scholarly journals L1-dependent neuritogenesis involves ankyrinB that mediates L1-CAM coupling with retrograde actin flow

2003 ◽  
Vol 163 (5) ◽  
pp. 1077-1088 ◽  
Author(s):  
Kazunari Nishimura ◽  
Fumie Yoshihara ◽  
Takuro Tojima ◽  
Noriko Ooashi ◽  
Woohyun Yoon ◽  
...  
Keyword(s):  
Cell Adhesion Molecule ◽  
Traction Force ◽  
Neurite Growth ◽  
Growth Cones ◽  
Retrograde Flow ◽  
Actin Network ◽  
Filamentous Actin ◽  
Neurite Elongation ◽  
Neurite Initiation ◽  
Cell Adhesion Molecule L1

The cell adhesion molecule L1 (L1-CAM) plays critical roles in neurite growth. Its cytoplasmic domain (L1CD) binds to ankyrins that associate with the spectrin–actin network. This paper demonstrates that L1-CAM interactions with ankyrinB (but not with ankyrinG) are involved in the initial formation of neurites. In the membranous protrusions surrounding the soma before neuritogenesis, filamentous actin (F-actin) and ankyrinB continuously move toward the soma (retrograde flow). Bead-tracking experiments show that ankyrinB mediates L1-CAM coupling with retrograde F-actin flow in these perisomatic structures. Ligation of the L1-CAM ectodomain by an immobile substrate induces L1CD–ankyrinB binding and the formation of stationary ankyrinB clusters. Neurite initiation preferentially occurs at the site of these clusters. In contrast, ankyrinB is involved neither in L1-CAM coupling with F-actin flow in growth cones nor in L1-based neurite elongation. Our results indicate that ankyrinB promotes neurite initiation by acting as a component of the clutch module that transmits traction force generated by F-actin flow to the extracellular substrate via L1-CAM.

scholarly journals Growth cone behavior and production of traction force.

1990 ◽  
Vol 111 (5) ◽  
pp. 1949-1957 ◽  
Author(s):  
S R Heidemann ◽  
P Lamoureux ◽  
R E Buxbaum
Keyword(s):  
Growth Cone ◽  
Contractile Activity ◽  
Glass Fibers ◽  
Force Production ◽  
Traction Force ◽  
Dorsal Surface ◽  
Growth Cones ◽  
Retrograde Flow ◽  
Cortical Actin ◽  
Over The Top

The growth cone must push its substrate rearward via some traction force in order to propel itself forward. To determine which growth cone behaviors produce traction force, we observed chick sensory growth cones under conditions in which force production was accommodated by movement of obstacles in the environment, namely, neurites of other sensory neurons or glass fibers. The movements of these obstacles occurred via three, different, stereotyped growth cone behaviors: (a) filopodial contractions, (b) smooth rearward movement on the dorsal surface of the growth cone, and (c) interactions with ruffling lamellipodia. More than 70% of the obstacle movements were caused by filopodial contractions in which the obstacle attached at the extreme distal end of a filopodium and moved only as the filopodium changed its extension. Filopodial contractions were characterized by frequent changes of obstacle velocity and direction. Contraction of a single filopodium is estimated to exert 50-90 microdyn of force, which can account for the pull exerted by chick sensory growth cones. Importantly, all five cases of growth cones growing over the top of obstacle neurites (i.e., geometry that mimics the usual growth cone/substrate interaction), were of the filopodial contraction type. Some 25% of obstacle movements occurred by a smooth backward movement along the top surface of growth cones. Both the appearance and rate of movements were similar to that reported for retrograde flow of cortical actin near the dorsal growth cone surface. Although these retrograde flow movements also exerted enough force to account for growth cone pulling, we did not observe such movements on ventral growth cone surfaces. Occasionally obstacles were moved by interaction with ruffling lamellipodia. However, we obtained no evidence for attachment of the obstacles to ruffling lamellipodia or for directed obstacle movements by this mechanism. These data suggest that chick sensory growth cones move forward by contractile activity of filopodia, i.e., isometric contraction on a rigid substrate. Our data argue against retrograde flow of actin producing traction force.

