PI3K induced actin filament remodeling through Akt and p70S6K1: implication of essential role in cell migration

2004 ◽  
Vol 286 (1) ◽  
pp. C153-C163 ◽  
Author(s):  
Yong Qian ◽  
Linda Corum ◽  
Qiao Meng ◽  
John Blenis ◽  
Jenny Z. Zheng ◽  
...  
Keyword(s):  
Cell Migration ◽  
Actin Filament ◽  
Actin Filaments ◽  
Essential Role ◽  
Molecular Mechanisms ◽  
Chicken Embryo Fibroblast ◽  
Active Form ◽  
Specific Inhibitor ◽  
Phosphatidylinositol 3 Kinase ◽  
Pi3k Activity

This study was designed to identify the molecular mechanisms of phosphatidylinositol 3-kinase (PI3K)-induced actin filament remodeling and cell migration. Expression of active forms of PI3K, v-P3k or Myr-P3k, was sufficient to induce actin filament remodeling to lead to an increase in cell migration, as well as the activation of Akt in chicken embryo fibroblast (CEF) cells. Either the inhibition of PI3K activity using a PI3K-specific inhibitor, LY-294002, or the disruption of Akt activity restored the integrity of actin filaments in CEF cells and inhibited PI3K-induced cell migration. We also found that expression of an activated form of Akt (Myr-Akt) was sufficient to remodel actin filaments to lead to an increase in cell migration, which was unable to be inhibited by the presence of LY-294002. Furthermore, we found that p70S6K1 kinase was a downstream molecule that can mediate the effects of both PI3K and Akt on actin filaments and cell migration. Overexpression of an active form of p70S6K1 was sufficient to induce actin filament remodeling and cell migration in CEF cells, which requires Rac activity. These results demonstrate that activation of PI3K activity alone is sufficient to remodel actin filaments to increase cell migration through the activation of Akt and p70S6K1 in CEF cells.

scholarly journals Phosphatidylinositol-3-kinase activity is required for the anti-ig- mediated growth inhibition of a human B-lymphoma cell line

Blood ◽  
1996 ◽  
Vol 87 (1) ◽  
pp. 202-210 ◽  
Author(s):  
M Beckwith ◽  
RG Fenton ◽  
IM Katona ◽  
DL Longo
Keyword(s):  
Growth Inhibition ◽  
Tyrosine Kinases ◽  
Specific Inhibitor ◽  
Phosphatidylinositol 3 Kinase ◽  
Intact Cells ◽  
B Lymphoma ◽  
Cycle Arrest ◽  
Pi3k Activity ◽  
B Lymphoma Cells ◽  
Phosphatidylinositol 3

Stimulation of B lymphocytes through the Ig receptor initiates a cascade of biochemical changes, which can ultimately lead to either activation and growth, or cell-cycle arrest and cell death. One of the critical events that occurs in both cases is the activation of tyrosine kinases, and the resulting phosphorylation of a variety of proteins on tyrosine residues. In this report we identify one of the substrates of phosphorylation as the 85-kD subunit of the enzyme phosphatidylinositol-3 kinase (PI3K), and show that both anti-IgM and anti-IgD stimulation results in an increase in the anti-phosphotyrosine-precipitable PI3K activity. Furthermore, we show that the potent and specific inhibitor of PI3K, Wortmannin, can completely abrogate anti-Ig-mediated growth inhibition without affecting tyrosine kinase induction or protein kinase C (PKC) activation. Treatment of intact cells with Wortmannin results in an irreversible decrease in anti-Ig-induced PI3K activity, suggesting that the effect of Wortmannin on anti-Ig-mediated growth inhibition is caused by its inactivation of PI3K activity. Taken together, these data show that activation of PI3K is a critical component of the anti-Ig-initiated signaling cascade that leads to growth inhibition of human B lymphoma cells.

scholarly journals The dynamic instability of actin filament barbed ends

2021 ◽  
Vol 220 (4) ◽  
Author(s):  
Guillaume Romet-Lemonne ◽  
Antoine Jégou
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Molecular Mechanisms ◽  
Dynamic Instability ◽  
Filament Networks ◽  
In Cells

The turnover of actin filament networks in cells has long been considered to reflect the treadmilling behavior of pure actin filaments in vitro, where only the pointed ends depolymerize. Newly discovered molecular mechanisms challenge this notion, as they provide evidence of situations in which growing and depolymerizing barbed ends coexist.

