scholarly journals CRL5-dependent regulation of the small GTPases ARL4C and ARF6 controls hippocampal morphogenesis

2020 ◽  
Vol 117 (37) ◽  
pp. 23073-23084
Author(s):  
Jisoo S. Han ◽  
Keiko Hino ◽  
Wenzhe Li ◽  
Raenier V. Reyes ◽  
Cesar P. Canales ◽  
...  
Keyword(s):  
Pyramidal Neuron ◽  
Pyramidal Neurons ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Cullin 5 ◽  
Hippocampal Development ◽  
The Stability ◽  
Cytoskeletal Rearrangements ◽  
Apical Dendrites

The small GTPase ARL4C participates in the regulation of cell migration, cytoskeletal rearrangements, and vesicular trafficking in epithelial cells. The ARL4C signaling cascade starts by the recruitment of the ARF–GEF cytohesins to the plasma membrane, which, in turn, bind and activate the small GTPase ARF6. However, the role of ARL4C–cytohesin–ARF6 signaling during hippocampal development remains elusive. Here, we report that the E3 ubiquitin ligase Cullin 5/RBX2 (CRL5) controls the stability of ARL4C and its signaling effectors to regulate hippocampal morphogenesis. Both RBX2 knockout and Cullin 5 knockdown cause hippocampal pyramidal neuron mislocalization and development of multiple apical dendrites. We used quantitative mass spectrometry to show that ARL4C, Cytohesin-1/3, and ARF6 accumulate in the RBX2 mutant telencephalon. Furthermore, we show that depletion of ARL4C rescues the phenotypes caused by Cullin 5 knockdown, whereas depletion of CYTH1 or ARF6 exacerbates overmigration. Finally, we show that ARL4C, CYTH1, and ARF6 are necessary for the dendritic outgrowth of pyramidal neurons to the superficial strata of the hippocampus. Overall, we identified CRL5 as a key regulator of hippocampal development and uncovered ARL4C, CYTH1, and ARF6 as CRL5-regulated signaling effectors that control pyramidal neuron migration and dendritogenesis.

scholarly journals CRL5-dependent regulation of Arl4c and Arf6 controls hippocampal morphogenesis

2020 ◽  
Author(s):  
Jisoo S. Han ◽  
Keiko Hino ◽  
Raenier V. Reyes ◽  
Cesar P. Canales ◽  
Adam M. Miltner ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Pyramidal Neuron ◽  
Pyramidal Neurons ◽  
Small Gtpase ◽  
Knock Out ◽  
Hippocampal Pyramidal Neurons ◽  
Cullin 5 ◽  
Hippocampal Development ◽  
The Stability

SummaryThe small GTPase Arl4c participates in the regulation of cell migration, cytoskeletal rearrangements, and vesicular trafficking in epithelial cells. The Arl4c signaling cascade starts by the recruitment of the Arf-GEF cytohesins to the plasma membrane, which in turn engage the small GTPase Arf6. In the nervous system, Arf6 regulates dendrite outgrowth in vitro and neuronal migration in the developing cortex. However, the role of Arl4c-cytohesin-Arf6 signaling during brain development and particularly during hippocampal development remain elusive. Here, we report that the E3 ubiquitin ligase Cullin 5/Rbx2 (CRL5) controls the stability of Arl4c and its signaling effectors to regulate hippocampal morphogenesis. Rbx2 knock out causes hippocampal pyramidal neuron mislocalization and formation of multiple apical dendrites. The same phenotypes were observed when Cullin 5 was knocked down in pyramidal neurons by in utero electroporation. We used quantitative mass spectrometry to show that Arl4c, Cytohesin-1/3, and Arf6 accumulate in the telencephalon when Rbx2 is absent. Arl4c expression is post-transcriptionally regulated, with a peak in expression at early postnatal stages, and is localized at the plasma membrane and on intracellular vesicles in hippocampal pyramidal neurons. Furthermore, we show that depletion of Arl4c rescues the phenotypes caused by Cullin 5 knock down in the hippocampus, whereas depletion of Arf6 exacerbates over-migration. Finally, we show that Arl4c and Arf6 are necessary for the dendritic outgrowth of pyramidal neurons to the most superficial strata of the hippocampus. Overall, we identified CRL5 as a key regulator of hippocampal development and uncovered Arl4c and Arf6 as novel CRL5-regulated signaling effectors that control pyramidal neuron migration and dendritogenesis.

