scholarly journals Myosin is involved in postmitotic cell spreading.

1995 ◽  
Vol 131 (1) ◽  
pp. 179-189 ◽  
Author(s):  
L P Cramer ◽  
T J Mitchison
Keyword(s):  
Actin Filaments ◽  
Spatial Organization ◽  
Myosin Ii ◽  
Cell Spreading ◽  
Spatial Arrangement ◽  
Time Lapse ◽  
Myosin V ◽  
Nonmuscle Myosin Ii ◽  
Ptk2 Cell ◽  
Postmitotic Cell

We have investigated a role for myosin in postmitotic Potoroo tridactylis kidney (PtK2) cell spreading by inhibitor studies, time-lapse video microscopy, and immunofluorescence. We have also determined the spatial organization and polarity of actin filaments in postmitotic spreading cells. We show that butanedione monoxime (BDM), a known inhibitor of muscle myosin II, inhibits nonmuscle myosin II and myosin V adenosine triphosphatases. BDM reversibly inhibits PtK2 postmitotic cell spreading. Listeria motility is not affected by this drug. Electron microscopy studies show that some actin filaments in spreading edges are part of actin bundles that are also found in long, thin, structures that are connected to spreading edges and substrate (retraction fibers), and that 90% of this actin is oriented with barbed ends in the direction of spreading. The remaining actin in spreading edges has a more random orientation and spatial arrangement. Myosin II is associated with actin polymer in spreading cell edges, but not retraction fibers. Myosin II is excluded from lamellipodia that protrude from the cell edge at the end of spreading. We suggest that spreading involves myosin, possibly myosin II.

scholarly journals Myosin Motors and Not Actin Comets Are Mediators of the Actin-based Golgi-to-Endoplasmic Reticulum Protein Transport

2003 ◽  
Vol 14 (2) ◽  
pp. 445-459 ◽  
Author(s):  
Juan M. Durán ◽  
Ferran Valderrama ◽  
Susana Castel ◽  
Juana Magdalena ◽  
Mónica Tomás ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Light Chain ◽  
Shiga Toxin ◽  
Actin Filaments ◽  
Protein Transport ◽  
Myosin Ii ◽  
Nonmuscle Myosin ◽  
Nonmuscle Myosin Ii ◽  
Myosin Motors

We have previously reported that actin filaments are involved in protein transport from the Golgi complex to the endoplasmic reticulum. Herein, we examined whether myosin motors or actin comets mediate this transport. To address this issue we have used, on one hand, a combination of specific inhibitors such as 2,3-butanedione monoxime (BDM) and 1-[5-isoquinoline sulfonyl]-2-methyl piperazine (ML7), which inhibit myosin and the phosphorylation of myosin II by the myosin light chain kinase, respectively; and a mutant of the nonmuscle myosin II regulatory light chain, which cannot be phosphorylated (MRLC2AA). On the other hand, actin comet tails were induced by the overexpression of phosphatidylinositol phosphate 5-kinase. Cells treated with BDM/ML7 or those that express the MRLC2AA mutant revealed a significant reduction in the brefeldin A (BFA)-induced fusion of Golgi enzymes with the endoplasmic reticulum (ER). This delay was not caused by an alteration in the formation of the BFA-induced tubules from the Golgi complex. In addition, the Shiga toxin fragment B transport from the Golgi complex to the ER was also altered. This impairment in the retrograde protein transport was not due to depletion of intracellular calcium stores or to the activation of Rho kinase. Neither the reassembly of the Golgi complex after BFA removal nor VSV-G transport from ER to the Golgi was altered in cells treated with BDM/ML7 or expressing MRLC2AA. Finally, transport carriers containing Shiga toxin did not move into the cytosol at the tips of comet tails of polymerizing actin. Collectively, the results indicate that 1) myosin motors move to transport carriers from the Golgi complex to the ER along actin filaments; 2) nonmuscle myosin II mediates in this process; and 3) actin comets are not involved in retrograde transport.

scholarly journals Analysis of the Actin–Myosin II System in Fish Epidermal Keratocytes: Mechanism of Cell Body Translocation

1997 ◽  
Vol 139 (2) ◽  
pp. 397-415 ◽  
Author(s):  
Tatyana M. Svitkina ◽  
Alexander B. Verkhovsky ◽  
Kyle M. McQuade ◽  
Gary G. Borisy
Keyword(s):  
Cell Body ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Leading Edge ◽  
Time Lapse ◽  
Supramolecular Organization ◽  
Retrograde Flow ◽  
Body Boundary ◽  
Filament Bundles

