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Shin JW, Swift J, Ivanovska I, Spinler KR, Buxboim A, Discher DE. Mechanobiology of bone marrow stem cells: from myosin-II forces to compliance of matrix and nucleus in cell forms and fates. Differentiation 2013; 86:77-86. [PMID: 23790394 PMCID: PMC3964600 DOI: 10.1016/j.diff.2013.05.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 05/01/2013] [Accepted: 05/02/2013] [Indexed: 12/22/2022]
Abstract
Adult stem cells and progenitors are of great interest for their clinical application as well as their potential to reveal deep sensitivities to microenvironmental factors. The bone marrow is a niche for at least two types of stem cells, and the prototype is the hematopoietic stem cell/progenitors (HSC/Ps), which have saved many thousands of patients for several decades now. In bone marrow, HSC/Ps interact functionally with marrow stromal cells that are often referred to as mesenchymal stem cells (MSCs) or derivatives thereof. Myosin and matrix elasticity greatly affect MSC function, and these mechanobiological factors are now being explored with HSC/Ps both in vitro and in vivo. Also emerging is a role for the nucleus as a mechanically sensitive organelle that is semi-permeable to transcription factors which are modified for nuclear entry by cytoplasmic mechanobiological pathways. Since therapies envisioned with induced pluripotent stem cells and embryonic stem cells generally involve in vitro commitment to an adult stem cell or progenitor, a very deep understanding of stem cell mechanobiology is essential to progress with these multi-potent cells.
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202
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Murk K, Blanco Suarez EM, Cockbill LMR, Banks P, Hanley JG. The antagonistic modulation of Arp2/3 activity by N-WASP, WAVE2 and PICK1 defines dynamic changes in astrocyte morphology. J Cell Sci 2013; 126:3873-83. [PMID: 23843614 PMCID: PMC3757329 DOI: 10.1242/jcs.125146] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2013] [Indexed: 01/22/2023] Open
Abstract
Astrocytes exhibit a complex, branched morphology, allowing them to functionally interact with numerous blood vessels, neighboring glial processes and neuronal elements, including synapses. They also respond to central nervous system (CNS) injury by a process known as astrogliosis, which involves morphological changes, including cell body hypertrophy and thickening of major processes. Following severe injury, astrocytes exhibit drastically reduced morphological complexity and collectively form a glial scar. The mechanistic details behind these morphological changes are unknown. Here, we investigate the regulation of the actin-nucleating Arp2/3 complex in controlling dynamic changes in astrocyte morphology. In contrast to other cell types, Arp2/3 inhibition drives the rapid expansion of astrocyte cell bodies and major processes. This intervention results in a reduced morphological complexity of astrocytes in both dissociated culture and in brain slices. We show that this expansion requires functional myosin II downstream of ROCK and RhoA. Knockdown of the Arp2/3 subunit Arp3 or the Arp2/3 activator N-WASP by siRNA also results in cell body expansion and reduced morphological complexity, whereas depleting WAVE2 specifically reduces the branching complexity of astrocyte processes. By contrast, knockdown of the Arp2/3 inhibitor PICK1 increases astrocyte branching complexity. Furthermore, astrocyte expansion induced by ischemic conditions is delayed by PICK1 knockdown or N-WASP overexpression. Our findings identify a new morphological outcome for Arp2/3 activation in restricting rather than promoting outwards movement of the plasma membrane in astrocytes. The Arp2/3 regulators PICK1, and N-WASP and WAVE2 function antagonistically to control the complexity of astrocyte branched morphology, and this mechanism underlies the morphological changes seen in astrocytes during their response to pathological insult.
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203
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Hasegawa H, Hyodo T, Asano E, Ito S, Maeda M, Kuribayashi H, Natsume A, Wakabayashi T, Hamaguchi M, Senga T. The role of PLK1-phosphorylated SVIL in myosin II activation and cytokinetic furrowing. J Cell Sci 2013; 126:3627-37. [PMID: 23750008 DOI: 10.1242/jcs.124818] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Polo-like kinase 1 (PLK1) is a widely conserved serine/threonine kinase that regulates progression of multiple stages of mitosis. Although extensive studies about PLK1 functions during cell division have been performed, it is still not known how PLK1 regulates myosin II activation at the equatorial cortex and ingression of the cleavage furrow. In this report, we show that an actin/myosin-II-binding protein, supervillin (SVIL), is a substrate of PLK1. PLK1 phosphorylates Ser238 of SVIL, which can promote the localization of SVIL to the central spindle and association with PRC1. Expression of a PLK1 phosphorylation site mutant, S238A-SVIL, inhibited myosin II activation at the equatorial cortex and induced aberrant furrowing. SVIL has both actin- and myosin-II-binding regions in the N-terminus. Expression of ΔMyo-SVIL (deleted of the myosin-II-binding region), but not of ΔAct-SVIL (deleted of actin-binding region), reduced myosin II activation and caused defects in furrowing. Our study indicates a possible role of phosphorylated SVIL as a molecular link between the central spindle and the contractile ring to coordinate the activation of myosin II for the ingression of the cleavage furrow.
