A synthetic, chloride-selective channel that alters chloride transport in epithelial cells

Abstract

An Ussing chamber was used to demonstrate that synthetic amphiphilic anion transporters function as chloride transporters in mammalian airway epithelial cells.Proteins are generally required for the transport of ionic and molecular species through bilayer membranes. Because these proteins are both critical and complex, bioorganic chemists have devised a variety of functional model systems. Two decades ago, synthetic ion channels were virtually unknown, but several worthy examples have emerged recently. 1 In our laboratory, we have designed and characterized structurally different families of synthetic cation-2 and anion-selective 3 channels. We refer to the former as hydraphiles; 4 this family of cation channels is now well characterized. The cation channels incorporate macrocyclic "crown" polyethers and are thought to function as monomers within the bilayer. In contrast, the anion channels developed in our laboratory are amphiphilic peptides 3,5,6,7 that function, at least in some cases, as dimers. 8 The active molecules have the general structure (R 1 ) 2 NCOCH 2 OCH 2 CO-(Gly) 3 Pro(Gly) 3 -OR 2 . Extensive structural variation 5-7 and selectivity studies 9 have been conducted in liposomes.Vectorial ion transport across lung epithelial cell layers is essential for homeostasis in multicellular organisms and disruption of this process is pathological. 10,11 Epithelial cell layers control mass transport of water and solutes in alimentary, pulmonary, renal, and a variety of secretory organs. Anion regulation is critical in the function of epithelial layers. We now report that a synthetic anion channel, based on the general structure shown above, mediates anion regulation in airway epithelial cells.The preparation of (H 37 C 18 ) 2 NCOCH 2 OCH 2 CO-(Gly) 3 -Pro(Gly) 3 -OCH 2 Ph, 1, has been reported. 5 The ca. six-fold less effective variant, (H 37 C 18 ) 2 NCOCH 2 OCH 2 CO-(Gly) 3 Leu (Gly) 3 -OCH 2 Ph, 2 ,3 was chosen as a control. When 1 was added to DOPC-DOPA (7 : 3) liposomes containing chloride ion, an increase in Cl -permeability was observed. Compound

Structural and biophysical properties of a synthetic channel-forming peptide: Designing a clinically relevant anion selective pore

“…An alternative to existing therapies could be the use of synthetic channel-forming peptides (CFPs), which would generate an ion-conducting pore with the appropriate CFP selectivity in appropriate tissues. CFPs can be de novo sequences [9, 10] or based on segments of native proteins. The use of chemistry to design compounds corresponding to putative transmembrane regions of natural proteins yields detectable channel activities of CFPs in planar lipid bilayers [11–13] and human erythrocyte membranes [14].…”

Artificial Anion Transporters in Bilayer Membranes

“…However, the higher activity is counterbalanced by a partial loss of anion selectivity. Biological studies [42] using an Ussing chamber demonstrate that chloride transport across mouse trachea epithelial cells is stimulated by the action of 1, which appears to activate a new pathway for the transport of the anion. Again, the role of the proline residue is fundamental and an analogue with a leucine substituting the central proline does not show activity.…”

Supramolekulare Chemie von Anionen: von der Erkennung zur chemischen Anwendung

“…[214] Außerdem wurde (anhand von "Ussing-Chamber"-Experimenten) gezeigt, dass einige Verbindungen den Anionentransport in Epithelzellen beeinflussen. [215] Verhältnismäßig . [216] Nachfolgend berichtete dieselbe Gruppe über Calix [4]arene, die teilweise [217] oder vollständig [218] in Kegelkonformationen vorlagen, die ebenfalls Ionenkanäle für dasselbe Ionenpaar bilden.…”