scholarly journals The Role of Arp2/3 in Growth Cone Actin Dynamics and Guidance Is Substrate Dependent

2014 ◽  
Vol 34 (17) ◽  
pp. 5895-5908 ◽  
Author(s):  
J. E. San Miguel-Ruiz ◽  
P. C. Letourneau
Keyword(s):  
Growth Cone ◽  
Actin Dynamics

scholarly journals Enhanced Production of the Mical Redox Domain for Enzymology and F-actin Disassembly Assays

2021 ◽  
Vol 22 (4) ◽  
pp. 1991
Author(s):  
Jimok Yoon ◽  
Heng Wu ◽  
Ruei-Jiun Hung ◽  
Jonathan R. Terman
Keyword(s):  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Actin Dynamics ◽  
Specific Substrate ◽  
Actin Assembly ◽  
Redox Enzymes ◽  
Enhanced Production ◽  
Reversible Redox ◽  
Future Work ◽  
Signaling Process

To change their behaviors, cells require actin proteins to assemble together into long polymers/filaments—and so a critical goal is to understand the factors that control this actin filament (F-actin) assembly and stability. We have identified a family of unusual actin regulators, the MICALs, which are flavoprotein monooxygenase/hydroxylase enzymes that associate with flavin adenine dinucleotide (FAD) and use the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH) in Redox reactions. F-actin is a specific substrate for these MICAL Redox enzymes, which oxidize specific amino acids within actin to destabilize actin filaments. Furthermore, this MICAL-catalyzed reaction is reversed by another family of Redox enzymes (SelR/MsrB enzymes)—thereby revealing a reversible Redox signaling process and biochemical mechanism regulating actin dynamics. Interestingly, in addition to the MICALs’ Redox enzymatic portion through which MICALs covalently modify and affect actin, MICALs have multiple other domains. Less is known about the roles of these other MICAL domains. Here we provide approaches for obtaining high levels of recombinant protein for the Redox only portion of Mical and demonstrate its catalytic and F-actin disassembly activity. These results provide a ground state for future work aimed at defining the role of the other domains of Mical — including characterizing their effects on Mical’s Redox enzymatic and F-actin disassembly activity.

scholarly journals Dynein Light Chain 1 Regulates Dynamin-mediated F-Actin Assembly during Sperm Individualization in Drosophila

2005 ◽  
Vol 16 (7) ◽  
pp. 3107-3116 ◽  
Author(s):  
Anindya Ghosh-Roy ◽  
Bela S. Desai ◽  
Krishanu Ray
Keyword(s):  
Light Chain ◽  
Cytoplasmic Dynein ◽  
Actin Dynamics ◽  
Dynein Light Chain ◽  
Actin Assembly ◽  
Cellular Functions ◽  
Directed Movement ◽  
Cellular Processes ◽  
Dynactin Complex

Toward the end of spermiogenesis, spermatid nuclei are compacted and the clonally related spermatids individualize to become mature and active sperm. Studies in Drosophila showed that caudal end-directed movement of a microfilament-rich structure, called investment cone, expels the cytoplasmic contents of individual spermatids. F-actin dynamics plays an important role in this process. Here we report that the dynein light chain 1 (DLC1) of Drosophila is involved in two separate cellular processes during sperm individualization. It is enriched around spermatid nuclei during postelongation stages and plays an important role in the dynein-dynactin–dependent rostral retention of the nuclei during this period. In addition, DDLC1 colocalizes with dynamin along investment cones and regulates F-actin assembly at this organelle by retaining dynamin along the cones. Interestingly, we found that this process does not require the other subunits of cytoplasmic dynein-dynactin complex. Altogether, these observations suggest that DLC1 could independently regulate multiple cellular functions and established a novel role of this protein in F-actin assembly in Drosophila.

scholarly journals In Vivo Role of Focal Adhesion Kinase in Regulating Pancreatic  -Cell Mass and Function Through Insulin Signaling, Actin Dynamics, and Granule Trafficking

Diabetes ◽  
2012 ◽  
Vol 61 (7) ◽  
pp. 1708-1718 ◽  
Author(s):  
E. P. Cai ◽  
M. Casimir ◽  
S. A. Schroer ◽  
C. T. Luk ◽  
S. Y. Shi ◽  
...  
Keyword(s):  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Insulin Signaling ◽  
Cell Mass ◽  
Actin Dynamics ◽  
Pancreatic Cell ◽  
And Function

scholarly journals Differential Role of PTEN Phosphatase in Chemotactic Growth Cone Guidance

2013 ◽  
Vol 288 (29) ◽  
pp. 20837-20842 ◽  
Author(s):  
Steven J. Henle ◽  
Lucas P. Carlstrom ◽  
Thomas R. Cheever ◽  
John R. Henley
Keyword(s):  
Growth Cone ◽  
Essential Feature ◽  
Pten Expression ◽  
Spinal Neurons ◽  
Phosphoinositide Phosphatase ◽  
Integrin Clustering ◽  
Myelin Associated Glycoprotein ◽  
Phosphatase And Tensin Homologue ◽  
Regenerative Therapies

