scholarly journals Induction of De Novo Subcortical Actin Filament Assembly by Treponema denticola Major Outer Sheath Protein

2004 ◽  
Vol 72 (6) ◽  
pp. 3650-3654 ◽  
Author(s):  
Mohsen Amin ◽  
Andy C. S. Ho ◽  
Jenny Y. Lin ◽  
Andre Paes Batista da Silva ◽  
Michael Glogauer ◽  
...  
Keyword(s):  
Actin Filament ◽  
De Novo ◽  
Cell Types ◽  
Treponema Denticola ◽  
Actin Reorganization ◽  
Filament Assembly ◽  
Outer Sheath

ABSTRACT Treponema denticola and its major outer sheath protein (Msp) induce actin reorganization in fibroblasts. We adapted a barbed-end labeling/imaging assay to monitor Msp-induced subcortical actin filament assembly in neutrophils and fibroblasts. Msp, at an actin-reorganizing concentration, inhibited migration of these dissimilar cell types, whose cytoskeletal functions in locomotion and phagocytosis are crucial for immunity and healing of peripheral infections.

An Aplysia cell adhesion molecule associated with site-directed actin filament assembly in neuronal growth cones

1996 ◽  
Vol 109 (12) ◽  
pp. 2843-2854 ◽  
Author(s):  
C. Thompson ◽  
C.H. Lin ◽  
P. Forscher
Keyword(s):  
Cell Adhesion ◽  
Membrane Protein ◽  
Actin Filament ◽  
De Novo ◽  
Lateral Diffusion ◽  
Actin Assembly ◽  
Neuronal Growth ◽  
Cytoskeletal Remodeling ◽  
Interaction Sites ◽  
Filament Assembly

During neuronal growth cone-target interactions, a programmed sequence of cytoskeletal remodeling has been described, involving increased actin assembly at the target site and directed microtubule extension into it. The cell adhesion protein apCAM rapidly accumulates at such interaction sites, suggesting a possible role in regulating cytoskeletal remodeling. To test this hypothesis we crosslinked apCAM to varying degrees with antibodies. Secondary immunocomplexes exhibited a classical patching and capping response; in contrast, high density crosslinking of apCAM by antibody coated beads triggered localized actin assembly accompanied by formation of tail-like actin structures referred to as inductopodia. When beads were derivatized with increasing amounts of anti-apCAM they displayed three sequential dose-dependent kinetic states after binding: (1) lateral diffusion in the plane of the membrane; (2) restricted diffusion due to coupling with underlying F-actin; and (3) translocation in the plane of the membrane driven by de novo actin filament assembly local to bead binding sites, i.e. inductopodia formation. In contrast, lectin coated beads were far less efficient in triggering inductopodia formation despite demonstrated membrane protein binding. This work provides evidence that crosslinking of a diffusable membrane protein, apCAM, to threshold levels, can trigger highly localized actin filament assembly and rapid remodeling of neuronal cytoarchitecture.

scholarly journals LC3 and STRAP regulate actin filament assembly by JMY during autophagosome formation

2018 ◽  
Author(s):  
Xiaohua Hu ◽  
R. Dyche Mullins
Keyword(s):  
Actin Filament ◽  
Network Formation ◽  
De Novo ◽  
Actin Binding ◽  
Actin Assembly ◽  
Autophagosome Formation ◽  
Actin Networks ◽  
Filament Assembly ◽  
Filament Networks ◽  
Actin Comet Tails