scholarly journals Traction stress in focal adhesions correlates biphasically with actin retrograde flow speed

2008 ◽  
Vol 183 (6) ◽  
pp. 999-1005 ◽  
Author(s):  
Margaret L. Gardel ◽  
Benedikt Sabass ◽  
Lin Ji ◽  
Gaudenz Danuser ◽  
Ulrich S. Schwarz ◽  
...  
Keyword(s):  
Cell Migration ◽  
Focal Adhesions ◽  
Traction Force ◽  
Flow Speed ◽  
Retrograde Flow ◽  
Filamentous Actin ◽  
Rho Family ◽  
Guanosine Triphosphatase ◽  
Protein Density ◽  
Traction Stress

How focal adhesions (FAs) convert retrograde filamentous actin (F-actin) flow into traction stress on the extracellular matrix to drive cell migration is unknown. Using combined traction force and fluorescent speckle microscopy, we observed a robust biphasic relationship between F-actin speed and traction force. F-actin speed is inversely related to traction stress near the cell edge where FAs are formed and F-actin motion is rapid. In contrast, larger FAs where the F-actin speed is low are marked by a direct relationship between F-actin speed and traction stress. We found that the biphasic switch is determined by a threshold F-actin speed of 8–10 nm/s, independent of changes in FA protein density, age, stress magnitude, assembly/disassembly status, or subcellular position induced by pleiotropic perturbations to Rho family guanosine triphosphatase signaling and myosin II activity. Thus, F-actin speed is a fundamental regulator of traction force at FAs during cell migration.

scholarly journals Gradient-reading and mechano-effector machinery for netrin-1-induced axon guidance

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Kentarou Baba ◽  
Wataru Yoshida ◽  
Michinori Toriyama ◽  
Tadayuki Shimada ◽  
Colleen F Manning ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Axon Guidance ◽  
Cell Adhesion Molecule ◽  
Growth Cones ◽  
Spatial Cues ◽  
Commissural Axons ◽  
Guidance Cues ◽  
Cell Adhesion Molecule L1 ◽  
Axon Guidance Molecule ◽  
Guidance Molecule

Growth cones navigate axonal projection in response to guidance cues. However, it is unclear how they can decide the migratory direction by transducing the local spatial cues into protrusive forces. Here we show that knockout mice of Shootin1 display abnormal projection of the forebrain commissural axons, a phenotype similar to that of the axon guidance molecule netrin-1. Shallow gradients of netrin-1 elicited highly polarized Pak1-mediated phosphorylation of shootin1 within growth cones. We demonstrate that netrin-1–elicited shootin1 phosphorylation increases shootin1 interaction with the cell adhesion molecule L1-CAM; this, in turn, promotes F-actin–adhesion coupling and concomitant generation of forces for growth cone migration. Moreover, the spatially regulated shootin1 phosphorylation within growth cones is required for axon turning induced by netrin-1 gradients. Our study defines a mechano-effector for netrin-1 signaling and demonstrates that shootin1 phosphorylation is a critical readout for netrin-1 gradients that results in a directional mechanoresponse for axon guidance.

scholarly journals Role of Myosin II in Axon Outgrowth

2003 ◽  
Vol 51 (4) ◽  
pp. 421-428 ◽  
Author(s):  
Jacquelyn Brown ◽  
Paul C. Bridgman
Keyword(s):  
Extracellular Matrix ◽  
Cell Adhesion ◽  
Myosin Ii ◽  
Traction Force ◽  
Growth Cones ◽  
Matrix Proteins ◽  
Retrograde Flow ◽  
Complex Interactions ◽  
Cell Adhesion Proteins

