Biology subjects

Taniguchi, A.

Publications and source records attributed to Taniguchi, A..

8 recordsLinked to original sources

bioRxiv2026

Analytical methodology for unveiling the physical effect of detergents on the function of full-length membrane proteins using a single-molecule tracking system

G protein-coupled receptors (GPCRs) are important targets for drug discovery because they are the largest and most diverse family of membrane proteins in the human body. As exemplified by {beta}2-adrenergic receptor ({beta}2AR), which is a typical class-A GPCRs, they are prone to denaturation and inactivation after solubilization. Although diverse techniques have been developed, current structural and functional analyses are still limited to proteins with relatively stable and high expression. However, some mutant variants and misfolded proteins involved in diseases have extremely low expression levels and may be difficult to analyze. To overcome these limitations, we established a novel analytical platform for evaluating the ligand-binding ability of full-length {beta}2AR as a model at the single-molecule level without purification and addressing challenges such as membrane proteins with low expression levels and structural instability. This method enables the direct use of unpurified receptors immediately after solubilization and allows us to use only a small amount of sample ([~]10 ng) for observation and to distinguish between specific and nonspecific ligand binding by fitting. Furthermore, we unveiled the physical properties of detergents on the structural stability of solubilized receptors and found that the lateral pressure within detergent micelles affects ligand-binding ability. Detergents that provided a fluid microenvironment were able to maintain ligand-binding ability for several days even after solubilization; conversely, detergents that provided a rigid microenvironment caused the protein to lose its activity earlier. Our method could be a promising tool for the structural and functional analysis of membrane proteins untargeted until now. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/740883v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@3d274corg.highwire.dtl.DTLVardef@defd0forg.highwire.dtl.DTLVardef@1b81eb4org.highwire.dtl.DTLVardef@e7c275_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2026

Allocation pattern of fruiting bodies in plasmodial slime molds, and threshold size for sporulation of P. polycephalum

The plasmodium of Myxogastria (a group of amoeboid protists) species often crawls around the forest floor to feed while searching for places to form fruiting bodies for reproduction (sporulation). Certain environmental factors that trigger sporulation have been reported; however, other unknown factors are also expected. In this study, we reported field observations of Physarum rigidum and Fuligo septica. Inspired by the field observation, we examined the effects of multiple factors on sporulation in laboratory experiments using Physarum polycephalum. We found that:(1) there was a critical body size below which sporulation did not occur under our experimental conditions and (2) the plasmodium selected its sporulation sites from the available landscape of the experimental arena: dry and low sites for the majority and dry and high sites for the minority. Further analysis revealed that they preferred the edge area at the high site. We discuss the possible ecological importance of the threshold and location preference

animal behavior and cognition↗

bioRxiv2026

Mechanical analysis of spatiotemporal traction stress dynamics in a bleb-driven migrating cell, Amoeba proteus

Many adherent eukaryotic cells exhibit amoeboid locomotion, where traction stress exerted on the substrate is essential for movement. In this study, we investigated the spatiotemporal development of these forces in Amoeba proteus to clarify the mechanical dynamics underlying bleb-driven migration. By performing a multipole analysis of the stress distribution, we characterized the spatiotemporal patterns exhibited by motile cells. Furthermore, we tracked the behavior of individual localized peak structures within these profiles, which are thought to correspond to focal contact sites. These analyses revealed that the front-back asymmetry in the traction distribution correlates with the direction of migration. We also found that A. proteus exhibits a periodic pattern in which inward-directed stresses are alternately strengthened and weakened at the cell poles. Crucially, we identified a distinctive feature not observed in other cell types: the generation of large lateral traction forces at the cell center. Together, these results highlight both the universality and diversity of the biophysical mechanisms driving amoeboid locomotion.

biophysics↗

bioRxiv2025

Curvature-sensing peptide functions as a membrane interfactant that glues small extracellular vesicles to cell membranes and enhances vesicle cellular uptake

Small extracellular vesicles (sEVs) are lipid nanoparticles secreted from mammalian cells that are involved in the transfer of informational or therapeutically effective substances between cells. Although the scope of research on sEVs as biocompatible carriers for drug delivery to diseased tissues and cells is expanding, several challenges remain, such as low cellular uptake efficiency and difficulty in loading drugs. It is desirable to alleviate the energy barriers associated with the cellular uptake of sEVs and minimize perturbation of sEVs when loading drugs onto them. In this study, we developed a simple drug-loading system for sEVs using a dimeric curvature-sensing peptide, which enhances sEV accumulation on the cell surface by acting as an adhesive, subsequently inducing endocytic uptake of sEVs through a clathrin-mediated pathway. The dimeric curvature-sensing peptide selectively binds to the sEV surface within 10 min, even in the presence of serum proteins, and functions as a membrane interfactant to reduce the energy barriers for the cellular uptake of sEVs. The cellular uptake of sEVs and the dimeric curvature-sensing peptide under coexisting conditions increased to over fivefold and 20-fold, respectively, compared with those administered alone. Furthermore, the dimeric curvature-sensing peptide can efficiently load anticancer drugs onto the surface of sEVs, and the system effectively induces apoptosis in two types of cancer cells. Dimeric curvature-sensing peptide is a novel technique with potential applications in drug delivery.