AbstractDuring autophagy actin filament networks move and remodel cellular membranes to form autophagosomes that enclose and metabolize cytoplasmic contents. Two actin regulators, WHAMM and JMY, participate in autophagosome formation, but the signals linking autophagy to actin assembly are poorly understood. We show that, in non-starved cells, cytoplasmic JMY co-localizes with STRAP, a regulator of JMY’s nuclear functions, on non-motile vesicles with no associated actin networks. Upon starvation, JMY shifts to motile, LC3-containing membranes that move on actin comet tails. LC3 enhances JMY’s de novo actin nucleation activity via a cryptic actin-binding sequence near JMY’s N-terminus, and STRAP inhibits JMY’s ability to nucleate actin and activate the Arp2/3 complex. Cytoplasmic STRAP negatively regulates autophagy. Finally, we use purified proteins to reconstitute LC3‐ and JMY-dependent actin network formation on membranes, and inhibition of network formation by STRAP. We conclude that LC3 and STRAP regulate JMY’s actin assembly activities in trans during autophagy.eTOC BlurbThe actin regulator JMY creates filament networks that move membranes during autophagy. We find that, in unstarved cells, JMY is inhibited by interaction with the STRAP protein, but upon starvation JMY is recruited away from STRAP and activated by LC3.

scholarly journals LC3 and STRAP regulate actin filament assembly by JMY during autophagosome formation

2018 ◽  
Vol 218 (1) ◽  
pp. 251-266 ◽  
Author(s):  
Xiaohua Hu ◽  
R. Dyche Mullins
Keyword(s):  
Actin Filament ◽  
Network Formation ◽  
De Novo ◽  
Actin Binding ◽  
Actin Assembly ◽  
Autophagosome Formation ◽  
Actin Networks ◽  
Filament Assembly ◽  
Filament Networks ◽  
Actin Comet Tails

During autophagy, actin filament networks move and remodel cellular membranes to form autophagosomes that enclose and metabolize cytoplasmic contents. Two actin regulators, WHAMM and JMY, participate in autophagosome formation, but the signals linking autophagy to actin assembly are poorly understood. We show that, in nonstarved cells, cytoplasmic JMY colocalizes with STRAP, a regulator of JMY’s nuclear functions, on nonmotile vesicles with no associated actin networks. Upon starvation, JMY shifts to motile, LC3-containing membranes that move on actin comet tails. LC3 enhances JMY’s de novo actin nucleation activity via a cryptic actin-binding sequence near JMY’s N terminus, and STRAP inhibits JMY’s ability to nucleate actin and activate the Arp2/3 complex. Cytoplasmic STRAP negatively regulates autophagy. Finally, we use purified proteins to reconstitute LC3- and JMY-dependent actin network formation on membranes and inhibition of network formation by STRAP. We conclude that LC3 and STRAP regulate JMY’s actin assembly activities in trans during autophagy.

scholarly journals Visualization and Molecular Analysis of Actin Assembly in Living Cells

1998 ◽  
Vol 143 (7) ◽  
pp. 1919-1930 ◽  
Author(s):  
Dorothy A. Schafer ◽  
Matthew D. Welch ◽  
Laura M. Machesky ◽  
Paul C. Bridgman ◽  
Shelley M. Meyer ◽  
...  
Keyword(s):  
Actin Filament ◽  
Eukaryotic Cell ◽  
Cell Periphery ◽  
Actin Assembly ◽  
Cortical Actin ◽  
Lim Kinase ◽  
Permeabilized Cells ◽  
Capping Protein ◽  
Filament Assembly

Actin filament assembly is critical for eukaryotic cell motility. Arp2/3 complex and capping protein (CP) regulate actin assembly in vitro. To understand how these proteins regulate the dynamics of actin filament assembly in a motile cell, we visualized their distribution in living fibroblasts using green flourescent protein (GFP) tagging. Both proteins were concentrated in motile regions at the cell periphery and at dynamic spots within the lamella. Actin assembly was required for the motility and dynamics of spots and for motility at the cell periphery. In permeabilized cells, rhodamine-actin assembled at the cell periphery and at spots, indicating that actin filament barbed ends were present at these locations. Inhibition of the Rho family GTPase rac1, and to a lesser extent cdc42 and RhoA, blocked motility at the cell periphery and the formation of spots. Increased expression of phosphatidylinositol 5-kinase promoted the movement of spots. Increased expression of LIM–kinase-1, which likely inactivates cofilin, decreased the frequency of moving spots and led to the formation of aggregates of GFP–CP. We conclude that spots, which appear as small projections on the surface by whole mount electron microscopy, represent sites of actin assembly where local and transient changes in the cortical actin cytoskeleton take place.