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204
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Su L, Nalle SC, Shen L, Turner ES, Singh G, Breskin LA, Khramtsova EA, Khramtsova G, Tsai PY, Fu YX, Abraham C, Turner JR. TNFR2 activates MLCK-dependent tight junction dysregulation to cause apoptosis-mediated barrier loss and experimental colitis. Gastroenterology 2013; 145:407-15. [PMID: 23619146 PMCID: PMC3722284 DOI: 10.1053/j.gastro.2013.04.011] [Citation(s) in RCA: 275] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 04/08/2013] [Accepted: 04/09/2013] [Indexed: 12/25/2022]
Abstract
BACKGROUND & AIMS Tight junction dysregulation and epithelial damage contribute to barrier loss in patients with inflammatory bowel disease. However, the mechanisms that regulate these processes and their relative contributions to disease pathogenesis are not completely understood. We investigated these processes using colitis models in mice. METHODS We induced colitis by adoptive transfer of CD4(+)CD45RB(hi) cells or administration of dextran sulfate sodium to mice, including those deficient in tumor necrosis factor receptor (TNFR) 1, TNFR2, or the long isoform of myosin light chain kinase (MLCK). Intestinal tissues and isolated epithelial cells were analyzed by immunoblot, immunofluorescence, enzyme-linked immunosorbent assay, and real-time polymerase chain reaction assays. RESULTS Induction of immune-mediated colitis by CD4(+)CD45RB(hi) adoptive transfer increased intestinal permeability, epithelial expression of claudin-2, the long isoform of MLCK, and TNFR2 (but not TNFR1) and phosphorylation of the myosin II light chain. Long MLCK upregulation, myosin II light chain phosphorylation, barrier loss, and weight loss were attenuated in TNFR2(-/-) , but not TNFR1(-/-) , recipients of wild-type CD4(+)CD45RB(hi) cells. Similarly, long MLCK(-/-) mice had limited increases in myosin II light chain phosphorylation, claudin-2 expression, and intestinal permeability and delayed onset of adoptive transfer-induced colitis. However, coincident with onset of epithelial apoptosis, long MLCK(-/-) mice ultimately developed colitis. This indicates that disease progresses via apoptosis in the absence of MLCK-dependent tight junction regulation. In support of this conclusion, long MLCK(-/-) mice were not protected from epithelial apoptosis-mediated, damage-dependent dextran sulfate sodium colitis. CONCLUSIONS In immune-mediated inflammatory bowel disease models, TNFR2 signaling increases long MLCK expression, resulting in tight junction dysregulation, barrier loss, and induction of colitis. At advanced stages, colitis progresses by apoptosis and mucosal damage that result in tight junction- and MLCK-independent barrier loss. Therefore, barrier loss in immune-mediated colitis occurs via two temporally and morphologically distinct mechanisms. Differential targeting of these mechanisms can lead to improved inflammatory bowel disease therapies.
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MESH Headings
- Adoptive Transfer
- Animals
- Apoptosis/physiology
- Claudin-2/metabolism
- Colitis/immunology
- Colitis/metabolism
- Colitis/physiopathology
- Dextran Sulfate
- Disease Models, Animal
- Epithelial Cells/immunology
- Epithelial Cells/metabolism
- Epithelial Cells/physiology
- Inflammatory Bowel Diseases
- Intestinal Mucosa/immunology
- Intestinal Mucosa/metabolism
- Intestinal Mucosa/physiopathology
- Mice
- Mice, Inbred C57BL
- Myosin Light Chains/metabolism
- Myosin Type II/metabolism
- Myosin-Light-Chain Kinase/genetics
- Myosin-Light-Chain Kinase/physiology
- Permeability
- Phosphorylation
- Receptors, Tumor Necrosis Factor, Type I/genetics
- Receptors, Tumor Necrosis Factor, Type I/physiology
- Receptors, Tumor Necrosis Factor, Type II/genetics
- Receptors, Tumor Necrosis Factor, Type II/physiology
- Signal Transduction
- Tight Junctions/metabolism
- Tight Junctions/physiology
- Up-Regulation
- Weight Loss
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205
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Stricker J, Beckham Y, Davidson MW, Gardel ML. Myosin II-mediated focal adhesion maturation is tension insensitive. PLoS One 2013; 8:e70652. [PMID: 23923013 PMCID: PMC3726642 DOI: 10.1371/journal.pone.0070652] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 06/20/2013] [Indexed: 11/30/2022] Open
Abstract
Myosin II motors drive changes in focal adhesion morphology and composition in a "maturation process" that is crucial for regulating adhesion dynamics and signaling guiding cell adhesion, migration and fate. The underlying mechanisms of maturation, however, have been obscured by the intermingled effects of myosin II on lamellar actin architecture, dynamics and force transmission. Here, we show that focal adhesion growth rate stays constant even when cellular tension is reduced by 75%. Focal adhesion growth halts only when myosin stresses are sufficiently low to impair actin retrograde flow. Focal adhesion lifetime is reduced at low levels of cellular tension, but adhesion stability can be rescued at low levels of force by over-expression of α-actinin or constitutively active Dia1. Our work identifies a minimal myosin activity threshold that is necessary to drive lamellar actin retrograde flow is sufficient to permit focal adhesion elongation. Above this nominal threshold, myosin-mediated actin organization and dynamics regulate focal adhesion growth and stability in a force-insensitive fashion.
