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Biology subjects

Kwak, M.

Publications and source records attributed to Kwak, M..

13 recordsLinked to original sources

DynMoCo: a Novel AI Framework to Reveal Modular Substructures of Protein From Molecular Dynamics

Proteins are dynamic molecular machines whose functions are determined by their structures. While static structures can offer initial insights or hypotheses about protein function, they are often insufficient for a detailed mechanistic understanding. Molecular dynamics (MD) simulations provide atomistic view of proteins dynamic motion and conformational change, but the resulting high-dimensional data are challenging to interpret. Traditional summary statistics and dimensionality-reduction methods often focus on global motions and can overlook regional, yet functionally critical motions. Inspired by approaches from social network science, we introduce a novel perspective for analyzing MD simulations through dynamic community detection, where molecules are modeled as time-evolving graphs, and communities of residues or atoms that move coherently or exhibit functional coupling are identified. We present DynMoCo, a novel deep learning framework that integrates graph convolutional networks with recurrent models for end-to-end dynamic community detection on molecular graphs. Given a MD trajectory, DynMoCo identifies spatially grounded substructures, tracks their evolution over time, and can incorporate structural knowledge to ensure physically meaningful communities. We provide a library of custom-written scripts to allow users to extract and visualize these communites on the MD simulated molecules in motion. We demonstrate the method on force-ramp and force-clamp steered MD simulations of three integrin systems, revealing modular substructures within known domains and characterizing their conformational rearrangements during force-induced unbending. By reducing high-dimensional MD data into interpretable communities, this approach offers new insights into the intrinsic organization and dynamic function of complex biomolecular systems. SIGNIFICANCEProteins often perform their functions through dynamic, locally coordinated motions. Molecular dynamics simulations provide detailed views of these motions but produce high-dimensional data that are challenging to analyze and interpret. We present a novel deep learning model that analyzes molecular dynamics simulations data and identifies structurally coherent and potentially functionally related communities, while tracking their temporal evolution. This analysis tool provides a novel way to analyze MD data transforming it into interpretable representations of modular dynamic, enabling discovery of new mechanistic insights and advancing our understanding of how molecular motions drive biological function.

biophysics↗

Assessing the Effective Range for Individual Acoustic Identification: Comparison of Manual and Automatic Methods

Individual Acoustic Monitoring (IAM), especially when combined with passive acoustic monitoring (PAM), offers a non-invasive alternative to traditional mark-recapture methods to gain insights into species demography. Few studies have examined how identification decreases over distance along with degradation of identity cues. In this study, we conducted a song transmission experiment to quantify the range at which individual Yellowhammers (Emberiza citrinella) can be reliably identified. Songs from ten males (20 songs per individual, covering their full repertoire) were broadcast and re-recorded along a 200 m transect using AudioMoth recorders. Comparing manual classification by human observers with BirdNET classifier adapted for individual identification, we assess how well individuals could be distinguished at increasing distances. Humans were confident in assigning identity to a larger proportion of songs. Where identity has been assigned, both human and BirdNET were highly reliable at short distances (up to 50 m) discriminating even between very similar song types shared among males. At moderate distances (100 - 150 m), simple augmentation boosted BirdNETs performance remarkably, almost matching human classification accuracy. Our results indicate that individual recognition remains reliable up to 100 meters where both accuracy and agreement between assignment methods were high. Our results confirm that automated systems offer promising tools for large-scale, non-invasive individual monitoring, but challenges in accuracy and robustness persist at greater distances. We highlight the difference between signal detectability and individual identification range (much shorter) and its importance for optimizing PAM array designs.

zoology↗

MechanoMR microparticle (M3) sensors reveal dynamic stress loading as a driver of epithelial-mesenchymal transition

