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Ken-ichiro Ishida - One of the best experts on this subject based on the ideXlab platform.
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TAXONOMIC STUDY OF BIGELOWIELLA LONGIFILA SP. NOV. (CHLORARACHNIOPHYTA) AND A TIME-LAPSE VIDEO OBSERVATION OF THE UNIQUE MIGRATION OF AMOEBOID CELLS1
Journal of Phycology, 2007Co-Authors: Kunihiko Ueda, Ken-ichiro IshidaAbstract:A new species of a chlorarachniophyte alga, Bigelowiella longifila sp. nov., is described. It is classified as a member of Bigelowiella as flagellate cells constitute the main stage of the life cycle. However, this alga is different from the only described species of the genus, B. natans Moestrup, in having a unique amoeboid stage in the life cycle. We observed an interesting behavior of amoeboid daughter cells after cell division: One of the two daughter cells inherits the long Filopodium of the parental cell, and it subsequently transports its cell contents through the Filopodium to develop at its opposite end. The other daughter cell forms a new Filopodium. This unequal behavior of daughter cells may have evolved before the chlorarachniophytes and some colorless cercozoans diverged.
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TAXONOMIC STUDY OF BIGELOWIELLA LONGIFILA SP. NOV. (CHLORARACHNIOPHYTA) AND A TIME‐LAPSE VIDEO OBSERVATION OF THE UNIQUE MIGRATION OF AMOEBOID CELLS1
Journal of Phycology, 2007Co-Authors: Shuhei Ota, Kunihiko Ueda, Ken-ichiro IshidaAbstract:A new species of a chlorarachniophyte alga, Bigelowiella longifila sp. nov., is described. It is classified as a member of Bigelowiella as flagellate cells constitute the main stage of the life cycle. However, this alga is different from the only described species of the genus, B. natans Moestrup, in having a unique amoeboid stage in the life cycle. We observed an interesting behavior of amoeboid daughter cells after cell division: One of the two daughter cells inherits the long Filopodium of the parental cell, and it subsequently transports its cell contents through the Filopodium to develop at its opposite end. The other daughter cell forms a new Filopodium. This unequal behavior of daughter cells may have evolved before the chlorarachniophytes and some colorless cercozoans diverged.
Kunihiko Ueda - One of the best experts on this subject based on the ideXlab platform.
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TAXONOMIC STUDY OF BIGELOWIELLA LONGIFILA SP. NOV. (CHLORARACHNIOPHYTA) AND A TIME-LAPSE VIDEO OBSERVATION OF THE UNIQUE MIGRATION OF AMOEBOID CELLS1
Journal of Phycology, 2007Co-Authors: Kunihiko Ueda, Ken-ichiro IshidaAbstract:A new species of a chlorarachniophyte alga, Bigelowiella longifila sp. nov., is described. It is classified as a member of Bigelowiella as flagellate cells constitute the main stage of the life cycle. However, this alga is different from the only described species of the genus, B. natans Moestrup, in having a unique amoeboid stage in the life cycle. We observed an interesting behavior of amoeboid daughter cells after cell division: One of the two daughter cells inherits the long Filopodium of the parental cell, and it subsequently transports its cell contents through the Filopodium to develop at its opposite end. The other daughter cell forms a new Filopodium. This unequal behavior of daughter cells may have evolved before the chlorarachniophytes and some colorless cercozoans diverged.
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TAXONOMIC STUDY OF BIGELOWIELLA LONGIFILA SP. NOV. (CHLORARACHNIOPHYTA) AND A TIME‐LAPSE VIDEO OBSERVATION OF THE UNIQUE MIGRATION OF AMOEBOID CELLS1
Journal of Phycology, 2007Co-Authors: Shuhei Ota, Kunihiko Ueda, Ken-ichiro IshidaAbstract:A new species of a chlorarachniophyte alga, Bigelowiella longifila sp. nov., is described. It is classified as a member of Bigelowiella as flagellate cells constitute the main stage of the life cycle. However, this alga is different from the only described species of the genus, B. natans Moestrup, in having a unique amoeboid stage in the life cycle. We observed an interesting behavior of amoeboid daughter cells after cell division: One of the two daughter cells inherits the long Filopodium of the parental cell, and it subsequently transports its cell contents through the Filopodium to develop at its opposite end. The other daughter cell forms a new Filopodium. This unequal behavior of daughter cells may have evolved before the chlorarachniophytes and some colorless cercozoans diverged.
