Biology subjects

Kwon, H. Y.

Publications and source records attributed to Kwon, H. Y..

4 recordsLinked to original sources

bioRxiv2026

Structural basis for alternative 3' splice site selection in the human spliceosome active center

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/741260v1_ufig1.gif" ALT="Figure 1"> View larger version (97K): org.highwire.dtl.DTLVardef@279388org.highwire.dtl.DTLVardef@46d636org.highwire.dtl.DTLVardef@997672org.highwire.dtl.DTLVardef@12f40ee_HPS_FORMAT_FIGEXP M_FIG C_FIG Key findingsO_LICryo-EM reveals SDE2 as a novel factor stabilizing the spliceosome active center C_LIO_LISDE2 {Delta}N structures visualize a stalled C* state with impaired docking-factor engagement. C_LIO_LISDE2, Prp18, and FAM32A read a cis-code to stabilize weaker proximal 3'-ss. C_LIO_LISDE2 {Delta}N destabilizes 3'-ss docking and rescues BRCA1 and CFTR mis-splicing in vivo. C_LI Accurate alternative splicing requires discrimination between adjacent 3' splice sites (3'-ss) during catalysis and is disrupted by pathogenic AG-gain mutations that create competing 3'-ss. Here, we present cryo-EM structures of human spliceosomes assembled on native-sequence pre-mRNAs, revealing how the catalytic core controls alternative 3'-ss selection. SDE2 is a previously unrecognized active-center component that promotes a docking-competent spliceosome conformation. Machine learning, in vivo transcriptomics, and in vitro biochemistry show how SDE2 cooperates with FAM32A and Prp18 to act as readers of a cis-regulatory code that governs 3'-ss selection during catalysis. These factors promote weaker, proximal site use by counteracting an intrinsic distal bias generated by active-site interactions with the distal-site -4 nucleotide. Structural or genetic perturbation of these exon-ligation factors destabilizes proximal 3'-ss docking and restores canonical splicing in disease-relevant CFTR and BRCA1 AG-gain alleles. Our work establishes the spliceosome active center as a tunable regulatory hub for alternative splicing.

molecular biology↗

bioRxiv2024

Small Molecule Modulators of Beta-arrestins

{beta}-arrestins are multifunctional regulators of G protein-coupled receptor (GPCR) signaling, orchestrating diverse downstream signaling events and physiological responses across the vast GPCR superfamily. While GPCR pharmacology has advanced to target orthosteric and allosteric sites, as well as G proteins and GRKs, comparable chemical tools to study {beta}-arrestins remain lacking. Here, we report the discovery of small-molecule inhibitors that selectively target {beta}-arrestins and delineate their mechanism of action through integrated pharmacological, biochemical, biophysical, and structural analyses. These inhibitors disrupt {beta}-arrestin-engagement with agonist-activated GPCRs, impairing desensitization, internalization, and {beta}-arrestin-dependent functions while sparing G protein-receptor coupling. Cryo-EM, MD simulations, and structure-guided mutagenesis reveal that one modulator, Cmpd-5, engages a cryptic pocket formed by the middle, C-, and lariat loops of {beta}-arrestin1--a critical receptor-binding interface--stabilizing a distinct conformation incompatible with GPCR engagement. Together, these findings provide a mechanistic framework for {beta}-arrestin modulation, introducing transducer-targeted strategies to fine-tune GPCR signaling and guide the development of pathway-specific therapeutics.

biochemistry↗

bioRxiv2024

TGF-β expressed by M2 macrophages promotes wound healing by inhibiting TSG-6 expression by mesenchymal stem cells

Wound healing involves the collaboration of multiple cells, including macrophages and fibroblasts, and requires the coordination of cytokines, growth factors, and matrix proteins to regulate the repair response. In this study, we investigated how M2 macrophages regulate expression of the anti-fibrotic and anti-inflammatory regulator tumor necrosis factor- (TNF-)-stimulated gene 6 (TSG-6) secreted by adipose tissue-derived stem cells (ASCs) during wound healing. Interleukin (IL)-4/IL-13, which is used to differentiate macrophage M2 phenotypes, increases TSG-6 in ASCs; however, M2 macrophages significantly decrease TSG-6 in ASCs. Transforming growth factor (TGF)-{beta} expression was increased, and TNF- expression was decreased in M2 macrophages. TGF-{beta} inhibited IL-4/IL-13-induced ASC TSG-6 expression. In addition, TSG-6 suppressed TGF-{beta}-triggered wound closure and fibrogenic responses in LX-2 cells. Collectively, TSG-6 inhibited wound healing, but M2 macrophage-expressed TGF-{beta} prevented TSG-6 production from ASCs, which ultimately helped wound healing. Our results indicate that the balance of TNF- and TGF-{beta} levels during wound healing regulates TSG-6 production from ASCs, which may ultimately modulate the healing process. Our study findings could contribute to novel therapeutic strategies that manipulate the delicate balance between TNF- and TGF-{beta} to enhance wound repair and mitigate fibrosis.

cell biology↗

bioRxiv2024

Convective forces contribute to post-traumatic degeneration after spinal cord injury

Spinal cord injury (SCI) initiates a complex cascade of chemical and biophysical phenomena that result in tissue swelling, progressive neural degeneration, and formation of a fluid-filled cavity. Previous studies show fluid pressure above the spinal cord (supraspinal) is elevated for at least three days after injury and contributes to a phase of damage called secondary injury. Currently, it is unknown how fluid forces within the spinal cord itself (interstitial) are affected by SCI and if they contribute to secondary injury. We find spinal interstitial pressure increases from -3 mmHg in the naive cord to a peak of 13 mmHg at 3 days post-injury (DPI) but relatively normalizes to 2 mmHg by 7 DPI. A computational fluid dynamics model predicts interstitial flow velocities up to 0.9 m/s at 3 DPI, returning to near baseline by 7 DPI. By quantifying vascular leakage of Evans Blue dye after a cervical hemi-contusion in rats, we confirm an increase in dye infiltration at 3 DPI compared to 7 DPI, suggestive of higher fluid velocities at the time of peak fluid pressure. In vivo expression of the apoptosis marker caspase-3 is strongly correlated with regions of interstitial flow at 3 DPI, and exogenously enhancing interstitial flow exacerbates tissue damage. In vitro, we show overnight exposure of neuronal cells to low pathological shear stress (0.1 dynes/cm2) significantly reduces cell count and neurite length. Collectively, these results indicate that interstitial fluid flow and shear stress may play a detrimental role in post-traumatic neural degeneration. Translational Impact StatementTrauma to the central nervous system induces neural tissue degeneration, resulting in permanent disability and loss of function. A better understanding of this degenerative process is needed, towards developing new clinical treatments that effectively minimize tissue damage and preserve neural function after injury. The present study identifies a potential role for altered fluid transport within the injured spinal cord. These results provide new insight into basic pathophysiology and may inform therapeutic development for neuroprotection.

bioengineering↗