role in translocating an LPS precursor from the cytoplasmic to periplasmic facing leaflet of the inner membrane, and small molecules that inhibit its function exhibit bactericidal activity. Here, we use native mass spectrometry (MS) to determine lipid binding affinities of MsbA from P. aeruginosa (PaMsbA), a Gram-negative bacteria associated with hospital-acquired infections, in different conformations. We show the ATPase activity of the transporter is stimulated by Zn2+ and successfully trapping the protein with vanadate requires Zn2+ not Mg2+, which is necessary to trap MsbA from E. coli. We also present cryogenic-electron microscopy structures of PaMsbA in occluded and open outward-facing conformations determined to a resolution of 2.98 and 2.72 angstroms, respectively. The structures reveal a triad of histidine residues and mutation of these residues abolishes Zn2+ stimulation of PaMsbA activity. Together our studies provide detailed insight into PaMsbA structure, lipid binding preferences, and uncover a mechanism through which Zn2+ promotes the dimerization of the transporter, resulting in enhanced ATPase activity.

biochemistry↗

bioRxiv2024

Effects Of Extrinsic Reward Based Skill Learning On Motor Plasticity

Human motor skill acquisition is improved by performance feedback and coupling such feedback with extrinsic reward (such as money) can enhance skill learning. However, the neurophysiology underlying such behavioral effect is unclear. To bridge this gap, we assessed the effects of reward on multiple forms of motor plasticity during skill learning. Sixty-five healthy participants divided in three groups performed a pinch-grip skill task with sensory feedback only, sensory and reinforcement feedback or both feedback coupled with an extrinsic monetary reward during skill training. To probe motor plasticity, we applied transcranial magnetic stimulation on the left primary motor cortex at rest before, during and after training in the three groups. We evaluated the amplitude and variability of corticospinal output, GABA-ergic short-intracortical inhibition and use-dependent plasticity before training and at two time points during and after training. At the behavioral level, monetary reward accelerated skill learning. In parallel, corticospinal output became less variable early on during training in the presence of extrinsic reward. Interestingly, this effect was particularly pronounced for participants who were more sensitive to reward, as evaluated in an independent questionnaire. Other measures of motor excitability remained comparable across groups. These findings highlight that a mechanism underlying the benefit of reward on motor skill learning is the fine tuning of early-training resting-state corticospinal variability. SIGNIFICANCE STATEMENTSkill acquisition is enhanced in the presence of reward. Despite its potential clinical relevance for motor rehabilitation, the underlying neurophysiological mechanisms remain largely unexplored. Specifically, whether reward affects the plasticity of motor cortex in the context of skill learning is unclear. We show that reward reduces the variability of corticospinal output at an early stage during training and that this effect correlates with individual sensitivity to reward. Our results suggest that a key mechanism underlying the beneficial effect of reward on motor skill learning may be an increase in the stability of motor output in response to training during early stages of skill learning.

neuroscience↗

bioRxiv2024

ROLE OF WORKING MEMORY IN INTERLIMB GENERALIZATION OF NEWLY LEARNED SKILLS

Newly acquired skill memory can generalize/transfer to the untrained arm. Such interlimb generalization of a learned skill has been shown to be symmetric in nature and is thought to be mediated by cognitive processes that emerge during skill learning. However, it is unknown whether engaging in other cognitively demanding tasks following skill acquisition can influence skill generalization. Our research goal was to uncover how a secondary task, involving working memory, interacts with a newly formed skill memory and influences subsequent interlimb generalization. To test this idea, we conducted a set of three experiments by recruiting right-handed young healthy individuals (N=92) who learned a novel motor skill (long or short training on a skilled reaching task) followed by performing a working memory or control task with the right arm. Finally, all individuals were tested for immediate or delayed (after 24 hours) interlimb skill generalization to the untrained left arm. We found significant immediate as well as delayed generalization in individuals who received long training on the motor skill task, irrespective of whether they performed working memory or control task. On the other hand, performing the working memory but not control task following short skill training impaired generalization when the untrained arm was tested 24 hours later. These findings indicate that short training reflecting early stages of skill learning and the subsequent skill memory stabilization are dependent on working memory such that the underlying neural interactions mediating these processes can have implications for skill generalization. NEW AND NOTEWORTHYSkill learning is deemed successful if it can generalize to untrained conditions. Despite the potential clinical relevance of interlimb skill generalization for motor rehabilitation, such as in case of unilateral stroke, the underlying mechanisms that can influence such generalization are not fully understood. Specifically, whether interlimb skill memory generalization can be impacted by another memory system is unknown. Here, we show that engaging in a working memory task following short skill training is detrimental for interlimb skill generalization, and such interference caused by working memory is not evident when the skill training is longer. These behavioral findings bridge the link between traditionally distinct memory systems, i.e., procedural skill memory and working memory.