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206
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Kitagawa M, Fung SYS, Onishi N, Saya H, Lee SH. Targeting Aurora B to the equatorial cortex by MKlp2 is required for cytokinesis. PLoS One 2013; 8:e64826. [PMID: 23750214 PMCID: PMC3672163 DOI: 10.1371/journal.pone.0064826] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 04/18/2013] [Indexed: 11/18/2022] Open
Abstract
Although Aurora B is important in cleavage furrow ingression and completion during cytokinesis, the mechanism by which kinase activity is targeted to the cleavage furrow and the molecule(s) responsible for this process have remained elusive. Here, we demonstrate that an essential mitotic kinesin MKlp2 requires myosin-II for its localization to the equatorial cortex, and this event is required to recruit Aurora B to the equatorial cortex in mammalian cells. This recruitment event is also required to promote the highly focused accumulation of active RhoA at the equatorial cortex and stable ingression of the cleavage furrow in bipolar cytokinesis. Specifically, in drug-induced monopolar cytokinesis, targeting Aurora B to the cell cortex by MKlp2 is essential for cell polarization and furrow formation. Once the furrow has formed, MKlp2 further recruits Aurora B to the growing furrow. This process together with continuous Aurora B kinase activity at the growing furrow is essential for stable furrow propagation and completion. In contrast, a MKlp2 mutant defective in binding myosin-II does not recruit Aurora B to the cell cortex and does not promote furrow formation during monopolar cytokinesis. This mutant is also defective in maintaining the ingressing furrow during bipolar cytokinesis. Together, these findings reveal that targeting Aurora B to the cell cortex (or the equatorial cortex) by MKlp2 is essential for the maintenance of the ingressing furrow for successful cytokinesis.
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207
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Ivanov AI. Structure and regulation of intestinal epithelial tight junctions: current concepts and unanswered questions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 763:132-48. [PMID: 23397622 DOI: 10.1007/978-1-4614-4711-5_6] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Intestinal epithelium serves as a key interface between internal body compartments and the gut lumen. The epithelial layer forms a physical barrier that protects the body from the harmful environment of the lumen and also mediates vectorial fluxes of fluids, nutrients and waste. Increased permeability of the epithelial barrier is a common manifestation of different gastrointestinal diseases that enhances body exposure to external pathogens thereby exaggerating mucosal inflammation. Barrier properties of the intestinal epithelium are regulated by specialized adhesive plasma membrane structures known as tight junctions (TJs). It is gengrally believed that disease-related increase in intestinal permeability is caused by defects in TJ structure and functions. This chapter describes the molecular composition of intestinal epithelial TJs, basic mechanisms that regulate TJ functions in healthy gut mucosa as well as molecular events that contribute to increased mucosal permeability during intestinal inflammation. The chapter outlines our current understanding of TJ structure and dynamics and highlights several unresolved questions regarding regulation of this junctional complex under normal conditions and in gastroenterological diseases.
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208
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Heinemann F, Vogel S, Schwille P. Lateral membrane diffusion modulated by a minimal actin cortex. Biophys J 2013; 104:1465-75. [PMID: 23561523 PMCID: PMC3617436 DOI: 10.1016/j.bpj.2013.02.042] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 02/06/2013] [Accepted: 02/19/2013] [Indexed: 10/27/2022] Open
Abstract
Diffusion of lipids and proteins within the cell membrane is essential for numerous membrane-dependent processes including signaling and molecular interactions. It is assumed that the membrane-associated cytoskeleton modulates lateral diffusion. Here, we use a minimal actin cortex to directly study proposed effects of an actin meshwork on the diffusion in a well-defined system. The lateral diffusion of a lipid and a protein probe at varying densities of membrane-bound actin was characterized by fluorescence correlation spectroscopy (FCS). A clear correlation of actin density and reduction in mobility was observed for both the lipid and the protein probe. At high actin densities, the effect on the protein probe was ∼3.5-fold stronger compared to the lipid. Moreover, addition of myosin filaments, which contract the actin mesh, allowed switching between fast and slow diffusion in the minimal system. Spot variation FCS was in accordance with a model of fast microscopic diffusion and slower macroscopic diffusion. Complementing Monte Carlo simulations support the analysis of the experimental FCS data. Our results suggest a stronger interaction of the actin mesh with the larger protein probe compared to the lipid. This might point toward a mechanism where cortical actin controls membrane diffusion in a strong size-dependent manner.
