scholarly journals An electrophysiological approach to measure changes in the membrane surface potential in real time

2019 ◽  
Author(s):  
Verena Burtscher ◽  
Matej Hotka ◽  
Michael Freissmuth ◽  
Walter Sandtner
Keyword(s):  
Plasma Membrane ◽  
Real Time ◽  
Surface Potential ◽  
Membrane Surface ◽  
Membrane Capacitance ◽  
Current Response ◽  
Surface Charges ◽  
Fixed Charges ◽  
Capacitive Properties ◽  
A Cell

AbstractBiological membranes carry fixed charges at their surfaces. These arise primarily from phospholipid head groups. In addition, membrane proteins contribute to the surface potential with their charged residues. Membrane lipids are asymmetrically distributed. Because of this asymmetry the net negative charge at the inner leaflet exceeds that at the outer leaflet. Changes in surface potential are predicted to shape the capacitive properties of the membrane (i.e. the ability of the membrane to store electrical charges). Here, we show that it is possible to detect changes in surface potential by an electrophysiological approach: the analysis of cellular currents relies on assuming that the electrical properties of a cell are faithfully described by a three-element circuit - i.e. the minimal equivalent circuit - comprised of two resistors and one capacitor. However, to account for changes in surface potential it is necessary to add a battery to this circuit connected in series with the capacitor. This extended circuit model predicts that the current response to a square-wave voltage pulse harbors information, which allows for separating the changes in surface potential from a true capacitance change. We interrogated our model by investigating changes in capacitance induced by ligand binding to the serotonin transporter (SERT) and to the glycine transporters (GlyT1 and GlyT2). The experimental observations were consistent with the predictions of the extended circuit. We conclude that ligand-induced changes in surface potential (reflecting the binding event) and in true membrane capacitance (reflecting the concomitant conformational change) can be detected in real time even in instances where they occur simultaneously.Statement of SignificanceThe plasma membrane of a cell possesses fixed charges on both surfaces. Surface charges play an important role in many biological processes. However, the mechanisms, which regulate the surface charge densities at the plasma membrane, are poorly understood. This is in part due to lack of experimental approaches that allow for detecting changes in surface charges in real time. Here, we show that it is possible to track alterations in the electric potential at the membrane surface with high temporal resolution by an electrophysiological approach. Importantly, the described method allows for discriminating between a change in surface potential and a change in true membrane capacitance (e.g. a change in membrane area), even if these occur in parallel.

scholarly journals Changes in Plasma Membrane Surface Potential of PC12 Cells as Measured by Kelvin Probe Force Microscopy

PLoS ONE ◽  
2012 ◽  
Vol 7 (4) ◽  
pp. e33849 ◽  
Author(s):  
Chia-Chang Tsai ◽  
Hui-Hsing Hung ◽  
Chien-Pang Liu ◽  
Yit-Tsong Chen ◽  
Chien-Yuan Pan
Keyword(s):  
Plasma Membrane ◽  
Pc12 Cells ◽  
Surface Potential ◽  
Membrane Surface ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Plasma Membrane Surface

scholarly journals An Electrophysiological Approach to Measure Changes in the Membrane Surface Potential in Real Time

2020 ◽  
Vol 118 (4) ◽  
pp. 813-825
Author(s):  
Verena Burtscher ◽  
Matej Hotka ◽  
Michael Freissmuth ◽  
Walter Sandtner
Keyword(s):  
Real Time ◽  
Surface Potential ◽  
Membrane Surface

scholarly journals The Relationship between Camp, Ca2+, and Transport of Cftr to the Plasma Membrane

2001 ◽  
Vol 118 (2) ◽  
pp. 135-144 ◽  
Author(s):  
Peng Chen ◽  
Tzyh-Chang Hwang ◽  
Kevin D. Gillis
Keyword(s):  
Plasma Membrane ◽  
Membrane Conductance ◽  
Membrane Capacitance ◽  
Capacitance Measurement ◽  
Membrane Turnover ◽  
Open Probability ◽  
Fluorescence Measurements ◽  
Dependent Protein ◽  
A Cell ◽  
The Relationship

