著者

Satoru Takahashi Chieko Saito Ikuko Koyama-Honda Noboru Mizushima

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.22071, (Released:2022-11-22)

被引用文献数

17

---

In macroautophagy, disk-shaped double-membrane structures called phagophores elongate to form cup-shaped structures, becoming autophagosomes upon closure. These autophagosomes then fuse with lysosomes to become autolysosomes and degrade engulfed material. Autophagosome formation is reported to involve other organelles, including the endoplasmic reticulum (ER) and mitochondria. Organelles are also taken up by autophagosomes as autophagy cargos. However, few studies have performed systematic spatiotemporal analysis of inter-organelle relationships during macroautophagy. Here, we investigated the organelles in contact with phagophores, autophagosomes, and autolysosomes by using three-dimensional correlative light and electron microscopy with array tomography in cells starved 30 min. As previously reported, all phagophores associate with the ER. The surface area of phagophores in contact with the ER decreases gradually as they mature into autophagosomes and autolysosomes. However, the ER still associates with 92% of autophagosomes and 79% of autolysosomes, suggesting that most autophagosomes remain on the ER after closure and even when they fuse with lysosomes. In addition, we found that phagophores form frequently near other autophagic structures, suggesting the presence of potential hot spots for autophagosome formation. We also analyzed the contents of phagophores and autophagosomes and found that the ER is the most frequently engulfed organelle (detected in 65% of total phagophores and autophagosomes). These quantitative three-dimensional ultrastructural data provide insights into autophagosome–organelle relationships during macroautophagy. Key words: 3D-CLEM, autophagosome, electron microscopy, endoplasmic reticulum, lysosome

著者

Ryoko Ando Asako Sakaue-Sawano Keiko Shoda Atsushi Miyawaki

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.23028, (Released:2023-06-30)

被引用文献数

7

---

We cloned and characterized two new coral fluorescent proteins: h2-3 and 1-41. h2-3 formed an obligate dimeric complex and exhibited bright green fluorescence. On the other hand, 1-41 formed a highly multimeric complex and exhibited dim red fluorescence. We engineered 1-41 into AzaleaB5, a practically useful red-emitting fluorescent protein for cellular labeling applications. We fused h2-3 and AzaleaB5 to the ubiquitination domains of human Geminin and Cdt1, respectively, to generate a new color variant of Fucci (Fluorescent Ubiquitination-based Cell-Cycle Indicator): Fucci5. We found Fucci5 provided more reliable nuclear labeling for monitoring cell-cycle progression than the 1st and 2nd generations that used mAG/mKO2 and mVenus/mCherry, respectively. Key Words: fluorescent protein, cell cycle, time-lapse imaging, flow cytometry

著者

Tetsuya Watabe Shinya Yamahira Michiyuki Matsuda Kenta Terai

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.48, no.2, pp.241-249, 2023 (Released:2023-12-07)

参考文献数

25

被引用文献数

2

---

Calcium transients drive cells to discharge prostaglandin E2 (PGE2). We visualized PGE2-induced protein kinase A (PKA) activation and quantitated PGE2 secreted from a single cell by combining fluorescence microscopy and a simulation model. For this purpose, we first prepared PGE2-producer cells that express either an optogenetic or a chemogenetic calcium channel stimulator: OptoSTIM1 or Gq-DREADD, respectively. Second, we prepared reporter cells expressing the Gs-coupled PGE2 reporter EP2 and the PKA biosensor Booster-PKA, which is based on the principle of Förster resonance energy transfer (FRET). Upon the stimulation-induced triggering of calcium transients, a single producer cell discharges PGE2 to stimulate PKA in the surrounding reporter cells. Due to the flow of the medium, the PKA-activated area exhibited a comet-like smear when HeLa cells were used. In contrast, radial PKA activation was observed when confluent MDCK cells were used, indicating that PGE2 diffusion was restricted to the basolateral space. By fitting the radius of the PKA-activated area to a simulation model based on simple diffusion, we estimated that a single HeLa cell secretes 0.25 fmol PGE2 upon a single calcium transient to activate PKA in more than 1000 neighboring cells. This model also predicts that the PGE2 discharge rate is comparable to the diffusion rate. Thus, our method quantitatively envisions that a single calcium transient affects more than 1000 neighboring cells via PGE2.Key words: prostaglandin E2, imaging, intercellular communication, biosensor, quantification