The dynamic mechanical response of tissues underlies their physiological function, yet direct, quantitative measurement of tissue stress in vivo has remained a major challenge. Here, we introduce the mechanoMR microparticle (M3, "M-cube") sensor, a hybrid soft-matter/nanoparticle probe that integrates directly into tissue mechanical networks while transducing local stress into quantitative magnetic resonance (MR) readouts with single-particle resolution. We demonstrate the utility of this platform across diverse model systems, including tumor spheroids, Xenopus embryos, and mouse xenografts, where the M3 sensor enables noninvasive, spatiotemporally resolved mapping of tissue stress dynamics during cancer development. Using this approach, we reveal that epithelial-mesenchymal transition (EMT) is accompanied by distinctive stress-remodeling patterns observable in vivo. Strikingly, we find that abrupt stress increases, rather than cumulative or peak stress magnitude, are the key determinants of EMT induction in cancer cells within the tumor microenvironment. Transcriptomic profiling under controlled stress-loading dynamics shows that sustained yet gradual stress escalation activates cytoprotective antioxidation pathways (e.g., FOXO/AMPK) that reinforce epithelial stability, whereas acute stress surges overwhelm these defense mechanisms, predisposing cells toward mesenchymal reprogramming. These findings establish the M3 sensor as a broadly applicable technology for linking dynamic mechanical cues to cell-state transitions in development, homeostasis, and disease.

bioengineering↗

Asymmetric Social Representations in the Prefrontal Cortex for Cooperative Behavior

Cooperation is a hallmark of social species, enabling individuals to achieve goals that are unattainable alone. Across species, cooperative behaviors are often organized by distinct social roles such as leaders and followers, yet the neural mechanisms supporting such role-based coordination remain elusive. Here we introduce a new paradigm for studying cooperation in mice, where pairs of animals engage in a joint spatial foraging task that naturally gives rise to stable leader-follower roles predictive of learning speed. Disruption of medial prefrontal cortex (mPFC) activity, particularly in followers, impairs cooperation and induces reciprocal shifts in how animals weigh self- and partner-related cues for decision-making. Calcium imaging reveals that mPFC encodes both leadership dynamics and an egocentric social value map of the partners position, each in an asymmetric, role-specific manner. Combining this behavior with a novel multi-agent inverse reinforcement learning framework, we identify latent value functions that guide cooperative decisions and are decodable from mPFC activity. These findings uncover fundamental neural computations that support cooperation, revealing how social roles shape decision-making in real time. Our work opens new avenues for investigating the cellular and circuit basis of social cognition and collective behavior.

neuroscience↗

Angulin-1/LSR inhibition transiently disrupts the blood-tumor barrier to enhance doxil permeability and impair malignant glioma progression

