Electrophysiological Response of Cultured Trabecular Meshwork Cells to Synthetic Ion Channels

Abstract

The response of living cells of the trabecular meshwork to synthetic ion channels is described. The THF-gramicidin hybrids THF-gram and THF-gram-TBDPS as well as a linked gA-TBDPS and gramicidin A were applied to cultured ocular trabecular meshwork cells. THF-gram application (minimal concentration, 10(-8) M; saturation, 10(-7) M) led to an additional conductance which displayed characteristics of weak Eisenman-I-selective cation channels, no cell destruction, an asymmetric change of the inward/outward currents, and higher current densities using Cs(+) as charge carrier compared to Na(+) and K(+). Linked-gA-TBDPS showed at 10(-12) M increases of the membrane conductance comparable to gA at 10(-7) M and a much faster response of the cells. Thus, THF-gramicidin hybrids form a basis for the use of synthetic ion channels in biological systems, which eventually may lead to new therapeutic approaches.

Recent synthetic ion channels and pores

“…In trabecular meshwork cells, THF-peptides 36 and 37 cause, similar to gramicidin, some depolarization and a shift of the reversal potential toward zero. 90 In ion channel 38, only amino acids 11 and 12 of the succinyl-bridged, hydrophobically capped gramicidin 32 are replaced by one artificial L-THF-d-amino acid. 91 In ion channel 39, a D-THF-d-amino acid replaces amino acids 10 and 11.…”

“…Synthetic ion channels and pores formed by ionophoric(85,86), 'smart'(88,89) and cationic(90)(91)(92)(93)(94)(95)(96)(97)(98)(99)(100)(101)(102)(103)(104)(105) polymers of interest as antibiotics(90 -105) and for drug delivery with triggered endosomal escape(88,89).…”

Functional Studies of Synthetic Gramicidin Hybrid Ion Channels in CHO Cells

“…So far, only a few studies have been published that investigate the electrophysiological properties of synthetic ion‐channel‐forming compounds in living cells 11. 12, 14, 15 The main goals of these studies were to examine whether these compounds decrease cell viability, to show predictable functional ion‐channel properties, and to evaluate whether these compounds interfere with endogenously expressed ion channels. In one study, the influence of a compound that functioned as synthetic Cl − channel on cell function was reported 16.…”

“…Gramicidin A (gA) with its channel‐active β 6,3 helix is a well‐suited structural motif for synthetic modifications (Figure 1) 18. 19 In an earlier patch clamp study, we used THF–gramicidin hybrid channels,15, 20, 21 which increased the membrane conductance in smooth‐muscle‐like cells without disturbing the cellular ion homeostasis or destroying the cell 15. The currents elicited by the presence of THF–gramicidin channels showed the predicted weak Eisenman I selectivity.…”

A Voltage‐Responding Ion Channel Derived by C‐Terminal Modification of Gramicidin A

“…In a continuation of our studies on the implantation of synthetic gramicidin-hybrid channels into cells (trabecular meshwork cells, [5] CHO cells [6] ), we turned to synthetic voltage-gated channels. Terminal-charged amphiphilic compounds, [7] can self-assemble into voltage-dependent pores and rigid push-pull rods [8] with permanent axial macrodipoles to give voltage-sensitive pores.…”