scholarly journals Electrophysiological Properties of Ion Channels in Ascaris suum Tissue Incorporated into Planar Lipid Bilayers

2021 ◽  
Vol 59 (4) ◽  
pp. 329-339
Author(s):  
Kwon Moo Park ◽  
Sun-Don Kim ◽  
Jin Bong Park ◽  
Sung-Jong Hong ◽  
Pan Dong Ryu
Keyword(s):  
Ion Channels ◽  
Lipid Bilayers ◽  
Drug Targets ◽  
Ascaris Suum ◽  
Anion Channel ◽  
Cation Channel ◽  
Planar Lipid Bilayers ◽  
Ionic Selectivity ◽  
Voltage Range ◽  
Electrophysiological Properties

Ion channels are important targets of anthelmintic agents. In this study, we identified 3 types of ion channels in Ascaris suum tissue incorporated into planar lipid bilayers using an electrophysiological technique. The most frequent channel was a large-conductance cation channel (209 pS), which accounted for 64.5% of channels incorporated (n=60). Its open-state probability (Po) was ~0.3 in the voltage range of –60~+60 mV. A substate was observed at 55% of the main-state. The permeability ratio of Cl- to K+ (PCl/PK) was ~0.5 and PNa/PK was 0.81 in both states. Another type of cation channel was recorded in 7.5% of channels incorporated (n=7) and discriminated from the large-conductance cation channel by its smaller conductance (55.3 pS). Its Po was low at all voltages tested (~0.1). The third type was an anion channel recorded in 27.9% of channels incorporated (n=26). Its conductance was 39.0 pS and PCl/PK was 8.6±0.8. Po was ~1.0 at all tested potentials. In summary, we identified 2 types of cation and 1 type of anion channels in Ascaris suum. Gating of these channels did not much vary with voltage and their ionic selectivity is rather low. Their molecular nature, functions, and potentials as anthelmintic drug targets remain to be studied further.

scholarly journals Microfabricated Teflon Membranes for Low-Noise Recordings of Ion Channels in Planar Lipid Bilayers

2003 ◽  
Vol 85 (4) ◽  
pp. 2684-2695 ◽  
Author(s):  
Michael Mayer ◽  
Jennah K. Kriebel ◽  
Magdalena T. Tosteson ◽  
George M. Whitesides
Keyword(s):  
Ion Channels ◽  
Lipid Bilayers ◽  
Low Noise ◽  
Planar Lipid Bilayers

Formation of ion channels by Colicin B in planar lipid bilayers

1990 ◽  
Vol 114 (1) ◽  
pp. 79-95 ◽  
Author(s):  
J. O. Bullock ◽  
S. K. Armstrong ◽  
J. L. Shear ◽  
D. P. Lies ◽  
M. A. McIntosh
Keyword(s):  
Ion Channels ◽  
Lipid Bilayers ◽  
Planar Lipid Bilayers ◽  
Colicin B

scholarly journals Cation channel conductance and pH gating of the innate immunity factor APOL1 are governed by pore-lining residues within the C-terminal domain

2020 ◽  
Vol 295 (38) ◽  
pp. 13138-13149 ◽  
Author(s):  
Charles Schaub ◽  
Joseph Verdi ◽  
Penny Lee ◽  
Nada Terra ◽  
Gina Limon ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Plasma Membrane ◽  
Lipid Bilayers ◽  
Cation Channel ◽  
Planar Lipid Bilayers ◽  
Channel Formation ◽  
Cation Selectivity ◽  
Terminal Domain ◽  
Immunity Factor ◽  
Pore Lining