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209
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Schachtner H, Calaminus SDJ, Sinclair A, Monypenny J, Blundell MP, Leon C, Holyoake TL, Thrasher AJ, Michie AM, Vukovic M, Gachet C, Jones GE, Thomas SG, Watson SP, Machesky LM. Megakaryocytes assemble podosomes that degrade matrix and protrude through basement membrane. Blood 2013; 121:2542-52. [PMID: 23305739 DOI: 10.1182/blood-2012-07-443457] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Megakaryocytes give rise to platelets via extension of proplatelet arms, which are released through the vascular sinusoids into the bloodstream. Megakaryocytes and their precursors undergo varying interactions with the extracellular environment in the bone marrow during their maturation and positioning in the vascular niche. We demonstrate that podosomes are abundant in primary murine megakaryocytes adherent on multiple extracellular matrix substrates, including native basement membrane. Megakaryocyte podosome lifetime and density, but not podosome size, are dependent on the type of matrix, with podosome lifetime dramatically increased on collagen fibers compared with fibrinogen. Podosome stability and dynamics depend on actin cytoskeletal dynamics but not matrix metalloproteases. However, podosomes degrade matrix and appear to be important for megakaryocytes to extend protrusions across a native basement membrane. We thus demonstrate for the first time a fundamental requirement for podosomes in megakaryocyte process extension across a basement membrane, and our results suggest that podosomes may have a role in proplatelet arm extension or penetration of basement membrane.
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210
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Stachowiak MR, McCall PM, Thoresen T, Balcioglu HE, Kasiewicz L, Gardel ML, O'Shaughnessy B. Self-organization of myosin II in reconstituted actomyosin bundles. Biophys J 2013; 103:1265-74. [PMID: 22995499 DOI: 10.1016/j.bpj.2012.08.028] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 07/27/2012] [Accepted: 08/09/2012] [Indexed: 11/19/2022] Open
Abstract
Cells assemble a variety of bundled actomyosin structures in the cytoskeleton for activities such as cell-shape regulation, force production, and cytokinesis. Although these linear structures exhibit varied architecture, two common organizational themes are a punctate distribution of myosin II and distinct patterns of actin polarity. The mechanisms that cells use to assemble and maintain these organizational features are poorly understood. To study these, we reconstituted actomyosin bundles in vitro that contained only actin filaments and myosin II. Upon addition of ATP, the bundles contracted and the uniformly distributed myosin spontaneously reorganized into discrete clusters. We developed a mathematical model in which the motion of myosin II filaments is governed by the polarities of the actin filaments with which they interact. The model showed that the assembly of myosins into clusters is driven by their tendency to migrate to locations with zero net actin filament polarity. With no fitting parameters, the predicted distribution of myosin cluster separations was in close agreement with our experiments, including a -3/2 power law decay for intermediate length scales. Thus, without an organizing template or accessory proteins, a minimal bundle of actin and myosin has the inherent capacity to self-organize into a heterogeneous banded structure.
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211
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Kondo T, Hamao K, Hosoya H. [Roles of myosin II regulatory light chain at the constricting area of dividing cells]. SEIKAGAKU. THE JOURNAL OF JAPANESE BIOCHEMICAL SOCIETY 2013; 85:102-106. [PMID: 23539964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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212
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Aldaz S, Escudero LM, Freeman M. Dual role of myosin II during Drosophila imaginal disc metamorphosis. Nat Commun 2013; 4:1761. [PMID: 23612302 PMCID: PMC3736102 DOI: 10.1038/ncomms2763] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 03/18/2013] [Indexed: 11/23/2022] Open
Abstract
The motor protein non-muscle myosin II is a major driver of the movements that sculpt three-dimensional organs from two-dimensional epithelia. The machinery of morphogenesis is well established but the logic of its control remains unclear in complex organs. Here we use live imaging and ex vivo culture to report a dual role of myosin II in regulating the development of the Drosophila wing. First, myosin II drives the contraction of a ring of cells that surround the squamous peripodial epithelium, providing the force to fold the whole disc through about 90°. Second, myosin II is needed to allow the squamous cells to expand and then retract at the end of eversion. The combination of genetics and live imaging allows us to describe and understand the tissue dynamics, and the logic of force generation needed to transform a relatively simple imaginal disc into a more complex and three-dimensional adult wing.
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213
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Rees MD, Dang L, Thai T, Owen DM, Malle E, Thomas SR. Targeted subendothelial matrix oxidation by myeloperoxidase triggers myosin II-dependent de-adhesion and alters signaling in endothelial cells. Free Radic Biol Med 2012; 53:2344-56. [PMID: 23059132 PMCID: PMC3529214 DOI: 10.1016/j.freeradbiomed.2012.10.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 09/27/2012] [Accepted: 10/01/2012] [Indexed: 12/11/2022]
Abstract
During inflammation, myeloperoxidase (MPO) released by circulating leukocytes accumulates within the subendothelial matrix by binding to and transcytosing the vascular endothelium. Oxidative reactions catalyzed by subendothelial-localized MPO are implicated as a cause of endothelial dysfunction in vascular disease. While the subendothelial matrix is a key target for MPO-derived oxidants during disease, the implications of this damage for endothelial morphology and signaling are largely unknown. We found that endothelial-transcytosed MPO produced hypochlorous acid (HOCl) that reacted locally with the subendothelial matrix and induced covalent cross-linking of the adhesive matrix protein fibronectin. Real-time biosensor and live cell imaging studies revealed that HOCl-mediated matrix oxidation triggered rapid membrane retraction from the substratum and adjacent cells (de-adhesion). De-adhesion was linked with the alteration of Tyr-118 phosphorylation of paxillin, a key adhesion-dependent signaling process, as well as Rho kinase-dependent myosin light chain-2 phosphorylation. De-adhesion dynamics were dependent on the contractile state of cells, with myosin II inhibition with blebbistatin attenuating the rate of membrane retraction. Rho kinase inhibition with Y-27632 also conferred protection, but not during the initial phase of membrane retraction, which was driven by pre-existing actomyosin tensile stress. Notably, diversion of MPO from HOCl production by thiocyanate or nitrite attenuated de-adhesion and associated signaling responses, despite the latter substrate supporting MPO-catalyzed fibronectin nitration. These data show that subendothelial-localized MPO employs a novel "outside-in" mode of redox signaling, involving HOCl-mediated matrix oxidation. These MPO-catalyzed oxidative events are likely to play a previously unrecognized role in altering endothelial integrity and signaling during inflammatory vascular disorders.
