Biology subjects

Lee, L. S.

Publications and source records attributed to Lee, L. S..

3 recordsLinked to original sources

bioRxiv2026

Myosin-9b Controls Epithelial Brush Border Architecture through Motility-Dependent RhoA Signaling

Genetic variations in the MYO9B gene have been associated with Crohn's disease, celiac disease, and ulcerative colitis. These diseases have been characterized as primarily immune disorders. However, the overall molecular basis for the influence of Myo9b in these diseases remains poorly understood. Using in vivo small intestine ileum and human cell culture models, we identify a molecular function for Myo9b in the regulation of epithelial brush border microvilli. Using live-cell super-resolution microscopy, we characterize the motility of Myo9b as it moves toward enriched puncta at the tips of microvilli and visualize its direct regulation of small GTPase signaling using an active RhoA biosensor. In Myo9b knockout cells, microvilli abundance and dynamics are altered, but the cells ultimately maintain the presence of microvilli and the appropriate incorporation of microvilli specific cytoskeletal to membrane regulators such as Ezrin. Alternatively, expression of the Myo9b-S1011A disease variant as the only genetic copy in human cells results in a total loss of microvilli and Ezrin apical localization. These results indicate that Myo9b is a critical regulator of epithelial cell morphology and microvilli. Further, our data establish that the S1011A disease variant disrupts microvilli in human cells, suggesting a potential mechanistic link to its involvement in disease states.

cell biology↗

bioRxiv2024

The Rho effector ARHGAP18 coordinates a Hippo pathway feedback loop through YAP and Merlin to regulate the cytoskeleton and epithelial cell polarity.

The organization of the cells cytoskeletal filaments is coordinated through a complex network of signaling cascades activated by both internal and external cues. Two major actin regulatory pathways are signal transduction through Rho family GTPases and growth and proliferation signaling through the Hippo pathway. These two pathways define the actin cytoskeleton, controlling foundational cellular attributes such as morphology and polarity and are hijacked to promote proliferation and motility in aggressive cancers. In this study, we use human epithelial cells to investigate the interplay between the Hippo and Rho Family signaling pathways, which have predominantly been characterized as independent actin regulatory mechanisms. We identify that the RhoA effector, ARHGAP18, forms a complex with the Hippo pathway transcription factor YAP to address a long-standing enigma in the field. Using super resolution STORM microscopy, we characterize single-filament-level changes in the actin cytoskeleton that arise from CRISPR/CAS9 knockout of ARHGAP18. We report that the loss of ARHGAP18 results in cytoskeletal alterations driven by both dysregulated RhoA signaling and aberrant nuclear localization of YAP. These findings indicate that the Hippo and Rho family GTPase signaling cascades are temporally and spatially coordinated in their regulation of the actin cytoskeleton.

cell biology↗

bioRxiv2019

Developmental exposure to perfluorooctane sulfononate (PFOS) and perfluorooctanoic acid (PFOA) selectively decreases brain dopamine levels in northern leopard frogs

Per- and polyfluoroalkyl substances (PFAS) are synthetic compounds that are a major public health concern due to widespread use, long environmental and biological half-lives, detection in most human plasma samples, and links to multiple adverse health outcomes. The literature suggests that some PFAS may be neurotoxic. However, there are major gaps in the literature with respect to how environmentally-relevant doses during development may influence the nervous system. To address this gap, we utilized a sentinel species, Northern leopard frogs (Lithobates pipiens) to determine the effects of developmental exposure to environmentally relevant perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) on major neurotransmitter systems. Frog larvae at Gosner stage 25 were exposed to 10, 100, or 1000 ppb PFOS or PFOA for 30 days before neurochemical analysis. High performance liquid chromatography (HPLC) with electrochemical detection or fluorescent detection assays was used to measure neurotransmitter levels, which were normalized to protein levels in each sample. Dopamine (DA) decreased significantly in the brains of frogs treated with PFOA (1000 ppb) and PFOS (100 and 1000 ppb). Significant increases in DA turnover also resulted from PFOA and PFOS treatment. Neither PFOS, nor PFOA produced detectable alterations in serotonin (nor its metabolite), norepinephrine, gamma-amino butyric acid (GABA), glutamate, or acetylcholine. PFAS body burdens showed that PFOS accumulated relative to dose, while PFOA did not. These data suggest that DArgic neurotransmission is selectively affected in developmentally exposed amphibians and that PFAS should be evaluated for a potential role in diseases that target the DA system.

pharmacology and toxicology↗