Inflammation-induced PINCH expression leads to actin depolymerization and mitochondrial mislocalization in neurons

Polymerization of the actin cytoskeleton has been found to be essential for B-cell activation. We show here, however, that stimulation of BCR induces a rapid global actin depolymerization in a BCR signal strength-dependent manner, followed by polarized actin repolymerization. Depolymerization of actin enhances and blocking actin depolymerization inhibits BCR signaling, leading to altered BCR and lipid raft clustering, ERK activation, and transcription factor activation. Furthermore actin depolymerization by itself induces altered lipid raft clustering and ERK activation, suggesting that F-actin may play a role in separating lipid rafts and in setting the threshold for cellular activation.

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Metabolic amplifying pathway increases both phases of insulin secretion independently of β-cell actin microfilaments

AJP Cell Physiology ◽

10.1152/ajpcell.00138.2010 ◽

2010 ◽

Vol 299 (2) ◽

pp. C389-C398 ◽

Cited By ~ 34

Author(s):

Nizar I. Mourad ◽

Myriam Nenquin ◽

Jean-Claude Henquin

Keyword(s):

Insulin Secretion ◽

Actin Polymerization ◽

Second Phase ◽

Actin Microfilaments ◽

Actin Depolymerization ◽

Inhibitory Function ◽

Insulin Granules ◽

Priming Process ◽

Underlying Mechanisms ◽

Amplifying Pathway

Two pathways control glucose-induced insulin secretion (IS) by β-cells. The triggering pathway involves ATP-sensitive potassium (KATP) channel-dependent depolarization, Ca2+ influx, and a rise in the cytosolic Ca2+ concentration ([Ca2+]c), which triggers exocytosis of insulin granules. The metabolic amplifying pathway augments IS without further increasing [Ca2+]c. The underlying mechanisms are unknown. Here, we tested the hypothesis that amplification implicates actin microfilaments. Mouse islets were treated with latrunculin B and cytochalasin B to depolymerize actin or jasplakinolide to polymerize actin. They were then perifused to measure [Ca2+]c and IS. Metabolic amplification was studied during imposed steady elevation of [Ca2+]c by tolbutamide or KCl or by comparing the magnitude of [Ca2+]c and IS changes produced by glucose and tolbutamide. Both actin polymerization and depolymerization augmented IS triggered by all stimuli without increasing (sometimes decreasing) [Ca2+]c, which indicates a predominantly inhibitory function of microfilaments in exocytosis at a step distal to [Ca2+]c increase. When [Ca2+]c was elevated and controlled by KCl or tolbutamide, the amplifying action of glucose was facilitated by actin depolymerization and unaffected by polymerization. Both phases of IS were larger in response to high-glucose than to tolbutamide in low-glucose, although triggering [Ca2+]c was lower. This difference in IS, due to amplification, persisted when the IS rate was doubled by actin depolymerization or polymerization. In conclusion, metabolic amplification is rapid and influences the first as well as the second phase of IS. It is a late step of stimulus-secretion coupling, which does not require functional actin microfilaments and could correspond to acceleration of the priming process conferring release competence to insulin granules.

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Dithiocarbamate propineb induces acetylcholine release through cytoskeletal actin depolymerization in PC12 cells

Toxicology Letters ◽

10.1016/j.toxlet.2008.08.016 ◽

2008 ◽

Vol 182 (1-3) ◽

pp. 63-68 ◽

Cited By ~ 3

Author(s):

B VIVIANI ◽

S BARTESAGHI ◽

M BINAGLIA ◽

E CORSINI ◽

M BORASO ◽

...

Keyword(s):

Pc12 Cells ◽

Acetylcholine Release ◽

Actin Depolymerization

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Mechanisms responsible for F-actin stabilization after lysis of polymorphonuclear leukocytes.