著者

Ryoko Ando Asako Sakaue-Sawano Keiko Shoda Atsushi Miyawaki

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.48, no.2, pp.135-144, 2023 (Released:2023-07-29)

参考文献数

24

被引用文献数

7

---

We cloned and characterized two new coral fluorescent proteins: h2-3 and 1-41. h2-3 formed an obligate dimeric complex and exhibited bright green fluorescence. On the other hand, 1-41 formed a highly multimeric complex and exhibited dim red fluorescence. We engineered 1-41 into AzaleaB5, a practically useful red-emitting fluorescent protein for cellular labeling applications. We fused h2-3 and AzaleaB5 to the ubiquitination domains of human Geminin and Cdt1, respectively, to generate a new color variant of Fucci (Fluorescent Ubiquitination-based Cell-Cycle Indicator): Fucci5. We found Fucci5 provided more reliable nuclear labeling for monitoring cell-cycle progression than the 1st and 2nd generations that used mAG/mKO2 and mVenus/mCherry, respectively.Key words: fluorescent protein, cell cycle, time-lapse imaging, flow cytometry

著者

Jun-ichi Sakamaki Noboru Mizushima

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.23016, (Released:2023-04-06)

被引用文献数

2

---

Protein–lipid conjugation is a widespread modification involved in many biological processes. Various lipids, including fatty acids, isoprenoids, sterols, glycosylphosphatidylinositol, sphingolipids, and phospholipids, are covalently linked with proteins. These modifications direct proteins to intracellular membranes through the hydrophobic nature of lipids. Some of these membrane-binding processes are reversible through delipidation or by reducing the affinity to membranes. Many signaling molecules undergo lipid modification, and their membrane binding is important for proper signal transduction. The conjugation of proteins to lipids also influences the dynamics and function of organellar membranes. Dysregulation of lipidation has been associated with diseases such as neurodegenerative diseases. In this review, we first provide an overview of diverse forms of protein–lipid conjugation and then summarize the catalytic mechanisms, regulation, and roles of these modifications.Key words: Lipid, lipidation, membrane, organelle, protein modification

著者

Gembu Maryu Haruko Miura Yoichi Uda Akira T. Komatsubara Michiyuki Matsuda Kazuhiro Aoki

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.18003, (Released:2018-03-17)

被引用文献数

22

---

Protein kinases play pivotal roles in intracellular signal transduction, and dysregulation of kinases leads to pathological results such as malignant tumors. Kinase activity has hitherto been measured by biochemical methods such as in vitro phosphorylation assay and western blotting. However, these methods are less useful to explore spatial and temporal changes in kinase activity and its cell-to-cell variation. Recent advances in fluorescent proteins and live-cell imaging techniques enable us to visualize kinase activity in living cells with high spatial and temporal resolutions. Several genetically encoded kinase activity reporters, which are based on the modes of action of kinase activation and phosphorylation, are currently available. These reporters are classified into single-fluorophore kinase activity reporters and Förster (or fluorescence) resonance energy transfer (FRET)-based kinase activity reporters. Here, we introduce the principles of genetically encoded kinase activity reporters, and discuss the advantages and disadvantages of these reporters.Key words: kinase, FRET, phosphorylation, KTR

著者

Junya Hasegawa Bethany S. Strunk Lois S. Weisman

出版者

日本細胞生物学会

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.17003, (Released:2017-03-07)

被引用文献数

109

---

In most eukaryotes, phosphoinositides (PIs) have crucial roles in multiple cellular functions. Although the cellular levels of phosphatidylinositol 5-phosphate (PI5P) and phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) are extremely low relative to some other PIs, emerging evidence demonstrates that both lipids are crucial for the endocytic pathway, intracellular signaling, and adaptation to stress. Mutations that causes defects in the biosynthesis of PI5P and PI(3,5)P2 are linked to human diseases including neurodegenerative disorders. Here, we review recent findings on cellular roles of PI5P and PI(3,5)P2, as well as the pathophysiological importance of these lipids.