Contributions of the structural domains of filensin in polymer formation and filament distribution

1996 ◽  
Vol 109 (2) ◽  
pp. 447-456
Author(s):  
G. Goulielmos ◽  
S. Remington ◽  
F. Schwesinger ◽  
S.D. Georgatos ◽  
F. Gounari
Keyword(s):  
De Novo ◽  
Chimeric Proteins ◽  
Tail Domain ◽  
Structural Domains ◽  
Filament Assembly ◽  
Polymer Formation ◽  
Filament Bundles ◽  
Specific Contribution ◽  
Mcf 7

Filensin and phakinin constitute the subunits of a heteropolymeric, lens-specific intermediate filament (IF) system known as the beaded-chain filaments (BFs). Since the rod of filensin is four heptads shorter than the rods of all other IF proteins, we decided to examine the specific contribution of this protein in filament assembly. For these purposes, we constructed chimeric proteins in which regions of filensin were exchanged with the equivalent ones of vimentin, a self-polymerizing IF protein. Our in vitro studies show that the filensin rod domain does not allow homopolymeric filament elongation. However, the filensin rod is necessary for co-polymerization of filensin with phakinin and seems to counteract the inherent tendency of the latter protein to homopolymerize into large, laterally associated filament bundles. Apart from the rod domain, the presence of an authentic or substituted tail domain in filensin is also essential for co-assembly with the naturally tail-less phakinin and formation of extended filaments in vitro. Finally, transfection experiments in CHO and MCF-7 cells show that the rod domain of filensin plays an important role in de novo filament formation and distribution. The same type of analysis further suggests that the end-domains of filensin interact with cell-specific, assembly-modulating factors.

scholarly journals The major outer sheath protein forms distinct conformers and multimeric complexes in the outer membrane and periplasm of Treponema denticola

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Robbins Puthenveetil ◽  
Sanjiv Kumar ◽  
Melissa J. Caimano ◽  
Abhishek Dey ◽  
Arvind Anand ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Treponema Denticola ◽  
Outer Sheath

Antileukemic activity of rapamycin in acute myeloid leukemia

Blood ◽  
2005 ◽  
Vol 105 (6) ◽  
pp. 2527-2534 ◽  
Author(s):  
Christian Récher ◽  
Odile Beyne-Rauzy ◽  
Cécile Demur ◽  
Gaëtan Chicanne ◽  
Cédric Dos Santos ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
De Novo ◽  
Mammalian Target Of Rapamycin ◽  
Cell Types ◽  
Mtor Inhibition ◽  
Growth And Survival ◽  
Clinical Responses ◽  
De Novo Aml ◽  
Acute Myeloid

AbstractThe mammalian target of rapamycin (mTOR) is a key regulator of growth and survival in many cell types. Its constitutive activation has been involved in the pathogenesis of various cancers. In this study, we show that mTOR inhibition by rapamycin strongly inhibits the growth of the most immature acute myeloid leukemia (AML) cell lines through blockade in G0/G1 phase of the cell cycle. Accordingly, 2 downstream effectors of mTOR, 4E-BP1 and p70S6K, are phosphorylated in a rapamycin-sensitive manner in a series of 23 AML cases. Interestingly, the mTOR inhibitor markedly impairs the clonogenic properties of fresh AML cells while sparing normal hematopoietic progenitors. Moreover, rapamycin induces significant clinical responses in 4 of 9 patients with either refractory/relapsed de novo AML or secondary AML. Overall, our data strongly suggest that mTOR is aberrantly regulated in most AML cells and that rapamycin and analogs, by targeting the clonogenic compartment of the leukemic clone, may be used as new compounds in AML therapy.