The Journal of Cell Biology ◽

10.1083/jcb.116.5.1123 ◽

1992 ◽

Vol 116 (5) ◽

pp. 1123-1134 ◽

Cited By ~ 26

Author(s):

M L Cano ◽

L Cassimeris ◽

M Fechheimer ◽

S H Zigmond

Keyword(s):

Polymorphonuclear Leukocytes ◽

Actin Polymerization ◽

Cell Movement ◽

Actin Binding ◽

Cross Linking ◽

Macromolecular Complex ◽

Actin Depolymerization ◽

Gravitational Forces ◽

End Capping

While actin polymerization and depolymerization are both essential for cell movement, few studies have focused on actin depolymerization. In vivo, depolymerization can occur exceedingly rapidly and in a spatially defined manner: the F-actin in the lamellipodia depolymerizes in 30 s after chemoattractant removal (Cassimeris, L., H. McNeill, and S. H. Zigmond. 1990. J. Cell Biol. 110:1067-1075). To begin to understand the regulation of F-actin depolymerization, we have examined F-actin depolymerization in lysates of polymorphonuclear leukocytes (PMNs). Surprisingly, much of the cell F-actin, measured with a TRITC-phalloidin-binding assay, was stable after lysis in a physiological salt buffer (0.15 M KCl): approximately 50% of the F-actin did not depolymerize even after 18 h. This stable F-actin included lamellar F-actin which could still be visualized one hour after lysis by staining with TRITC-phalloidin and by EM. We investigated the basis for this stability. In lysates with cell concentrations greater than 10(7) cells/ml, sufficient globular actin (G-actin) was present to result in a net increase in F-actin. However, the F-actin stability was not solely because of the presence of free G-actin since addition of DNase I to the lysate did not increase the F-actin loss. Nor did it appear to be because of barbed end capping factors since cell lysates provided sites for barbed end polymerization of exogenous added actin. The stable F-actin existed in a macromolecular complex that pelleted at low gravitational forces. Increasing the salt concentration of the lysis buffer decreased the amount of F-actin that pelleted at low gravitational forces and increased the amount of F-actin that depolymerized. Various actin-binding and cross-linking proteins such as tropomyosin, alpha-actinin, and actin-binding protein pelleted with the stable F-actin. In addition, we found that alpha-actinin, a filament cross-linking protein, inhibited the rate of pyrenyl F-actin depolymerization. These results suggested that actin cross-linking proteins may contribute to the stability of cellular actin after lysis. The activity of crosslinkers may be regulated in vivo to allow rapid turnover of lamellipodia F-actin.

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Arteriolar vasodilation involves actin depolymerization

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00723.2017 ◽

2018 ◽

Vol 315 (2) ◽

pp. H423-H428

Author(s):