neuroscience↗

bioRxiv2023

The coexistence of localized and distributed behavioral information in neural activity

The degree to which control of an animals behavior is localized within particular neurons or distributed over large populations is central to understanding mechanisms of decision-making in brains. A first step in answering this question comes from understanding the scales at which neural activity is predictive of behavior. Here, we demonstrate how information measures at the individual, pairwise, and larger group levels characterize the localization of predictive information. We demonstrate these tools using high-dimensional neural data related to nematode and macaque behavioral decisions. Intriguingly, in both examples we find that similar behavioral information coexists across scales: the same information can be extracted from small groups of individually informative neurons or larger groups of randomly chosen neurons that individually have little predictive power. Our results suggest that methods for causal inference may miss potential causal pathways if they are biased toward finding localized control mechanisms.

neuroscience↗

bioRxiv2022

Effect of Zn fertilization on yield, protein content, protein yield and zinc use efficiency in pearl millet

Two year field experiment was conducted at Rajasthan Agriculture Research Institute, Durgapura, during rainy seasons of 2019 and 2020 in factorial block design with three replications to study the growth, productivity and economics of pearl millet - chickpea cropping system by using three genotypes (RHB-173, MPMH-17 and RHB-177) and five treatments of zinc [0, 5, 7.5 kg Zn/ha through ZnSO4.7H2O and 5, 7.5 kg Zn/ha through Zn-EDTA) applied to pearl millet and two foliar spray treatments applied in both of crop at booting stage in pearl millet and pre-flowering stage in chickpea. Results revealed that total nitrogen and zinc contents of chickpea were increased significantly and highest with the residual effect of 7.5 kg Zn/ha through Zn-EDTA and 7.5 kg Zn/ha through ZnSO4.7H2O and phosphorus contents of chickpea was recorded depressive effect on residual zinc fertilization, while, potassium contents was not influenced significantly. However, the significant increase in uptake of nutrients nitrogen, phosphorous, potassium and zinc were obtained with 7.5 kg Zn/ha through Zn-EDTA higher per cent over control, during the years 2019-20 and 2020-21. The highest nitrogen, protein content and zinc contents and uptake values were obtained with 5, 7.5 kg Zn/ha through Zn-EDTA. The residual effect of 7.5 kg Zn/ha through Zn-EDTA was at par with 7.5 kg Zn/ha through ZnSO4.7H2O. The increased in total uptake of nitrogen, it could be ultimately increased protein yield were 16.54 and 27.48 per cent, during respective years over control. The highest nutrient use efficiency was obtain with lowest of fertilizer dose of Zn-EDTA as compare to zinc sulphate.

plant biology↗

bioRxiv2021

Quantifying the Invasive Secondary Metabolome

Invasive plants drive ecosystem degradation through developing aggressive phenotypes that can outcompete native flora. Several hypotheses explain this, like the Evolution of Increased Competitive Ability hypothesis and the Novel Weapons Hypothesis, but none have been proven conclusively. Changes in plant metabolites are critical to these hypotheses, but complete invasive secondary metabolomes have not been quantified. Here, statistical and unsupervised machine-learning approaches were used to analyse chemotype-to-phenotype relationships in invasive and non-invasive populations in species Ageratum conyzoides, Lantana camara, Melaleuca quinquenervia and Psidium cattleainum and on a family level analysing Asteraceae, Myrtaceae and Verbenaceae. Invasive metabolomes evolved according to the EICA and NWH, involving optimisation of aggressive strategies present in native populations and local adaptation. O_FIG O_LINKSMALLFIG WIDTH=135 HEIGHT=200 SRC="FIGDIR/small/471125v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1bd2d02org.highwire.dtl.DTLVardef@d5e660org.highwire.dtl.DTLVardef@107d008org.highwire.dtl.DTLVardef@1eaf62a_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2020

