Insight into the Structure-Function Relation of Chloride Channels

Abstract

Chloride channels are highly selective transport proteins ubiquitously expressed in eukaryotic cells. Biophysical methods allow discrimination between several different types of chloride channels with respect to their gating properties, single-channel conductances and main regulatory mechanisms. The common feature is, however, their high selectivity for chloride ions. Beside the cystic fibrosis transmembrane conductance regulator and ligand-gated channels, five different protein families involved in chloride transport have so far been described in terms of their molecular structure. All of them show distinct structural characteristics and, according to mutation experiments, are believed to be genuine channels.

Glucose and a-ketoisocaproate induce transient inward currents in rat pancreatic beta cells

“…The finding that the nutrient-induced transient inward currents closely resembled currents elicited during hypotonically induced cell swelling raises the possibility that these currents arise from activation of a volume-sensitive conductance, possibly the anion conductance recently described in beta-cells [14][15][16]. This possibility is further supported by the finding that the effects of nutrients on electrical activity and whole cell current were inhibited by DIDS and NPPB, inhibitors of this conductance [15,17], although the selectivity of these compounds is at present uncertain. In view of this suggestion, it is of interest that glucose has been reported to stimulate the efflux of 36 …”

“…This current pattern contrasts with the more sustained inward current observed upon exposure to a larger (30 %) hypotonic shock [14] and suggests that transient currents could be carried by a swelling-activated anion conductance, recently described in insulin-secreting cells [14][15][16]. In order to further investigate this possibility, nutrientstimulated beta-cells were exposed to two inhibitors of this conductance, 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS, 100 m mol/l) and NPPB, 50 m mol/l [15,17]. As shown in Figure 6, both compounds caused repolarization of beta-cells and abolished the transient inward currents.…”

Cloning and functional expression of a plant voltage-dependent chloride channel.

“…This contrasts with the different classes of anion channel proteins that have been identified in animals (Paulmich et al, 1993). Among these, the family of voltage-dependent chloride channels or CIC family has received much attention (Jentsch et al, 1995).…”

Determination of Protein-Protein Interactions of ICln by the Yeast Two-Hybrid System

“…ICln was originally cloned from MDCK (MadinDarby canine kidney) -cells, and the expression of the ICln protein in Xenopus laevis oocytes led to a chloride current [3] whose kinetics, pharmacology and ion selectivity are similar to that of swelling-activated channels (SAC) [4]. SAC are present in many different cells [5,6], their activation helps the cells to regain the cytoplasmatic volume after swelling -a process termed regulatory volume decrease (RVD) [7].…”