The human innate immunity factor apolipoprotein L-I (APOL1) protects against infection by several protozoan parasites, including Trypanosoma brucei brucei. Endocytosis and acidification of high-density lipoprotein–associated APOL1 in trypanosome endosomes leads to eventual lysis of the parasite due to increased plasma membrane cation permeability, followed by colloid-osmotic swelling. It was previously shown that recombinant APOL1 inserts into planar lipid bilayers at acidic pH to form pH-gated nonselective cation channels that are opened upon pH neutralization. This corresponds to the pH changes encountered during endocytic recycling, suggesting APOL1 forms a cytotoxic cation channel in the parasite plasma membrane. Currently, the mechanism and domains required for channel formation have yet to be elucidated, although a predicted helix-loop-helix (H-L-H) was suggested to form pores by virtue of its similarity to bacterial pore-forming colicins. Here, we compare recombinant human and baboon APOL1 orthologs, along with interspecies chimeras and individual amino acid substitutions, to identify regions required for channel formation and pH gating in planar lipid bilayers. We found that whereas neutralization of glutamates within the H-L-H may be important for pH-dependent channel formation, there was no evidence of H-L-H involvement in either pH gating or ion selectivity. In contrast, we found two residues in the C-terminal domain, tyrosine 351 and glutamate 355, that influence pH gating properties, as well as a single residue, aspartate 348, that determines both cation selectivity and pH gating. These data point to the predicted transmembrane region closest to the APOL1 C terminus as the pore-lining segment of this novel channel-forming protein.

Cation channels from Tetrahymena cilia incorporated into planar lipid bilayers

1985 ◽  
Vol 249 (1) ◽  
pp. C177-C179 ◽  
Author(s):  
Y. Oosawa ◽  
M. Sokabe
Keyword(s):  
Lipid Bilayers ◽  
Single Channel ◽  
Cation Channel ◽  
Cation Channels ◽  
Planar Lipid Bilayers ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
Ciliary Membrane ◽  
Voltage Dependent

A single cation channel from Tetrahymena cilia was incorporated into planar lipid bilayers. This channel selected for K+, Na+, and Li+ over Cl- and gluconate-, and its single channel conductance (at +25 mV) was 211 +/- 8 pS (mean +/- SE) in 100 mM K+-gluconate. The channel was not voltage dependent and may contribute to the resting K+ conductance of ciliary membrane.

scholarly journals Batrachotoxin-activated Na+ channels in planar lipid bilayers. Competition of tetrodotoxin block by Na+.

1984 ◽  
Vol 84 (5) ◽  
pp. 665-686 ◽  
Author(s):  
E Moczydlowski ◽  
S S Garber ◽  
C Miller
Keyword(s):  
Lipid Bilayers ◽  
Membrane Vesicles ◽  
Receptor Site ◽  
Single Channels ◽  
Planar Lipid Bilayers ◽  
Na Channels ◽  
Plasma Membrane Vesicles ◽  
Voltage Range ◽  
Conduction Pathway ◽  
Almost All

Single Na+ channels from rat skeletal muscle plasma membrane vesicles were inserted into planar lipid bilayers formed from neutral phospholipids and were observed in the presence of batrachotoxin. The batrachotoxin-modified channel activates in the voltage range -120 to -80 mV and remains open almost all the time at voltages positive to -60 mV. Low levels of tetrodotoxin (TTX) induce slow fluctuations of channel current, which represent the binding and dissociation of single TTX molecules to single channels. The rates of association and dissociation of TTX are both voltage dependent, and the association rate is competitively inhibited by Na+. This inhibition is observed only when Na+ is increased on the TTX binding side of the channel. The results suggest that the TTX receptor site is located at the channel's outer mouth, and that the Na+ competition site is not located deeply within the channel's conduction pathway.

scholarly journals Ion channels formed in planar lipid bilayers byBacillus thuringiensistoxins in the presence ofManduca sextamidgut receptors

FEBS Letters ◽  
1997 ◽  
Vol 412 (2) ◽  
pp. 270-276 ◽  
Author(s):  
Jean-Louis Schwartz ◽  
Yiang-Jiang Lu ◽  
Petra Söhnlein ◽  
Roland Brousseau ◽  
Raynald Laprade ◽  
...  
Keyword(s):  
Ion Channels ◽  
Lipid Bilayers ◽  
Planar Lipid Bilayers
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