Voltage-gated Cl- channel

Table 4.5 CFTR, voltage-gated Cl channels and Na+—K+—2C1 co-transporter...

Schroeder Cl, Smythe ML, Lewis RJ. (2004) Development of small mole-cnles that mimic the binding of co-conotoxins at the A-type voltage-gated calcinm channel. Mol Divers 8 127-134. 

When comparing transmitter-gated ion channels on a functional level, one can discern between anion and cation channels. The former ones comprise the GABAa and glycine receptors, which display a rank order of anion selectivity of I- > Hr > Cl- and which are also permeable to HC()3. All other ionotropic receptors mentioned here are cation channels, which discriminate rather poorly between various monovalent cations, at least when compared with voltage-gated ion channels. Some... 

Ion channels are essential for a wide range of functions such as neurotransmitters secretion and muscle contraction. Ion channels mediate Na, Ca +, and Cl conductance induced by membrane potential changes. These channels propagate action potentials in excitable cells and are also involved in the regulation of membrane potential and intracellular Ca + transients in most eukaryotic cells. About 300 genes code for subunits of voltage-gated ion channels. 

G protein-coupled receptors (e.g., (5-adrenergic receptor) Glucose transporters (e.g., GLUT1) Voltage-gated Ca2+ channels ABC small molecule pumps CFTR (Cl ) channel Sec61 Connexin... 

Qiou CL, Shirahata M. Two types of voltage-gated K channels in carotid body cells of adult cats. Brain Res 1996 742(l-2) 34-42. 

Synaptic Transmission. Figure 1 Synaptic transmission. The presynaptic terminal contains voltage-dependent Na Superscript and Ca2+ channels, vesicles with a vesicular neurotransmitter transporter VNT, a plasmalemmal neurotransmitter transporter PNT, and a presynaptic G protein-coupled receptor GPCR with its G protein and its effector E the inset also shows the vesicular H+ pump. The postsynaptic cell contains two ligand-gated ion channels LGIC, one for Na+ and K+ and one for Cl-, a postsynaptic GPRC, and a PNT. In this synapse, released transmitter is inactivated by uptake into cells. 

Other neuronal Cl -channels are Ca " -controlled. Increases in cytosolic Ca enhances the probability of these channels being open [26,27]. These channels stabilize the membrane voltage by clamping it towards the Cl -equilibrium potential. Such channels have been found, e.g., in cultured mouse spinal neurones and in molluscan neurones. They subserve the repolarization phenomena and hence assist Ca -activated -channels. Their conductance is in the small to intermediate range. They are usually gated by depolarization. 

Another way the SR might modulate excitability in the uterus is via Ca2+-activated Cl- (ClCa) channels. The evidence for ClCa in the uterus is limited but Arnaudeau et al (1994b) showed that oxytocin in rat cells appeared able to stimulate these channels, and we also find their activation via voltage-gated Ca2+ entry (K. Jones, A.V. Shmigol S. Wray, unpublished observation). 

Recently, Cl" channels have been discovered. These channels have no sequence relationship to the voltage-gated Na, and Ca channels. One such channel is involved in the disease, cystic fibrosis. In this disease, regulation of the channel is defective. The altered function of the channel in epithelia causes elevated levels of sodium and chloride ions in sweat and, through unknown processes, the accumulation of mucus in the respiratory tract and failure of exocrine secretion in glands, such as the pancreas. Blockage of airways leads to chronic lung infections that, with other effects of the Cl" transport deficiency, can be fatal. 

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