Plant Prionome maps reveal specific roles of prion-like proteins in stress and memory

Prions can be considered as molecular memory devices, generating reproducible memory of a conformational change. Prion-like proteins (PrLPs) have been demonstrated to be present in plants, but their role in plant stress and memory remains largely unexplored. In this work, we report the widespread presence of PrLPs in plants through a comprehensive analysis of 39 genomes representing major taxonomic groups. We find diverse functional roles associated with plant prionomes. Investigation of the rice transcriptome further delineated the role of PrLPs in stress and developmental responses, leading us to explore whether and to what extent PrLPs may build stress memory. The rice prionome is significantly enriched for Transposons/Retrotransposons (Ts/RTRs), and we derived transcriptional regulatory inferences from diurnal gene expression revealing a complex regulatory network between PrLPs, transcription factors and genes known to be involved in stress priming, as well as transient and trans-generational plant memory. Overall, our data suggest that plant memory mechanisms may rely upon protein-based signals embedded in PrLPs, in addition to chromatin-based epigenetic signals and provides important insights into the anticipated role of prions in stress and memory.

plant biology↗

bioRxiv2020

Decision Support Systems based on Scientific Evidence: Bibliometric Networks of Invasive Lantana camara.

Extraction and analysis of useful knowledge from the vast amount of relevant published literature can add valuable insights to any research theme or area of interest. We introduce a simplified bibliometric data analysis protocol for gaining substantial insights into research thematics, which can also serve as a handy practical skill for researchers, while working from home. In this paper, we provide ways of developing a holistic research strategy using bibliometric-data driven approaches that integrate network analysis and information management, without the need of full paper access. This protocol is a comprehensive multi-modular pathway for analysis of metadata obtained from major scientific publishing houses by use of a Decision Support System (DSS). A simple case study on the invasive species Lantana camara has been presented as a proof-of-concept to show how one can implement this DSS based protocol. Some perspectives are also provided on how the outcomes can be used directly or scaled up for long term research interventions. We hope that this work will simplify exploratory literature review, and enable rational design of research objectives for scholars, as well as development of comprehensive grant proposals that address gaps in research.

scientific communication and education↗

bioRxiv2020

TOR coordinates with transcriptional and chromatin machinery to regulate thermotolerance and thermomemory

Global warming exhibits profound effects on plant fitness and productivity. To withstand stress, plants sacrifice their growth and activate protective stress responses for ensuring survival. However, the switch between growth and stress is largely elusive. In the past decade, emerging role of Target of Rapamycin (TOR) has been studied linking energy and stress signaling. Here, we have identified an important role of Glc-TOR signaling in plant adaptation to heat stress (HS). Glc-TOR via the E2Fa signaling module regulates the transcription of heat shock factor genes through direct recruitment of E2Fa onto their promoter regions. Glc also epigenetically governs the transcription of core HS signaling genes in a TOR-dependent manner. TOR acts in concert with p300/CREB HISTONE ACETYLTRANSFERASE1 (HAC1) and dictates the epigenetic landscape of HS loci to regulate thermotolerance. Arabidopsis plants defective in TOR and HAC1 exhibited reduced thermotolerance with a decrease in expression of core HS signaling genes. In addition, TOR also promotes accumulation of histone H3K4me3 marks at the promoters of thermomemory-related genes and therefore, governs thermomemory. Collectively, our findings thus reveal a mechanistic framework in which Glc-TOR signaling through different modules determines the integration of stress and energy signaling to regulate thermotolerance and thermomemory.

plant biology↗

bioRxiv2020

Comparative genomics of StAR-related lipid transfer (START) domains across wild and cultivated rice