scholarly journals Pointed-end capping by tropomodulin3 negatively regulates endothelial cell motility

2003 ◽  
Vol 161 (2) ◽  
pp. 371-380 ◽  
Author(s):  
Robert S. Fischer ◽  
Kimberly L. Fritz-Six ◽  
Velia M. Fowler
Keyword(s):  
Cell Migration ◽  
Cell Motility ◽  
Actin Filament ◽  
Actin Filaments ◽  
Critical Role ◽  
Leading Edge ◽  
Average Cell ◽  
Transient Overexpression ◽  
End Capping ◽  
Pointed End

Actin filament pointed-end dynamics are thought to play a critical role in cell motility, yet regulation of this process remains poorly understood. We describe here a previously uncharacterized tropomodulin (Tmod) isoform, Tmod3, which is widely expressed in human tissues and is present in human microvascular endothelial cells (HMEC-1). Tmod3 is present in sufficient quantity to cap pointed ends of actin filaments, localizes to actin filament structures in HMEC-1 cells, and appears enriched in leading edge ruffles and lamellipodia. Transient overexpression of GFP–Tmod3 leads to a depolarized cell morphology and decreased cell motility. A fivefold increase in Tmod3 results in an equivalent decrease in free pointed ends in the cells. Unexpectedly, a decrease in the relative amounts of F-actin, free barbed ends, and actin-related protein 2/3 (Arp2/3) complex in lamellipodia are also observed. Conversely, decreased expression of Tmod3 by RNA interference leads to faster average cell migration, along with increases in free pointed and barbed ends in lamellipodial actin filaments. These data collectively demonstrate that capping of actin filament pointed ends by Tmod3 inhibits cell migration and reveal a novel control mechanism for regulation of actin filaments in lamellipodia.

scholarly journals Activation of Phosphatidylinositol 3-Kinase Signaling Promotes Aberrant Pituitary Growth in a Mouse Model of Thyroid-Stimulating Hormone-Secreting Pituitary Tumors

Endocrinology ◽  
2008 ◽  
Vol 149 (7) ◽  
pp. 3339-3345 ◽  
Author(s):  
Changxue Lu ◽  
Mark C. Willingham ◽  
Fumihiko Furuya ◽  
Sheue-yann Cheng
Keyword(s):  
Cell Proliferation ◽  
Mouse Model ◽  
Signaling Pathway ◽  
Molecular Mechanisms ◽  
Thyroid Hormone Receptor ◽  
Specific Inhibitor ◽  
Pituitary Tumors ◽  
Akt Pathway ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

TSH-secreting pituitary tumors (TSHomas) are pituitary tumors that constitutively secrete TSH. Molecular mechanisms underlying this abnormality are largely undefined. We recently created a knock-in mutant mouse harboring a mutation (denoted as PV) in the thyroid hormone receptor-β gene (TRβPV/PV mouse). As these mice age, they spontaneously develop TSHomas. Using this mouse model, we investigated the role of the phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway in the pathogenesis of TSHomas. Concurrent with aberrant growth of pituitaries, AKT and its downstream effectors, mammalian target rapamycin and p70S6K, were activated to contribute to increased cell proliferation and pituitary growth. In addition, activation of AKT led to decreased apoptosis by inhibiting proapoptotic activity of Bcl-2-associated death promoter, further contributing to the aberrant cell proliferation. These results suggest an activated PI3K-AKT pathway could underscore tumorigenesis, raising the possibility that this pathway could be a potential therapeutic target in TSHomas. Indeed, TRβPV/PV mice treated with a PI3K-specific inhibitor, LY294002, showed a significant decrease in pituitary growth. The progrowth signaling via AKT-mammalian target rapamycin-p70S6K and cyclin D1/cyclin-dependent kinase were inhibited, and proapoptotic activity of Bcl-2-associated death promoter was increased by LY294002 treatment. Thus, activation of the PI3K-AKT pathway mediates, at least in part, the aberrant pituitary growth, and the intervention of this signaling pathway presents a novel therapeutic opportunity for TSHomas.