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214
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Wang Y, Teng HL, Huang ZH. Intrinsic migratory properties of cultured Schwann cells based on single-cell migration assay. PLoS One 2012; 7:e51824. [PMID: 23251634 PMCID: PMC3522601 DOI: 10.1371/journal.pone.0051824] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 11/06/2012] [Indexed: 11/18/2022] Open
Abstract
The migration of Schwann cells is critical for development of peripheral nervous system and is essential for regeneration and remyelination after nerve injury. Although several factors have been identified to regulate Schwann cell migration, intrinsic migratory properties of Schwann cells remain elusive. In this study, based on time-lapse imaging of single isolated Schwann cells, we examined the intrinsic migratory properties of Schwann cells and the molecular cytoskeletal machinery of soma translocation during migration. We found that cultured Schwann cells displayed three motile phenotypes, which could transform into each other spontaneously during their migration. Local disruption of F-actin polymerization at leading front by a Cytochalasin D or Latrunculin A gradient induced collapse of leading front, and then inhibited soma translocation. Moreover, in migrating Schwann cells, myosin II activity displayed a polarized distribution, with the leading process exhibiting higher expression than the soma and trailing process. Decreasing this front-to-rear difference of myosin II activity by frontal application of a ML-7 or BDM (myosin II inhibitors) gradient induced the collapse of leading front and reversed soma translocation, whereas, increasing this front-to-rear difference of myosin II activity by rear application of a ML-7 or BDM gradient or frontal application of a Caly (myosin II activator) gradient accelerated soma translocation. Taken together, these results suggest that during migration, Schwann cells display malleable motile phenotypes and the extension of leading front dependent on F-actin polymerization pulls soma forward translocation mediated by myosin II activity.
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215
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Huda S, Soh S, Pilans D, Byrska-Bishop M, Kim J, Wilk G, Borisy GG, Kandere-Grzybowska K, Grzybowski BA. Microtubule guidance tested through controlled cell geometry. J Cell Sci 2012; 125:5790-9. [PMID: 22992457 PMCID: PMC3575711 DOI: 10.1242/jcs.110494] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2012] [Indexed: 01/09/2023] Open
Abstract
In moving cells dynamic microtubules (MTs) target and disassemble substrate adhesion sites (focal adhesions; FAs) in a process that enables the cell to detach from the substrate and propel itself forward. The short-range interactions between FAs and MT plus ends have been observed in several experimental systems, but the spatial overlap of these structures within the cell has precluded analysis of the putative long-range mechanisms by which MTs growing through the cell body reach FAs in the periphery of the cell. In the work described here cell geometry was controlled to remove the spatial overlap of cellular structures thus allowing for unambiguous observation of MT guidance. Specifically, micropatterning of living cells was combined with high-resolution in-cell imaging and gene product depletion by means of RNA interference to study the long-range MT guidance in quantitative detail. Cells were confined on adhesive triangular microislands that determined cell shape and ensured that FAs localized exclusively at the vertices of the triangular cells. It is shown that initial MT nucleation at the centrosome is random in direction, while the alignment of MT trajectories with the targets (i.e. FAs at vertices) increases with an increasing distance from the centrosome, indicating that MT growth is a non-random, guided process. The guided MT growth is dependent on the presence of FAs at the vertices. The depletion of either myosin IIA or myosin IIB results in depletion of F-actin bundles and spatially unguided MT growth. Taken together our findings provide quantitative evidence of a role for long-range MT guidance in MT targeting of FAs.
