Biology subjects

Chung, B. M.

Publications and source records attributed to Chung, B. M..

5 recordsLinked to original sources

bioRxiv2024

Canonical Notch2 Signaling Regulates the Development of Iron-recycling Macrophages and Iron Homeostasis

Red pulp macrophages (RPM) and bone marrow macrophages (BMM) are iron-recycling cells involved in iron homeostasis and erythropoiesis. Here, we show, using conditional deletion strategies of Notch signaling components, that the development of RPM and BMM is regulated by canonical Notch2 signaling. Loss of functional Notch2, or its nuclear mediator Rbpj, causes impairment in RPM and BMM and iron overload in the spleen and bone marrow, while prototypic RPM genes required for iron handling are downregulated. This was accompanied by splenic extramedullary hematopoiesis and changes in splenic microarchitecture. Furthermore, early postnatal transfer of bone marrow and fetal liver progenitors rescued the defects in RPM and BMM and iron overload in a Notch2-dependent manner, demonstrating the potential to restore defective tissue resident macrophage niches by Notch-competent progenitors. Thus, canonical Notch2 is required for development and function of iron-recycling macrophages.

immunology↗

bioRxiv2024

Parabrachial CGRP neurons modulates conditioned active defensive behavior under a naturalistic threat

Recent studies suggest that calcitonin gene-related peptide (CGRP) neurons in the parabrachial nucleus (PBN) represent aversive information and signal a general alarm to the forebrain. If CGRP neurons serve as a true general alarm, activation of CGRP neurons can trigger either freezing or fleeing defensive behavior, depending on the circumstances. However, the majority of previous findings have reported that CGRP neurons modulate only freezing behavior. Thus, the present study examined the role of CGRP neurons in active defensive behavior, using a predator-like robot programmed to chase mice in fear conditioning. Our electrophysiological results showed that CGRP neurons encoded the intensity of various unconditioned stimuli (US) through different firing durations and amplitudes. Optogenetic and behavioral results revealed that activation of CGRP neurons in the presence of the chasing robot intensified fear memory and significantly elevated conditioned fleeing behavior during recall of an aversive memory. Animals with inactivated CGRP neurons exhibited significantly low levels of fleeing behavior even when the robot was set to be more threatening during conditioning. Our findings expand the known role of CGRP neurons in the PBN as a crucial part of the brains alarm system, showing they can regulate not only passive but also active defensive behaviors.

neuroscience↗

bioRxiv2022

HNRNPK is retained in the cytoplasm by Keratin 19 to stabilize target mRNAs

Heterogeneous nuclear ribonucleoprotein K (HNRNPK) regulates pre-mRNA processing and long non-coding RNA localization in the nucleus. It was previously shown that shuttling of HNRNPK to the cytoplasm promotes cell proliferation and cancer metastasis. However, the mechanism of HNRNPK cytoplasmic localization, its cytoplasmic RNA ligands, and impact on posttranscriptional gene regulation remain uncharacterized. Here we show that the intermediate filament protein Keratin 19 (K19) directly interacts with HNRNPK and sequesters it in the cytoplasm. Correspondingly, in K19 knockout breast cancer cells, HNRNPK does not localize in the cytoplasm, resulting in reduced cell proliferation. We mapped cytoplasmic HNRNPK target mRNAs using PAR-CLIP where transcriptome data to show that, in the cytoplasm, HNRNPK stabilizes target mRNAs bound to the 3 untranslated region at the expected C-rich sequence elements. Furthermore, these mRNAs are typically involved in cancer progression and include the p53 signaling pathway that is dysregulated upon HNRNPK knockdown or K19 knockout. This study identifies how a cytoskeletal protein can directly regulate gene expression by controlling subcellular localization of RNA binding proteins to support pathways involved in cancer progression.

molecular biology↗

bioRxiv2021

Keratin 19 interacts with GSK3β to regulate its nuclear accumulation and degradation of cyclin D3

Cyclin D3 regulates the G1/S transition and is frequently overexpressed in several cancer types including breast cancer, where it promotes tumor progression. Here, we show that a cytoskeletal protein keratin 19 (K19) physically interacts with a serine/threonine kinase GSK3{beta} and prevents GSK3{beta}-dependent degradation of cyclin D3. The absence of K19 allowed active GSK3{beta} to accumulate in the nucleus and degrade cyclin D3. Specifically, the head domain of K19 was required to sustain inhibitory phosphorylation of GSK3{beta} Ser9, prevent nuclear accumulation of GSK3{beta}, and maintain cyclin D3 levels and cell proliferation. K19 was found to interact with GSK3{beta} and K19-GSK3{beta} interaction was mapped out to require Ser10 and Ser35 residues on the head domain of K19. Unlike wildtype K19, S10A and S35A mutants failed to maintain total and nuclear cyclin D3 levels and induce cell proliferation. Finally, we show that the K19-GSK3{beta}-cyclin D3 pathway affected sensitivity of cells towards inhibitors to cyclin dependent kinase 4 and 6 (CDK4/6). Overall, these findings establish a role for K19 in the regulation of GSK3{beta}-cyclin D3 pathway and demonstrate a potential strategy for overcoming resistance to CDK4/6 inhibitors.

cancer biology↗

bioRxiv2020

Keratin 19 maintains E-cadherin localization at the cell surface and stabilizes cell-cell adhesion of MCF7 cells

A cytoskeletal protein keratin 19 (K19) is highly expressed in breast cancer but its effects on breast cancer cell mechanics are unclear. Using KRT19 knockout (KO) cells and cells where K19 expression was rescued, we found that K19 is required to maintain rounded epithelial-like shape and tight cell-cell adhesion of MCF7 cells. A loss of K19 resulted in a lower level of plakoglobin and internalization of E-cadherin in early and recycling endosomes. Inhibiting internalization restored cell-cell adhesion of KRT19 KO cells, suggesting E-cadherin internalization contributes to defective adhesion. Ultimately, while K19 inhibited cell migration, it was required for cells to form colonies in suspension. Our results suggest that K19 stabilizes E-cadherin complexes at the cell membrane to maintain cell-cell adhesion which inhibits cell migration but provides growth and survival advantages for circulating tumor cells. These findings provide context-dependent roles of K19 during metastasis.

cell biology↗