scholarly journals LMO7-dependent apical constriction requires the binding of the Myosin heavy chain

2021 ◽  
Author(s):  
Miho Matsuda ◽  
Chih-Wen Chu ◽  
Sergei S Sokol
Keyword(s):  
Heavy Chain ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Tube Formation ◽  
Epithelial Morphogenesis ◽  
Apical Constriction ◽  
Actomyosin Contractility ◽  
Apical Domain ◽  
Underlying Mechanisms ◽  
Muscle Myosin

The reduction of the apical domain, or apical constriction, is a process that occurs in a single cell or is coordinated in a group of cells in the epithelium. Coordinated apical constriction is particularly important when the epithelium is undergoing dynamic morphogenetic events such as furrow or tube formation. However, the underlying mechanisms remain incompletely understood. Here we show that Lim only protein 7 (Lmo7) is a novel activator of apical constriction in the Xenopus superficial ectoderm, which coordinates actomyosin contractility in a group of cells during epithelial morphogenesis. Like other apical constriction regulators, Lmo7 requires the activation of the Rho-Rock-Myosin II pathway to induce apical constriction. However, instead of increasing the phosphorylation of myosin light chain (MLC), Lmo7 binds muscle myosin II heavy chain A (NMIIA) and increases its association with actomyosin bundles at adherens junctions (AJs). Lmo7 overexpression modulates the subcellular distribution of Wtip, a tension marker at AJs, suggesting that Lmo7 generates mechanical forces at AJs. We propose that Lmo7 increases actomyosin contractility at AJs by promoting the formation of actomyosin bundles.

scholarly journals Mechanical bistability enabled by ectodermal compression facilitates Drosophila mesoderm invagination

2021 ◽  
Author(s):  
Hanqing Guo ◽  
Michael Swan ◽  
Shicheng Huang ◽  
Bing He
Keyword(s):  
Myosin Ii ◽  
Cell Sheet ◽  
Apical Surface ◽  
Apical Constriction ◽  
Out Of Plane ◽  
A Cell ◽  
Plane Compression ◽  
Contractile Forces ◽  
Tissue Relaxation ◽  
Muscle Myosin

Apical constriction driven by non-muscle myosin II (″myosin″) provides a well-conserved mechanism to mediate epithelial folding. It remains unclear how contractile forces near the apical surface of a cell sheet drive out-of-plane bending of the sheet and whether myosin contractility is required throughout folding. By optogenetic-mediated acute inhibition of myosin, we find that during Drosophila mesoderm invagination, myosin contractility is critical to prevent tissue relaxation during the early, ″priming″ stage of folding but is dispensable for the actual folding step after the tissue passes through a stereotyped transitional configuration, suggesting that the mesoderm is mechanically bistable during gastrulation. Combining computer modeling and experimental measurements, we show that the observed mechanical bistability arises from an in-plane compression from the surrounding ectoderm, which promotes mesoderm invagination by facilitating a buckling transition. Our results indicate that Drosophila mesoderm invagination requires a joint action of local apical constriction and global in-plane compression to trigger epithelial buckling.

scholarly journals Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila

1997 ◽  
Vol 139 (7) ◽  
pp. 1805-1819 ◽  
Author(s):  
Pascale Jordan ◽  
Roger Karess
Keyword(s):  
Amino Acids ◽  
Heavy Chain ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Germ Line ◽  
Myosin Ii ◽  
Oocyte Development ◽  
Nurse Cells ◽  
Ring Canals