著者

Mikio Furuse Daiki Nakatsu Wendy Hempstock Shiori Sugioka Noriko Ishizuka Kyoko Furuse Taichi Sugawara Yugo Fukazawa Hisayoshi Hayashi

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.22068, (Released:2022-12-09)

被引用文献数

9

---

The claudin family of membrane proteins is responsible for the backbone structure and function of tight junctions (TJs), which regulate the paracellular permeability of epithelia. It is thought that each claudin subtype has its own unique function and the combination of expressed subtypes determines the permeability property of each epithelium. However, many issues remain unsolved in regard to claudin functions, including the detailed functional differences between claudin subtypes and the effect of the combinations of specific claudin subtypes on the structure and function of TJs. To address these issues, it would be useful to have a way of reconstituting TJs containing only the claudin subtype(s) of interest in epithelial cells. In this study, we attempted to reconstitute TJs of individual claudin subtypes in TJ-deficient MDCK cells, designated as claudin quinKO cells, which were previously established from MDCK II cells by deleting the genes of claudin-1, -2, -3, -4, and -7. Exogenous expression of each of claudin-1, -2, -3, -4, and -7 in claudin quinKO cells resulted in the reconstitution of functional TJs. These TJs did not contain claudin-12 and -16, which are endogenously expressed in claudin quinKO cells. Furthermore, overexpression of neither claudin-12 nor claudin-16 resulted in the reconstitution of TJs, demonstrating the existence of claudin subtypes lacking TJ-forming activity in epithelial cells. Exogenous expressions of the channel-forming claudin-2, -10a, -10b, and -15 reconstituted TJs with reported paracellular channel properties, demonstrating that these claudin subtypes form paracellular channels by themselves without interaction with other subtypes. Thus, the reconstitution of TJs in claudin quinKO cells is advantageous for further investigations of claudin functions.Key words: Tight junction, Claudin, Paracellular permeability, Epithelial barrier

著者

Hiroyuki Katayama Akitsugu Yamamoto Noboru Mizushima Tamotsu Yoshimori Atsushi Miyawaki

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.33, no.1, pp.1-12, 2008 (Released:2008-03-27)

参考文献数

29

被引用文献数

115 192

---

Green fluorescent protein (GFP) from the jellyfish Aequorea victoria, its GFP variants (Aequorea GFPs), and more recently the novel GFP-like proteins from Anthozoa have greatly advanced our technologies for fluorescently labeling cells, organelles, and proteins. It has been shown, however, that some GFP-like proteins have a tendency to oligomerize and aggregate. Transfection of GFP-like proteins into cultured mammalian cells results in bright punctate structures, which are thought to be cytosolic protein aggregates. In this study, we demonstrate that these structures are not cytosolic aggregates but lysosomes that have accumulated the GFP-like proteins. Our biochemical and immunocytochemical experiments have revealed that certain GFP-like proteins expressed in the cytosol enter lysosomes possibly by an autophagy-related mechanism, but retain their fluorescence because of resistance not only to acidity but also to lysosomal proteases.

著者

Akira Nagasaki Saku T. Kijima Tenji Yumoto Miku Imaizumi Ayana Yamagishi Hyonchol Kim Chikashi Nakamura Taro Q.P. Uyeda

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.42, no.2, pp.131-140, 2017 (Released:2017-08-31)

参考文献数

44

被引用文献数

2 34

---

Actin, a major component of microfilaments, is involved in various eukaryotic cellular functions. Over the past two decades, actin fused with fluorescent protein has been used as a probe to detect the organization and dynamics of the actin cytoskeleton in living eukaryotic cells. It is generally assumed that the expression of fusion protein of fluorescent protein does not disturb the distribution of endogenous actin throughout the cell, and that the distribution of the fusion protein reflects that of endogenous actin. However, we noticed that EGFP-β-actin caused the excessive formation of microfilaments in several mammalian cell lines. To investigate whether the position of the EGFP tag on actin affected the formation of filaments, we constructed an expression vector harboring a β-actin-EGFP gene. In contrast to EGFP-β-actin, cells expressing β-actin-EGFP showed actin filaments in a high background from the monomer actin in cytosol. Additionally, the detergent insoluble assay revealed that the majority of the detergent-insoluble cytoskeleton from cells expressing EGFP-β-actin was recovered in the pellet. Furthermore, we found that the expression of EGFP-β-actin affects the migration of NBT-L2b cells and the mechanical stiffness of U2OS cells. These results indicate that EGFP fused to the N-terminus of actin tend to form excessive actin filaments. In addition, EGFP-actin affects both the cellular morphological and physiological phenotypes as compared to actin-EGFP.Key words: actin, GFP, cytoskeleton and probe