The blood-tumor barrier (BTB) prevents effective central nervous system (CNS) drug delivery, especially in malignant gliomas. Brain endothelium predominates the BTB and connects through bicellular and tricellular tight junctions (TJ). Angulin-1/LSR, is a highly expressed endothelial tricellular TJ. Our studies explore the role of Angubindin-1, an Angulin-1/LSR binder, to disrupt tricellular TJ integrity, increase drug entry and hamper glioma progression. Using rat brain endothelial cells (RBMVEC) we tracked Angulin-1/LSR localization and expression to the membrane; binding tightest to Angubindin-1 2-8 hours post-treatment (p < 0.05). Angubindin-1 dose-dependently reduced bicellular and tricellular TJs 1-4 hours post treatment (p < 0.05), returning to baseline by 24 hours (p < 0.05). In human and rat-derived glioma cells, Angubindin-1 transiently reduced Angulin-1/LSR expression between 2-8 hours (p < 0.05), with return to baseline by 24 hours (p < 0.001). Silenced Angulin-1/LSR expression on endothelium resulted in decreased mRNA levels of bicellular (occludin, claudin-5, ZO-1) and tricellular (tricellulin/MARVELD2, angulin-1/LSR) TJs compared to control (p < 0.01). Angubindin-1 treatment also inhibited efflux transporter P-gp in both RBMVECs and glioma cells with high P-gp expression only. Orthotopic rat glioma models were treated with Doxil (3 mg/kg), Angubindin-1 (10 mg/kg), or combination to evaluate BTB permeability/drug accumulation, and overall survival. Combination therapy enhanced Doxil tumor accumulation by 20% (p < 0.001), reduced tumor volume by day 14 (77.5% vs. 81.6%, p < 0.05), and significantly extended survival compared to Doxil alone (24 days vs. 18 days, p < 0.0001). These findings demonstrate the effects of tricellular tight junction inhibition on disrupting the BTB, enhancing CNS drug delivery, and improving rodent glioma survival. SignificanceThis study demonstrates that Angubindin-1, a targeted modulator of tricellular tight junction protein Angulin-1/LSR, transiently disrupts BTB integrity to enhance chemotherapy delivery and prolong survival in glioma-bearing rats. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/667901v1_ufig1.gif" ALT="Figure 1"> View larger version (76K): org.highwire.dtl.DTLVardef@b1b46corg.highwire.dtl.DTLVardef@bc552dorg.highwire.dtl.DTLVardef@7c1a74org.highwire.dtl.DTLVardef@1ace101_HPS_FORMAT_FIGEXP M_FIG C_FIG Angubindin-1 targets both bicellular tight junctions and the tricellular tight junction protein, Angulin-1/LSR, in brain endothelial and glioma cells leading to transient disruption of the blood-tumor barrier (BTB) and inhibition of P-glycoprotein towards enhanced Doxil penetration and reduced tumor burden.

cell biology↗

Synthetic lipid rafts formed by cholesterol nano-patch induce T cell activation

Lipid rafts cluster at the immunological synapse during activation and serve as signaling hubs in T cells. While cholesterol plays a crucial role in lipid raft formation, the impact of their spatial configuration remains less understood. Here, we introduce programmable DNA origami, cholesterol nano-patch, for nanoscale spatial control of cholesterols on live T cell membranes, enabling us to elucidate their roles in lipid raft formation, receptor activation, and intracellular signaling. We demonstrate that CNPs with high-density cholesterol arrangements efficiently bind to the T cell plasma membrane and form a large and polarized coalescence, leading to the stabilization of ordered lipid membrane domains by increasing the local concentration of cholesterols. These synthetic lipid rafts colocalize with flotillin-1, a raft-associated protein, and promote the membrane reorganization and physical segregation of key signaling molecules, such as T cell receptors, Lck and LAT kinases, and CD45. Consequently, this leads to early T cell activation in the absence of antigenic stimulation. Our DNA origami approach demonstrates the direct role of cholesterol in lipid raft formation, leading to membrane phase separation and protein reorganization, which are sufficient to induce early T cell activation.

bioengineering↗

Distributed information encoding and decoding using self-organized spatial patterns

Dynamical systems often generate distinct outputs according to different initial conditions, and one can infer the corresponding input configuration given an output. This property captures the essence of information encoding and decoding. Here, we demonstrate the use of self-organized patterns, combined with machine learning, to achieve distributed information encoding and decoding. Our approach exploits a critical property of many natural pattern-formation systems: in repeated realizations, each initial configuration generates similar but not identical output patterns due to randomness in the patterning process. However, for sufficiently small randomness, different groups of patterns that arise from different initial configurations can be distinguished from one another. Modulating the pattern generation and machine learning model training can tune the tradeoff between encoding capacity and security. We further show that this strategy is applicable to non-biological dynamical systems and scalable by implementing the encoding and decoding of all characters of the standard English keyboard. Significance StatementSelf-organized patterns are ubiquitous in biology. They arise from interactions in and between cells, and with the environment. These patterns are often used as a composite phenotype to distinguish cell states and environment conditions. Conceptually, pattern generation under an initial condition is encoding; discerning the initial condition from the pattern represents decoding. Inspired by these examples, we develop a scheme, integrating mathematical modeling and machine learning, to use self-organization for secure and accurate information encoding and decoding. We show that this strategy is applicable to non-biological dynamical systems. We further demonstrate the scalability of the scheme by generating a complete mapping of the standard English keyboard, allowing encoding of English text. Our work serves as an example of nature-inspired computation.