The flightless I protein colocalizes with actin- and microtubule-based structures in motile Swiss 3T3 fibroblasts: evidence for the involvement of PI 3-kinase and Ras-related small GTPases

2001 ◽  
Vol 114 (3) ◽  
pp. 549-562 ◽  
Author(s):  
D.A. Davy ◽  
H.D. Campbell ◽  
S. Fountain ◽  
D. de Jong ◽  
M.F. Crouch
Keyword(s):  
Specific Inhibitor ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Actin Binding ◽  
Serum Stimulation ◽  
3T3 Fibroblasts ◽  
Swiss 3T3 ◽  
Green Fluorescent ◽  
Cytoskeletal Rearrangements ◽  
Swiss 3T3 Fibroblasts

The flightless I protein contains an actin-binding domain with homology to the gelsolin family and is likely to be involved in actin cytoskeletal rearrangements. It has been suggested that this protein is involved in linking the cytoskeletal network with signal transduction pathways. We have developed antibodies directed toward the leucine rich repeat and gelsolin-like domains of the human and mouse homologues of flightless I that specifically recognize expressed and endogenous forms of the protein. We have also constructed a flightless I-enhanced green fluorescent fusion vector and used this to examine the localization of the expressed protein in Swiss 3T3 fibroblasts. The flightless I protein localizes predominantly to the nucleus and translocates to the cytoplasm following serum stimulation. In cells stimulated to migrate, the flightless I protein colocalizes with beta-tubulin- and actin-based structures. Members of the small GTPase family, also implicated in cytoskeletal control, were found to colocalize with flightless I in migrating Swiss 3T3 fibroblasts. LY294002, a specific inhibitor of PI 3-kinase, inhibits the translocation of flightless I to actin-based structures. Our results suggest that PI 3-kinase and the small GTPases, Ras, RhoA and Cdc42 may be part of a common functional pathway involved in Fliih-mediated cytoskeletal regulation. Functionally, we suggest that flightless I may act to prepare actin filaments or provide factors required for cytoskeletal rearrangements necessary for cell migration and/or adhesion.

scholarly journals Arp2/3-Branched Actin Maintains an Active Pool of GTP-RhoA and Controls RhoA Abundance

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1264
Author(s):  
Yuxing Huang ◽  
Xin Yi ◽  
Chenlu Kang ◽  
Congying Wu
Keyword(s):  
Signal Transduction ◽  
Cell Motility ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Protein Abundance ◽  
Rhoa Activity ◽  
Cytoskeletal Dynamics ◽  
Active Pool ◽  
Spatiotemporal Control

Small GTPases regulate cytoskeletal dynamics, cell motility, and division under precise spatiotemporal control. Different small GTPases exhibit cross talks to exert feedback response or to act in concert during signal transduction. However, whether and how specific cytoskeletal components’ feedback to upstream signaling factors remains largely elusive. Here, we report an intriguing finding that disruption of the Arp2/3-branched actin specifically reduces RhoA activity but upregulates its total protein abundance. We further dissect the mechanisms underlying these circumstances and identify the altered cortactin/p190RhoGAP interaction and weakened CCM2/Smurf1 binding to be involved in GTP-RhoA reduction and total RhoA increase, respectively. Moreover, we find that cytokinesis defects induced by Arp2/3 inhibition can be rescued by activating RhoA. Our study reveals an intricate feedback from the actin cytoskeleton to the small GTPase. Our work highlights the role of Arp2/3-branched actin in signal transduction aside from its function in serving as critical cytoskeletal components to maintain cell morphology and motility.

Role of Dendritic Spines in Action Potential Backpropagation: A Numerical Simulation Study

2002 ◽  
Vol 88 (5) ◽  
pp. 2834-2845 ◽  
Author(s):  
David Tsay ◽  
Rafael Yuste
Keyword(s):  
Action Potential ◽  
Sodium Channels ◽  
Dendritic Spines ◽  
Pyramidal Neurons ◽  
Excitatory Input ◽  
Spine Morphology ◽  
Dendritic Shaft ◽  
Apical Dendrites ◽  
Channel Properties

Two remarkable aspects of pyramidal neurons are their complex dendritic morphologies and the abundant presence of spines, small structures that are the sites of excitatory input. Although the channel properties of the dendritic shaft membrane have been experimentally probed, the influence of spine properties in dendritic signaling and action potential propagation remains unclear. To explore this we have performed multi-compartmental numerical simulations investigating the degree of consistency between experimental data on dendritic channel densities and backpropagation behavior, as well as the necessity and degree of influence of excitable spines. Our results indicate that measured densities of Na+ channels in dendritic shafts cannot support effective backpropagation observed in apical dendrites due to suprathreshold inactivation. We demonstrate as a potential solution that Na+ channels in spines at higher densities than those measured in the dendritic shaft can support extensive backpropagation. In addition, clustering of Na+ channels in spines appears to enhance their effect due to their unique morphology. Finally, we show that changes in spine morphology significantly influence backpropagation efficacy. These results suggest that, by clustering sodium channels, spines may serve to control backpropagation.

scholarly journals Rab18 regulates focal adhesion dynamics by interacting with kinectin-1 at the endoplasmic reticulum