Negatively targeting the tumor suppressor and phosphoinositide phosphatase PTEN (phosphatase and tensin homologue) promotes axon regrowth after injury. How PTEN functions in axon guidance has remained unknown. Here we report the differential role of PTEN in chemotactic guidance of axonal growth cones. Down-regulating PTEN expression in Xenopus laevis spinal neurons selectively abolished growth cone chemorepulsion but permitted chemoattraction. These findings persisted during cAMP-dependent switching of turning behaviors. Live cell imaging using a GFP biosensor revealed rapid PTEN-dependent depression of phosphatidylinositol 3,4,5-trisphosphate levels in the growth cone induced by the repellent myelin-associated glycoprotein. Moreover, down-regulating PTEN expression blocked negative remodeling of β1-integrin adhesions triggered by myelin-associated glycoprotein, yet permitted integrin clustering by a positive chemotropic treatment. Thus, PTEN negatively regulates growth cone phosphatidylinositol 3,4,5-trisphosphate levels and mediates chemorepulsion, whereas chemoattraction is PTEN-independent. Regenerative therapies targeting PTEN may therefore suppress growth cone repulsion to soluble cues while permitting attractive guidance, an essential feature for re-forming functional neural circuits.

scholarly journals Presynaptic AMPA Receptors in Health and Disease

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2260
Author(s):  
Letizia Zanetti ◽  
Maria Regoni ◽  
Elena Ratti ◽  
Flavia Valtorta ◽  
Jenny Sassone
Keyword(s):  
Ampa Receptors ◽  
Plasma Membranes ◽  
Actin Dynamics ◽  
Axonal Pathology ◽  
Pathological Conditions ◽  
Pain Transmission ◽  
Pharmacological Targets ◽  
Health And Disease ◽  
Excitatory Neurotransmission

AMPA receptors (AMPARs) are ionotropic glutamate receptors that play a major role in excitatory neurotransmission. AMPARs are located at both presynaptic and postsynaptic plasma membranes. A huge number of studies investigated the role of postsynaptic AMPARs in the normal and abnormal functioning of the mammalian central nervous system (CNS). These studies highlighted that changes in the functional properties or abundance of postsynaptic AMPARs are major mechanisms underlying synaptic plasticity phenomena, providing molecular explanations for the processes of learning and memory. Conversely, the role of AMPARs at presynaptic terminals is as yet poorly clarified. Accruing evidence demonstrates that presynaptic AMPARs can modulate the release of various neurotransmitters. Recent studies also suggest that presynaptic AMPARs may possess double ionotropic-metabotropic features and that they are involved in the local regulation of actin dynamics in both dendritic and axonal compartments. In addition, evidence suggests a key role of presynaptic AMPARs in axonal pathology, in regulation of pain transmission and in the physiology of the auditory system. Thus, it appears that presynaptic AMPARs play an important modulatory role in nerve terminal activity, making them attractive as novel pharmacological targets for a variety of pathological conditions.

scholarly journals The Two ADF-H Domains of Twinfilin Play Functionally Distinct Roles in Interactions with Actin Monomers

2002 ◽  
Vol 13 (11) ◽  
pp. 3811-3821 ◽  
Author(s):  
Pauli J. Ojala ◽  
Ville O. Paavilainen ◽  
Maria K. Vartiainen ◽  
Roman Tuma ◽  
Alan G. Weeds ◽  
...  
Keyword(s):  
Binding Site ◽  
Binding Activity ◽  
Size Exclusion ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Monomer ◽  
Wild Type ◽  
Native Page ◽  
Exclusion Chromatography

Twinfilin is a ubiquitous and abundant actin monomer–binding protein that is composed of two ADF-H domains. To elucidate the role of twinfilin in actin dynamics, we examined the interactions of mouse twinfilin and its isolated ADF-H domains with G-actin. Wild-type twinfilin binds ADP-G-actin with higher affinity (K D = 0.05 μM) than ATP-G-actin (K D = 0.47 μM) under physiological ionic conditions and forms a relatively stable (k off = 1.8 s−1) complex with ADP-G-actin. Data from native PAGE and size exclusion chromatography coupled with light scattering suggest that twinfilin competes with ADF/cofilin for the high-affinity binding site on actin monomers, although at higher concentrations, twinfilin, cofilin, and actin may also form a ternary complex. By systematic deletion analysis, we show that the actin-binding activity is located entirely in the two ADF-H domains of twinfilin. Individually, these domains compete for the same binding site on actin, but the C-terminal ADF-H domain, which has >10-fold higher affinity for ADP-G-actin, is almost entirely responsible for the ability of twinfilin to increase the amount of monomeric actin in cosedimentation assays. Isolated ADF-H domains associate with ADP-G-actin with rapid second-order kinetics, whereas the association of wild-type twinfilin with G-actin exhibits kinetics consistent with a two-step binding process. These data suggest that the association with an actin monomer induces a first-order conformational change within the twinfilin molecule. On the basis of these results, we propose a kinetic model for the role of twinfilin in actin dynamics and its possible function in cells.