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216
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Iwanicki MP, Davidowitz RA, Ng MR, Besser A, Muranen T, Merritt M, Danuser G, Ince TA, Brugge JS. Ovarian cancer spheroids use myosin-generated force to clear the mesothelium. Cancer Discov 2012; 1:144-57. [PMID: 22303516 DOI: 10.1158/2159-8274.cd-11-0010] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dissemination of ovarian tumors involves the implantation of cancer spheroids into the mesothelial monolayer on the walls of peritoneal and pleural cavity organs. Biopsies of tumors attached to peritoneal organs show that mesothelial cells are not present under tumor masses. We have developed a live, image-based in vitro model in which interactions between tumor spheroids and mesothelial cells can be monitored in real time to provide spatial and temporal understanding of mesothelial clearance. Here we provide evidence that ovarian cancer spheroids utilize integrin- and talin- dependent activation of myosin and traction force to promote mesothelial cells displacement from underneath a tumor cell spheroid. These results suggest that ovarian tumor cell clusters gain access to the sub-mesothelial environment by exerting force on the mesothelial cells lining target organs, driving migration and clearance of the mesothelial cells.
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217
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Plosa EJ, Gooding KA, Zent R, Prince LS. Nonmuscle myosin II regulation of lung epithelial morphology. Dev Dyn 2012; 241:1770-81. [PMID: 22972683 DOI: 10.1002/dvdy.23866] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2012] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND The regulation of epithelial cell shape and orientation during lung branching morphogenesis is not clearly understood. Nonmuscle myosins regulate cell size, morphology, and planar cell polarity. Here, we test the hypothesis that nonmuscle myosin II (NM II) regulates lung epithelial morphology in a spatially restricted manner. RESULTS Epithelial cell orientation at airway tips in fetal mouse lungs underwent a significant transformation at embryonic day (E) E17. Treatment of E15 lung explants with the NM II inhibitor blebbistatin increased airway branching, epithelial cell size, and the degree of anisotropy in epithelial cells lining the airway stalks. In cultured MLE-12 lung epithelial cells, blebbistatin increased cell velocity, but left the migratory response to FGF-10 unchanged. CONCLUSIONS In the developing lung, NM II acts to constrain cell morphology and orientation, but may be suppressed at sites of branching and cell migration. The regulation of epithelial orientation may therefore undergo dynamic variations from E15 to E17.
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218
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Köhler S, Schmoller KM, Crevenna AH, Bausch AR. Regulating contractility of the actomyosin cytoskeleton by pH. Cell Rep 2012; 2:433-9. [PMID: 22999933 DOI: 10.1016/j.celrep.2012.08.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 07/02/2012] [Accepted: 08/15/2012] [Indexed: 12/16/2022] Open
Abstract
The local interaction of F-actin with myosin-II motor filaments and crosslinking proteins is crucial for the force generation, dynamics, and reorganization of the intracellular cytoskeleton. By using a bottom-up approach, we are able to show that the contractility of reconstituted active actin systems is tightly controlled by the local pH. The pH-dependent intrinsic crossbridge strength of myosin-II is identified to account for a sharp transition of the actin/myosin-II activity from noncontractile to contractile by a change in pH of only 0.1. This pH-dependent contractility is a generic feature, which is observed in all studied crosslinked actin/myosin-II systems. The specific type and concentration of crosslinking protein allows one to sensitively adjust the range of pH where contraction occurs, which can recover the behavior found in Xenopus laevis oocyte extracts. Small variations in pH provide a mechanism of controlling the contractility of cytoskeletal structures, which can be expected to have broad implications in our understanding of cytoskeletal regulation.
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219
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Moore SW, Zhang X, Lynch CD, Sheetz MP. Netrin-1 attracts axons through FAK-dependent mechanotransduction. J Neurosci 2012; 32:11574-85. [PMID: 22915102 PMCID: PMC3461192 DOI: 10.1523/jneurosci.0999-12.2012] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/01/2012] [Accepted: 06/29/2012] [Indexed: 11/21/2022] Open
Abstract
The mechanism by which extracellular cues influence intracellular biochemical cascades that guide axons is important, yet poorly understood. Because of the mechanical nature of axon extension, we explored whether the physical interactions of growth cones with their guidance cues might be involved. In the context of mouse spinal commissural neuron axon attraction to netrin-1, we found that mechanical attachment of netrin-1 to the substrate was required for axon outgrowth, growth cone expansion, axon attraction and phosphorylation of focal adhesion kinase (FAK) and Crk-associated substrate (CAS). Myosin II activity was necessary for traction forces >30 pN on netrin-1. Interestingly, while these myosin II-dependent forces on netrin-1 substrates or beads were needed to increase the kinase activity and phosphorylation of FAK, they were not necessary for netrin-1 to increase CAS phosphorylation. When FAK kinase activity was inhibited, the growth cone's ability to recruit additional adhesions and to generate forces >60 pN on netrin-1 was disrupted. Together, these findings demonstrate an important role for mechanotransduction during chemoattraction to netrin-1 and that mechanical activation of FAK reinforces interactions with netrin-1 allowing greater forces to be exerted.