著者

Manuela Malatesta Chiara Caporaloni Stefano Gavaudan Marco B.L. Rocchi Sonja Serafini Cinzia Tiberi Giancarlo Gazzanelli

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.27, no.4, pp.173-180, 2002 (Released:2002-11-19)

参考文献数

29

被引用文献数

55 76

---

No direct evidence that genetically modified (GM) food may represent a possible danger for health has been reported so far; however, the scientific literature in this field is still quite poor. Therefore, we carried out an ultrastructural morphometrical and immunocytochemical study on hepatocytes from mice fed on GM soybean, in order to investigate eventual modifications of nuclear components of these cells involved in multiple metabolic pathways related to food processing. Our observations demonstrate significant modifications of some nuclear features in GM-fed mice. In particular, GM fed-mice show irregularly shaped nuclei, which generally represents an index of high metabolic rate, and a higher number of nuclear pores, suggestive of intense molecular trafficking. Moreover, the roundish nucleoli of control animals change in more irregular nucleoli with numerous small fibrillar centres and abundant dense fibrillar component in GM-fed mice, modifications typical of increased metabolic rate. Accordingly, nucleoplasmic (snRNPs and SC-35) and nucleolar (fibrillarin) splicing factors are more abundant in hepatocyte nuclei of GM-fed than in control mice. In conclusion, our data suggest that GM soybean intake can influence hepatocyte nuclear features in young and adult mice; however, the mechanisms responsible for such alterations remain unknown.

著者

Tetsuya Watabe Shinya Yamahira Michiyuki Matsuda Kenta Terai

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.23047, (Released:2023-10-07)

被引用文献数

2

---

Calcium transients drive cells to discharge prostaglandin E2 (PGE2). We visualized PGE2-induced protein kinase A (PKA) activation and quantitated PGE2 secreted from a single cell by combining fluorescence microscopy and a simulation model. For this purpose, we first prepared PGE2-producer cells that express either an optogenetic or a chemogenetic calcium channel stimulator: OptoSTIM1 or Gq-DREADD, respectively. Second, we prepared reporter cells expressing the Gs-coupled PGE2 reporter EP2 and the PKA biosensor Booster-PKA, which is based on the principle of Förster resonance energy transfer. Upon the stimulation-induced triggering of calcium transients, a single producer cell discharges PGE2 to stimulate PKA in the surrounding reporter cells. Due to the flow of the medium, the PKA-activated area exhibited a comet-like smear when HeLa cells were used. In contrast, radial PKA activation was observed when confluent MDCK cells were used, indicating that PGE2 diffusion was restricted to the basolateral space. By fitting the radius of the PKA-activated area to a simulation model based on simple diffusion, we estimated that a single HeLa cell secretes 0.25 fmol PGE2 upon a single calcium transient to activate PKA in more than 1000 neighboring cells. This model also predicts that the PGE2 discharge rate is comparable to the diffusion rate. Thus, our method quantitatively envisions that a single calcium transient affects more than 1000 neighboring cells via PGE2.Keywords: prostaglandin E2, imaging, intercellular communication, biosensor, quantification

著者

Koji Saito Sakino Ozawa Yosuke Chiba Ruri Takahashi Ryoya Ogomori Kojiro Mukai Tomohiko Taguchi Hiroyasu Hatakeyama Yasutaka Ohta

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.23032, (Released:2023-07-22)