biochemistry↗

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↗

bioRxiv2023

Discovery of essential kinetoplastid-insect adhesion proteins and their function in Leishmania-sand fly interactions

Leishmania species, members of the kinetoplastid parasites, cause leishmaniasis, a neglected tropical disease, in millions of people worldwide1. Leishmania has a complex life cycle with multiple developmental forms, as it cycles between a sand fly vector and a mammalian host; understanding their life cycle is critical to understanding disease spread2. One of the key life cycle stages is the haptomonad form, which is attached to the insect through its flagellum. This adhesion, which is conserved across kinetoplastid parasites, is implicated to have an important function within their life cycles and hence on disease transmission3-5. Here, we discovered kinetoplastid-insect adhesion proteins (KIAPs), which are localised in the attached haptomonad flagellum. Deletion of these KIAPs impaired cell adhesion in vitro and prevented Leishmania from colonising the stomodeal valve in the sand fly, without affecting cell growth. This result will provide important insights for a comprehensive understanding of the Leishmania life cycle.

microbiology↗

bioRxiv2023

Left-right asymmetry is formed in the basal bodies of the mouse node cilia in a cilia motility-dependent manner

Laterality of the shapes and arrangements of the visceral organs in mice is determined in the node, a small cavity found at the ventral side of 7.5 dpc (days post coitum) embryos. On the node cells, motile cilia which are tilted toward the posterior side of the embryos show clockwise movement and thus produce fluid flow in the node toward the left side of the embryos. This left-ward flow regulates left/right (L/R) asymmetric gene expressions and L/R asymmetric morphogenesis in later stages. Structurally, node cilia have the characteristics of primary cilia and their basal body (mother centriole) is accompanied by a daughter centriole. Here, to obtain insights into the process of symmetry breaking by node cilia, we investigated whether the structure of the cilia themselves have L/R asymmetry, and found that positions of the daughter centrioles become biased to the right side of the mother centrioles in a stage-dependent manner. We found that this L/R asymmetry of the basal bodies is absent in iv mutant mice, in which node cilia are immotile, suggesting that formation of this L/R asymmetry in the basal bodies requires cilia motility. It has been reported that culturing embryos in a flow chamber with artificial counter-flow, which is toward the opposite direction to the endogenous leftward flow in the node, results in reversed laterality of the visceral organs in later stages. However, we found that applying such artificial counter-flow did not reverse the L/R asymmetry of the basal bodies, and the daughter centrioles were still biased to the right side of the mother centrioles, suggesting that the L/R asymmetry of the basal bodies is formed independently from the direction of the fluid flow in the node and that it is independent from the laterality of the visceral organs. Although the biological significance of this phenomenon is unknown so far, these results suggest that node cilia have a previously unknown mechanism to produce L/R asymmetry in the basal bodies inside the cells in early development, independently from the canonical fluid flow-dependent L/R determining pathway.

developmental biology↗

bioRxiv2022

Formation and three-dimensional architecture of Leishmania adhesion in the sand fly vector

Attachment to a substrate to maintain position in a specific ecological niche is a common strategy across biology, especially for eukaryotic parasites. During development in the sand fly vector, the eukaryotic parasite Leishmania adheres to the stomodeal valve, as the specialised haptomonad form. Dissection of haptomonad adhesion is a critical step for understanding parasite transmission. Nevertheless, haptomonad studies are limited, as this is a technically challenging life cycle form to investigate. Here, we have combined three-dimensional electron microscopy approaches, including serial block face scanning electron microscopy (SBFSEM) and serial tomography to dissect the organisation and architecture of haptomonads in the sand fly. We showed that the attachment plaque contains distinct structural elements. Using time-lapse light microscopy, we identified five stages of haptomonad differentiation, and showed that calcium is necessary for haptomonad adhesion to the surface. This study provides the structural and regulatory foundations of the haptomonad form, which are critical for a holistic understanding of Leishmania transmission.

microbiology↗