scholarly journals Exploring new roles for actin upon LTP induction in dendritic spines

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mayte Bonilla-Quintana ◽  
Florentin Wörgötter
Keyword(s):  
Membrane Fusion ◽  
Dendritic Spines ◽  
Dendritic Spine ◽  
Actin Filaments ◽  
3D Model ◽  
Membrane Properties ◽  
Membrane Tension ◽  
Spine Stabilization ◽  
Cell Processes

AbstractDendritic spines, small protrusions of the dendrites, enlarge upon LTP induction, linking morphological and functional properties. Although the role of actin in spine enlargement has been well studied, little is known about its relationship with mechanical membrane properties, such as membrane tension, which is involved in many cell processes, like exocytosis. Here, we use a 3D model of the dendritic spine to investigate how polymerization of actin filaments can effectively elevate the membrane tension to trigger exocytosis in a domain close to the tip of the spine. Moreover, we show that the same pool of actin promotes full membrane fusion after exocytosis and spine stabilization.

scholarly journals Exploring new roles for actin upon LTP induction in dendritic spines

2020 ◽  
Author(s):  
Mayte Bonilla-Quintana ◽  
Florentin Wörgötter
Keyword(s):  
Membrane Fusion ◽  
Dendritic Spines ◽  
Dendritic Spine ◽  
Actin Filaments ◽  
3D Model ◽  
Membrane Properties ◽  
Membrane Tension ◽  
Spine Stabilization ◽  
Cell Processes

AbstractDendritic spines, small protrusions of the dendrites, enlarge upon LTP induction, linking morphological and functional properties. Although the role of actin in spine enlargement has been well studied, little is known about its relationship with mechanical membrane properties, such as membrane tension, which is involved in many cell processes, like exocytosis. Here, we use a 3D model of the dendritic spine to investigate how polymerization of actin filaments can effectively elevate the membrane tension to trigger exocytosis in a domain close to the tip of the spine. Moreover, we show that the same pool of actin promotes full membrane fusion after exocytosis and spine stabilization.

scholarly journals BDNF signaling during the lifetime of dendritic spines

2020 ◽  
Vol 382 (1) ◽  
pp. 185-199 ◽  
Author(s):  
Marta Zagrebelsky ◽  
Charlotte Tacke ◽  
Martin Korte
Keyword(s):  
Dendritic Spines ◽  
Dendritic Spine ◽  
Neurological Disorders ◽  
Current Knowledge ◽  
Conclusive Evidence ◽  
Excitatory Synapses ◽  
Neuronal Homeostasis ◽  
Bdnf Signaling ◽  
Spine Number

Abstract Dendritic spines are tiny membrane specialization forming the postsynaptic part of most excitatory synapses. They have been suggested to play a crucial role in regulating synaptic transmission during development and in adult learning processes. Changes in their number, size, and shape are correlated with processes of structural synaptic plasticity and learning and memory and also with neurodegenerative diseases, when spines are lost. Thus, their alterations can correlate with neuronal homeostasis, but also with dysfunction in several neurological disorders characterized by cognitive impairment. Therefore, it is important to understand how different stages in the life of a dendritic spine, including formation, maturation, and plasticity, are strictly regulated. In this context, brain-derived neurotrophic factor (BDNF), belonging to the NGF-neurotrophin family, is among the most intensively investigated molecule. This review would like to report the current knowledge regarding the role of BDNF in regulating dendritic spine number, structure, and plasticity concentrating especially on its signaling via its two often functionally antagonistic receptors, TrkB and p75NTR. In addition, we point out a series of open points in which, while the role of BDNF signaling is extremely likely conclusive, evidence is still missing.

scholarly journals Hippocampal CA1 Pyramidal Neurons ofMecp2Mutant Mice Show a Dendritic Spine Phenotype Only in the Presymptomatic Stage

