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.

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 Functions of Nonmuscle Myosin II in Assembly of the Cellular Contractile System

PLoS ONE ◽  
2012 ◽  
Vol 7 (7) ◽  
pp. e40814 ◽  
Author(s):  
Maria Shutova ◽  
Changsong Yang ◽  
Jury M. Vasiliev ◽  
Tatyana Svitkina
Keyword(s):  
Myosin Ii ◽  
Nonmuscle Myosin ◽  
Contractile System ◽  
Nonmuscle Myosin Ii

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 Carboxyl-terminal-dependent recruitment of nonmuscle myosin II to megakaryocyte contractile ring during polyploidization

Blood ◽  
2014 ◽  
Vol 124 (16) ◽  
pp. 2564-2568 ◽  
Author(s):  
Idinath Badirou ◽  
Jiajia Pan ◽  
Céline Legrand ◽  
Aibing Wang ◽  
Larissa Lordier ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Specific Role ◽  
Nonmuscle Myosin ◽  
Contractile Ring ◽  
Terminal Domain ◽  
Nonmuscle Myosin Ii ◽  
Key Points ◽  
Carboxyl Terminal

Key Points C-terminal domain determines myosin II localization to the MK contractile ring and the specific role of NMII-B in MK polyploidization.

scholarly journals Electrostatic and bending energies predict staggering and splaying in nonmuscle myosin II minifilaments

2020 ◽  
Author(s):  
Tom Kaufmann ◽  
Ulrich S. Schwarz
Keyword(s):  
Elasticity Theory ◽  
Stochastic Dynamics ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Super Resolution ◽  
Live Cells ◽  
Sequence Information ◽  
Nonmuscle Myosin ◽  
Resolution Limit ◽  
Nonmuscle Myosin Ii

AbstractRecent experiments with super-resolution live cell microscopy revealed that nonmuscle myosin II minifilaments are much more dynamic than formerly appreciated, often showing plastic processes such as splitting, concatenation and stacking. Here we combine sequence information, electrostatics and elasticity theory to demonstrate that the parallel staggers at 14.3, 43.2 and 72 nm have a strong tendency to splay their heads away from the minifilament, thus potentially initiating the diverse processes seen in live cells. In contrast, the straight antiparallel stagger with an overlap of 43 nm is very stable and likely initiates minifilament nucleation. Using stochastic dynamics in a newly defined energy landscape, we predict that the optimal parallel staggers between the myosin rods are obtained by a trial-and-error process in which two rods attach and re-attach at different staggers by rolling and zipping motion. The experimentally observed staggers emerge as the configurations with the largest contact times. We find that contact times increase from isoforms C to B to A, that A-B-heterodimers are surprisingly stable and that myosin 18A should incorporate into mixed filaments with a small stagger. Our findings suggest that nonmuscle myosin II minifilaments in the cell are first formed by isoform A and then convert to mixed A-B-filaments, as observed experimentally.Author summaryNonmuscle myosin II (NM2) is a non-processive molecular motor that assembles into minifilaments with a typical size of 300 nm to generate force and motion in the actin cytoskeleton. This process is essential for many cellular processes such as adhesion, migration, division and mechanosensing. Due to their small size below the resolution limit, minifilaments are a challenge for imaging with traditional light microscopy. With the advent of super-resolution microscopy, however, it has become apparent that the formation of NM2-minifilaments is much more dynamic than formerly appreciated. Modeling the electrostatic interaction between the rigid rods of the myosin monomers has confirmed the main staggers observed in experiments, but cannot explain these high dynamics. Here we complement electrostatics by elasticity theory and stochastic dynamics to show that the parallel staggers are likely to splay away from the main axis of the minifilament and that monomers attach and deattach with rolling and zipping motions. Based on the sequences of the different NM2-isoforms, we predict that isoform A forms the most stable homofilaments and that A-B-heterofilaments are also very stable.

Drosophila nonmuscle myosin II is required for rapid cytoplasmic transport during oogenesis and for axial nuclear migration in early embryos

Development ◽  
1995 ◽  
Vol 121 (6) ◽  
pp. 1937-1946 ◽  
Author(s):  
S. Wheatley ◽  
S. Kulkarni ◽  
R. Karess
Keyword(s):  
Nurse Cell ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Posterior Pole ◽  
Nonmuscle Myosin ◽  
Rapid Phase ◽  
Hypomorphic Mutation ◽  
Cytoplasmic Transport ◽  
Nonmuscle Myosin Ii ◽  
Egg Chambers

The X-linked Drosophila gene spaghetti squash (sqh) encodes the regulatory light chain of nonmuscle myosin II. To assess the requirement for myosin II in oogenesis and early embryogenesis, we induced homozygous germline clones of the hypomorphic mutation sqh1 in otherwise heterozygous mothers. Developing oocytes in such sqh1 germline clones often failed to attain full size due to a defect in ‘dumping’, the rapid phase of cytoplasmic transport from nurse cells. In contrast to other dumpless mutants described to date, sqh1 egg chambers showed no evidence of ring canal obstruction, and no obvious alteration in the actin network. However the distribution of myosin II was abnormal. We conclude that the molecular motor responsible for cytoplasmic dumping is supplied largely, if not exclusively, by nurse cell myosin II and we suggest that regulation of myosin activity is one means by which cytoplasmic transport may be controlled during oocyte development. The eggs resulting from sqh1 clones, though smaller than normal, began development but exhibited an early defect in axial migration of cleavage nuclei towards the posterior pole of the embryo, in a similar manner to that seen in early cleavage eggs in which the actin cytoskeleton is disrupted. Thus both nurse cell dumping and axial migration require a maternally supplied myosin II.

scholarly journals Anillin Binds Nonmuscle Myosin II and Regulates the Contractile Ring

2005 ◽  
Vol 16 (1) ◽  
pp. 193-201 ◽  
Author(s):  
Aaron F. Straight ◽  
Christine M. Field ◽  
Timothy J. Mitchison
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Cultured Cells ◽  
Contractile Activity ◽  
Myosin Ii ◽  
Human Cells ◽  
Myosin Light Chain Phosphorylation ◽  
Nonmuscle Myosin ◽  
Contractile Ring ◽  
Nonmuscle Myosin Ii

We demonstrate that the contractile ring protein anillin interacts directly with nonmuscle myosin II and that this interaction is regulated by myosin light chain phosphorylation. We show that despite their interaction, anillin and myosin II are independently targeted to the contractile ring. Depletion of anillin in Drosophila or human cultured cells results in cytokinesis failure. Human cells depleted for anillin fail to properly regulate contraction by myosin II late in cytokinesis and fail in abscission. We propose a role for anillin in spatially regulating the contractile activity of myosin II during cytokinesis.

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