The Experts below are selected from a list of 150 Experts worldwide ranked by ideXlab platform
Shinya Inoue - One of the best experts on this subject based on the ideXlab platform.
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Amoeboid Movement anchored by eupodia new actin rich knobby feet in dictyostelium
Cytoskeleton, 1997Co-Authors: Yoshio Fukui, Shinya InoueAbstract:To date, protrusion of pseudopodia has been considered to be primarily responsible for translocation of free-living amoebae and leukocytes of higher organisms. Although there is little question that the pseudopodium plays an important role, little attention has been given to the cortical structures that are responsible for cell-substratum anchorage in Amoeboid Movement. Here, we report on a new knobby foot-like structure in amoebae of a cellular slime mold, Dictyostelium discoideum. These feet, each about 1 μm in diameter, appear transiently in multiple units at the base of certain pseudopodia where the amoeba contacts a partially deformable substrate. The feet were discovered, and their spatial and temporal behavior relative to pseudopodial anchorage and invasive locomotion were observed, by examining Dictyostelium amoebae using a DIC video microscope providing an 0.3 μm depth of field. Key evidence for the anchoring role of the knobby feet was obtained by investigating amoebae, flattened in a specially devised observation chamber, and attracted by chemotaxis towards 3',5' cyclic-adenosine monophosphate (cAMP). The cAMP was released by highly localized, pulsed UV-microbeam irradiation of caged cAMP. We show by indirect immunofluorescence that the knobby feet contain a high concentration of filamentous (F-) actin, myoB (a member of Dictyostelium myosin-I family), and α-actinin (an actin-binding protein). Interestingly, myoB exhibits a circular disposition around each foot. Neither myosin-II (conventional myosin) nor the 269 kD protein, which has been recently identified as a talin homologue of Dictyostelium [Kreitmeier et al., 1995: J. Cell Biol. 129:179–188], are concentrated at the feet. We propose that the knobby feet provide anchorage to the substratum needed by lamellipodia to exert projectile forces for invading narrow spaces or otherwise for a flattened amoeba to secure itself to the deformable substratum. Some forms of adhesion plaques in higher organisms such as “podosomes” or “invadopodia” may perform functions similar to the knobby feet, but appear to differ in life time, cytoskeletal organization and composition. We have named the knobby foot “eupodium.” Cell Motil. Cytoskeleton 36:339–354, 1997. © 1997 Wiley-Liss, Inc.
Murray Stewart - One of the best experts on this subject based on the ideXlab platform.
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Localized depolymerization of the major sperm protein cytoskeleton correlates with the forward Movement of the cell body in the Amoeboid Movement of nematode sperm.
The Journal of cell biology, 1999Co-Authors: Joseph E. Italiano, Murray Stewart, Thomas M. RobertsAbstract:The major sperm protein (MSP)-based Amoeboid motility of Ascaris suum sperm requires coordinated lamellipodial protrusion and cell body retraction. In these cells, protrusion and retraction are tightly coupled to the assembly and disassembly of the cytoskeleton at opposite ends of the lamellipodium. Although polymerization along the leading edge appears to drive protrusion, the behavior of sperm tethered to the substrate showed that an additional force is required to pull the cell body forward. To examine the mechanism of cell body Movement, we used pH to uncouple cytoskeletal polymerization and depolymerization. In sperm treated with pH 6.75 buffer, protrusion of the leading edge slowed dramatically while both cytoskeletal disassembly at the base of the lamellipodium and cell body retraction continued. At pH 6.35, the cytoskeleton pulled away from the leading edge and receded through the lamellipodium as its disassembly at the cell body continued. The cytoskeleton disassembled rapidly and completely in cells treated at pH 5.5, but reformed when the cells were washed with physiological buffer. Cytoskeletal reassembly occurred at the lamellipodial margin and caused membrane protrusion, but the cell body did not move until the cytoskeleton was rebuilt and depolymerization resumed. These results indicate that cell body retraction is mediated by tension in the cytoskeleton, correlated with MSP depolymerization at the base of the lamellipodium.
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Nematode sperm: Amoeboid Movement without actin.
Trends in cell biology, 1997Co-Authors: Thomas M. Roberts, Murray StewartAbstract:Nematodes produce Amoeboid sperm that crawl over surfaces in a manner reminiscent of many actin-rich cells. However, these sperm contain no F-actin, and their motility is powered by a dynamic filament system composed of polymers of the 14-kDa major sperm protein (MSP). These simple cells use this unique motility apparatus exclusively for locomotion. Recent studies have capitalized on this feature to explore the key structural properties of MSP related to its role in motility and to reconstitute the motility apparatus both in vivo and in vitro. This review discusses how these investigations have laid the foundation for understanding the physical basis of Amoeboid Movement by identifying the mechanistic properties shared by the MSP-based machinery and the more familiar actin-based systems.