The mechanism whereby cAMP stimulates Cl− flux through CFTR ion channels in secretory epithelia remains controversial. It is generally accepted that phosphorylation by cAMP-dependent protein kinase increases the open probability of the CFTR channel. A more controversial hypothesis is that cAMP triggers the translocation of CFTR from an intracellular pool to the cell surface. We have monitored membrane turnover in Calu-3 cells, a cell line derived from human airway submucosal glands that expresses high levels of CFTR using membrane capacitance and FM1–43 fluorescence measurements. Using a conventional capacitance measurement technique, we observe an apparent increase in membrane capacitance in most cells that exhibit an increase in Cl− current. However, after we carefully correct our recordings for changes in membrane conductance, the apparent changes in capacitance are eliminated. Measurements using the fluorescent membrane marker FM1–43 also indicate that no changes in membrane turnover accompany the activation of CFTR. Robust membrane insertion can be triggered with photorelease of caged Ca2+ in Calu-3 cells. However, no increase in Cl− current accompanies Ca2+-evoked membrane fusion. We conclude that neither increases in cAMP or Ca2+ lead to transport of CFTR to the plasma membrane in Calu-3 cells. In addition, we conclude that membrane capacitance measurements must be interpreted with caution when large changes in membrane conductance occur.

scholarly journals Alamethicin channels incorporated into frog node of ranvier: calcium-induced inactivation and membrane surface charges.

1982 ◽  
Vol 79 (3) ◽  
pp. 411-436 ◽  
Author(s):  
M D Cahalan ◽  
J Hall
Keyword(s):  
Lipid Bilayer ◽  
Surface Potential ◽  
Single Channel ◽  
Membrane Surface ◽  
Internal Surface ◽  
Peptide Antibiotic ◽  
Lipid Bilayer Membranes ◽  
Surface Charges ◽  
Myelinated Nerve ◽  
Bilayer Membranes

Alamethicin, a peptide antibiotic, partitions into artificial lipid bilayer membranes and into frog myelinated nerve membranes, inducing a voltage-dependent conductance. Discrete changes in conductance representing single-channel events with multiple open states can be detected in either frog node or lipid bilayer membranes. In 120 mM salt solution, the average conductance of a single channel is approximately 600 pS. The channel lifetimes are roughly two times longer in the node membrane than in a phosphatidylethanolamine bilayer at the same membrane potential. With 2 or 20 mM external Ca and internal CsCl, the alamethicin-induced conductance of frog nodal membrane inactivates. Inactivation is abolished by internal EGTA, suggesting that internal accumulation of calcium ions is responsible for the inactivation, through binding of Ca to negative internal surface charges. As a probe for both external and internal surface charges, alamethicin indicates a surface potential difference of approximately -20 to -30 mV, with the inner surface more negative. This surface charge asymmetry is opposite to the surface potential distribution near sodium channels.

A Journey with Platelet P-Selectin: The Molecular Basis of Granule Secretion, Signalling and Cell Adhesion

2001 ◽  
Vol 86 (07) ◽  
pp. 214-221 ◽  
Author(s):  
Barbara Furie ◽  
Robert Flaumenhaft ◽  
Bruce Furie
Keyword(s):  
Plasma Membrane ◽  
Cell Adhesion ◽  
Secretory Pathway ◽  
Transmembrane Protein ◽  
Membrane Surface ◽  
Leukocyte Accumulation ◽  
Granule Membrane ◽  
A Cell ◽  
Granule Secretion ◽  
Cell Adhesion Receptor

SummaryP-selectin is a transmembrane protein that resides within the alpha granule membrane of unstimulated platelets. The “extracellular” domains face into the lumen of the granule and the cytoplasmic tail extends into the platelet cytoplasm. Upon platelet stimulation, P-selectin is phosphorylated and translocated to the plasma membrane via a secretory pathway. P-selectin in the plasma membrane surface is exposed and serves as a cell adhesion receptor to interact with other cell receptors, including PSGL-1 and GPIb. P-selectin upregulates tissue factor in monocytes and leads to leukocyte accumulation in areas of vascular injury associated with thrombosis and inflammation.

scholarly journals Modulation of potassium channel gating by external divalent cations.