Linyi Chen - One of the best experts on this subject based on the ideXlab platform.
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SH2B1 orchestrates signaling events to Filopodium formation during neurite outgrowth
Communicative & integrative biology, 2015Co-Authors: Kuan-wei Chen, Yu-jung Chang, Linyi ChenAbstract:Morphogenesis during development is fundamental to the differentiation of several cell types. As neurite outgrowth marks neuritogenesis, formation of filopodia precede the formation of dendrites and axons. While the structure of filopodia is well-known, the initiation of filopodia during neurite outgrowth is not clear. SH2B1 is known to promote neurite outgrowth of PC12 cells, hippocampal and cortical neurons. As a signaling adaptor protein, SH2B1 interacts with several neurotrophin receptors, and regulates signaling as well as gene expression. Our recent findings suggest that SH2B1 can be recruited to the plasma membrane and F-actin fractions by IRSp53. IRSp53 bends plasma membrane and facilitates actin bundling to set the stage for Filopodium formation. We further demonstrate that SH2B1-IRSp53 complexes enhance the formation of filopodia, dendrites and dendritic branches of hippocampal and cortical neurons. While the molecular mechanism underlying Filopodium initiation is not clear, we propose that SH2B1-neurotrophin interacting sites may mark the putative sites of Filopodium initiation.
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SH2B1 and IRSp53 proteins promote the formation of dendrites and dendritic branches.
The Journal of biological chemistry, 2015Co-Authors: Chien-jen Chen, Shao-jing Hong, Yu-jung Chang, Chien-hung Shih, Lily Hui-ching Wang, Linyi ChenAbstract:SH2B1 is an adaptor protein known to enhance neurite outgrowth. In this study, we provide evidence suggesting that the SH2B1 level is increased during in vitro culture of hippocampal neurons, and the β isoform (SH2B1β) is the predominant isoform. The fact that formation of filopodia is prerequisite for neurite initiation suggests that SH2B1 may regulate Filopodium formation and thus neurite initiation. To investigate whether SH2B1 may regulate Filopodium formation, the effect of SH2B1 and a membrane and actin regulator, IRSp53 (insulin receptor tyrosine kinase substrate p53), is investigated. Overexpressing both SH2B1β and IRSp53 significantly enhances Filopodium formation, neurite outgrowth, and branching. Both in vivo and in vitro data show that SH2B1 interacts with IRSp53 in hippocampal neurons. This interaction depends on the N-terminal proline-rich domains of SH2B1. In addition, SH2B1 and IRSp53 co-localize at the plasma membrane, and their levels increase in the Triton X-100-insoluble fraction of developing neurons. These findings suggest that SH2B1-IRSp53 complexes promote the formation of filopodia, neurite initiation, and neuronal branching.
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SH2B1 increases the numbers of IRSp53-induced filopodia
Biochimica et biophysica acta, 2014Co-Authors: Shao-jing Hong, Szu-ting Liu, Chien-jen Chen, Linyi ChenAbstract:Abstract Background Filopodia are actin-rich membrane protrusions that play instrumental roles in development, cell migration, pathogen detection, and wound healing. During neurogenesis, Filopodium formation precedes the formation of dendrites and spines. The insulin receptor substrate protein of 53 kDa (IRSp53) has been implicated in regulating the formation of filopodia. Our previous results suggest that a signaling adaptor protein SH2B1β is required for neurite outgrowth of hippocampal neurons and neurite initiation of PC12 cells. Thus, we hypothesize that IRSp53 and SH2B1β may act together to regulate Filopodium formation. Methods To determine the contribution of IRSp53 and SH2B1β in the formation of filopodia, we transiently transfect IRSp53 and/or SH2B1β to 293T cells. Cell morphology and protein distribution are assessed via confocal microscopy and subcellular fractionation. Total numbers of filopodia and Filopodium numbers per perimeter are calculated to show the relative contribution of IRSp53 and SH2B1β. Results In this study, we show that SH2B1β interacts with IRSp53 and increases the number of IRSp53-induced filopodia. One mechanism for this enhancement is that IRSp53 recruits SH2B1β to the plasma membrane to actively promote membrane protrusion. The increased numbers of filopodia likely result from SH2B1-mediated cytoplasmic extension and thus increased cell perimeter as well as IRSp53-mediated Filopodium formation. Conclusions Taken together, this study provides a novel finding that SH2B1β interacts with IRSp53-containing complexes to increase the number of filopodia. General significance A better understanding of how SH2B1β and IRSp53 promote Filopodium formation may have clinical implication in neurogenesis and regeneration.