The Drosophila spaghetti squash (sqh) gene encodes the regulatory myosin light chain (RMLC) of nonmuscle myosin II. Biochemical analysis of vertebrate nonmuscle and smooth muscle myosin II has established that phosphorylation of certain amino acids of the RMLC greatly increases the actin-dependent myosin ATPase and motor activity of myosin in vitro. We have assessed the in vivo importance of these sites, which in Drosophila correspond to serine-21 and threonine-20, by creating a series of transgenes in which these specific amino acids were altered. The phenotypes of the transgenes were examined in an otherwise null mutant background during oocyte development in Drosophila females. Germ line cystoblasts entirely lacking a functional sqh gene show severe defects in proliferation and cytokinesis. The ring canals, cytoplasmic bridges linking the oocyte to the nurse cells in the egg chamber, are abnormal, suggesting a role of myosin II in their establishment or maintenance. In addition, numerous aggregates of myosin heavy chain accumulate in the sqh null cells. Mutant sqh transgene sqh-A20, A21 in which both serine-21 and threonine-20 have been replaced by alanines behaves in most respects identically to the null allele in this system, with the exception that no heavy chain aggregates are found. In contrast, expression of sqh-A21, in which only the primary phosphorylation target serine-21 site is altered, partially restores functionality to germ line myosin II, allowing cystoblast division and oocyte development, albeit with some cytokinesis failure, defects in the rapid cytoplasmic transport from nurse cells to cytoplasm characteristic of late stage oogenesis, and some damaged ring canals. Substituting a glutamate for the serine-21 (mutant sqh-E21) allows oogenesis to be completed with minimal defects, producing eggs that can develop normally to produce fertile adults. Flies expressing sqh-A20, in which only the secondary phosphorylation site is absent, appear to be entirely wild type. Taken together, this genetic evidence argues that phosphorylation at serine-21 is critical to RMLC function in activating myosin II in vivo, but that the function can be partially provided by phosphorylation at threonine-20.

scholarly journals RhoA effectors LOK/SLK activate ERM proteins to locally inhibit RhoA and define apical morphology

2020 ◽  
Author(s):  
Riasat Zaman ◽  
Andrew Lombardo ◽  
Cécile Sauvanet ◽  
Raghuvir Viswanatha ◽  
Valerie Awad ◽  
...  
Keyword(s):  
Feedback Loop ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Stress Fiber ◽  
Myosin Light Chain Phosphorylation ◽  
Negative Regulators ◽  
Erm Proteins ◽  
Major Function ◽  
Apical Domain ◽  
Local Feedback

AbstractActivated Ezrin-Radixin-Moesin (ERM) proteins link the plasma membrane to the actin cytoskeleton to generate apical structures, including microvilli. Among many kinases implicated in ERM activation are the homologs LOK and SLK. CRISPR/Cas9 was used to knockout all ERM proteins or LOK/SLK in human cells. LOK/SLK knockout eliminates all ERM activating phosphorylation. The apical domain of cells lacking LOK/SLK or ERMs is strikingly similar and selectively altered, with loss of microvill, and junctional actin replaced by ectopic myosin-II containing apical stress-fiber-like structures. Constitutively active ezrin can reverse the phenotypes of either ERMs or LOK/SLK knockouts, showing that the major function of LOK/SLK is to activate ERMs. Both knockout lines have elevated active RhoA with concomitant enhanced myosin light chain phosphorylation, revealing that active ERMs are negative regulators of RhoA. As RhoA-GTP activates LOK/SLK to activate ERM proteins, the ability of active ERMs to negatively regulate RhoA-GTP represents a novel local feedback loop necessary for the proper apical morphology of epithelial cells.

scholarly journals Cortical contraction drives the 3D patterning of epithelial cell surfaces

2019 ◽  
Author(s):  
Aaron P. van Loon ◽  
Ivan S. Erofeev ◽  
Ivan V. Maryshev ◽  
Andrew B. Goryachev ◽  
Alvaro Sagasti
Keyword(s):  
Surface Tension ◽  
Myosin Ii ◽  
Biomechanical Model ◽  
Cell Surfaces ◽  
Apical Constriction ◽  
Skin Cells ◽  
In Vivo Experiments ◽  
Surface Topographies ◽  
Muscle Myosin

ABSTRACTCellular protrusions create complex cell surface topographies, but biomechanical mechanisms regulating their formation and arrangement are largely unknown. To study how protrusions form, we focused on the morphogenesis of microridges, elongated actin-based structures projecting from the apical surfaces of zebrafish skin cells that are arranged in labyrinthine patterns. Microridges form by accreting simple finger-like precursors. Live imaging demonstrated that microridge morphogenesis is linked to apical constriction. A non-muscle myosin II (NMII) reporter revealed pulsatile contractions of the actomyosin cortex; inhibiting NMII demonstrated that contractions are required for apical constriction and microridge formation. A biomechanical model suggested that contraction reduces surface tension to permit the fusion of precursors into microridges. Indeed, reducing surface tension with hyperosmolar media promoted microridge formation. In anisotropically stretched cells, microridges formed by precursor fusion along the stretch axis, which computational modeling explained as a consequence of stretch-induced cortical flow. Collectively, our results demonstrate how contraction within the 2D plane of the cortex patterns 3D cell surfaces.SUMMARYMicroridges, elongated 3D protrusions arranged in maze-like patterns on zebrafish skin cells, form by the accretion of simple precursor projections. Modeling and in vivo experiments showed that cortical contractions promote the coalescence of precursors into microridges by reducing membrane tension.