Critical roles of actin-interacting protein 1 in cytokinesis and chemotactic migration of mammalian cells

2008 ◽  
Vol 414 (2) ◽  
pp. 261-270 ◽  
Author(s):  
Asuka Kato ◽  
Souichi Kurita ◽  
Aya Hayashi ◽  
Noriko Kaji ◽  
Kazumasa Ohashi ◽  
...  
Keyword(s):  
Cell Migration ◽  
Actin Filament ◽  
Mammalian Cells ◽  
Critical Role ◽  
Active Form ◽  
Chemotactic Migration ◽  
Interacting Protein ◽  
Repeat Protein ◽  
Wd Repeat

Cofilin regulates actin filament dynamics by stimulating actin filament disassembly and plays a critical role in cytokinesis and chemotactic migration. Aip1 (actin-interacting protein 1), also called WDR1 (WD-repeat protein 1), is a highly conserved WD-repeat protein in eukaryotes and promotes cofilin-mediated actin filament disassembly in vitro; however, little is known about the mechanisms by which Aip1 functions in cytokinesis and cell migration in mammalian cells. In the present study, we investigated the roles of Aip1 in cytokinesis and chemotactic migration of human cells by silencing the expression of Aip1 using siRNA (small interfering RNA). Knockdown of Aip1 in HeLa cells increased the percentage of multinucleate cells; this effect was reversed by expression of an active form of cofilin. In Aip1-knockdown cells, the cleavage furrow ingressed normally from anaphase to early telophase; however, an excessive accumulation of actin filaments was observed on the contractile ring in late telophase. These results suggest that Aip1 plays a crucial role in the completion of cytokinesis by promoting cofilin-mediated actin filament disassembly in telophase. We have also shown that Aip1 knockdown significantly suppressed chemokine-induced chemotactic migration of Jurkat T-lymphoma cells, and this was blocked by expression of an active form of cofilin. Whereas control cells mostly formed a single lamellipodium in response to chemokine stimulation, Aip1 knockdown cells abnormally exhibited multiple protrusions around the cells before and after cell stimulation. This indicates that Aip1 plays an important role in directional cell migration by restricting the stimulus-induced membrane protrusion to one direction via promoting cofilin activity.

scholarly journals α-Adducin dissociates from F-actin and spectrin during platelet activation

2003 ◽  
Vol 161 (3) ◽  
pp. 557-570 ◽  
Author(s):  
Kurt L. Barkalow ◽  
Joseph E. Italiano ◽  
Denise E. Chou ◽  
Yoichiro Matsuoka ◽  
Vann Bennett ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Platelet Activation ◽  
Actin Filament ◽  
Actin Filaments ◽  
Ternary Complex ◽  
Cell Activation ◽  
Active Form ◽  
Membrane Skeleton ◽  
Protease Activated Receptor 1

Aspectrin-based skeleton uniformly underlies and supports the plasma membrane of the resting platelet, but remodels and centralizes in the activated platelet. α-Adducin, a phosphoprotein that forms a ternary complex with F-actin and spectrin, is dephosphorylated and mostly bound to spectrin in the membrane skeleton of the resting platelet at sites where actin filaments attach to the ends of spectrin molecules. Platelets activated through protease-activated receptor 1, FcγRIIA, or by treatment with PMA phosphorylate adducin at Ser726. Phosphoadducin releases from the membrane skeleton concomitant with its dissociation from spectrin and actin. Inhibition of PKC blunts adducin phosphorylation and release from spectrin and actin, preventing the centralization of spectrin that normally follows cell activation. We conclude that adducin targets actin filament ends to spectrin to complete the assembly of the resting membrane skeleton. Dissociation of phosphoadducin releases spectrin from actin, facilitating centralization of spectrin, and leads to the exposure of barbed actin filament ends that may then participate in converting the resting platelet's disc shape into its active form.

scholarly journals Direct observation of actin filament severing by gelsolin and binding by gCap39 and CapZ.

1991 ◽  
Vol 115 (6) ◽  
pp. 1629-1638 ◽  
Author(s):  
E L Bearer
Keyword(s):  
Actin Filament ◽  
Direct Observation ◽  
Actin Filaments ◽  
Molecular Mechanisms ◽  
Actin Binding ◽  
Filamentous Actin ◽  
Rhodamine Phalloidin ◽  
Capping Protein ◽  
Calcium Dependent ◽  
Definition Of