Garegin A. Papoian - One of the best experts on this subject based on the ideXlab platform.
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Multiscale stochastic reaction-diffusion modelling: application to actin dynamics in filopodia
2015Co-Authors: Radek Erban, Mark B. Flegg, Garegin A. PapoianAbstract:Two multiscale (hybrid) stochastic reaction-diffusion models of actin dynamics in a Filopodium are investigated. Both hybrid algorithms combine compartment-based and molecular-based sto-chastic reaction-diffusion models. The first hybrid model is based on the models previously developed in the literature. The second hybrid model is based on the application of a recently developed two-regime method (TRM) to a fully molecular-based model which is also developed in this paper. The results of hybrid models are compared with the results of the molecular-based model. It is shown that both approaches give comparable results, although the TRM model better agrees quantitatively with the molecular-based model
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Multiscale Stochastic Reaction–Diffusion Modeling: Application to Actin Dynamics in Filopodia
Bulletin of Mathematical Biology, 2014Co-Authors: Radek Erban, Mark B. Flegg, Garegin A. PapoianAbstract:Two multiscale (hybrid) stochastic reaction–diffusion models of actin dynamics in a Filopodium are investigated. Both hybrid algorithms combine compartment-based and molecular-based stochastic reaction–diffusion models. The first hybrid model is based on the models previously developed in the literature. The second hybrid model is based on the application of a recently developed two-regime method (TRM) to a fully molecular-based model, which is also developed in this paper. The results of hybrid models are compared with the results of the molecular-based model. It is shown that both approaches give comparable results, although the TRM model better agrees quantitatively with the molecular-based model.
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Protein fluxes along the Filopodium as a framework for understanding the growth-retraction dynamics: the interplay between diffusion and active transport.
Cell adhesion & migration, 2011Co-Authors: Pavel I. Zhuravlev, Garegin A. PapoianAbstract:We present a picture of filopodial growth and retraction from physics perspective, where we emphasize the significance of the role played by protein fluxes due to spatially extended nature of the Filopodium. We review a series of works, which used stochastic simulations and mean field analytical modeling to find the concentration profile of G-actin inside a Filopodium, which, in turn, determines the stationary filopodial length. In addition to extensively reviewing the prior works, we also report some new results on the role of active transport in regulating the length of filopodia. We model a Filopodium where delivery of actin monomers towards the tip can occur both through passive diffusion and active transport by myosin motors. We found that the concentration profile of G-actin along the Filopodium is rather non-trivial, containing a narrow minimum near the base followed by a broad maximum. For efficient enough actin transport, this non-monotonous shape is expected to occur under a broad set of conditi...
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The Stochastic Dynamics of Filopodial Growth
Biophysical journal, 2008Co-Authors: Yueheng Lan, Garegin A. PapoianAbstract:A Filopodium is a cytoplasmic projection, exquisitely built and regulated, which extends from the leading edge of the migrating cell, exploring the cell's neighborhood. Commonly, filopodia grow and retract after their initiation, exhibiting rich dynamical behaviors. We model the growth of a Filopodium based on a stochastic description which incorporates mechanical, physical, and biochemical components. Our model provides a full stochastic treatment of the actin monomer diffusion and polymerization of each individual actin filament under stress of the fluctuating membrane. We investigated the length distribution of individual filaments in a growing Filopodium and studied how it depends on various physical parameters. The distribution of filament lengths turned out to be narrow, which we explained by the negative feedback created by the membrane load and monomeric G-actin gradient. We also discovered that filopodial growth is strongly diminished upon increasing retrograde flow, suggesting that regulating the retrograde flow rate would be a highly efficient way to control filopodial extension dynamics. The filopodial length increases as the membrane fluctuations decrease, which we attributed to the unequal loading of the membrane force among individual filaments, which, in turn, results in larger average polymerization rates. We also observed significant diffusional noise of G-actin monomers, which leads to smaller G-actin flux along the filopodial tube compared with the prediction using the diffusion equation. Overall, partial cancellation of these two fluctuation effects allows a simple mean field model to rationalize most of our simulation results. However, fast fluctuations significantly renormalize the mean field model parameters. The biological significance of our filopodial model and avenues for future development are also discussed.