scholarly journals A novel coordinated function of Myosin II with GOLPH3 controls centralspindlin localization during cytokinesis in Drosophila

2020 ◽  
Vol 133 (21) ◽  
pp. jcs252965
Author(s):  
Stefano Sechi ◽  
Anna Frappaolo ◽  
Angela Karimpour-Ghahnavieh ◽  
Roberta Fraschini ◽  
Maria Grazia Giansanti
Keyword(s):  
Plasma Membrane ◽  
Heavy Chain ◽  
Light Chain ◽  
Animal Cell ◽  
Myosin Ii ◽  
Contractile Ring ◽  
Ring Assembly ◽  
Missense Allele ◽  
Phosphatidylinositol 4 ◽  
Muscle Myosin

ABSTRACTIn animal cell cytokinesis, interaction of non-muscle myosin II (NMII) with F-actin provides the dominant force for pinching the mother cell into two daughters. Here we demonstrate that celibe (cbe) is a missense allele of zipper, which encodes the Drosophila Myosin heavy chain. Mutation of cbe impairs binding of Zipper protein to the regulatory light chain Spaghetti squash (Sqh). In dividing spermatocytes from cbe males, Sqh fails to concentrate at the equatorial cortex, resulting in thin actomyosin rings that are unable to constrict. We show that cbe mutation impairs localization of the phosphatidylinositol 4-phosphate [PI(4)P]-binding protein Golgi phosphoprotein 3 (GOLPH3, also known as Sauron) and maintenance of centralspindlin at the cell equator of telophase cells. Our results further demonstrate that GOLPH3 protein associates with Sqh and directly binds the centralspindlin subunit Pavarotti. We propose that during cytokinesis, the reciprocal dependence between Myosin and PI(4)P–GOLPH3 regulates centralspindlin stabilization at the invaginating plasma membrane and contractile ring assembly.

scholarly journals The adherens junction–associated LIM domain protein Smallish regulates epithelial morphogenesis

2018 ◽  
Vol 217 (3) ◽  
pp. 1079-1095 ◽  
Author(s):  
Hamze Beati ◽  
Irina Peek ◽  
Paulina Hordowska ◽  
Mona Honemann-Capito ◽  
Jade Glashauser ◽  
...  
Keyword(s):  
Planar Cell Polarity ◽  
Adherens Junction ◽  
Epithelial Morphogenesis ◽  
Lim Domain ◽  
Core Component ◽  
Apical Constriction ◽  
Binding Partner ◽  
Actomyosin Contractility ◽  
Lim Domain Protein ◽  
Embryonic Morphogenesis

In epithelia, cells adhere to each other in a dynamic fashion, allowing the cells to change their shape and move along each other during morphogenesis. The regulation of adhesion occurs at the belt-shaped adherens junction, the zonula adherens (ZA). Formation of the ZA depends on components of the Par–atypical PKC (Par-aPKC) complex of polarity regulators. We have identified the Lin11, Isl-1, Mec-3 (LIM) protein Smallish (Smash), the orthologue of vertebrate LMO7, as a binding partner of Bazooka/Par-3 (Baz), a core component of the Par-aPKC complex. Smash also binds to Canoe/Afadin and the tyrosine kinase Src42A and localizes to the ZA in a planar polarized fashion. Animals lacking Smash show loss of planar cell polarity (PCP) in the embryonic epidermis and reduced cell bond tension, leading to severe defects during embryonic morphogenesis of epithelial tissues and organs. Overexpression of Smash causes apical constriction of epithelial cells. We propose that Smash is a key regulator of morphogenesis coordinating PCP and actomyosin contractility at the ZA.

scholarly journals Non-muscle Myosin II and Myosin Light Chain Kinase Are Downstream Targets for Vasopressin Signaling in the Renal Collecting Duct