Philip S. Clifford ◽

Brian S. Ferguson ◽

Jeffrey L. Jasperse ◽

Michael A. Hill

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Sodium Nitroprusside ◽

Light Chain ◽

Myosin Light Chain ◽

Muscle Relaxation ◽

Nitric Oxide Donor ◽

Smooth Muscle Relaxation ◽

Myosin Light Chain Phosphorylation ◽

Actin Depolymerization

It is generally assumed that relaxation of arteriolar vascular smooth muscle occurs through hyperpolarization of the cell membrane, reduction in intracellular Ca2+ concentration, and activation of myosin light chain phosphatase/inactivation of myosin light chain kinase. We hypothesized that vasodilation is related to depolymerization of F-actin. Cremaster muscles were dissected in rats under pentobarbital sodium anesthesia (50 mg/kg). First-order arterioles were dissected, cannulated on glass micropipettes, pressurized, and warmed to 34°C. Internal diameter was monitored with an electronic video caliper. The concentration of G-actin was determined in flash-frozen intact segments of arterioles by ultracentrifugation and Western blot analyses. Arterioles dilated by ~40% of initial diameter in response to pinacidil (1 × 10−6 mM) and sodium nitroprusside (5 × 10−5 mM). The G-actin-to-smooth muscle 22α ratio was 0.67 ± 0.09 in arterioles with myogenic tone and increased significantly to 1.32 ± 0.34 ( P < 0.01) when arterioles were dilated with pinacidil and 1.14 ± 0.18 ( P < 0.01) with sodium nitroprusside, indicating actin depolymerization. Compared with control vessels (49 ± 5%), the percentage of phosphorylated myosin light chain was significantly reduced by pinacidil (24 ± 2%, P < 0.01) but not sodium nitroprusside (42 ± 4%). These findings suggest that actin depolymerization is an important mechanism for vasodilation of resistance arterioles to external agonists. Furthermore, pinacidil produces smooth muscle relaxation via both decreases in myosin light chain phosphorylation and actin depolymerization, whereas sodium nitroprusside produces smooth muscle relaxation primarily via actin depolymerization. NEW & NOTEWORTHY This article adds to the accumulating evidence on the contribution of the actin cytoskeleton to the regulation of vascular smooth muscle tone in resistance arterioles. Actin depolymerization appears to be an important mechanism for vasodilation of resistance arterioles to pharmacological agonists. Dilation to the K+ channel opener pinacidil is produced by decreases in myosin light chain phosphorylation and actin depolymerization, whereas dilation to the nitric oxide donor sodium nitroprusside occurs primarily via actin depolymerization. Listen to this article’s corresponding podcast at https://ajpheart.podbean.com/e/vascular-smooth-muscle-actin-depolymerization/ .

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Crystal Structures Explain Functional Differences in the Two Actin Depolymerization Factors of the Malaria Parasite

Journal of Biological Chemistry ◽

10.1074/jbc.m110.211730 ◽

2011 ◽

Vol 286 (32) ◽

pp. 28256-28264 ◽

Cited By ~ 14

Author(s):

Bishal K. Singh ◽

Julia M. Sattler ◽

Moon Chatterjee ◽

Jani Huttu ◽

Herwig Schüler ◽

...

Keyword(s):

Crystal Structures ◽

Malaria Parasite ◽

Actin Depolymerization ◽

Functional Differences

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Isoflurane Neurotoxicity Is Mediated by p75NTR-RhoA Activation and Actin Depolymerization

Anesthesiology ◽

10.1097/aln.0b013e318201dcb3 ◽

2011 ◽

Vol 114 (1) ◽

pp. 49-57 ◽

Cited By ~ 89

Author(s):

Brian P. Lemkuil ◽

Brian P. Head ◽

Matthew L. Pearn ◽

Hemal H. Patel ◽

John C. Drummond ◽

...

Keyword(s):

Caspase 3 ◽

Hippocampal Slice ◽

Hippocampal Slices ◽

Neurotrophin Receptor ◽

P75 Neurotrophin Receptor ◽

Actin Depolymerization ◽

Rhoa Activation ◽

Hippocampal Slice Cultures ◽

Developing Neurons

Background The mechanisms by which isoflurane injured the developing brain are not clear. Recent work has demonstrated that it is mediated in part by activation of p75 neurotrophin receptor. This receptor activates RhoA, a small guanosine triphosphatase that can depolymerize actin. It is therefore conceivable that inhibition of RhoA or prevention of cytoskeletal depolymerization might attenuate isoflurane neurotoxicity. This study was conducted to test these hypotheses using primary cultured neurons and hippocampal slice cultures from neonatal mouse pups. Methods Primary neuron cultures (days in vitro, 4-7) and hippocampal slice cultures from postnatal day 4-7 mice were exposed to 1.4% isoflurane (4 h). Neurons were pretreated with TAT-Pep5, an intracellular inhibitor of p75 neurotrophin receptor, the cytoskeletal stabilizer jasplakinolide, or their corresponding vehicles. Hippocampal slice cultures were pretreated with TAT-Pep5 before isoflurane exposure. RhoA activation was evaluated by immunoblot. Cytoskeletal depolymerization and apoptosis were evaluated with immunofluorescence microscopy using drebrin and cleaved caspase-3 staining, respectively. Results RhoA activation was increased after 30 and 120 min of isoflurane exposure in neurons; TAT-Pep5 (10 μm) decreased isoflurane-mediated RhoA activation at both time intervals. Isoflurane decreased drebrin immunofluorescence and enhanced cleaved caspase-3 in neurons, effects that were attenuated by pretreatment with either jasplakinolide (1 μm) or TAT-Pep5. TAT-Pep5 attenuated the isoflurane-mediated decrease in phalloidin immunofluorescence. TAT-Pep5 significantly attenuated isoflurane-mediated loss of drebrin immunofluorescence in hippocampal slices. Conclusions Isoflurane results in RhoA activation, cytoskeletal depolymerization, and apoptosis. Inhibition of RhoA activation or prevention of downstream actin depolymerization significantly attenuated isoflurane-mediated neurotoxicity in developing neurons.

