scholarly journals Analysis of Hemichannels and Gap Junctions: Application and Extension of the Passive Transmembrane Ion Transport Model

2021 ◽  
Vol 15 ◽  
Author(s):  
Qiqian Wang ◽  
Shenquan Liu
Keyword(s):  
Synaptic Transmission ◽  
Gap Junctions ◽  
Ion Transport ◽  
Numerical Simulations ◽  
Plasma Membranes ◽  
Channel Model ◽  
Transport Model ◽  
Gene Families ◽  
Adjacent Cell ◽  
Gap Junctional

Electrical synaptic transmission is an essential form of interneuronal communication which is mediated by gap junctions that permit ion flow. Three gene families (connexins, innexins, and pannexins) have evolved to form gap junctional channels. Each gap junctional channel is formed by the docking of the hemichannel of one cell with the corresponding hemichannel of an adjacent cell. To date, there has been a lack of study models to describe this structure in detail. In this study, we demonstrate that numerical simulations suggest that the passive transmembrane ion transport model, based on the generality of ion channels, also applies to hemichannels in non-junctional plasma membranes. On this basis, we established a gap junctional channel model, which describes hemichannels' docking. We simulated homotypic and heterotypic gap junctions formed by connexins, innexins, and pannexins. Based on the numerical results and our theoretical model, we discussed the physiology of hemichannels and gap junctions, including ion blockage of hemichannels, voltage gating of gap junctions, and asymmetry and delay of electrical synaptic transmission, for which the numerical simulations are first comprehensively realized.

scholarly journals Analysis of Hemichannels and Gap Junctions: Application and Extension of the Passive Transmembrane Ion Transport Model

2020 ◽  
Author(s):  
Qiqian Wang ◽  
Shenquan Liu
Keyword(s):  
Synaptic Transmission ◽  
Gap Junctions ◽  
Ion Transport ◽  
Numerical Simulations ◽  
Plasma Membranes ◽  
Channel Model ◽  
Transport Model ◽  
Gene Families ◽  
Adjacent Cell ◽  
Gap Junctional

Electrical synaptic transmission is an essential form of interneuronal communication, mediated by gap junctions that permit ion flow. Three gene families (connexins, innexins, and pannexins) have evolved to form gap junctional channels. Each gap junctional channel is formed by the docking of the hemichannel of one cell with the corresponding hemichannel of an adjacent cell. To date, there is a lack of models describing this structure in detail. In this study, we demonstrate that numerical simulations suggest that the passive transmembrane ion transport model, based on the generality of ion channels, also applies to hemichannels in non-junctional plasma membranes. On this basis, we established a gap junctional channel model, which describes hemichannels' docking. We simulated homotypic and heterotypic gap junctions formed by connexins, innexins, and pannexins. Based on the numerical results and our theoretical model, we discussed the physiology of hemichannels and gap junctions, including ion blockage of hemichannels, voltage gating of gap junctions, and asymmetry and delay of electrical synaptic transmission, for which the numerical simulations are first comprehensively realized.

scholarly journals Direct Actions of Carbenoxolone on Synaptic Transmission and Neuronal Membrane Properties

2009 ◽  
Vol 102 (2) ◽  
pp. 974-978 ◽  
Author(s):  
Kenneth R. Tovar ◽  
Brady J. Maher ◽  
Gary L. Westbrook
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
Gap Junctions ◽  
Hippocampal Neurons ◽  
Electrical Coupling ◽  
Network Activity ◽  
Membrane Properties ◽  
Neuronal Membrane ◽  
Postsynaptic Currents ◽  
Gap Junctional

The increased appreciation of electrical coupling between neurons has led to many studies examining the role of gap junctions in synaptic and network activity. Although the gap junctional blocker carbenoxolone (CBX) is effective in reducing electrical coupling, it may have other actions as well. To study the non–gap junctional effects of CBX on synaptic transmission, we recorded from mouse hippocampal neurons cultured on glial micro-islands. This recording configuration allowed us to stimulate and record excitatory postsynaptic currents (EPSCs) or inhibitory postsynaptic currents (IPSCs) in the same neuron or pairs of neurons. CBX irreversibly reduced evoked α-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid (AMPA) receptor–mediated EPSCs. Consistent with a presynaptic site of action, CBX had no effect on glutamate-evoked whole cell currents and increased the paired-pulse ratio of AMPA and N-methyl-d-aspartate (NMDA) receptor–mediated EPSCs. CBX also reversibly reduced GABAA receptor–mediated IPSCs, increased the action potential width, and reduced the action potential firing rate. Our results indicate CBX broadly affects several neuronal membrane conductances independent of its effects on gap junctions. Thus effects of carbenoxolone on network activity cannot be interpreted as resulting from specific block of gap junctions.