scholarly journals Actin dynamics in growth cone motility and navigation

2013 ◽  
Vol 129 (2) ◽  
pp. 221-234 ◽  
Author(s):  
Timothy M. Gomez ◽  
Paul C. Letourneau
Keyword(s):  
Growth Cone ◽  
Actin Dynamics

Actin reorganization and proplatelet formation in murine megakaryocytes: the role of protein kinase Cα

Blood ◽  
2001 ◽  
Vol 97 (1) ◽  
pp. 154-161 ◽  
Author(s):  
Ponlapat Rojnuckarin ◽  
Kenneth Kaushansky
Keyword(s):  
Protein Kinase ◽  
Actin Polymerization ◽  
Map Kinases ◽  
Molecular Mechanisms ◽  
Marrow Cell ◽  
Actin Dynamics ◽  
Actin Reorganization ◽  
Murine Bone Marrow ◽  
Proplatelet Formation

Abstract With the recent cloning and characterization of thrombopoietin, appreciation of the molecular events surrounding megakaryocyte (MK) development is growing. However, the final stages of platelet formation are less well understood. Platelet production occurs after the formation of MK proplatelet processes. In a study to explore the molecular mechanisms underlying this process, mature MKs isolated from suspension murine bone marrow cell cultures were induced to form proplatelets by exposure to plasma, and the role of various cell-signaling pathways was assessed. The results showed that (1) bis-indolylmaleimide I, which blocks protein kinase C (PKC) activation; (2) down-modulation of conventional or novel classes of PKC by phorbol myristate acetate; and (3) ribozymes specific for PKCα each inhibited proplatelet formation. Inhibition of several MAP kinases, PI3 kinase, or protein kinase A failed to affect MK proplatelet formation. To gain further insights into the function of PKCα in proplatelet formation, its subcellular localization was investigated. In cultures containing active proplatelet formation, cytoplasmic polymerized actin was highly aggregated, its subcellular distribution was reorganized, and PKCα colocalized with the cellular actin aggregates. A number of MK manipulations, including blockade of integrin signaling with a disintegrin or inhibition of actin polymerization with cytochalasin D, interrupted actin reorganization, PKC relocalization, and proplatelet formation. These findings suggest an important role for PKCα in proplatelet development and suggest that it acts by altering actin dynamics in proplatelet-forming MKs. Identification of the upstream and downstream pathways involved in proplatelet formation should provide greater insights into thrombopoiesis, potentially allowing pharmacologic manipulation of the process.

scholarly journals Early herpes simplex virus type 1 infection is dependent on regulated Rac1/Cdc42 signalling in epithelial MDCKII cells

2006 ◽  
Vol 87 (12) ◽  
pp. 3483-3494 ◽  
Author(s):  
Sven Hoppe ◽  
Mario Schelhaas ◽  
Verena Jaeger ◽  
Timo Liebig ◽  
Philipp Petermann ◽  
...  
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Virus Type ◽  
Herpes Simplex Virus Type ◽  
Dominant Negative ◽  
Actin Dynamics ◽  
Simplex Virus ◽  
Hsv 1

The aim of this study was to understand how molecular determinants of epithelial cells influence initial infection by herpes simplex virus type 1 (HSV-1). Upon infection of the epithelial MDCKII cell line, enhanced association of virus particles with cells forming actin protrusions was observed, suggesting a putative role of actin dynamics in HSV-1 infection. Thus, the impact of the small Rho-like GTPases Rac1, Cdc42 and RhoA acting as key regulators of actin dynamics was addressed. Endogenous Rac1 and Cdc42 were temporarily activated at 15 and 30 min after HSV-1 infection. When constitutively active Cdc42 or Rac1 mutants were expressed transiently, a significant decrease in infectivity was observed, whereas expression of RhoA mutants had no influence. Furthermore, dominant-negative Cdc42 led to decreased infectivity, whereas dominant-negative Rac1 had no effect. So far, the study of potential effectors indicated that Rac1/Cdc42 mutants inhibited infectivity independently of p21-activated kinase (Pak1). The inhibitory effect of Rac1/Cdc42 mutant expression on HSV-1 infection was characterized further and it was found that binding, internalization and transport of HSV-1 were not affected by expression of Rac1/Cdc42 mutants. Thus, these results provide the first evidence for a role of Rac1/Cdc42 signalling during early HSV-1 infection and suggest a mechanism relying on virus-induced regulation of Rac1/Cdc42 activities.

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