---

Invadopodia are protrusive structures that mediate the extracellular matrix (ECM) degradation required for tumor invasion and metastasis. Rho small GTPases regulate invadopodia formation, but the molecular mechanisms of how Rho small GTPase activities are regulated at the invadopodia remain unclear. Here we have identified FilGAP, a GTPase-activating protein (GAP) for Rac1, as a negative regulator of invadopodia formation in tumor cells. Depletion of FilGAP in breast cancer cells increased ECM degradation and conversely, overexpression of FilGAP decreased it. FilGAP depletion promoted the formation of invadopodia with ECM degradation. In addition, FilGAP depletion and Rac1 overexpression increased the emergence of invadopodia induced by epidermal growth factor, whereas FilGAP overexpression suppressed it. Overexpression of GAP-deficient FilGAP mutant enhanced invadopodia emergence as well as FilGAP depletion. The pleckstrin-homology (PH) domain of FilGAP binds phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2], which is distributed on membranes of the invadopodia. FilGAP localized to invadopodia in breast cancer cells on the ECM, but FilGAP mutant lacking PI(3,4)P2-binding showed low localization. Similarly, the decrease of PI(3,4)P2 production reduced the FilGAP localization. Our results suggest that FilGAP localizes to invadopodia through its PH domain binding to PI(3,4)P2 and down-regulates invadopodia formation by inactivating Rac1, inhibiting ECM degradation in invasive tumor cells.Key Words: Invadopodia, breast carcinoma, Rac1, FilGAP, PI(3,4)P2

著者

Taisei Tanaka Yoshinobu Konishi Hiroshi Ichise Shinya Tsukiji Michiyuki Matsuda Kenta Terai

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.21052, (Released:2021-11-06)

被引用文献数

1

---

IFN-γ secreted from immune cells exerts pleiotropic effects on tumor cells, including induction of immune checkpoint and antigen presentation, growth inhibition, and apoptosis induction. We combined a dual promoter system with an IFN-γ signaling responsive promoter to generate a reporter named the interferon sensing probe (ISP), which quantitates the response to IFN-γ by means of fluorescence and bioluminescence. The integration site effect of the transgene is compensated for by the PGK promoter-driven expression of a fluorescent protein. Among five potential IFN-γ-responsive elements, we found that the interferon γ-activated sequence (GAS) exhibited the best performance. When ISP-GAS was introduced into four cell lines and subjected to IFN-γ stimulation, dose-dependency was observed with an EC50 ranging from 0.2 to 0.9 ng/mL, indicating that ISP-GAS can be generally used as a sensitive biosensor of IFN-γ response. In a syngeneic transplantation model, the ISP-GAS-expressing cancer cells exhibited bioluminescence and fluorescence signals in an IFN-γ receptor-dependent manner. Thus, ISP-GAS could be used to quantitatively monitor the IFN-γ response both in vitro and in vivo.Key words: in vivo imaging, tumor microenvironment, interferon-gamma, dual promoter system

著者

Koji Saito Sakino Ozawa Yosuke Chiba Ruri Takahashi Ryoya Ogomori Kojiro Mukai Tomohiko Taguchi Hiroyasu Hatakeyama Yasutaka Ohta

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.48, no.2, pp.161-174, 2023 (Released:2023-09-23)

参考文献数

47

---

Invadopodia are protrusive structures that mediate the extracellular matrix (ECM) degradation required for tumor invasion and metastasis. Rho small GTPases regulate invadopodia formation, but the molecular mechanisms of how Rho small GTPase activities are regulated at the invadopodia remain unclear. Here we have identified FilGAP, a GTPase-activating protein (GAP) for Rac1, as a negative regulator of invadopodia formation in tumor cells. Depletion of FilGAP in breast cancer cells increased ECM degradation and conversely, overexpression of FilGAP decreased it. FilGAP depletion promoted the formation of invadopodia with ECM degradation. In addition, FilGAP depletion and Rac1 overexpression increased the emergence of invadopodia induced by epidermal growth factor, whereas FilGAP overexpression suppressed it. Overexpression of GAP-deficient FilGAP mutant enhanced invadopodia emergence as well as FilGAP depletion. The pleckstrin-homology (PH) domain of FilGAP binds phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2], which is distributed on membranes of the invadopodia. FilGAP localized to invadopodia in breast cancer cells on the ECM, but FilGAP mutant lacking PI(3,4)P2-binding showed low localization. Similarly, the decrease of PI(3,4)P2 production reduced the FilGAP localization. Our results suggest that FilGAP localizes to invadopodia through its PH domain binding to PI(3,4)P2 and down-regulates invadopodia formation by inactivating Rac1, inhibiting ECM degradation in invasive tumor cells.Key words: invadopodia, breast carcinoma, Rac1, FilGAP, PI(3,4)P2