While the protrusive event of cell locomotion is thought to be driven by actin polymerization, the mechanism of forward translocation of the cell body is unclear. To elucidate the mechanism of cell body translocation, we analyzed the supramolecular organization of the actin–myosin II system and the dynamics of myosin II in fish epidermal keratocytes. In lamellipodia, long actin filaments formed dense networks with numerous free ends in a brushlike manner near the leading edge. Shorter actin filaments often formed T junctions with longer filaments in the brushlike area, suggesting that new filaments could be nucleated at sides of preexisting filaments or linked to them immediately after nucleation. The polarity of actin filaments was almost uniform, with barbed ends forward throughout most of the lamellipodia but mixed in arc-shaped filament bundles at the lamellipodial/cell body boundary. Myosin II formed discrete clusters of bipolar minifilaments in lamellipodia that increased in size and density towards the cell body boundary and colocalized with actin in boundary bundles. Time-lapse observation demonstrated that myosin clusters appeared in the lamellipodia and remained stationary with respect to the substratum in locomoting cells, but they exhibited retrograde flow in cells tethered in epithelioid colonies. Consequently, both in locomoting and stationary cells, myosin clusters approached the cell body boundary, where they became compressed and aligned, resulting in the formation of boundary bundles. In locomoting cells, the compression was associated with forward displacement of myosin features. These data are not consistent with either sarcomeric or polarized transport mechanisms of cell body translocation. We propose that the forward translocation of the cell body and retrograde flow in the lamellipodia are both driven by contraction of an actin–myosin network in the lamellipodial/cell body transition zone.

scholarly journals Different contributions of nonmuscle myosin IIA and IIB to the organization of stress fiber subtypes in fibroblasts

2018 ◽  
Vol 29 (8) ◽  
pp. 911-922 ◽  
Author(s):  
Masahiro Kuragano ◽  
Taro Q. P. Uyeda ◽  
Keiju Kamijo ◽  
Yota Murakami ◽  
Masayuki Takahashi
Keyword(s):  
Actin Filaments ◽  
Myosin Ii ◽  
Contractile Force ◽  
Stress Fiber ◽  
Stress Fibers ◽  
Proper Function ◽  
Nonmuscle Myosin ◽  
Nonmuscle Myosin Ii ◽  
Exogenous Expression ◽  
Main Component

Stress fibers (SFs) are contractile, force-generating bundled structures that can be classified into three subtypes, namely ventral SFs (vSFs), transverse arcs (TAs), and dorsal SFs. Nonmuscle myosin II (NMII) is the main component of SFs. This study examined the roles of the NMII isoforms NMIIA and NMIIB in the organization of each SF subtype in immortalized fibroblasts. Knockdown (KD) of NMIIA (a major isoform) resulted in loss of TAs from the lamella and caused the lamella to lose its flattened shape. Exogenous expression of NMIIB rescued this defect in TA formation. However, the TAs that formed on exogenous NMIIB expression in NMIIA-KD cells and the remaining TAs in NMIIB-KD cells, which mainly consisted of NMIIB and NMIIA, respectively, failed to rescue the defect in lamellar flattening. These results indicate that both isoforms are required for the proper function of TAs in lamellar flattening. KD of NMIIB resulted in loss of vSFs from the central region of the cell body, and this defect was not rescued by exogenous expression of NMIIA, indicating that NMIIA cannot replace the function of NMIIB in vSF formation. Moreover, we raised the possibility that actin filaments in vSFs are in a stretched conformation.

scholarly journals Expansion and concatenation of nonmuscle myosin IIA filaments drive cellular contractile system formation during interphase and mitosis

2016 ◽  
Vol 27 (9) ◽  
pp. 1465-1478 ◽  
Author(s):  
Aidan M. Fenix ◽  
Nilay Taneja ◽  
Carmen A. Buttler ◽  
John Lewis ◽  
Schuyler B. Van Engelenburg ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Cell Movement ◽  
Nonmuscle Myosin ◽  
Contractile Ring ◽  
Contractile System ◽  
Nonmuscle Myosin Ii ◽  
Dividing Cells ◽  
Contractile Forces