scholarly journals Seeing Is Believing: Gap Junctions in Motion

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 494
Author(s):  
Xinbo Li
Keyword(s):  
Gap Junctions ◽  
Intercellular Communication ◽  
Plasma Membranes ◽  
Gap Junctional Intercellular Communication ◽  
Connexin Proteins ◽  
Gap Junctional

Gap junctional intercellular communication (GJIC) channels between cells are composed of connexin proteins that form hexamers (connexons) in adjacent plasma membranes [...]

scholarly journals Towards explicit regulating-ion-transport: nanochannels with only function-elements at outer-surface

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Qun Ma ◽  
Yu Li ◽  
Rongsheng Wang ◽  
Hongquan Xu ◽  
Qiujiao Du ◽  
...  
Keyword(s):  
Ion Transport ◽  
Numerical Simulations ◽  
Power Density ◽  
Outer Surface ◽  
Internal Resistance ◽  
Porous Membranes ◽  
Two Dimensional ◽  
Ionic Selectivity ◽  
Key Features ◽  
Energy Conversion Devices

AbstractFunction elements (FE) are vital components of nanochannel-systems for artificially regulating ion transport. Conventionally, the FE at inner wall (FEIW) of nanochannel−systems are of concern owing to their recognized effect on the compression of ionic passageways. However, their properties are inexplicit or generally presumed from the properties of the FE at outer surface (FEOS), which will bring potential errors. Here, we show that the FEOS independently regulate ion transport in a nanochannel−system without FEIW. The numerical simulations, assigned the measured parameters of FEOS to the Poisson and Nernst-Planck (PNP) equations, are well fitted with the experiments, indicating the generally explicit regulating-ion-transport accomplished by FEOS without FEIW. Meanwhile, the FEOS fulfill the key features of the pervious nanochannel systems on regulating-ion-transport in osmotic energy conversion devices and biosensors, and show advantages to (1) promote power density through concentrating FE at outer surface, bringing increase of ionic selectivity but no obvious change in internal resistance; (2) accommodate probes or targets with size beyond the diameter of nanochannels. Nanochannel-systems with only FEOS of explicit properties provide a quantitative platform for studying substrate transport phenomena through nanoconfined space, including nanopores, nanochannels, nanopipettes, porous membranes and two-dimensional channels.

scholarly journals Low pH enhances connexin32 degradation in the pancreatic acinar cell

2014 ◽  
Vol 307 (1) ◽  
pp. G24-G32 ◽  
Author(s):  
Anamika M. Reed ◽  
Thomas Kolodecik ◽  
Sohail Z. Husain ◽  
Fred S. Gorelick
Keyword(s):  
Gap Junctions ◽  
Acinar Cell ◽  
Intercellular Communication ◽  
Pancreatic Acinar Cell ◽  
Low Ph ◽  
Extracellular Ph ◽  
Gap Junctional Intercellular Communication ◽  
Junction Protein ◽  
Clinical Conditions ◽  
Gap Junctional

Decreased extracellular pH is observed in a number of clinical conditions and can sensitize to the development and worsen the severity of acute pancreatitis. Because intercellular communication through gap junctions is pH-sensitive and modulates pancreatitis responses, we evaluated the effects of low pH on gap junctions in the rat pancreatic acinar cell. Decreasing extracellular pH from 7.4 to 7.0 significantly inhibited gap junctional intracellular communication. Acidic pH also significantly reduced levels of connexin32, the predominant gap junction protein in acinar cells, and altered its localization. Increased degradation through the proteasomal, lysosomal, and autophagic pathways mediated the decrease in connexin32 under low-pH conditions. These findings provide the first evidence that low extracellular pH can regulate gap junctional intercellular communication by enhancing connexin degradation.