著者

Kenju Kobachi Sota Kuno Shinya Sato Kenta Sumiyama Michiyuki Matsuda Kenta Terai

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.45, no.2, pp.131-141, 2020 (Released:2020-08-21)

参考文献数

46

被引用文献数

2 13

---

Tissue absorbance, light scattering, and autofluorescence are significantly lower in the near-infrared (NIR) range than in the visible range. Because of these advantages, NIR fluorescent proteins (FPs) are in high demand for in vivo imaging. Nevertheless, application of NIR FPs such as iRFP is still limited due to their dimness in mammalian cells. In contrast to GFP and its variants, iRFP requires biliverdin (BV) as a chromophore. The dimness of iRFP is at least partly due to rapid reduction of BV by biliverdin reductase-A (BLVRA). Here, we established biliverdin reductase-a knockout (Blvra–/–) mice to increase the intracellular BV concentration and, thereby, to enhance iRFP fluorescence intensity. As anticipated, iRFP fluorescence intensity was significantly increased in all examined tissues of Blvra–/– mice. Similarly, the genetically encoded calcium indicator NIR-GECO1, which is engineered based on another NIR FP, mIFP, exhibited a marked increase in fluorescence intensity in mouse embryonic fibroblasts derived from Blvra–/– mice. We expanded this approach to an NIR light-sensing optogenetic tool, the BphP1-PpsR2 system, which also requires BV as a chromophore. Again, deletion of the Blvra gene markedly enhanced the light response in HeLa cells. These results indicate that the Blvra–/– mouse is a versatile tool for the in vivo application of NIR FPs and NIR light-sensing optogenetic tools.Key words: in vivo imaging, near-infrared fluorescent protein, biliverdin, biliverdin reductase, optogenetic tool

著者

Kanako Tokuda Shiou-Ling Lu Zhang Zidi Yumiko Kato Siyu Chen Kazuya Noda Katsutoshi Hirose Yu Usami Narikazu Uzawa Shinya Murakami Satoru Toyosawa Mitsunori Fukuda Ge-Hong Sun-Wada Yoh Wada Takeshi Noda

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.23061, (Released:2023-10-04)

被引用文献数

1

---

Osteoclasts play a crucial role in bone homeostasis by forming resorption pits on bone surfaces, resulting in bone resorption. The osteoclast expression of Rab38 protein is highly induced during differentiation from macrophages. Here we generated mice with double knockout (DKO) of Rab38 and its paralogue, Rab32, to investigate the roles of these proteins in osteoclasts. Bone marrow–derived macrophages from Rab32/38 DKO mice differentiated normally into osteoclasts in vitro. However, DKO osteoclasts showed reduced bone resorption activity. These osteoclasts also demonstrated defective secretion of tartrate-resistant acid phosphatase and cathepsin K into culture medium. Furthermore, the plasma membrane localization of a3, an osteoclast-specific a subunit of V-ATPase, was abrogated in DKO mice, substantiating the reduced resorption activity. In vivo, Rab32- and Rab38-positive cells were attached to the bone surface. Eight-week-old DKO mice showed significantly thickened trabecular bones in micro-CT and histomorphometry analysis, as well as reduced serum levels of cross-linked C-telopeptide of type I collagen, indicating diminished bone resorption in vivo. In DKO male mice over 10 weeks of age, hyperostosis appeared at the talofibular syndesmosis, the distal junction of the tibia and fibula. Furthermore, middle-aged mice (10 to 12 months of age) exhibited kyphosis, which is not usually observed in wild-type male mice until around 24 months of age. These results indicate that Rab32 and Rab38 contribute to osteoclast function by supporting intracellular traffic, thereby maintaining normal bone homeostasis.Keywords: Rab32, Rab38, osteoclast, lysosome-related organelle, secretory lysosome

著者

Takahide Matsui Yuriko Sakamaki Shu Hiragi Mitsunori Fukuda

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

pp.23067, (Released:2023-09-14)

