Biology subjects

Le, K. M.

Publications and source records attributed to Le, K. M..

3 recordsLinked to original sources

bioRxiv2026

Nuclear wrinkles result from geometric adaptations to cellular and nuclear morphological changes in epithelial cells

Mechanical cues influence cell behavior and fate and are frequently accompanied by changes in nuclear shape; however, how epithelial nuclei accommodate such deformations remains incompletely understood. Here, we investigated the formation and regulation of nuclear wrinkles (NWs), inward folds of the nuclear envelope, in human epithelial cells. Using quantitative confocal imaging in 2.5D spheroid cultures and controlled 2D monolayers, we found that NWs formed frequently in MCF10A cells but rarely in hTERT-RPE1 cells, indicating pronounced cell-type specificity. NW frequency increased with cell density and was tightly associated with coordinated geometric changes consistent with nuclear rounding. Disruption of F-actin organization, but not microtubules, robustly induced NW formation, and acute cell rounding triggered by trypsinization was sufficient to induce widespread wrinkling across multiple cell types. Live-cell imaging revealed that NWs are dynamic and reversible at low cell density but become stabilized under sustained confinement. NW formation occurred without detectable nuclear envelope rupture, DNA damage, or stress-associated histone phosphorylation. Quantitative analysis supports a passive geometric model in which redistribution of excess nuclear surface area accommodates nuclear shape remodeling, allowing epithelial nuclei to buffer mechanical constraints while preserving nuclear integrity.

cell biology↗

bioRxiv2024

Frustration in the Protein-Protein interface Plays a Central Role in the Cooperativity of PROTAC Ternary Complexes

Targeted protein degradation of a protein of interest (POI) by Proteolysis Targeting Chimeras (PROTACs) is an attractive approach for dealing with formerly undruggable protein targets. PROTACs are heterobifunctional molecules that connect a POI-binding and an E3-ligase (E3) binding motif with a linker. The simultaneous binding and formation of a ternary POI::PROTAC::E3 complex (TC) induces proximity between the POI and the E3, allowing for POI-ubiquitination and subsequent induction of proteasomal degradation. Despite the availability of many three-dimensional structures of TCs, unveiling the structure-function relationships for the design of PROTACs remains a challenge. This is because the TCs can be dynamic with a complex conformational landscape that individual crystal structures may not capture. In this work, we used SMARCA2 as the POI and VHL as the E3-ligase and solved the X-ray crystal structures of the respective ternary complexes with four different PROTACs. Molecular dynamics (MD) simulations were used to show that the SMARCA2-VHL interface is flexible with multiple energy minima. The protein-protein (POI-E3) interactions are largely formed by residues located in structurally disordered loops in both VHL and SMARCA2. The residue pairs in the SMARCA2-VHL interface are frustrated, i.e., adopt a suboptimal energetic state. The number of frustrated residue pairs averaged over the MD ensemble shows a positive correlation with the experimentally determined cooperativity of the PROTACs. This indicates that protein-protein interface frustration can play an important role in PROTAC function. The TC ensembles of VHL, SMARCA2 and 11 different PROTACs were modeled by comparative modeling followed by MD. The frustration was subsequently calculated from the MD trajectories and correlated with the cooperativity. We found that identification of the dynamic protein-protein contacts and frustrated residue pairs in the interface can provide a rational framework for the structure-based design of PROTACs.

biophysics↗

bioRxiv2018

CEACAM1 regulates the IL-6 mediated fever response to LPS through the RP105 receptor in murine monocytes

Systemic inflammation and the fever response to pathogens are coordinately regulated by IL-6 and IL-1{beta}. We previously showed that CEACAM1 regulates the LPS driven expression of IL-1{beta} in murine neutrophils through its ITIM receptor. We now show that the prompt secretion of IL-6 in response to LPS is regulated by CEACAM1 expression on bone marrow monocytes. Ceacam1-/- mice over-produce IL-6 in response to an i.p. LPS challenge, resulting in prolonged surface temperature depression and overt diarrhea compared to their wild type counterparts. Intraperitoneal injection of a 64Cu-labeled LPS, PET imaging agent shows confined localization to the peritoneal cavity, and fluorescent labeled LPS is taken up by myeloid splenocytes and muscle endothelial cells. While bone marrow monocytes and their progenitors (CD11b+Ly6G-) express IL-6 in the early response (<2 hours) to LPS in vitro, these cells are not detected in the bone marrow after in vivo LPS treatment due to their rapid and complete mobilization to the periphery. Notably, tissue macrophages are not involved in the early IL-6 response to LPS. In contrast to human monocytes, TLR4 is not expressed on murine bone marrow monocytes. Instead, the alternative LPS receptor RP105 is expressed and recruits MD1, CD14, Src, VAV1 and {beta}-actin in response to LPS to produce IL-6. CEACAM1 negatively regulates RP105 signaling in monocytes by recruitment of SHP-1, resulting in the sequestration of pVAV1 and {beta}-actin from RP105. This novel pathway and regulation of IL-6 producing by CEACAM1 defines a novel role for monocytes in the fever of mice to LPS.\n\nAUTHOR SUMMARYFever is one of the most common signs of the immune response to pathogens. The fever response to LPS or endotoxin of gram-negative bacteria is mediated by the combined action of two cytokines, IL-1{beta} and IL-6. Regulation of their production in response to LPS is an important area of investigation. While we previously showed that the regulation of IL-1{beta} production in neutrophils is through the lymphocyte receptor CEACAM1, we were interested if a similar mechanism operated for IL-6. Using a mouse model in which the CEACAM1 gene was knocked out, we show that IL-6 is over-produced compared to normal mice, and that monocytes, rather than neutrophils were the principal IL-6 producing cells. Surprisingly, murine monocytes do not express TLR4, the most commonly studied receptor for LPS, but instead express the low affinity LPS receptor, RP105, a receptor common expressed on B-cells. Furthermore, we show that bone marrow monocytes are rapidly released into the blood and home to tissues throughout the body in response to LPS. These findings explain much of the confusion in the literature concerning the immediate source of IL-6 and the distinct differences between murine and human monocytes in their in responses to LPS.

immunology↗