Cell movement and cytokinesis are facilitated by contractile forces generated by the molecular motor, nonmuscle myosin II (NMII). NMII molecules form a filament (NMII-F) through interactions of their C-terminal rod domains, positioning groups of N-terminal motor domains on opposite sides. The NMII motors then bind and pull actin filaments toward the NMII-F, thus driving contraction. Inside of crawling cells, NMIIA-Fs form large macromolecular ensembles (i.e., NMIIA-F stacks), but how this occurs is unknown. Here we show NMIIA-F stacks are formed through two non–mutually exclusive mechanisms: expansion and concatenation. During expansion, NMIIA molecules within the NMIIA-F spread out concurrent with addition of new NMIIA molecules. Concatenation occurs when multiple NMIIA-Fs/NMIIA-F stacks move together and align. We found that NMIIA-F stack formation was regulated by both motor activity and the availability of surrounding actin filaments. Furthermore, our data showed expansion and concatenation also formed the contractile ring in dividing cells. Thus interphase and mitotic cells share similar mechanisms for creating large contractile units, and these are likely to underlie how other myosin II–based contractile systems are assembled.

Differential localization of unconventional myosin I and nonmuscle myosin II during B cell spreading

2006 ◽  
Vol 312 (17) ◽  
pp. 3312-3322 ◽  
Author(s):  
Adriana Sumoza-Toledo ◽  
Peter G. Gillespie ◽  
Hector Romero-Ramirez ◽  
Hellen C. Ferreira-Ishikawa ◽  
Roy E. Larson ◽  
...  
Keyword(s):  
B Cell ◽  
Myosin Ii ◽  
Cell Spreading ◽  
Nonmuscle Myosin ◽  
Unconventional Myosin ◽  
Myosin I ◽  
Nonmuscle Myosin Ii ◽  
Differential Localization

scholarly journals Association of a Nonmuscle Myosin II with Axoplasmic Organelles

2002 ◽  
Vol 13 (3) ◽  
pp. 1046-1057 ◽  
Author(s):  
Joseph A. DeGiorgis ◽  
Thomas S. Reese ◽  
Elaine L. Bearer
Keyword(s):  
Myosin Ii ◽  
Stellate Ganglion ◽  
Giant Axon ◽  
Peptide Sequence ◽  
Immunogold Electron Microscopy ◽  
Nonmuscle Myosin ◽  
Myosin V ◽  
Cloning And Sequencing ◽  
Specific Primers ◽  
Nonmuscle Myosin Ii

Association of motor proteins with organelles is required for the motors to mediate transport. Because axoplasmic organelles move on actin filaments, they must have associated actin-based motors, most likely members of the myosin superfamily. To gain a better understanding of the roles of myosins in the axon we used the giant axon of the squid, a powerful model for studies of axonal physiology. First, a ∼220 kDa protein was purified from squid optic lobe, using a biochemical protocol designed to isolate myosins. Peptide sequence analysis, followed by cloning and sequencing of the full-length cDNA, identified this ∼220 kDa protein as a nonmuscle myosin II. This myosin is also present in axoplasm, as determined by two independent criteria. First, RT-PCR using sequence-specific primers detected the transcript in the stellate ganglion, which contains the cell bodies that give rise to the giant axon. Second, Western blot analysis using nonmuscle myosin II isotype-specific antibodies detected a single ∼220 kDa band in axoplasm. Axoplasm was fractionated through a four-step sucrose gradient after 0.6 M KI treatment, which separates organelles from cytoskeletal components. Of the total nonmuscle myosin II in axoplasm, 43.2% copurified with organelles in the 15% sucrose fraction, while the remainder (56.8%) was soluble and found in the supernatant. This myosin decorates the cytoplasmic surface of 21% of the axoplasmic organelles, as demonstrated by immunogold electron-microscopy. Thus, nonmuscle myosin II is synthesized in the cell bodies of the giant axon, is present in the axon, and is associated with isolated axoplasmic organelles. Therefore, in addition to myosin V, this myosin is likely to be an axoplasmic organelle motor.