被引用文献数

2

---

Small extracellular vesicles (sEVs) are largely classified into two types, plasma-membrane derived sEVs and endomembrane-derived sEVs. The latter type (referred to as exosomes herein) is originated from late endosomes or multivesicular bodies (MVBs). In order to release exosomes extracellularly, MVBs must fuse with the plasma membrane, not with lysosomes. In contrast to the mechanism responsible for MVB–lysosome fusion, the mechanism underlying the MVB–plasma membrane fusion is poorly understood. Here, we systematically analyze soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family proteins and identify VAMP5 as an MVB-localized SNARE protein required for exosome release. Depletion of VAMP5 in HeLa cells impairs exosome release. Mechanistically, VAMP5 mediates exosome release by interacting with SNAP47 and plasma membrane SNARE Syntaxin 1 (STX1) or STX4 to release exosomes. VAMP5 is also found to mediate asymmetric exosome release from polarized Madin-Darby canine kidney (MDCK) epithelial cells through interaction with the distinct sets of Q-SNAREs, suggesting that VAMP5 is a general exosome regulator in both polarized cells and non-polarized cells.Key words: Exosome, small extracellular vesicle (sEV), multivesicular body, SNARE, VAMP5

著者

Satoru Takahashi Chieko Saito Ikuko Koyama-Honda Noboru Mizushima

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.47, no.2, pp.89-99, 2022 (Released:2022-12-22)

参考文献数

48

被引用文献数

17

---

In macroautophagy, disk-shaped double-membrane structures called phagophores elongate to form cup-shaped structures, becoming autophagosomes upon closure. These autophagosomes then fuse with lysosomes to become autolysosomes and degrade engulfed material. Autophagosome formation is reported to involve other organelles, including the endoplasmic reticulum (ER) and mitochondria. Organelles are also taken up by autophagosomes as autophagy cargos. However, few studies have performed systematic spatiotemporal analysis of inter-organelle relationships during macroautophagy. Here, we investigated the organelles in contact with phagophores, autophagosomes, and autolysosomes by using three-dimensional correlative light and electron microscopy with array tomography in cells starved 30 min. As previously reported, all phagophores associate with the ER. The surface area of phagophores in contact with the ER decreases gradually as they mature into autophagosomes and autolysosomes. However, the ER still associates with 92% of autophagosomes and 79% of autolysosomes, suggesting that most autophagosomes remain on the ER after closure and even when they fuse with lysosomes. In addition, we found that phagophores form frequently near other autophagic structures, suggesting the presence of potential hot spots for autophagosome formation. We also analyzed the contents of phagophores and autophagosomes and found that the ER is the most frequently engulfed organelle (detected in 65% of total phagophores and autophagosomes). These quantitative three-dimensional ultrastructural data provide insights into autophagosome–organelle relationships during macroautophagy.Key words: 3D-CLEM, autophagosome, electron microscopy, endoplasmic reticulum, lysosome

著者

Ryosuke Nishimura Kagayaki Kato Misako Saida Yasuhiro Kamei Masahiro Takeda Hiromi Miyoshi Yutaka Yamagata Yu Amano Shigenobu Yonemura

出版者

Japan Society for Cell Biology

雑誌

Cell Structure and Function (ISSN:03867196)

巻号頁・発行日

vol.47, no.2, pp.55-73, 2022 (Released:2022-07-27)

参考文献数

76

被引用文献数

2

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The adherens junction (AJ) is an actin filament-anchoring junction. It plays a central role in epithelial morphogenesis through cadherin-based recognition and adhesion among cells. The stability and plasticity of AJs are required for the morphogenesis. An actin-binding α-catenin is an essential component of the cadherin-catenin complex and functions as a tension transducer that changes its conformation and induces AJ development in response to tension. Despite much progress in understanding molecular mechanisms of tension sensitivity of α-catenin, its significance on epithelial morphogenesis is still unknown. Here we show that the tension sensitivity of α-catenin is essential for epithelial cells to form round spheroids through proper multicellular rearrangement. Using a novel in vitro suspension culture model, we found that epithelial cells form round spheroids even from rectangular-shaped cell masses with high aspect ratios without using high tension and that increased tension sensitivity of α-catenin affected this morphogenesis. Analyses of AJ formation and cellular tracking during rounding morphogenesis showed cellular rearrangement, probably through AJ remodeling. The rearrangement occurs at the cell mass level, but not single-cell level. Hypersensitive α-catenin mutant-expressing cells did not show cellular rearrangement at the cell mass level, suggesting that the appropriate tension sensitivity of α-catenin is crucial for the coordinated round morphogenesis.Key words: α-catenin, vinculin, adherens junction, morphogenesis, mechanotransduction