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ER sheet persistence is coupled to myosin 1c–regulated dynamic actin filament arrays

Molecular Biology of the Cell ◽

10.1091/mbc.e13-12-0712 ◽

2014 ◽

Vol 25 (7) ◽

pp. 1111-1126 ◽

Cited By ~ 36

Author(s):

Merja Joensuu ◽

Ilya Belevich ◽

Olli Rämö ◽

Ilya Nevzorov ◽

Helena Vihinen ◽

...

Keyword(s):

Actin Filament ◽

Actin Filaments ◽

Network Architecture ◽

Live Cell Imaging ◽

Cell Imaging ◽

Three Dimensional ◽

Actin Depolymerization ◽

Specific Subset ◽

3D Network ◽

3D Electron Microscopy

The endoplasmic reticulum (ER) comprises a dynamic three-dimensional (3D) network with diverse structural and functional domains. Proper ER operation requires an intricate balance within and between dynamics, morphology, and functions, but how these processes are coupled in cells has been unclear. Using live-cell imaging and 3D electron microscopy, we identify a specific subset of actin filaments localizing to polygons defined by ER sheets and tubules and describe a role for these actin arrays in ER sheet persistence and, thereby, in maintenance of the characteristic network architecture by showing that actin depolymerization leads to increased sheet fluctuation and transformations and results in small and less abundant sheet remnants and a defective ER network distribution. Furthermore, we identify myosin 1c localizing to the ER-associated actin filament arrays and reveal a novel role for myosin 1c in regulating these actin structures, as myosin 1c manipulations lead to loss of the actin filaments and to similar ER phenotype as observed after actin depolymerization. We propose that ER-associated actin filaments have a role in ER sheet persistence regulation and thus support the maintenance of sheets as a stationary subdomain of the dynamic ER network.

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Calcium dependence of villin-induced actin depolymerization

Biochemistry ◽

10.1021/bi00320a030 ◽

1984 ◽

Vol 23 (25) ◽

pp. 6099-6102 ◽

Cited By ~ 31

Author(s):

T. P. Walsh ◽

A. Weber ◽

K. Davis ◽

E. Bonder ◽

M. Mooseker

Keyword(s):

Calcium Dependence ◽

Actin Depolymerization

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Myosin 1b is an actin depolymerase

Nature Communications ◽

10.1038/s41467-019-13160-y ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 5

Author(s):

Julien Pernier ◽

Remy Kusters ◽

Hugo Bousquet ◽

Thibaut Lagny ◽

Antoine Morchain ◽

...

Keyword(s):

Myosin Ii ◽

Actin Dynamics ◽

Myosin Motor ◽

Actin Depolymerization ◽

Cellular Processes ◽

Myosin Motors ◽

Singular Interactions ◽

Sliding Motility

AbstractThe regulation of actin dynamics is essential for various cellular processes. Former evidence suggests a correlation between the function of non-conventional myosin motors and actin dynamics. Here we investigate the contribution of myosin 1b to actin dynamics using sliding motility assays. We observe that sliding on myosin 1b immobilized or bound to a fluid bilayer enhances actin depolymerization at the barbed end, while sliding on myosin II, although 5 times faster, has no effect. This work reveals a non-conventional myosin motor as another type of depolymerase and points to its singular interactions with the actin barbed end.

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