Computational Micrograph Registration with Sieve Processes

1996 ◽  
Vol 54 ◽  
pp. 440-441
Author(s):  
P.J. Phillips ◽  
J. Huang ◽  
S. M. Dunn
Keyword(s):  
Planar Graph ◽  
Efficient Algorithm ◽  
Spatial Organization ◽  
Spatial Arrangement ◽  
Stereo Image ◽  
Image Model ◽  
Geometric Invariants ◽  
Point Set

In this paper we present an efficient algorithm for automatically finding the correspondence between pairs of stereo micrographs, the key step in forming a stereo image. The computation burden in this problem is solving for the optimal mapping and transformation between the two micrographs. In this paper, we present a sieve algorithm for efficiently estimating the transformation and correspondence.In a sieve algorithm, a sequence of stages gradually reduce the number of transformations and correspondences that need to be examined, i.e., the analogy of sieving through the set of mappings with gradually finer meshes until the answer is found. The set of sieves is derived from an image model, here a planar graph that encodes the spatial organization of the features. In the sieve algorithm, the graph represents the spatial arrangement of objects in the image. The algorithm for finding the correspondence restricts its attention to the graph, with the correspondence being found by a combination of graph matchings, point set matching and geometric invariants.

ЛАНДШАФТНАЯ ОРГАНИЗАЦИЯ БЕРЕГОВОЙ ГЕОСТРУКТУРЫ ОСТРОВА ШКОТА (ЗАЛИВ ПЕТРА ВЕЛИКОГО)

2019 ◽  
Author(s):  
K.S. Ganzei ◽  
V.V. Zharikov ◽  
N.F. Pshenichnikova ◽  
A.M. Lebedev ◽  
A.G. Kiselyova ◽  
...  
Keyword(s):  
Spatial Organization ◽  
Peter The Great Bay ◽  
Spatial Arrangement ◽  
Water Area ◽  
Marine Spatial Planning ◽  
Landscape Approach ◽  
Important Condition ◽  
Statistical Comparison ◽  
Peter The Great ◽  
Comprehensive Study

Важнейшим условием достижения устойчивого развития прибрежноморского природопользования в заливе Петра Великого системы является морское пространственное планирование. Основой для этого является информация о природных комплексах территории и акватории, полученная на основе ландшафтного подхода. Ключевым районом для изучения пространственной организации ландшафтов прибрежных геоструктур стала территория острова Шкота и его подводных склонов. Для наземных ландшафтов было описано 49 наблюдательных пунктов, 4 профиля были заложены для подводных ландшафтов описано 64 наблюдательных пункта, проложено 18 профилей. Выделено 22 вида ландшафтов, из них 16 наземных, 6 подводных. Берега острова сформированы преобладанием абразивноденудационного и абразивного типов. В результате всестороннего изучения показаны особенности пространственной организации воздушных и водных природных комплексов. Особенностью исследуемой территории является экспозиция дифференциации ландшафтов между юговосточной и северозападной частями острова, обусловленная муссонной природой климата. Результаты полевых и картографических работ послужили основой для выбора зон интенсивного, умеренного и ослабленного взаимодействия наземных и подводных ландшафтов. Пространственное расположение зон взаимодействия четко иллюстрируется значительными различиями экспозиции. Результаты статистического сравнения ландшафтов суши и мелководья, окружающего остров, на основе картометрических характеристик указывают на неоднородность геоструктуры острова, обусловленную, прежде всего, сочетанием ландшафтообразующих факторов. The most important condition for achieving sustainable development of coastalmarine environmental management in Peter the Great Bay is marine spatial planning. The basis for this is information about the natural complexes of the territory and water area, obtained based on the landscape approach. The main area for studying the spatial organization of landscapes of coastal geostructures was the territory of the island of Shkota and its underwater slopes. For terrestrial landscapes, 49 observation points were described, 4 profiles were laid 64 observation points were described for underwater landscapes, 18 profiles were laid. 22 species of landscapes have been identified, of which 16 are terrestrial, 6 are underwater. The shores of the island are formed by the predominance of abrasivedenudation and abrasive types. Because of a comprehensive study, features of the spatial organization of air and aquatic natural complexes are shown. A special feature of the study area is the exposure of the differentiation of landscapes between the southeastern and northwestern parts of the island, due to the monsoon nature of the climate. The results of field and cartographic works served as the basis for selecting areas of intense, moderate and weakened interaction of land and underwater landscapes. The spatial arrangement of the interaction zones is clearly illustrated by significant differences in exposure. The results of a statistical comparison of the land and shallow water landscapes surrounding the island, based on the cartometric characteristics, indicate the heterogeneity of the islands geostructure, primarily due to the combination of landscapeforming factors.

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