Functional Properties of Ca2%2b-Dependent Cl- Channels and Bestrophins: Do They Correlate?

Calcium-dependent chloride channels (CaCCs) play an important role in numerous physiological processes including electrolyte and water secretion, sensory transduction, and regulation of neuronal and cardiac excitability, as well as vascular tone. In spite of this, the molecular domains that bestow sensitivity to intracellular calcium ([Ca2%2b]i), voltage (Vm) and second messengers, as well as domains that participate in CaCC gating are still unknown. Characterization of these domains awaits the discovery of a gene (or genes) that when expressed in heterologous systems will recapitulate key functional properties of CaCCs observed in native cells. Thus, findings that point out the bestrophin family as molecular candidates for CaCCs have been received with interest. However, there are many properties of CaCCs that have been studied in endogenous channels that are not yet characterized in bestrophins. In this chapter, we will review the functional properties (activation, kinetics, permeation, ion selectivity, pharmacology, and regulation) of CaCCs and bestrophins in an attempt to highlight the similarities and differences between these two families of chloride (Cl-) channels. © 2007 Elsevier Inc. All rights reserved.

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