2020 ◽  
Vol 219 (7) ◽  
Author(s):  
Noemi Antonella Guadagno ◽  
Azzurra Margiotta ◽  
Synne Arstad Bjørnestad ◽  
Linda Hofstad Haugen ◽  
Ingrid Kjos ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Focal Adhesion ◽  
Focal Adhesions ◽  
Molecular Switches ◽  
Underlying Mechanism ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Canonical Function ◽  
Dependent Transport

The members of the Rab family of small GTPases are molecular switches that regulate distinct steps in different membrane traffic pathways. In addition to this canonical function, Rabs can play a role in other processes, such as cell adhesion and motility. Here, we reveal the role of the small GTPase Rab18 as a positive regulator of directional migration in chemotaxis, and the underlying mechanism. We show that knockdown of Rab18 reduces the size of focal adhesions (FAs) and influences their dynamics. Furthermore, we found that Rab18, by directly interacting with the endoplasmic reticulum (ER)-resident protein kinectin-1, controls the anterograde kinesin-1–dependent transport of the ER required for the maturation of nascent FAs and protrusion orientation toward a chemoattractant. Altogether, our data support a model in which Rab18 regulates kinectin-1 transport toward the cell surface to form ER–FA contacts, thus promoting FA growth and cell migration during chemotaxis.

scholarly journals Involvement of Rac/Cdc42/PAK pathway in cytoskeletal rearrangements.

2009 ◽  
Vol 56 (2) ◽  
Author(s):  
Joanna Szczepanowska
Keyword(s):  
Neurodegenerative Diseases ◽  
Protein Kinases ◽  
Small Gtpases ◽  
Cytoskeletal Reorganization ◽  
Cellular Processes ◽  
Cytoskeletal Structure ◽  
Binding Partners ◽  
Evolutionarily Conserved ◽  
Cytoskeletal Rearrangements

The p21-activated kinases (PAKs) are serine/threonine protein kinases interacting with small GTPases - Rac and Cdc42. PAKs are found in most eukaryotes and play an evolutionarily conserved role in many cellular processes. Six human PAKs have been identified, and based on homology, they can be classified into two groups. This review focuses specifically on the role of Rac/Cdc42 regulated PAKs in maintaining and remodeling cytoskeletal structure in various organisms. A list of PAKs substrates and binding partners implicated directly and indirectly in cytoskeletal reorganization is presented. Also perturbations of the Rac/Cdc42/PAK pathway leading to tumorigenesis and neurodegenerative diseases are reviewed.

scholarly journals The NF-κB essential modulator (NEMO) controls podocyte cytoskeletal dynamics independently of NF-κB

2015 ◽  
Vol 309 (7) ◽  
pp. F617-F626 ◽  
Author(s):  
Sebastian Brähler ◽  
Christina Ising ◽  
Belén Barrera Aranda ◽  
Martin Höhne ◽  
Bernhard Schermer ◽  
...  
Keyword(s):  
Map Kinases ◽  
Small Gtpases ◽  
Migratory Response ◽  
Filtration Barrier ◽  
Tnf Α ◽  
Cytoskeletal Dynamics ◽  
Fenestrated Endothelium ◽  
End Stage ◽  
Cytoskeletal Rearrangements

Maintenance of the glomerular filtration barrier with its fenestrated endothelium, the glomerular basement membrane, and the podocytes as the outer layer, is a major prerequisite for proper renal function. Tight regulation of the balance between plasticity and rigidity of the podocytes' architecture is required to prevent the onset of glomerular disease, mainly proteinuria. The underlying cellular signaling pathways that regulate the organization of the podocytes' cytoskeleton are still a matter of controversial debate. In this study, we investigated the role of the NF-κB signaling pathway in podocyte cytoskeletal dynamics. As previously published, genetic inhibition of the NF-κB essential modulator (NEMO) in podocytes does not affect glomerular function under physiological, nonstressed conditions nor does it alter the initial podocyte response in an experimental glomerulonephritis (NTN) model (Brähler S, Ising C, Hagmann H, Rasmus M, Hoehne M, Kurschat C, Kisner T, Goebel H, Shankland SJ, Addicks K, Thaiss F, Schermer B, Pasparakis M, Benzing T, Brinkkoetter PT. Am J Physiol Renal Physiol 303: F1473–F1475, 2012). Quite the contrary, podocyte-specific NEMO null mice recovered significantly faster and did not develop glomerulosclerosis and end-stage renal failure over time. Here, we show that cytoskeletal rearrangements and increased podocyte motility following stimulation with IL-1, TNF-α, or LPS depend on NEMO. NEMO also regulates the phosphorylation of the MAP kinase ERK1/2 and suppresses the activation of RhoA following stimulation with IL-1. The migratory response and altered ERK1/2 phosphorylation is independent of NF-κB signaling as demonstrated by expression of a mutant IκB resistant to phosphorylation and degradation. In conclusion, signaling through NEMO might not only be involved in the production of NF-κB proinflammatory chemokines but also regulates podocyte dynamics independently of NF-κB, most likely through small GTPases and MAP kinases.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

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