Naoki Mochizuki - One of the best experts on this subject based on the ideXlab platform.
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a novel actin bundling Filopodium forming domain conserved in insulin receptor tyrosine kinase substrate p53 and missing in metastasis protein
Journal of Biological Chemistry, 2004Co-Authors: Akiko Yamagishi, Michitaka Masuda, Takashi Ohki, Hirofumi Onishi, Naoki MochizukiAbstract:Insulin receptor tyrosine kinase substrate p53 (IRSp53) has been identified as an SH3 domain-containing adaptor that links Rac1 with a Wiskott-Aldrich syndrome family verprolin-homologous protein 2 (WAVE2) to induce lamellipodia or Cdc42 with Mena to induce filopodia. The recruitment of these SH3-binding partners by IRSp53 is thought to be crucial for F-actin rearrangements. Here, we show that the N-terminal predicted helical stretch of 250 amino acids of IRSp53 is an evolutionarily conserved F-actin bundling domain involved in Filopodium formation. Five proteins including IRSp53 and missing in metastasis (MIM) protein share this unique domain and are highly conserved in vertebrates. We named the conserved domain IRSp53/MIM homology domain (IMD). The IMD has domain relatives in invertebrates but does not show obvious homology to any known actin interacting proteins. The IMD alone, derived from either IRSp53 or MIM, induced filopodia in HeLa cells and the formation of tightly packed parallel F-actin bundles in vitro. These results suggest that IRSp53 and MIM belong to a novel actin bundling protein family. Furthermore, we found that Filopodium-inducing IMD activity in the full-length IRSp53 was regulated by active Cdc42 and Rac1. The SH3 domain was not necessary for IMD-induced Filopodium formation. Our results indicate that IRSp53, when activated by small GTPases, participates in F-actin reorganization not only in an SH3-dependent manner but also in a manner dependent on the activity of the IMD.
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A Novel Actin Bundling/Filopodium-forming Domain Conserved in Insulin Receptor Tyrosine Kinase Substrate p53 and Missing in Metastasis Protein
The Journal of biological chemistry, 2004Co-Authors: Akiko Yamagishi, Michitaka Masuda, Takashi Ohki, Hirofumi Onishi, Naoki MochizukiAbstract:Insulin receptor tyrosine kinase substrate p53 (IRSp53) has been identified as an SH3 domain-containing adaptor that links Rac1 with a Wiskott-Aldrich syndrome family verprolin-homologous protein 2 (WAVE2) to induce lamellipodia or Cdc42 with Mena to induce filopodia. The recruitment of these SH3-binding partners by IRSp53 is thought to be crucial for F-actin rearrangements. Here, we show that the N-terminal predicted helical stretch of 250 amino acids of IRSp53 is an evolutionarily conserved F-actin bundling domain involved in Filopodium formation. Five proteins including IRSp53 and missing in metastasis (MIM) protein share this unique domain and are highly conserved in vertebrates. We named the conserved domain IRSp53/MIM homology domain (IMD). The IMD has domain relatives in invertebrates but does not show obvious homology to any known actin interacting proteins. The IMD alone, derived from either IRSp53 or MIM, induced filopodia in HeLa cells and the formation of tightly packed parallel F-actin bundles in vitro. These results suggest that IRSp53 and MIM belong to a novel actin bundling protein family. Furthermore, we found that Filopodium-inducing IMD activity in the full-length IRSp53 was regulated by active Cdc42 and Rac1. The SH3 domain was not necessary for IMD-induced Filopodium formation. Our results indicate that IRSp53, when activated by small GTPases, participates in F-actin reorganization not only in an SH3-dependent manner but also in a manner dependent on the activity of the IMD.