systems biology↗

Magneto-acoustic protein nanostructures for non-invasive imaging of tissue mechanics in vivo

Measuring cellular and tissue mechanics inside intact living organisms is essential for interrogating the roles of force in physiological and disease processes, and is a major goal in the field of mechanobiology. However, existing biosensors for 3D tissue mechanics, primarily based on fluorescent emissions and deformable materials, are limited for in vivo measurement due to the limited light penetration and poor material stability inside intact, living organisms. While magneto-motive ultrasound (MMUS), which uses superparamagnetic nanoparticles as imaging contrast agents, has emerged as a promising modality for real-time in vivo imaging of tissue mechanics, it has poor sensitivity and spatiotemporal resolution. To overcome these limitations, we introduce magneto-gas vesicles (MGVs), a unique class of protein nanostructures based on gas vesicles and magnetic nanoparticles that produces differential ultrasound signals in response to varying mechanical properties of surrounding tissues. These hybrid protein nanostructures significantly improve signal strength and detection sensitivity. Furthermore, MGVs enable non-invasive, long-term, and quantitative measurement of mechanical properties within 3D tissues and organs in vivo. We demonstrated the performance of MGV-based mechano-sensors in vitro, in fibrosis models of organoids, and in vivo in mouse liver fibrosis models.

biochemistry↗

Phylogenomic analyses in the apple genus Malus s.l. reveal widespread hybridization and allopolyploidy driving the diversifications, with insights into the complex biogeographic history in the Northern Hemisphere

Phylogenomic evidence from an increasing number of studies has demonstrated that different data sets and analytical approaches often reconstruct strongly supported but conflicting relationships. In this study, hundreds of single-copy nuclear (SCN) genes (785) and complete plastomes (75) were used to infer the phylogenetic relationships and estimate the historical biogeography of the apple genus Malus sensu lato, an economically important lineage disjunctly distributed in the Northern Hemisphere involved in known and suspected hybridization and allopolyploidy events. The nuclear phylogeny recovered the monophyly of Malus s.l. (including Docynia); however, it was supported to be biphyletic in the plastid phylogeny. An ancient chloroplast capture event best explains the cytonuclear discordance that occurred in the Eocene in western North America. Our conflict analysis demonstrated that ILS, hybridization, and allopolyploidy could explain the widespread nuclear gene tree discordance. We detected one deep hybridization event (Malus doumeri) involving the ancestor of pome-bearing species and Docynia delavayi, and one recent hybridization event (Malus coronaria) between M. sieversii and a combined clade of M. ioensis and M. angustifolia. Furthermore, our historical biogeographic analysis combining living and fossil species supported a widespread East Asian-western North American origin of Malus s.l., followed by a series of extinction events in the Eocene in northern East Aisa and western North America. This study provides a valuable evolutionary framework for the breeding and crop improvement of apples and their close relatives.

evolutionary biology↗

Testing in vitro toxicity of nanoparticles in 3D cell culture with various extracellular matrix scaffold

Nanomaterials are used in a variety of fields and toxicity assessment is paramount for their development and application. Although most toxicity assessments have been performed in 2D (2-Dimensional) cell culture, the inability to adequately replicate the in vivo environment and toxicity is a limitation. To overcome the limitation, a 3D (3-Dimensional) cell culture method has been developed to make an environment closer to an in vivo system. In this study, 20 nm SiO2 nanoparticles were dispersed in serum-containing (SC) and serum-free (SF) media to compare 2D cell culture and 3D cell culture toxicity. The cells were subjected to a 3D cell culture method in which HepG2, a human-derived liver cancer cell line, was mixed on a scaffold. We found that nanoparticles induced toxicity in 2D cell culture, but toxicity was not observed in 3D cell culture similar to in vivo environment. However, differences in toxicity were observed between the three types of scaffolds in the absence of serum as the number of cells decreased.