Yoshio Fukui - One of the best experts on this subject based on the ideXlab platform.
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Amoeboid Movement anchored by eupodia, new actin-rich knobby feet
1997Co-Authors: Yoshio FukuiAbstract:To date, protrusion of pseudopodia has been considered to be primarily responsible for translocation of free-living amoebae and leukocytes of higher organisms. Although there is little question that the pseudopodium plays an important role, little attention has been given to the cortical structures that are responsible for cell-substratum anchorage in Amoeboid Movement. Here, we report on a new knobby foot-like structure in amoebae of a cellullar slime mold, Dictyostelium discoideum. These feet, each about 1 µm in diameter, appear transiently in multiple units at the base of certain pseudopodia where the amoeba contacts a partially deformable substrate. The feet were discovered, and their spatial and temporal behavior relative to pseudopodial anchorage and invasive locomotion were observed, by examining Dictyostelium amoebae using a DIC video microscope providing an 0.3 µm depth of field. Key evidence for the anchoring role of the knobby feet was obtained by investigating amoebae, flattened in a specially devised observation chamber, and attracted by chemotaxis towards 3’,5 ’ cyclic-adenosine monophosphate (cAMP). The cAMP was released by highly localized
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Amoeboid Movement anchored by eupodia new actin rich knobby feet in dictyostelium
Cytoskeleton, 1997Co-Authors: Yoshio Fukui, Shinya InoueAbstract:To date, protrusion of pseudopodia has been considered to be primarily responsible for translocation of free-living amoebae and leukocytes of higher organisms. Although there is little question that the pseudopodium plays an important role, little attention has been given to the cortical structures that are responsible for cell-substratum anchorage in Amoeboid Movement. Here, we report on a new knobby foot-like structure in amoebae of a cellular slime mold, Dictyostelium discoideum. These feet, each about 1 μm in diameter, appear transiently in multiple units at the base of certain pseudopodia where the amoeba contacts a partially deformable substrate. The feet were discovered, and their spatial and temporal behavior relative to pseudopodial anchorage and invasive locomotion were observed, by examining Dictyostelium amoebae using a DIC video microscope providing an 0.3 μm depth of field. Key evidence for the anchoring role of the knobby feet was obtained by investigating amoebae, flattened in a specially devised observation chamber, and attracted by chemotaxis towards 3',5' cyclic-adenosine monophosphate (cAMP). The cAMP was released by highly localized, pulsed UV-microbeam irradiation of caged cAMP. We show by indirect immunofluorescence that the knobby feet contain a high concentration of filamentous (F-) actin, myoB (a member of Dictyostelium myosin-I family), and α-actinin (an actin-binding protein). Interestingly, myoB exhibits a circular disposition around each foot. Neither myosin-II (conventional myosin) nor the 269 kD protein, which has been recently identified as a talin homologue of Dictyostelium [Kreitmeier et al., 1995: J. Cell Biol. 129:179–188], are concentrated at the feet. We propose that the knobby feet provide anchorage to the substratum needed by lamellipodia to exert projectile forces for invading narrow spaces or otherwise for a flattened amoeba to secure itself to the deformable substratum. Some forms of adhesion plaques in higher organisms such as “podosomes” or “invadopodia” may perform functions similar to the knobby feet, but appear to differ in life time, cytoskeletal organization and composition. We have named the knobby foot “eupodium.” Cell Motil. Cytoskeleton 36:339–354, 1997. © 1997 Wiley-Liss, Inc.
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toward a new concept of cell motility cytoskeletal dynamics in Amoeboid Movement and cell division
International Review of Cytology-a Survey of Cell Biology, 1993Co-Authors: Yoshio FukuiAbstract:Publisher Summary This chapter reviews historical and current studies relevant to cytoskeletal dynamics, with emphasis on Dictyostelium cytoskeletons. Cytoskeletal dynamics is the cytoskeletal reorganization that occurs as a consequence of monomer–polymer transition and protein–protein as well as protein–membrane interactions. Actin constitutes as much as 10% of the total protein in nonmuscle cells. The dynamism of cytoplasm exhibits as a thixotropic transition with polymerization and crosslinking of the filaments through regulation of pH, calcium, and associating proteins. The cortical-gel contraction hypothesis predicted that actomyosin ATPase produces the energy of contraction in nonmuscle systems. The dynamics of nonmuscle-cell motility also manifests as projection rather than contraction. Many signal-transduction events relate significantly to cytoskeletal dynamics, such as chemotactic and growth stimulation that cause transient changes in cell shape, cell motility, and cell division. The actin cytoskeleton is probably regulated by the factors involved in the signal-transduction cascade. Profilin which is a low-molecular weight G-actin-binding protein, might play a significant role in regulating actin polymerization in the cytoplasm by binding to G-actin.