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Christopher A. Chapleau ◽  
Elena Maria Boggio ◽  
Gaston Calfa ◽  
Alan K. Percy ◽  
Maurizio Giustetto ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Dendritic Spine ◽  
Pyramidal Neurons ◽  
Mutant Mice ◽  
Spine Density ◽  
Ca1 Pyramidal Neurons ◽  
Dendritic Spine Density ◽  
Presymptomatic Stage ◽  
Deficient Mice

Alterations in dendritic spines have been documented in numerous neurodevelopmental disorders, including Rett Syndrome (RTT). RTT, an X chromosome-linked disorder associated with mutations inMECP2, is the leading cause of intellectual disabilities in women. Neurons inMecp2-deficient mice show lower dendritic spine density in several brain regions. To better understand the role of MeCP2 on excitatory spine synapses, we analyzed dendritic spines of CA1 pyramidal neurons in the hippocampus ofMecp2tm1.1Jaemale mutant mice by either confocal microscopy or electron microscopy (EM). At postnatal-day 7 (P7), well before the onset of RTT-like symptoms, CA1 pyramidal neurons from mutant mice showed lower dendritic spine density than those from wildtype littermates. On the other hand, at P15 or later showing characteristic RTT-like symptoms, dendritic spine density did not differ between mutant and wildtype neurons. Consistently, stereological analyses at the EM level revealed similar densities of asymmetric spine synapses in CA1stratum radiatumof symptomatic mutant and wildtype littermates. These results raise caution regarding the use of dendritic spine density in hippocampal neurons as a phenotypic endpoint for the evaluation of therapeutic interventions in symptomaticMecp2-deficient mice. However, they underscore the potential role of MeCP2 in the maintenance of excitatory spine synapses.

scholarly journals Polymerization of actin. IV. Role of Ca++ and H+ in the assembly of actin and in membrane fusion in the acrosomal reaction of echinoderm sperm

1978 ◽  
Vol 77 (2) ◽  
pp. 536-550 ◽  
Author(s):  
LG Tilney ◽  
DP Kiehart ◽  
C Sardet ◽  
M Tilney
Keyword(s):  
Cell Surface ◽  
Membrane Fusion ◽  
Intracellular Ph ◽  
Actin Filaments ◽  
External Medium ◽  
Ionophore A23187 ◽  
Natural Stimulus ◽  
High Affinity ◽  
Acrosomal Reaction

When Pisaster, Asterias, or Thyone sperm are treated with the ionophore A23187 or X537A, an acrosomal reaction similar but not identical to a normal acrosomal reaction is induced in all the sperm. Based upon the response of the sperm, the acrosomal reaction consists of a series of temporally related steps. These include the fusion of the acrosomal vacuole with the cell surface, the polymerization of the actin, the alignment of the actin filaments, an increase in volume, an increase in the limiting membrane, and changes in the shape of the nucleus. In this report, we have concentrated on the first two steps in this sequence. Although fusion of the acrosomal vacuole with the cell surface requires Ca++, we found that the polymerization of actin instead appears to be dependent upon an increase in intracellular pH. This conclusion was reached by applying to sperm A23187, X537A, or nigericin, ionophores which all carry H+ at high affinity, yet vary in their affinity for other cations. When sperm are suspended in isotonic NaCl, isotonic KCl, calcium-free seawater, or seawater, all at pH 8.0, and the ionophore is added, the actin polymerizes explosively and an efflux of H+ from the cell occurs. However, if the pH, of the external medium is maintained at 6.5, the presumed intracellular pH, no effect is observed. And, finally, if egg jelly is added to sperm (the natural stimulus for the acrosomal reaction) at pH 8.0, H+ is also released. On the basis of these observations and those presented in earlier papers in this series, we conclude that a rise in intracellular pH induces the actin to disassociate from its binding proteins. Now it can polymerize.

scholarly journals Modeling membrane nanotube morphology: the role of heterogeneity in composition and material properties

2018 ◽  
Author(s):  
Haleh Alimohamadi ◽  
Ben Ovryn ◽  
Padmini Rangamani
Keyword(s):  
Membrane Properties ◽  
Membrane Tension ◽  
Membrane Mechanics ◽  
Membrane Composition ◽  
Tube Radius ◽  
Cylindrical Tubes ◽  
Dynamic Structures ◽  
Protein Density ◽  
Membrane Protein Interaction