Insulin-Sensitive Phospholipid Signaling Systems and Glucose Transport. Update II

2001 ◽  
Vol 226 (4) ◽  
pp. 283-295 ◽  
Author(s):  
Robert V. Farese
Keyword(s):  
Protein Kinase ◽  
Glucose Metabolism ◽  
Glucose Transport ◽  
Intracellular Signaling ◽  
Glucose Transporter ◽  
De Novo ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Cell Types ◽  
Biologically Active

Insulin provokes rapid changes in phospholipid metabolism and thereby generates biologically active lipids that serve as intracellular signaling factors that regulate glucose transport and glycogen synthesis. These changes include: (i) activation of phosphatidylinositol 3-kinase (PI3K) and production of PIP3; (ii) PIP3-dependent activation of atypical protein kinase Cs (PKCs); (iii) PIP3-dependent activation of PKB; (iv) PI3K-dependent activation of phospholipase D and hydrolysis of phosphatidyicholine with subsequent increases in phosphatidic acid (PA) and diacyiglycerol (DAG); (v) PI3K-independent activation of glycerol-3-phosphate acylytansferase and increases in de novo synthesis of PA and DAG; and (vi) activation of DAG-sensitive PKCs. Recent findings suggest that atypical PKCs and PKB serve as important positive regulators of insulin-stimulated glucose metabolism, whereas mechanisms that result in the activation of DAG-sensitive PKCs serve mainly as negative regulators of insulin signaling through PI3K. Atypical PKCs and PKB are rapidly activated by insulin in adipocytes, liver, skeletal muscles, and other cell types by a mechanism requiring PI3K and its downstream effector, 3-phosphoinositide-dependent protein kinase-1 (PDK-1), which, in conjunction with PIP3, phosphorylates critical threonine residues in the activation loops of atypical PKCs and PKB. PIP3 also promotes increases in autophosphorylation and allosteric activation of atypical PKCs. Atypical PKCs and perhaps PKB appear to be required for insulin-induced translocation of the GLUT 4 glucose transporter to the plasma membrane and subsequent glucose transport. PKB also appears to be the major regulator of glycogen synthase. Together, atypical PKCs and PKB serve as a potent, integrated PI3K/PDK-1-directed signaling system that is used by insulin to regulate glucose metabolism.

scholarly journals Epithelial argininosuccinate synthetase is dispensable for intestinal regeneration and tumorigenesis

2021 ◽  
Vol 12 (10) ◽  
Author(s):  
Jonathan H. M. van der Meer ◽  
Ruben J. de Boer ◽  
Bartolomeus J. Meijer ◽  
Wouter L. Smit ◽  
Jacqueline L. M. Vermeulen ◽  
...  
Keyword(s):  
Amino Acid ◽  
Intestinal Epithelium ◽  
De Novo ◽  
Cell Types ◽  
Intestinal Epithelial ◽  
Argininosuccinate Synthetase ◽  
Important Amino Acid ◽  
Tissue Specimens ◽  
Colorectal Cancer Patients

AbstractThe epithelial signaling pathways involved in damage and regeneration, and neoplastic transformation are known to be similar. We noted upregulation of argininosuccinate synthetase (ASS1) in hyperproliferative intestinal epithelium. Since ASS1 leads to de novo synthesis of arginine, an important amino acid for the growth of intestinal epithelial cells, its upregulation can contribute to epithelial proliferation necessary to be sustained during oncogenic transformation and regeneration. Here we investigated the function of ASS1 in the gut epithelium during tissue regeneration and tumorigenesis, using intestinal epithelial conditional Ass1 knockout mice and organoids, and tissue specimens from colorectal cancer patients. We demonstrate that ASS1 is strongly expressed in the regenerating and Apc-mutated intestinal epithelium. Furthermore, we observe an arrest in amino acid flux of the urea cycle, which leads to an accumulation of intracellular arginine. However, loss of epithelial Ass1 does not lead to a reduction in proliferation or increase in apoptosis in vivo, also in mice fed an arginine-free diet. Epithelial loss of Ass1 seems to be compensated by altered arginine metabolism in other cell types and the liver.

Sign in / Sign up

Export Citation Format

Share Document