Biology subjects

Lee, D.-h.

Publications and source records attributed to Lee, D.-h..

3 recordsLinked to original sources

bioRxiv2025

Characterizing Traction Forces in Upstream-Migrating Hematopoietic-like KG1a Cells Under Shear Flow

Cell migration is critical to leukocyte function, enabling leukocytes to patrol tissues and respond to inflammatory cues. Upstream migration is a distinct form of cell motility which enables leukocytes to move against the direction of fluid flow on Intercellular Adhesion Molecule-1 (ICAM-1) surfaces. Upstream migration is mediated by the leukocyte integrin, Lymphocyte Function-Associated Antigen-1 (LFA-1). While this behavior has been observed across multiple immune cell types, the mechanical forces underlying upstream migration have not been measured. Here, we demonstrate the use of Traction Force Microscopy (TFM) to quantify spatiotemporal patterns of force generation during upstream migration of KG1a cells, a hematopoietic progenitor cell line that exhibits robust upstream migration on ICAM-1 functionalized hydrogels. Under static (no-flow) conditions, KG1a cells displayed random motility and traction profiles that varied with time. In contrast, cells exposed to shear flow generated persistent, polarized tractions aligned with the axis of migration. Population analysis showed that maximum RMS traction forces were significantly elevated during upstream migration compared to static conditions (mean: 428.5 {+/-} 63.0 nN vs 220.8 {+/-} 22.2 nN, p = 0.0078), as were average RMS forces (mean: 82.6 {+/-} 12.9 nN vs 45.9 {+/-} 4.4 nN, p = 0.0184), while minimum force values remained comparable between groups. These findings indicate a specific amplification of stresses required to overcome applied forces during upstream migration. By integrating single-cell and population-level force analyses, this study defines upstream migration as a mechanically reinforced state characterized by amplified, directionally coherent traction dynamics. Our methods enable future dissection of the molecular regulators that coordinate force generation with migration under flow. SIGNIFICANCEUpstream migration is a critical yet poorly understood mode of immune cell motility. Here, we use traction force microscopy under physiologically relevant shear stresses to provide the first quantitative characterization of traction dynamics during upstream migration. We show that upstream migrating cells generate significantly greater average and peak forces than cells under static conditions, revealing a distinct mechanical program for directed migration against flow. These findings establish a platform for dissecting the molecular regulators of force generation in immune cells and set the stage for future perturbation-based studies aimed at understanding how mechanical forces shape immune cell trafficking and vascular navigation.

biophysics↗

bioRxiv2023

HUWE1 Amplifies Ubiquitin Modifications to Broadly Stimulate Clearance of Proteins and Aggregates

Selective breakdown of proteins and aggregates is crucial for maintaining normal cellular activities and is involved in the pathogenesis of diverse diseases. How the cell recognizes and tags these targets in different structural states for degradation by the proteasome and autophagy pathways has not been well understood. Here, we discovered that a HECT-family ubiquitin ligase HUWE1 is broadly required for the efficient degradation of soluble factors and for the clearance of protein aggregates/condensates. Underlying this capacity of HUWE1 is a novel Ubiquitin-Directed ubiquitin Ligase (UDL) activity which recognizes both soluble substrates and aggregates that carry a high density of ubiquitin chains and rapidly expand the ubiquitin modifications on these targets. Ubiquitin signal amplification by HUWE1 recruits the ubiquitin-dependent segregase p97/VCP to process these targets for subsequent degradation or clearance. HUWE1 controls the cytotoxicity of protein aggregates, mediates Targeted Protein Degradation and regulates cell-cycle transitions with its UDL activity.

molecular biology↗

bioRxiv2019

Agricultural and geographic factors shaped the North American 2015 highly pathogenic avian influenza H5N2 outbreak

The 2014 - 2015 highly pathogenic avian influenza (HPAI) H5NX outbreak represents the largest and most expensive HPAI outbreak in the United States to date. Despite extensive traditional and molecular epidemiological studies, factors associated with the spread of HPAI among midwestern poultry premises remain unclear. To better understand the dynamics of this outbreak, 182 full genome HPAI H5N2 sequences isolated from commercial layer chicken and turkey production premises were analyzed using evolutionary models modified to incorporate epidemiological and geographic information. Epidemiological compartmental models constructed in a phylogenetic framework provided evidence that poultry type acted as a barrier to the transmission of virus among midwestern poultry farms. Furthermore, after initial introduction, a continuous external source of virus was not needed to explain the propagation of HPAI cases within the commercial poultry industries. Discrete trait diffusion models indicated that within state viral transitions occurred more frequently than inter-state transitions. Distance, road density and proportion of water coverage were all supported as associated with viral transition between county groups (Bayes Factor > 3.0). Together these findings indicate that the midwestern poultry industries were not a single homogenous population, but rather, the outbreak was shaped by poultry sectors and geographic factors.\n\nAUTHOR SUMMARYThe highly pathogenic avian influenza outbreak among poultry farms in the midwestern United States appears to be influenced by agricultural and geographic factors. After initial introduction of the virus into the poultry industries, no further introductions (such as from a wild bird reservoir) were necessary to explain the continuation of the outbreak from March to June 2015. Additionally, evidence suggests that proximity increases the chances of viral movement between two locations. While many hypotheses have been proposed to explain the transmission of virus among poultry farms, the support for road density as an important driver of viral movement suggests human-mediated viral transportation played a key role in the spread of the highly pathogenic H5N2 outbreak in North America.

epidemiology↗