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Foronda D, Martín P, Sánchez-Herrero E. Drosophila Hox and sex-determination genes control segment elimination through EGFR and extramacrochetae activity. PLoS Genet 2012; 8:e1002874. [PMID: 22912593 PMCID: PMC3415437 DOI: 10.1371/journal.pgen.1002874] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 06/18/2012] [Indexed: 11/20/2022] Open
Abstract
The formation or suppression of particular structures is a major change occurring in development and evolution. One example of such change is the absence of the seventh abdominal segment (A7) in Drosophila males. We show here that there is a down-regulation of EGFR activity and fewer histoblasts in the male A7 in early pupae. If this activity is elevated, cell number increases and a small segment develops in the adult. At later pupal stages, the remaining precursors of the A7 are extruded under the epithelium. This extrusion requires the up-regulation of the HLH protein Extramacrochetae and correlates with high levels of spaghetti-squash, the gene encoding the regulatory light chain of the non-muscle myosin II. The Hox gene Abdominal-B controls both the down-regulation of spitz, a ligand of the EGFR pathway, and the up-regulation of extramacrochetae, and also regulates the transcription of the sex-determining gene doublesex. The male Doublesex protein, in turn, controls extramacrochetae and spaghetti-squash expression. In females, the EGFR pathway is also down-regulated in the A7 but extramacrochetae and spaghetti-squash are not up-regulated and extrusion of precursor cells is almost absent. Our results show the complex orchestration of cellular and genetic events that lead to this important sexually dimorphic character change.
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221
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Chen L, Vicente-Manzanares M, Potvin-Trottier L, Wiseman PW, Horwitz AR. The integrin-ligand interaction regulates adhesion and migration through a molecular clutch. PLoS One 2012; 7:e40202. [PMID: 22792239 PMCID: PMC3391238 DOI: 10.1371/journal.pone.0040202] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 06/04/2012] [Indexed: 01/15/2023] Open
Abstract
Adhesive and migratory behavior can be cell type, integrin, and substrate dependent. We have compared integrin and substrate differences using three integrin receptors: α5β1, α6β1, and αLβ2 expressed in a common cell type, CHO.B2 cells, which lack integrin α subunits, as well as in different cell types that express one or more of these integrins. We find that CHO.B2 cells expressing either α6β1 or αLβ2 integrins migrate and protrude faster and are more directionally persistent on laminin or ICAM-1, respectively, than CHO.B2 cells expressing α5β1 on fibronectin. Despite rapid adhesion maturation and the presence of large adhesions in both the α6β1- and αLβ2-expressing cells, they display robust tyrosine phosphorylation. In addition, whereas myosin II regulates adhesion maturation and turnover, protrusion rates, and polarity in cells migrating on fibronectin, surprisingly, it does not have comparable effects in cells expressing α6β1 or αLβ2. This apparent difference in the integration of myosin II activity, adhesion, and migration arises from alterations in the ligand-integrin-actin linkage (molecular clutch). The elongated adhesions in the protrusions of the α6β1-expressing cells on laminin or the αLβ2-expressing cells on ICAM-1 display a novel, rapid retrograde flux of integrin; this was largely absent in the large adhesions in protrusions of α5β1-expressing cells on fibronectin. Furthermore, the force these adhesions exert on the substrate in protrusive regions is reduced compared to similar regions in α5-expressing cells, and the adhesion strength is reduced. This suggests that intracellular forces are not efficiently transferred from actomyosin to the substratum due to altered adhesion strength, that is, avidity, affinity, or the ligand-integrin-actin interaction. Finally, we show that the migration of fast migrating leukocytes on fibronectin or ICAM-1 is also largely independent of myosin II; however, their adhesions are small and do not show retrograde fluxing suggesting other intrinsic factors determine their migration differences.
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Beemiller P, Jacobelli J, Krummel MF. Integration of the movement of signaling microclusters with cellular motility in immunological synapses. Nat Immunol 2012; 13:787-95. [PMID: 22751140 PMCID: PMC3902181 DOI: 10.1038/ni.2364] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 05/31/2012] [Indexed: 02/07/2023]
Abstract
Immune synapses form between T cells and antigen-presenting cells (APCs). Increasing evidence suggests synapses must form flexibly to accommodate ongoing motility and displacement of the synapse. Here, time-lapse total internal reflection fluorescence (TIRF) microscopy showed that signaling via the T cell antigen receptor (TCR) occurred during synapse translation. TCR microclusters in motile synapses did not flow directly into supramolecular activating complexes (SMACs) but were directed, independently of myosin II contractility, toward an F-actin-poor 'sink' region. Inward microcluster flow often followed collapse of the leading edge, which suggested that actin depolymerization regulated microcluster flow and the formation of SMACs. The coordination of TCR movement with the translocation of this 'sink' shows how T cells coordinate TCR signaling and microcluster flow in dynamic physiological synapses.
