Faculty Opinions recommendation of The lysosomal Ragulator complex plays an essential role in leukocyte trafficking by activating myosin II.

Using a microchannel assay, we demonstrate that cells adopt distinct signaling strategies to modulate cell migration in different physical microenvironments. We studied α4β1 integrin–mediated signaling, which regulates cell migration pertinent to embryonic development, leukocyte trafficking, and melanoma invasion. We show that α4β1 integrin promotes cell migration through both unconfined and confined spaces. However, unlike unconfined (2D) migration, which depends on enhanced Rac1 activity achieved by preventing α4/paxillin binding, confined migration requires myosin II–driven contractility, which is increased when Rac1 is inhibited by α4/paxillin binding. This Rac1–myosin II cross talk mechanism also controls migration of fibroblast-like cells lacking α4β1 integrin, in which Rac1 and myosin II modulate unconfined and confined migration, respectively. We further demonstrate the distinct roles of myosin II isoforms, MIIA and MIIB, which are primarily required for confined and unconfined migration, respectively. This work provides a paradigm for the plasticity of cells migrating through different physical microenvironments.

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Enucleation of human erythroblasts involves non-muscle myosin IIB

Blood ◽

10.1182/blood-2011-06-361907 ◽

2012 ◽

Vol 119 (4) ◽

pp. 1036-1044 ◽

Cited By ~ 46

Author(s):

Kumi Ubukawa ◽

Yong-Mei Guo ◽

Masayuki Takahashi ◽

Makoto Hirokawa ◽

Yoshihiro Michishita ◽

...

Keyword(s):

Cell Division ◽

Essential Role ◽

Myosin Ii ◽

Target Cells ◽

Colony Forming Unit ◽

Cd34 Cells ◽

Exogenous Expression ◽

Muscle Myosin ◽

Myosin Rod

Abstract Mammalian erythroblasts undergo enucleation, a process thought to be similar to cytokinesis. Although an assemblage of actin, non-muscle myosin II, and several other proteins is crucial for proper cytokinesis, the role of non-muscle myosin II in enucleation remains unclear. In this study, we investigated the effect of various cell-division inhibitors on cytokinesis and enucleation. For this purpose, we used human colony-forming unit-erythroid (CFU-E) and mature erythroblasts generated from purified CD34+ cells as target cells for cytokinesis and enucleation assay, respectively. Here we show that the inhibition of myosin by blebbistatin, an inhibitor of non-muscle myosin II ATPase, blocks both cell division and enucleation, which suggests that non-muscle myosin II plays an essential role not only in cytokinesis but also in enucleation. When the function of non-muscle myosin heavy chain (NMHC) IIA or IIB was inhibited by an exogenous expression of myosin rod fragment, myosin IIA or IIB, each rod fragment blocked the proliferation of CFU-E but only the rod fragment for IIB inhibited the enucleation of mature erythroblasts. These data indicate that NMHC IIB among the isoforms is involved in the enucleation of human erythroblasts.

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The lysosomal Ragulator complex plays an essential role in leukocyte trafficking by activating myosin II

Nature Communications ◽

10.1038/s41467-021-23654-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Takeshi Nakatani ◽

Kohei Tsujimoto ◽

JeongHoon Park ◽

Tatsunori Jo ◽

Tetsuya Kimura ◽

...

Keyword(s):

Immune Responses ◽

Essential Role ◽

Myosin Ii ◽

Nutrient Sensing ◽

Leukocyte Migration ◽

Interacting Protein ◽

Mechanistic Target Of Rapamycin ◽

Motile Cells ◽

A Subunit ◽

Actomyosin Contraction

AbstractLysosomes are involved in nutrient sensing via the mechanistic target of rapamycin complex 1 (mTORC1). mTORC1 is tethered to lysosomes by the Ragulator complex, a heteropentamer in which Lamtor1 wraps around Lamtor2–5. Although the Ragulator complex is required for cell migration, the mechanisms by which it participates in cell motility remain unknown. Here, we show that lysosomes move to the uropod in motile cells, providing the platform where Lamtor1 interacts with the myosin phosphatase Rho-interacting protein (MPRIP) independently of mTORC1 and interferes with the interaction between MPRIP and MYPT1, a subunit of myosin light chain phosphatase (MLCP), thereby increasing myosin II–mediated actomyosin contraction. Additionally, formation of the complete Ragulator complex is required for leukocyte migration and pathophysiological immune responses. Together, our findings demonstrate that the lysosomal Ragulator complex plays an essential role in leukocyte migration by activating myosin II through interacting with MPRIP.

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Faint Hα Emission in the Corona and Its Relation to the Prominences

International Astronomical Union Colloquium ◽

10.1017/s0252921100025550 ◽

1994 ◽

Vol 144 ◽

pp. 339-342

Author(s):

V. N. Dermendjiev ◽

Z. Mouradian ◽

J.- L. Leroy ◽

P. Duchlev

Keyword(s):

Magnetic Field ◽

Solar Corona ◽

Essential Role ◽

Hα Emission

AbstractThe relation between episodically observed in the solar corona faint Hαemission structures and the long lived prominences was studied. Particular consideration was given for cases in which the corresponding prominences had undergone DB process. An MHD interpretation of the phenomenon “emissions froides” (cool emission) is proposed in which an essential role plays the prominence supporting magnetic field.

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Freeze-fracture observations on changes in the distribution of Filipin-sterol complexes during epididymal maturation and capacitation of boar spermatozoa

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100157991 ◽

1990 ◽

Vol 48 (3) ◽

pp. 90-91

Author(s):

N. Seki ◽

Y. Toyama ◽

T. Nagano

Keyword(s):

Plasma Membrane ◽

Essential Role ◽

Freeze Fracture ◽

Final Concentration ◽

Freeze Fracturing ◽

Physiological Conditions ◽

Epididymal Maturation ◽

Cacodylate Buffer ◽

Sperm Membrane ◽

Boar Spermatozoa

It is believed that i ntramembra.nous sterols play an essential role in membrane stability and permeability. To investigate the distribution changes of sterols in sperm membrane during epididymal maturation and capacitation, filipin has been used as a cytochemical probe for the detection for membrane sterols. Using this technique in combination with freeze fracturing, we examined the boar spermatozoa under various physiological conditions.The spermatozoa were collected from: 1) caput, corpus and cauda epididymides, 2) sperm rich fraction of ejaculates, and 3)the uterus 2hr after natural coition. They were fixed with 2.5% glutaraldehyde in 0.05M cacodylate buffer (pH 7.4), and treated with the filipin solution (final concentration : 0.02.0.05%) for 24hr at 4°C with constant agitation. After the filipin treatment, replicas were made by conventional freeze-fracture technique. The density of filipin-sterol complexes (FSCs) was determined in the E face of the plasma membrane of head regions.

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