1994 ◽  
Vol 104 (4) ◽  
pp. 675-692 ◽  
Author(s):  
S Spires ◽  
T Begenisich
Keyword(s):  
Surface Potential ◽  
Open Channel ◽  
Divalent Cations ◽  
Membrane Surface ◽  
External Solution ◽  
Trinitrobenzene Sulfonic Acid ◽  
Surface Charges ◽  
K Channels ◽  
Channel Opening ◽  
Common Motif

We have examined the actions of Zn2+ ions on Shaker K channels. We found that low (100 microM) concentrations of Zn2+ produced a substantial (approximately three-fold) slowing of the kinetics of macroscopic activation and inactivation. Channel deactivation was much less affected. These results were obtained in the presence of 5 mM Mg2+ and 4 mM Ca2+ in the external solution and so are unlikely to be due to modification of membrane surface charges. Furthermore, the action of 100 microM Zn2+ on activation was equivalent to a 70-mV reduction of a negative surface potential whereas the effects on deactivation would require a 15-mV increase in surface potential. External H+ ions reduced the Zn-induced slowing of macroscopic activation with an apparent pK of 7.3. Treatment of Shaker K channels with the amino group reagent, trinitrobenzene sulfonic acid (TNBS), substantially reduced the effects of Zn2+. All these results are qualitatively similar to the actions of Zn2+ on squid K channels, indicating that the binding site may be a common motif in potassium channels. Studies of single Shaker channel properties showed that Zn2+ ions had little or no effect on the open channel current level or on the open channel lifetime. Rather, Zn2+ substantially delayed the time to first channel opening. Thus, K channels appear to contain a site to which divalent cations bind and in so doing act to slow one or more of the rate constants controlling transitions among closed conformational states of the channel.

scholarly journals Plasma Membrane Surface Potential: Dual Effects upon Ion Uptake and Toxicity

2010 ◽  
Vol 155 (2) ◽  
pp. 808-820 ◽  
Author(s):  
Peng Wang ◽  
Thomas B. Kinraide ◽  
Dongmei Zhou ◽  
Peter M. Kopittke ◽  
Willie J.G.M. Peijnenburg
Keyword(s):  
Plasma Membrane ◽  
Surface Potential ◽  
Membrane Surface ◽  
Ion Uptake ◽  
Plasma Membrane Surface

scholarly journals A combinatorial lipid code shapes the electrostatic landscape of plant endomembranes

2018 ◽  
Author(s):  
Matthieu Pierre Platre ◽  
Mehdi Doumane ◽  
Vincent Bayle ◽  
Mathilde Laetitia Audrey Simon ◽  
Lilly Maneta-Peyret ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Lipid Composition ◽  
Intracellular Trafficking ◽  
Membrane Surface ◽  
Endocytic Pathway ◽  
Surface Charges ◽  
Membrane Electrostatics ◽  
Phosphatidylinositol 4 ◽  
Membrane Surface Charge ◽  
Cellular Organelles

AbstractMembrane surface charge is critical for the transient, yet specific recruitment of proteins with polybasic regions to certain organelles. In all eukaryotes, the plasma membrane (PM) is the most electronegative compartment of the cell, which specifies its identity. As such, membrane electrostatics is a central parameter in signaling, intracellular trafficking and polarity. Here, we explore which are the lipids that control membrane electrostatics using plants as a model. We show that phosphatidic acidic (PA), phosphatidylserine (PS) and phosphatidylinositol-4-phosphate (PI4P) are separately required to generate the electrostatic signature of the plant PM. In addition, we reveal the existence of an electrostatic territory that is organized as a gradient along the endocytic pathway and is controlled by PS/PI4P combination. Altogether, we propose that combinatorial lipid composition of the cytosolic leaflet of cellular organelles not only defines the plant electrostatic territory but also distinguishes different compartments within this territory by specifying their varying surface charges.

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