START proteins, encoded by a plant amplified family of evolutionary conserved genes, are known to bind lipids/sterols in mammals. In the plant kingdom, they have been reported in proteins involved in lipid binding, transport, signaling, as well as modulation of transcriptional activity, but there is very limited information on sub-functionalization or evolution of new function within the amplified gene family. Availability of ten fully annotated wild and cultivated rice varieties enables a comprehensive analysis of this family across the rice pangenome, across functional categories, as well as across START sub-families. The presence of START domains in all seven wild and three cultivated rice genomes suggests low dispensability and critical functional roles for this family, further supported by chromosomal mapping, duplication analysis and conservation of domain structure. Analysis of synteny highlights a preponderance of segmental and dispersed modes of duplication among STARTs, while transcriptomic investigation of the main cultivated variety Oryza sativa var. japonica reveals sub-functionalization among START genes family members in terms of preferential expression across various developmental stages and anatomical parts, especially flowering related parts. Importance of this family was further supported by Ka/Ks ratios confirming strong negative/purifying selection, implying that START family duplication is strongly constrained and evolutionarily stable.

bioinformatics↗

bioRxiv2020

Multi-omics analysis of aspirin treatment response in mice provide molecular insights and targets linked to liver fibrosis regression.

Background & Aims Aspirin has potent anti-platelet activities and possibly helps regression of fibrosis. We investigated antifibrotic mechanisms of aspirin in the murine CCl4 model and in patients with hepatic fibrosis.Methods Multiomics analysis identified networks and molecular targets regulated by aspirin which were validated in murine model and in patients with liver fibrosis.Results Biochemical/histopathological changes and hepatic fibrosis were greater in CCl4-treated mice compared to CCl4-aspirin (CCl4+ASA) or control mice (p<0.05). In CCl4+ASA mice, integrated proteome-metabolome analysis showed an increase in autophagy, drug metabolism, glutathione and energy metabolism (p<0.05) and decrease in inflammatory pathways, arachidonic acid and butanoate metabolism (p<0.05). Global cross-correlation analysis linked fibrosis markers with protein-metabolite pathways (r2>0.5, p<0.05). Liver proteome enrichment for immune clusters using blood transcription module correlated with histidine and tryptophan metabolism (r2>0.5, p<0.05). Aspirin decreased Ryanodine-receptor-2 (RYR2;oxidative-stress), Arginase-1 (ARG-1;urea cycle), Arachidonate-5-lipoxygenase (ALOX5;leukotriene metabolism), and Kynurenine-3-monooxygenase (KMO;tryptophan metabolism; p<0.05) which correlated with reduction in α-SMA, PDGFR-β and degree of hepatic fibrosis (r2>0.75; p<0.05) in animal and human studies, and, in-vitro analysis. Aspirin modulated intracellular-calcium and oxidative-stress levels by reducing RYR2 expression in activated LX-2 cells. It modulated the liver microbiome and its functions which also correlated with ARG1, ALOX5, RYR2 expression (r2>0.5, p<0.05). Metaproteome analysis showed significant microbiome similarity at phylum level in murine liver tissues and fecal samples. Aspirin increased the abundance of Firmicutes (Ruminococcaceae, Lachnospiraceae, and Clostridiaceae) and their functionality, as assessed by glycerol-3-phosphate dehydrogenase (NAD(P)(+) and dTMP-kinase activity (p<0.05).Conclusions Aspirin demonstrates broad beneficial effects following oxidative injury, inflammation, and hepatic fibrosis. Aspirin induces distinctive hepatic proteome/metabolome and intrahepatic microbiome changes which are indicative of fibrosis regression and could be further explored as therapeutic targets.Competing Interest StatementThe authors have declared no competing interest.View Full Text

molecular biology↗

bioRxiv2020

Gjd2b-mediated gap junctions promote glutamatergic synapse formation and dendritic elaboration in Purkinje neurons