AbstractMembrane nanotubes have been identified as dynamic structures for cells to connect over long distances. Nanotubes typically appear as thin and cylindrical tubes, but they may also have a beaded architecture along the tube. In this paper, we study the role of membrane mechanics in governing the architecture of these tubes and show that the formation of beadlike structures along the nanotubes can result from local heterogeneities in the membrane either due to protein aggregation or due to membrane composition. We present numerical results that predict how membrane properties, protein density, and local tension compete to create a phase space that governs the morphology of a nanotube. We also find that there is an energy barrier that prevents two beads from fusing. These results suggest that the membrane-protein interaction, membrane composition, and membrane tension closely govern the tube radius, number of beads, and the bead morphology.

scholarly journals KLHL17/Actinfilin, a brain-specific gene associated with infantile spasms and autism, regulates dendritic spine enlargement

2020 ◽  
Vol 27 (1) ◽  
Author(s):  
Hsiao-Tang Hu ◽  
Tzyy-Nan Huang ◽  
Yi-Ping Hsueh
Keyword(s):  
Dendritic Spines ◽  
Dendritic Spine ◽  
Brain Function ◽  
Infantile Spasms ◽  
Actin Binding ◽  
Behavioral Impairment ◽  
Actin Remodeling ◽  
Spine Formation ◽  
Behavioral Assays

Abstract Background Dendritic spines, the actin-rich protrusions emerging from dendrites, are the subcellular locations of excitatory synapses in the mammalian brain. Many actin-regulating molecules modulate dendritic spine morphology. Since dendritic spines are neuron-specific structures, it is reasonable to speculate that neuron-specific or -predominant factors are involved in dendritic spine formation. KLHL17 (Kelch-like 17, also known as Actinfilin), an actin-binding protein, is predominantly expressed in brain. Human genetic study has indicated an association of KLHL17/Actinfilin with infantile spasms, a rare form of childhood epilepsy also resulting in autism and mental retardation, indicating that KLHL17/Actinfilin plays a role in neuronal function. However, it remains elusive if and how KLHL17/Actinfilin regulates neuronal development and brain function. Methods Fluorescent immunostaining and electrophysiological recording were performed to evaluate dendritic spine formation and activity in cultured hippocampal neurons. Knockdown and knockout of KLHL17/Actinfilin and expression of truncated fragments of KLHL17/Actinfilin were conducted to investigate the function of KLHL17/Actinfilin in neurons. Mouse behavioral assays were used to evaluate the role of KLHL17/Actinfilin in brain function. Results We found that KLHL17/Actinfilin tends to form circular puncta in dendritic spines and are surrounded by or adjacent to F-actin. Klhl17 deficiency impairs F-actin enrichment at dendritic spines. Knockdown and knockout of KLHL17/Actinfilin specifically impair dendritic spine enlargement, but not the density or length of dendritic spines. Both N-terminal Broad-Complex, Tramtrack and Bric-a-brac (BTB) domain and C-terminal Kelch domains of KLHL17/Actinfilin are required for F-actin remodeling and enrichment at dendritic spines, as well as dendritic spine enlargement. A reduction of postsynaptic and presynsptic markers at dendritic spines and altered mEPSC profiles due to Klhl17 deficiency evidence impaired synaptic activity in Klhl17-deficient neurons. Our behavioral assays further indicate that Klhl17 deficiency results in hyperactivity and reduced social interaction, strengthening evidence for the physiological role of KLHL17/Actinfilin. Conclusion Our findings provide evidence that KLHL17/Actinfilin modulates F-actin remodeling and contributes to regulation of neuronal morphogenesis, maturation and activity, which is likely relevant to behavioral impairment in Klhl17-deficient mice. Trial registration Non-applicable.

scholarly journals Getting in shape and swimming: the role of cortical forces and membrane heterogeneity in eukaryotic cells