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Pathak A, Kumar S. Independent regulation of tumor cell migration by matrix stiffness and confinement. Proc Natl Acad Sci U S A 2012; 109:10334-9. [PMID: 22689955 PMCID: PMC3387066 DOI: 10.1073/pnas.1118073109] [Citation(s) in RCA: 401] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Tumor invasion and metastasis are strongly regulated by biophysical interactions between tumor cells and the extracellular matrix (ECM). While the influence of ECM stiffness on cell migration, adhesion, and contractility has been extensively studied in 2D culture, extension of this concept to 3D cultures that more closely resemble tissue has proven challenging, because perturbations that change matrix stiffness often concurrently change cellular confinement. This coupling is particularly problematic given that matrix-imposed steric barriers can regulate invasion speed independent of mechanics. Here we introduce a matrix platform based on microfabrication of channels of defined wall stiffness and geometry that allows independent variation of ECM stiffness and channel width. For a given ECM stiffness, cells confined to narrow channels surprisingly migrate faster than cells in wide channels or on unconstrained 2D surfaces, which we attribute to increased polarization of cell-ECM traction forces. Confinement also enables cells to migrate increasingly rapidly as ECM stiffness rises, in contrast with the biphasic relationship observed on unconfined ECMs. Inhibition of nonmuscle myosin II dissipates this traction polarization and renders the relationship between migration speed and ECM stiffness comparatively insensitive to matrix confinement. We test these hypotheses in silico by devising a multiscale mathematical model that relates cellular force generation to ECM stiffness and geometry, which we show is capable of recapitulating key experimental trends. These studies represent a paradigm for investigating matrix regulation of invasion and demonstrate that matrix confinement alters the relationship between cell migration speed and ECM stiffness.
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Pagán-Mercado G, Santiago-Cartagena E, Akamine P, Rodríguez-Medina JR. Functional and genetic interactions of TOR in the budding yeast Saccharomyces cerevisiae with myosin type II-deficiency (myo1Δ). BMC Cell Biol 2012; 13:13. [PMID: 22646158 PMCID: PMC3470973 DOI: 10.1186/1471-2121-13-13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 05/18/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Yeast has numerous mechanisms to survive stress. Deletion of myosin type II (myo1Δ) in Saccharomyces cerevisiae results in a cell that has defective cytokinesis. To survive this genetically induced stress, this budding yeast up regulates the PKC1 cell wall integrity pathway (CWIP). More recently, our work indicated that TOR, another stress signaling pathway, was down regulated in myo1Δ strains. Since negative signaling by TOR is known to regulate PKC1, our objectives in this study were to understand the cross-talk between the TOR and PKC1 signaling pathways and to determine if they share upstream regulators for mounting the stress response in myo1Δ strains. RESULTS Here we proved that TORC1 signaling was down regulated in the myo1Δ strain. While a tor1Δ mutant strain had increased viability relative to myo1Δ, a combined myo1Δtor1Δ mutant strain showed significantly reduced cell viability. Synthetic rescue of the tor2-21(ts) lethal phenotype was observed in the myo1Δ strain in contrast to the chs2Δ strain, a chitin synthase II null mutant that also activates the PKC1 CWIP and exhibits cytokinesis defects very similar to myo1Δ, where the rescue effect was not observed. We observed two pools of Slt2p, the final Mitogen Activated Protein Kinase (MAPK) of the PKC1 CWIP; one pool that is up regulated by heat shock and one that is up regulated by the myo1Δ stress. The cell wall stress sensor WSC1 that activates PKC1 CWIP under other stress conditions was shown to act as a negative regulator of TORC1 in the myo1Δ mutant. Finally, the repression of TORC1 was inversely correlated with the activation of PKC1 in the myo1Δ strain. CONCLUSIONS Regulated expression of TOR1 was important in the activation of the PKC1 CWIP in a myo1Δ strain and hence its survival. We found evidence that the PKC1 and TORC1 pathways share a common upstream regulator associated with the cell wall stress sensor WSC1. Surprisingly, essential TORC2 functions were not required in the myo1Δ strain. By understanding how yeast mounts a concerted stress response, one can further design pharmacological cocktails to undermine their ability to adapt and to survive.
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Villanueva J, Torres V, Torregrosa-Hetland CJ, Garcia-Martinez V, López-Font I, Viniegra S, Gutiérrez LM. F-actin-myosin II inhibitors affect chromaffin granule plasma membrane distance and fusion kinetics by retraction of the cytoskeletal cortex. J Mol Neurosci 2012; 48:328-38. [PMID: 22588981 DOI: 10.1007/s12031-012-9800-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 04/30/2012] [Indexed: 11/25/2022]
Abstract
Chromaffin cell catecholamines are released when specialized secretory vesicles undergo exocytotic membrane fusion. Evidence indicates that vesicle supply and fusion are controlled by the activity of the cortical F-actin-myosin II network. To study in detail cell cortex and vesicle interactions, we use fluorescent labeling with GFP-lifeact and acidotropic dyes in confocal and evanescent wave microscopy. These techniques provide structural details and dynamic images of chromaffin granules caged in a complex cortical structure. Both the movement of cortical structures and granule motion appear to be linked, and this motion can be restricted by the myosin II-specific inhibitor, blebbistatin, and the F-actin stabilizer, jasplakinolide. These treatments also affect the position of the vesicles in relation to the plasma membrane, increasing the distance between them and the fusion sites. Consequently, we observed slower single vesicle fusion kinetics in treated cells after neutralization of acridine orange-loaded granules during exocytosis. Increasing the distance between the granules and the fusion sites appears to be linked to the retraction of the F-actin cytoskeleton when treated with jasplakinolide. Thus, F-actin-myosin II inhibitors appear to slow granule fusion kinetics by altering the position of vesicles after relaxation of the cortical network.
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