The initial stages of nerve outgrowth carried out by growth cones occur in three fundamental cyclic steps. Each of these steps appears to require myosin II activity to variable degrees. The steps include the following: (a) exploration, involving extensions and retractions that are driven and controlled by the interaction of actin retrograde flow and polymerization; (b) adhesion of new extensions to the substrate, which has been shown to be mediated by complex interactions between extracellular matrix proteins, cell adhesion proteins, and the actin cytoskeleton; and (c) traction force generated during forward advance of the growth cone, resulting in the production of tension on the neurite.

scholarly journals Src and cortactin promote lamellipodia protrusion and filopodia formation and stability in growth cones

2015 ◽  
Vol 26 (18) ◽  
pp. 3229-3244 ◽  
Author(s):  
Yingpei He ◽  
Yuan Ren ◽  
Bingbing Wu ◽  
Boris Decourt ◽  
Aih Cheun Lee ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Growth Cones ◽  
Network Density ◽  
Retrograde Flow ◽  
Actin Assembly ◽  
Actin Network ◽  
Cellular Mechanisms ◽  
Down Regulation ◽  
Actin Organization ◽  
Neuronal Growth Cones

Src tyrosine kinases have been implicated in axonal growth and guidance; however, the underlying cellular mechanisms are not well understood. Specifically, it is unclear which aspects of actin organization and dynamics are regulated by Src in neuronal growth cones. Here, we investigated the function of Src2 and one of its substrates, cortactin, in lamellipodia and filopodia of Aplysia growth cones. We found that up-regulation of Src2 activation state or cortactin increased lamellipodial length, protrusion time, and actin network density, whereas down-regulation had opposite effects. Furthermore, Src2 or cortactin up-regulation increased filopodial density, length, and protrusion time, whereas down-regulation promoted lateral movements of filopodia. Fluorescent speckle microscopy revealed that rates of actin assembly and retrograde flow were not affected in either case. In summary, our results support a model in which Src and cortactin regulate growth cone motility by increasing actin network density and protrusion persistence of lamellipodia by controlling the state of actin-driven protrusion versus retraction. In addition, both proteins promote the formation and stability of actin bundles in filopodia.

Assembly of actin-containing cortex occurs at distal regions of growing neurites in PC12 cells

1991 ◽  
Vol 100 (4) ◽  
pp. 771-780 ◽  
Author(s):  
M.C. Sanders ◽  
Y.L. Wang
Keyword(s):  
De Novo Assembly ◽  
Actin Filaments ◽  
De Novo ◽  
Neurite Growth ◽  
Retrograde Transport ◽  
Time Lapse ◽  
Growth Cones ◽  
Distal Region ◽  
Dark Spot ◽  
Neurite Elongation

Although actin filaments are known to be localized in the cortex of axons and in the growth cones of nerve cells, it is unclear how actin-containing structures are assembled during nerve growth. We have studied the formation of actin structures in growing neurites by microinjecting fluorescent phalloidin or actin into PC12 neuron-like cells to label endogenous actin filaments. Upon stimulation of neurite growth in cells microinjected with fluorescent phalloidin, little or no fluorescence was detected in nascent growth cones and adjacent neurites despite the presence of actin filaments in these regions, suggesting that actin filaments were primarily formed by de novo assembly rather than the transport and reorganization of pre-existing, phalloidin-labeled actin filaments. Time-lapse observations of the distribution of phalloidin-labeled actin filaments during neurite elongation confirmed that fluorescence associated with pre-existing neurite cortex spread out more slowly than the elongation of neurites. Furthermore, when a dark spot was photobleached with a laser microbeam along neurites of cells microinjected with either fluorescent phalloidin or actin, the spot showed no appreciable translocation during active neurite elongation. Taken together, these results suggest that de novo assembly of actin filaments plays a crucial role in the formation of growth cones and adjacent cortex in the distal region of neurites, but does not appear to require the anterograde or retrograde transport of cortical filaments, or the passive stretching of the proximal segment of the neurite cortex.

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