pharmacology and toxicology↗

Size-dependent protein segregation creates a spatial switch for Notch and APP signaling

Aberrant cleavage of Notch by {gamma}-secretase is implicated in numerous diseases, but how cleavage is regulated in space and time is unclear. Here, we report that cadherin-based adherens junctions (cadAJs) are sites of high cell-surface {gamma}-secretase activity, as well as sites of constrained physical space that excludes {gamma}-secretase substrates having large extracellular domains (ECDs) like Notch. ECD shedding initiates drastic spatial relocalization of Notch to cadAJs, allowing enzyme-substrate interactions and downstream signaling. Spatial mutations by adjusting the ECD size or the physical constraint alter signaling. Dysregulation of this spatial switch promotes precocious differentiation of ventricular zone neural progenitor cells in vivo. We show the generality of this spatial switch for amyloid precursor protein proteolysis. Thus, cadAJs create spatially distinct biochemical compartments regulating cleavage events involving {gamma}-secretase and preventing aberrant activation of receptors. One Sentence SummaryNotch cleavage by {gamma}-secretase is regulated through dynamic spatial control of receptors, adhesion molecules, and activating proteases

cell biology↗

Diverse Epithelial Cell Populations Contribute to Regeneration of Secretory Units in Injured Salivary Glands

Salivary glands exert exocrine secretory function to provide saliva for lubrication and protection of the oral cavity. Its epithelium consists of several differentiated cell types including acinar, ductal and myoepithelial cells that are maintained in a lineage-restricted manner during homeostasis or after mild injuries. Glandular regeneration following a near complete loss of secretory cells, however, may involve cellular plasticity, although the mechanism and extent of such plasticity remain unclear. Here, by combining lineage-tracing experiments with a model of severe glandular injury in the mouse submandibular gland, we show that de novo formation of secretory units involves induction of cellular plasticity in multiple non-acinar cell populations. Fate-mapping analysis revealed that although ductal stem cells marked by cytokeratin K14 and Axin2 undergo a multipotency switch, they do not make a significant contribution to acinar regeneration. Intriguingly, more than 80% of regenerated acini derive from differentiated cells including myoepithelial and ductal cells that dedifferentiate to a progenitor-like state before redifferentiation to acinar cells. The potential of diverse cell populations serving as a reserve source for acini widens the therapeutic options for hyposalivation. SummarySalivary glands rely in recruitment of committed and fully differentiated cell populations as well as stem cells to ensure rapid regeneration and recovery of secretory cells.

cell biology↗

Single-cell microRNA/mRNA co-sequencing reveals non-genetic heterogeneity and novel regulatory mechanisms

Co-measurement of multiple omic profiles from the same single cells opens up the opportunity to decode molecular regulation that underlie intercellular heterogeneity in development and disease. Here, we present co-sequencing of microRNAs and mRNAs in the same single cells using a half-cell genomics approach. This method demonstrates good robustness (~95% success rate) and reproducibility (R2=0.93 for both miRNAs and mRNAs), and yields paired half-cell miRNA and mRNA profiles that could be independently validated. Linking the level of miRNAs to the expression of predicted target mRNAs across 19 single cells that are phenotypically identical, we observe that the predicted targets are significantly anti-correlated with the variation of abundantly expressed miRNAs, suggesting that miRNA expression variability alone may lead to non-genetic cell-to-cell heterogeneity. Genome-scale analysis of paired miRNA-mRNA co-profiles further allows us to derive and validate new regulatory relationships of cellular pathways controlling miRNA expression and variability.

systems biology↗