Biology subjects

Ikenouchi, J.

Publications and source records attributed to Ikenouchi, J..

5 recordsLinked to original sources

bioRxiv2024

Chemotherapy resistance due to epithelial-to-mesenchymal transition is caused by abnormal lipid metabolic balance

Invasive cancer is defined by the loss of epithelial cell traits resulting from the ectopic expression of epithelial-mesenchymal transition (EMT)-related transcription factors such as Snail. Although EMT is known to impart chemoresistance to cancer cells, the precise molecular mechanisms remain elusive. We found that Snail expression confers chemoresistance by upregulating the cholesterol efflux pump ABCA1 as a countermeasure to the excess of cytotoxic free cholesterol relative to its major interaction partner in cellular membranes, sphingomyelin. This imbalance is introduced by the transcriptional repression of enzymes involved in the biosynthesis of sphingomyelin by Snail. Inhibiting esterification of cholesterol, which renders it inert, selectively suppresses growth of a xenograft model of Snail-positive kidney cancer. Our findings offer a new perspective on lipid-targeting strategies for invasive cancer therapy.

cell biology↗

bioRxiv2024

Rho-ROCK liberates sequestered claudin for rapid de novo tight junction formation

The epithelial cell sheet maintains its integrity as a barrier while undergoing turnover of constituent cells. To sustain the barrier continuously, its essential to preserve the old tight junctions (TJs) between cells being excluded from the sheet and their neighbors while simultaneously forming de novo TJs between newly adjacent cells. However, the molecular mechanisms involved in the formation of de novo TJs remain largely unknown. This study investigates two scenarios: the formation of de novo TJs during the removal of apoptotic cells from monolayer epithelial sheets and during the differentiation of the granular layer in stratified epidermis. We revealed that rapid claudin assembly is achieved by actively regulating the dissociation of the EpCAM/TROP2-claudin complex in both situations. Furthermore, we found that the Rho-ROCK pathway initiates the activation of matriptase, which cleaves EpCAM/TROP2, resulting in the supply of polymerizable claudin from the stockpiled EpCAM/TROP2-claudin complex at the plasma membrane to induce rapid de novo TJ formation.

cell biology↗

bioRxiv2024

The yolk sac vasculature in early avian embryo provides a novel model for the analysis of cancer extravasation

Hematogenous metastasis, a key trait of cancer cells, involves a complex sequence of cell migration steps, including intravasation, circulation, arrest in capillary vessels, and extravasation. Among these steps, extravasation is challenging to image in amniotes like humans and mice due to its unpredictable timing and location, limiting our understanding of cellular and molecular mechanisms through imaging. Establishing a new cancer carrier model with high-resolution imaging capabilities in amniotes is crucial. In this study, we investigated the yolk sac vasculature (YSV) of early avian embryos (chickens and quail) as a new model for studying extravasation, offering excellent imaging capabilities. We examined the YSV structure and attempted fluorescent labeling to enhance visibility. We then injected mCherry-labeled HT-1080 cells into YSV and observed their behavior, revealing distinct morphologies and extravasation dynamics. Our findings suggest that the YSV model holds promise as a novel cancer carrier model for elucidating cellular and molecular mechanisms through imaging-based approaches.

cancer biology↗

bioRxiv2023

The SOCE system is critical for membrane bleb formation to drive avian primordial germ cell migration

Amoeboid cell migration is driven by the specialized cell protrusion, membrane bleb. A recent in vitro analysis of bleb formation using a cancer cell line showed that store-operated calcium entry (SOCE)-mediated local elevation of Ca2+ concentration triggers bleb formation, but it remains unknown how commonly this system is utilized in the bleb formation and bleb-driven cell migration in vivo. We demonstrate with avian primordial germ cell (PGC) model that that chick PGCs use SOCE, triggered by stem cell factor (SCF), to induce bleb formation and that it is essential for in vivo migration including trans-endothelial and mesenchymal cell migration. Our discovery also provides insight into the correlation between cancer metastasis/invasion and SOCE-mediated bleb formation.

developmental biology↗

bioRxiv2022

Cholesterol-mediated tight junction formation

Lipids have the ability to self-organize but the significance of this phenomenon in the assembly of membrane structures is unknown. We previously reported that cholesterol enrichment directs the formation of tight junctions (TJs), adhesion structures responsible for the epithelial barrier (Shigetomi et al., 2018). However, it is unclear how cholesterol accumulates and informs TJ formation. Cholesterol typically accumulates in the vicinity of apical cell junctions (Shigetomi et al., 2018). Surprisingly, cholesterol distribution is unaltered in an epithelial cell line that lacks TJs, generated by suppressing the expression of claudins, membrane proteins that determine the barrier properties of TJs. Assembly of claudin into hallmark strands is canonically thought to require binding to Zonula occludens (ZO) proteins but a claudin mutant that cannot bind to ZO proteins still form strands. These results suggest a novel mechanism for TJ formation that is dependent on cholesterol and reveal an unexpected role of ZO proteins as organizers of the cholesterol domain.

cell biology↗