2004 ◽  
Vol 279 (47) ◽  
pp. 49026-49035 ◽  
Author(s):  
Chung-Lin Chou ◽  
Birgitte M. Christensen ◽  
Sebastian Frische ◽  
Henrik Vorum ◽  
Ravi A. Desai ◽  
...  
Keyword(s):  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Collecting Duct ◽  
Myosin Ii ◽  
Downstream Targets ◽  
Renal Collecting Duct ◽  
Muscle Myosin

scholarly journals Non-muscle myosin II induces disassembly of actin stress fibres independently of myosin light chain dephosphorylation

2011 ◽  
Vol 1 (5) ◽  
pp. 754-766 ◽  
Author(s):  
Tsubasa S. Matsui ◽  
Roland Kaunas ◽  
Makoto Kanzaki ◽  
Masaaki Sato ◽  
Shinji Deguchi
Keyword(s):  
Light Chain ◽  
Actin Filaments ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Physiological Level ◽  
Cell Shortening ◽  
Applied Forces ◽  
Selective Disassembly ◽  
The Individual ◽  
Muscle Myosin

Dynamic remodelling of actin stress fibres (SFs) allows non-muscle cells to adapt to applied forces such as uniaxial cell shortening. However, the mechanism underlying rapid and selective disassembly of SFs oriented in the direction of shortening remains to be elucidated. Here, we investigated how myosin crossbridge cycling induced by MgATP is associated with SF disassembly. Moderate concentrations of MgATP, or [MgATP], induced SF contraction. Meanwhile, at [MgATP] slightly higher than the physiological level, periodic actin patterns emerged along the length of SFs and dispersed within seconds. The actin fragments were diverse in length, but comparable to those in characteristic sarcomeric units of SFs. These results suggest that MgATP-bound non-muscle myosin II dissociates from the individual actin filaments that constitute the sarcomeric units, resulting in unbundling-induced disassembly rather than end-to-end actin depolymerization. This rapid SF disassembly occurred independent of dephosphorylation of myosin light chain. In terms of effects on actin–myosin interactions, a rise in [MgATP] is functionally equivalent to a temporal decrease in the total number of actin–myosin crossbridges. Actin–myosin crossbridges are known to be reduced by an assisting load on myosin. Thus, the present study suggests that reducing the number of actin–myosin crossbridges promotes rapid and orientation-dependent disassembly of SFs after cell shortening.

scholarly journals An Alternatively Spliced Isoform of Non-muscle Myosin II-C Is Not Regulated by Myosin Light Chain Phosphorylation

2009 ◽  
Vol 284 (17) ◽  
pp. 11563-11571 ◽  
Author(s):  
Siddhartha S. Jana ◽  
Kye-Young Kim ◽  
Jian Mao ◽  
Sachiyo Kawamoto ◽  
James R. Sellers ◽  
...  
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Myosin Light Chain Phosphorylation ◽  
Alternatively Spliced ◽  
Muscle Myosin

scholarly journals Jak-Stat pathway induces Drosophila follicle elongation by a gradient of apical contractility

2017 ◽  
Author(s):  
Hervé Alégot ◽  
Pierre Pouchin ◽  
Olivier Bardot ◽  
Vincent Mirouse
Keyword(s):  
Cell Polarity ◽  
Planar Cell Polarity ◽  
Myosin Ii ◽  
Cell Polarization ◽  
Follicular Epithelium ◽  
Morphogen Gradient ◽  
Apical Constriction ◽  
Activity Inhibition ◽  
Apical Domain ◽  
Stat Pathway

AbstractTissue elongation and its control by spatiotemporal signals is a major developmental question. Currently, it is thought that Drosophila ovarian follicular epithelium elongation requires the planar polarization of the basal domain cytoskeleton and of the extra-cellular matrix, associated with a dynamic process of rotation around the anteroposterior axis. Here we show, by careful kinetic analysis of fat2 mutants, that neither basal planar polarization nor rotation is required during a first phase of follicle elongation. Conversely, a JAK-STAT signaling gradient from each follicle pole orients early elongation. JAK-STAT controls apical pulsatile contractions, and Myosin II activity inhibition affects both pulses and early elongation. Early elongation is associated with apical constriction at the poles and oriented cell rearrangements, but without any visible planar cell polarization of the apical domain. Thus, a morphogen gradient can trigger tissue elongation via a control of cell pulsing and without planar cell polarity requirement.Impact StatementFollicle elongation does not rely solely on the basal side of the cells but also requires a mechanism integrating a developmental cue with a morphogenetic process involving their apical domain.

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