2017 ◽  
Author(s):  
Hao Wu ◽  
Marco Avila Ponce de León ◽  
Hans G. Othmer
Keyword(s):  
Cell Movement ◽  
Membrane Properties ◽  
Membrane Tension ◽  
Actin Cortex ◽  
Bending Modulus ◽  
Motile Cells ◽  
Cell Shapes ◽  
Direction Of Movement ◽  
Shape Changes

AbstractRecent research has shown that motile cells can adapt their mode of propulsion to the mechanical properties of the environment in which they find themselves – crawling in some environments while swimming in others. The latter can involve movement by blebbing or other cyclic shape changes, and both highly-simplified and more realistic models of these modes have been studied previously. Herein we study swimming that is driven by membrane tension gradients that arise from flows in the actin cortex underlying the membrane, and does not involve imposed cyclic shape changes. Such gradients can lead to a number of different characteristic cell shapes, and our first objective is to understand how different distributions of membrane tension influence the shape of cells in a quiescent fluid. We then analyze the effects of spatial variation in other membrane properties, and how they interact with tension gradients to determine the shape. We also study the effect of fluid-cell interactions and show how tension leads to cell movement, how the balance between tension gradients and a variable bending modulus determine the shape and direction of movement, and how the efficiency of movement depends on the properties of the fluid and the distribution of tension and bending modulus in the membrane.Dedicated to the memory of Karl P. Hadeler, a pioneer in the field of Mathematical Biology and a friend and mentor to many.

Dynamic changes in plasma membrane properties of semliki forest virus infected cells related to cell fusion

1988 ◽  
Vol 8 (3) ◽  
pp. 241-254 ◽  
Author(s):  
C. Kempf ◽  
M. R. Michel ◽  
U. Kohler ◽  
H. Koblet ◽  
H. Oetliker
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Membrane Fusion ◽  
Cell Fusion ◽  
Semliki Forest Virus ◽  
Membrane Properties ◽  
Acidic Ph ◽  
Dynamic Changes ◽  
Infected Cells

The mechanism of the processes leading to membrane fusion is as yet unknown. In this report we demonstrate that changes in membrane potential and potassium fluxes correlate with Semliki Forest virus induced cell-cell fusion at mildly acidic pH. The changes observed occur only at pH's below 6.2 corresponding to values required to trigger the fusion process. A possible role of these alterations of the plasma membrane related to membrane fusion phenomena is discussed.

scholarly journals Abl2:cortactin interactions regulate dendritic spine stability via control of a stable filamentous actin pool

2020 ◽  
Author(s):  
Juliana E. Shaw ◽  
Michaela B. C. Kilander ◽  
Yu-Chih Lin ◽  
Anthony J. Koleske
Keyword(s):  
Dendritic Spines ◽  
Dendritic Spine ◽  
Actin Filaments ◽  
Synaptic Activity ◽  
Spine Density ◽  
Filamentous Actin ◽  
Nonreceptor Tyrosine Kinase ◽  
Spine Stability ◽  
Small Pool ◽  
Activity Dependent

AbstractDendritic spines are enriched with stable and dynamic actin filaments, which determine their structure and shape. Disruption of the Abl2/Arg nonreceptor tyrosine kinase in mice compromises spine stability and size. We provide evidence that binding to cortactin tethers Abl2 in spines, where Abl2 and cortactin maintain the small pool of stable actin required for dendritic spine stability. Using fluorescence recovery after photobleaching of GFP-actin, we find that disruption of Abl2:cortactin interactions eliminates stable actin filaments in dendritic spines, significantly reducing spine density. A subset of spines remaining after Abl2 depletion retain their stable actin pool and undergo activity-dependent spine enlargement associated with increased cortactin levels. Finally, tonic increases in synaptic activity rescue spine loss upon Abl2 depletion by promoting cortactin enrichment in vulnerable spines. Together, our findings strongly suggest Abl2:cortactin interactions promote spine stability by maintaining pools of stable actin filaments in spines.

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