Dynamic behavior of actin filaments in cells is the basis of many different cellular activities. Remodeling of the actin filament network involves polymerization and depolymerization of the filaments. Proteins that regulate these behaviors include proteins that sever and/or cap actin filaments. This report presents direct observation of severing of fluorescently-labeled actin filaments. Coverslips coated with gelsolin, a multi-domain, calcium-dependent capping and severing protein, bound rhodamine-phalloidin-saturated filaments along their length in the presence of EGTA. Upon addition of calcium, attached filaments bent as they broke. Actophorin, a low molecular weight, monomer sequestering, calcium-independent severing protein did not sever phalloidin-saturated filaments. Both gCap 39, a gelsolin-like, calcium-dependent capping protein that does not sever filaments, and CapZ, a heterodimeric, non-calcium-dependent capping protein, bound the filaments by one end to the coverslip. Visualization of individual filaments also revealed severing activity present in mixtures of actin-binding proteins isolated by filamentous actin affinity chromatography from early Drosophila embryos. This activity was different from either gelsolin or actophorin because it was not inhibited by phalloidin, but was calcium independent. The results of these studies provide new information about the molecular mechanisms of severing and capping by well-characterized proteins as well as definition of a novel type of severing activity.

scholarly journals Phosphatidylinositol-3-kinase activity is required for the anti-ig- mediated growth inhibition of a human B-lymphoma cell line

Blood ◽  
1996 ◽  
Vol 87 (1) ◽  
pp. 202-210 ◽  
Author(s):  
M Beckwith ◽  
RG Fenton ◽  
IM Katona ◽  
DL Longo
Keyword(s):  
Growth Inhibition ◽  
Tyrosine Kinases ◽  
Specific Inhibitor ◽  
Phosphatidylinositol 3 Kinase ◽  
Intact Cells ◽  
B Lymphoma ◽  
Cycle Arrest ◽  
Pi3k Activity ◽  
B Lymphoma Cells ◽  
Phosphatidylinositol 3

Abstract Stimulation of B lymphocytes through the Ig receptor initiates a cascade of biochemical changes, which can ultimately lead to either activation and growth, or cell-cycle arrest and cell death. One of the critical events that occurs in both cases is the activation of tyrosine kinases, and the resulting phosphorylation of a variety of proteins on tyrosine residues. In this report we identify one of the substrates of phosphorylation as the 85-kD subunit of the enzyme phosphatidylinositol-3 kinase (PI3K), and show that both anti-IgM and anti-IgD stimulation results in an increase in the anti-phosphotyrosine-precipitable PI3K activity. Furthermore, we show that the potent and specific inhibitor of PI3K, Wortmannin, can completely abrogate anti-Ig-mediated growth inhibition without affecting tyrosine kinase induction or protein kinase C (PKC) activation. Treatment of intact cells with Wortmannin results in an irreversible decrease in anti-Ig-induced PI3K activity, suggesting that the effect of Wortmannin on anti-Ig-mediated growth inhibition is caused by its inactivation of PI3K activity. Taken together, these data show that activation of PI3K is a critical component of the anti-Ig-initiated signaling cascade that leads to growth inhibition of human B lymphoma cells.

Nebulin and N-WASP Cooperate to Cause IGF-1–Induced Sarcomeric Actin Filament Formation

Science ◽  
2010 ◽  
Vol 330 (6010) ◽  
pp. 1536-1540 ◽  
Author(s):  
Kazunori Takano ◽  
Haruko Watanabe-Takano ◽  
Shiro Suetsugu ◽  
Souichi Kurita ◽  
Kazuya Tsujita ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Muscle Hypertrophy ◽  
Glycogen Synthase ◽  
Akt Signaling ◽  
Glycogen Synthase Kinase 3Β ◽  
Filament Formation ◽  
Phosphatidylinositol 3 Kinase ◽  
Actin Nucleation ◽  
Signaling Mechanisms

Insulin-like growth factor 1 (IGF-1) induces skeletal muscle maturation and enlargement (hypertrophy). These responses require protein synthesis and myofibril formation (myofibrillogenesis). However, the signaling mechanisms of myofibrillogenesis remain obscure. We found that IGF-1–induced phosphatidylinositol 3-kinase–Akt signaling formed a complex of nebulin and N-WASP at the Z bands of myofibrils by interfering with glycogen synthase kinase-3β in mice. Although N-WASP is known to be an activator of the Arp2/3 complex to form branched actin filaments, the nebulin–N-WASP complex caused actin nucleation for unbranched actin filament formation from the Z bands without the Arp2/3 complex. Furthermore, N-WASP was required for IGF-1–induced muscle hypertrophy. These findings present the mechanisms of IGF-1–induced actin filament formation in myofibrillogenesis required for muscle maturation and hypertrophy and a mechanism of actin nucleation.

Sign in / Sign up

Export Citation Format

Share Document