Gap junctions between neurons serve as electrical synapses, in addition to conducting metabolites and signaling molecules. These functions of gap junctions have led to the idea that during development, gap junctions could prefigure chemical synapses. We present evidence for this idea at a central, glutamatergic synapse and provide some mechanistic insights. Here, we show that reduction or loss of Gjd2b-containing gap junctions led to a decrease in glutamatergic synapse density in cerebellar Purkinje neurons (PNs) in larval zebrafish. Gjd2b-/- larvae exhibited faster mEPSCs and a consistent decrease in dendritic arbor size. These PNs also showed decreased branch elongations but normal rate of branch retractions. Further, the dendritic growth deficits in gjd2b-/- mutants were rescued by expressing full length Gjd2b in single PNs. This suggests that Gjd2b may form heterotypic channels with other connexins in gjd2b-/- larvae, though it is not clear if PNs in wild type animals make homotypic or heterotypic gap junction channels. Dendritic growth deficits were not rescued by expressing a deletion mutant of Gjd2b unable to form functional channels. Finally, the expression levels of five isoforms of camkii were increased in gjd2b-/- larvae and inhibition of CaMKII restored dendritic arbor lengths of mutant larvae to wild type levels. These results suggest a link between signaling via Gjd2b-containing gap junctions, CaMKII function and dendritic growth. In sum, our results demonstrate that Gjd2b-mediated gap junctions are key regulators of glutamatergic synapse formation and dendritic elaboration in PNs.

neuroscience↗

bioRxiv2019

Membrane insertion of chromogranin B for granule maturation in regulated secretion

Regulated secretion serves responses to specific stimuli in eukaryotes. An anion conductance was found essential for maturation and acidification of secretory granules four decades ago, but its genetic identity was unknown. We now demonstrate that chromogranin B (CHGB), an obligate granule protein, constitutes the long-sought anion channel. High-pressure freezing immuno-electron microscopy and biochemical assays showed native CHGB in close proximity to secretory granule membranes, and its membrane-bound and soluble forms both reconstituted Cl- channels. Release of secretory granules delivered CHGB clusters to plasma membranes, which dominate whole-cell anion conductance. Intragranular pH measurements and cargo maturation assays found that CHGB channels supported proinsulin - insulin conversion and dopamine-loading in neuroendocrine cells. {beta}-cells from Chgb-/- mice exhibited significant granule deacidification, accounting for hyperproinsulinemia, altered glucose-tolerance response and lower dopamine concentration in chromaffin granules in these animals. Membrane insertion of well-conserved CHGB is thus indispensable for granule maturation in exocrine, endocrine and neuronal cells. HighlightsO_LINative CHGB is amphipathic and distributes in the lumen and membranes of secretory granules with contrastingly different destinies and functions. C_LIO_LINative CHGB, once delivered to cell surface via granule exocytosis, dominates anion conductance in plasma membranes. C_LIO_LICHGB channels facilitate granule acidification and cargo maturation in cultured and primary neuroendocrine cells. C_LIO_LICHGB channels from bovine, rat and mouse cells all serve the long-missing, intra-organellar anion shunt pathway in the secretory granules for regulated secretion. C_LI

cell biology↗

bioRxiv2019

A dynamic control of human telomerase holoenzyme

Human telomerase functions in maintaining genome stability by adding telomeric repeats to the termini of linear chromosomes. Past studies have revealed profound insights into telomerase functions. However, low abundance of functional telomerase and difficulty in quantifying its activity leave partially characterized its thermodynamic and kinetic properties. Using a newly developed method to count individual extension products, we demonstrate that human telomerase holoenzymes contain fast- and slow-acting catalytic sites. Surprisingly, both active sites become inactive after two consecutive rounds of catalysis. The fast active sites turn off ~40-fold quicker than the slow ones and exhibit higher affinity to substrates. In dimeric enzymes, the two sites work in tandem with the faster site functioning before the slower one. In monomeric enzymes, the active sites also perform single-run catalysis. Interestingly, the inactive enzymes can be reactivated by intracellular telomerase-activating factors (iTAFs) available in multiple cell types. Together, the single-run catalysis and the iTAF-triggered reactivation serve as a novel control circuit to ensure that the telomerase holoenzymes are dynamically controlled to match their number of active sites with the number of telomeres they extend. Such exquisite kinetic control of telomerase activity is expected to play important roles in cell division and ageing.

cell biology↗