Thomas M. Roberts - One of the best experts on this subject based on the ideXlab platform.
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Localized depolymerization of the major sperm protein cytoskeleton correlates with the forward Movement of the cell body in the Amoeboid Movement of nematode sperm.
The Journal of cell biology, 1999Co-Authors: Joseph E. Italiano, Murray Stewart, Thomas M. RobertsAbstract:The major sperm protein (MSP)-based Amoeboid motility of Ascaris suum sperm requires coordinated lamellipodial protrusion and cell body retraction. In these cells, protrusion and retraction are tightly coupled to the assembly and disassembly of the cytoskeleton at opposite ends of the lamellipodium. Although polymerization along the leading edge appears to drive protrusion, the behavior of sperm tethered to the substrate showed that an additional force is required to pull the cell body forward. To examine the mechanism of cell body Movement, we used pH to uncouple cytoskeletal polymerization and depolymerization. In sperm treated with pH 6.75 buffer, protrusion of the leading edge slowed dramatically while both cytoskeletal disassembly at the base of the lamellipodium and cell body retraction continued. At pH 6.35, the cytoskeleton pulled away from the leading edge and receded through the lamellipodium as its disassembly at the cell body continued. The cytoskeleton disassembled rapidly and completely in cells treated at pH 5.5, but reformed when the cells were washed with physiological buffer. Cytoskeletal reassembly occurred at the lamellipodial margin and caused membrane protrusion, but the cell body did not move until the cytoskeleton was rebuilt and depolymerization resumed. These results indicate that cell body retraction is mediated by tension in the cytoskeleton, correlated with MSP depolymerization at the base of the lamellipodium.
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Nematode sperm: Amoeboid Movement without actin.
Trends in cell biology, 1997Co-Authors: Thomas M. Roberts, Murray StewartAbstract:Nematodes produce Amoeboid sperm that crawl over surfaces in a manner reminiscent of many actin-rich cells. However, these sperm contain no F-actin, and their motility is powered by a dynamic filament system composed of polymers of the 14-kDa major sperm protein (MSP). These simple cells use this unique motility apparatus exclusively for locomotion. Recent studies have capitalized on this feature to explore the key structural properties of MSP related to its role in motility and to reconstitute the motility apparatus both in vivo and in vitro. This review discusses how these investigations have laid the foundation for understanding the physical basis of Amoeboid Movement by identifying the mechanistic properties shared by the MSP-based machinery and the more familiar actin-based systems.
Ulrich H Von Andrian - One of the best experts on this subject based on the ideXlab platform.
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rulers over randomness stroma cells guide lymphocyte migration in lymph nodes
Immunity, 2006Co-Authors: Thorsten R Mempel, Tobias Junt, Ulrich H Von AndrianAbstract:How is the Amoeboid Movement of lymphocytes in secondary lymphoid organs orchestrated? In this issue of Immunity, Bajenoff et al. (2006) demonstrate that stromal cell networks serve as guidance structures that direct and limit the migration of B and T cells in lymph nodes.
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compensation mechanism in tumor cell migration mesenchymal Amoeboid transition after blocking of pericellular proteolysis
Journal of Cell Biology, 2003Co-Authors: Katarina Wolf, Irina Mazo, Harry Leung, Katharina Engelke, Ulrich H Von Andrian, Elena I Deryugina, Alex Y Strongin, Eva B Brocker, Peter FriedlAbstract:Invasive tumor dissemination in vitro and in vivo involves the proteolytic degradation of ECM barriers. This process, however, is only incompletely attenuated by protease inhibitor–based treatment, suggesting the existence of migratory compensation strategies. In three-dimensional collagen matrices, spindle-shaped proteolytically potent HT-1080 fibrosarcoma and MDA-MB-231 carcinoma cells exhibited a constitutive mesenchymal-type Movement including the coclustering of β1 integrins and MT1–matrix metalloproteinase (MMP) at fiber bindings sites and the generation of tube-like proteolytic degradation tracks. Near-total inhibition of MMPs, serine proteases, cathepsins, and other proteases, however, induced a conversion toward spherical morphology at near undiminished migration rates. Sustained protease-independent migration resulted from a flexible amoeba-like shape change, i.e., propulsive squeezing through preexisting matrix gaps and formation of constriction rings in the absence of matrix degradation, concomitant loss of clustered β1 integrins and MT1-MMP from fiber binding sites, and a diffuse cortical distribution of the actin cytoskeleton. Acquisition of protease-independent Amoeboid dissemination was confirmed for HT-1080 cells injected into the mouse dermis monitored by intravital multiphoton microscopy. In conclusion, the transition from proteolytic mesenchymal toward nonproteolytic Amoeboid Movement highlights a supramolecular plasticity mechanism in cell migration and further represents a putative escape mechanism in tumor cell dissemination after abrogation of pericellular proteolysis.