Structural diversity of band 4.1 superfamily members

1994 ◽  
Vol 107 (7) ◽  
pp. 1921-1928 ◽  
Author(s):  
K. Takeuchi ◽  
A. Kawashima ◽  
A. Nagafuchi ◽  
S. Tsukita
Keyword(s):  
Plasma Membrane ◽  
Tyrosine Kinases ◽  
Plasma Membranes ◽  
Structural Diversity ◽  
Gene Families ◽  
Cdna Clones ◽  
New Members ◽  
F9 Cells ◽  
Novel Proteins ◽  
Cellular Events

Several proteins contain the domain homologous to the N-terminal half of band 4.1 protein, indicating the existence of a superfamily. The members of this ‘band 4.1’ superfamily are thought to play crucial roles in the regulation of cytoskeleton-plasma membrane interaction just beneath plasma membranes. We examined the structural diversity of this superfamily by means of the polymerase chain reaction using synthesized mixed primers. We thus identified many members of the band 4.1 superfamily that were expressed in mouse teratocarcinoma F9 cells and mouse brain tissue. In total, 15 cDNA clones were obtained; 8 were identical to the corresponding parts of cDNAs for the known members, while 7 appeared to encode novel proteins (NBL1-7: novel band 4.1-like proteins). Sequence analyses of these clones revealed that the band 4.1 superfamily can be subdivided into 5 gene families; band 4.1 protein, ERM (ezrin/radixin/moesin/merlin/NBL6/NBL7+ ++), talin, PTPH1 (PTPH1/PTPMEG/NBL1-3), and NBL4 (NBL4/NBL5) families. The NBL4 family was first identified here, and the full-length cDNA encoding NBL4 was cloned. The deduced amino acid sequence revealed a myristoylation site, as well as phosphorylation sites for A-kinase and tyrosine kinases in its N-terminal half, suggesting its involvement in the phosphorylation-dependent regulation of cellular events just beneath the plasma membrane. In this study, we describe the initial characterization of these new members and discuss the evolution of the band 4.1 superfamily.

Tetraethylammonium modifies gap junctions between pancreatic beta-cells

1981 ◽  
Vol 240 (3) ◽  
pp. C116-C120 ◽  
Author(s):  
M. S. Sheppard ◽  
P. Meda
Keyword(s):  
Beta Cell ◽  
Gap Junctions ◽  
Beta Cells ◽  
Insulin Release ◽  
Pancreatic Beta Cells ◽  
Freeze Fracture ◽  
Potassium Conductance ◽  
Median Number ◽  
Rat Islets Of Langerhans ◽  
Gap Junctional

Gap junctions between pancreatic beta-cells were quantitatively assessed in freeze-fracture replicas of isolated rat islets of Langerhans incubated for 90 min with or without the potassium conductance blocker tetraethylammonium (TEA). The results show that TEA increases the median number of particles per beta-cell gap junction but not the frequency of gap junctions at both nonstimulating and threshold-stimulating concentrations of glucose. TEA increased the relative gap junctional area at both concentrations of glucose. TEA had no effect on insulin release at a basal concentration of glucose but potentiated that release at the threshold glucose level. Thus TEA modifies beta-cell gap junctions independently of its effect on insulin release. However, the junctional changes observed were greater when insulin release was also elevated.

scholarly journals Electrical synaptic transmission requires a postsynaptic scaffolding protein

2020 ◽  
Author(s):  
Abagael M. Lasseigne ◽  
Fabio A. Echeverry ◽  
Sundas Ijaz ◽  
Jennifer Carlisle Michel ◽  
E. Anne Martin ◽  
...  
Keyword(s):  
Synaptic Transmission ◽  
Gap Junctions ◽  
Functional Organization ◽  
Scaffolding Protein ◽  
Scaffolding Proteins ◽  
Electrical Transmission ◽  
Critical Function ◽  
Electrical Synapses ◽  
Intercellular Channels ◽  
Chemical Synapses

SUMMARYElectrical synaptic transmission relies on neuronal gap junctions containing channels constructed by Connexins. While at chemical synapses neurotransmitter-gated ion channels are critically supported by scaffolding proteins, it is unknown if channels at electrical synapses require similar scaffold support. Here we investigated the functional relationship between neuronal Connexins and Zonula Occludens 1 (ZO1), an intracellular scaffolding protein localized to electrical synapses. Using model electrical synapses in zebrafish Mauthner cells, we demonstrated that ZO1 is required for robust synaptic Connexin localization, but Connexins are dispensable for ZO1 localization. Disrupting this hierarchical ZO1/Connexin relationship abolishes electrical transmission and disrupts Mauthner-cell-initiated escape responses. We found that ZO1 is asymmetrically localized exclusively postsynaptically at neuronal contacts where it functions to assemble intercellular channels. Thus, forming functional neuronal gap junctions requires a postsynaptic scaffolding protein. The critical function of a scaffolding molecule reveals an unanticipated complexity of molecular and functional organization at electrical synapses.

Sign in / Sign up

Export Citation Format

Share Document