Voltage-dependent channels

Many different voltage-dependent channels have been analyzed, and have... 

Taste cells have multiple types of ion channels. TRCs are electrically excitable and capable of generating action-potentials voltage-dependent channels for Na+, Ca2+ and K+, similar to those in neurons, have been detected in vertebrate TRCs. The surface distribution of these channels... 

Bolton-. The SR normally underlies the rows of caveolae. Between those are the dense bars where the contractile proteins are attached. It seems likely that the caveolae contain receptors and channels, and that the SR occurs under the voltage-dependent channels. 

An alternative approach is to use antibody fragments (the Fab domian) raised against a particular protein. This technique has been used with some success for crystallizing a number of membrane proteins, including the CIC chloride channel (Dutzler et al., 2002), a K+ voltage-dependent channel (Jiang et al., 2003), and a cytochrome c oxidase (Iwata et al., 1995). 

Due to the increase in the membrane potential, voltage-dependent channels open and IC ions flow out. In addition, Na" / IC ATPase (see A) pumps the Na+ ions that have entered back out again. This leads to repolarization of the membrane. 

A circuit that uses a differential amplifier to maintain constant membrane potential by electronically balancing the ion channel current. This method allows the experimenter to analyze action potentials of excitable membranes resulting from an initial transient rise in sodium ion permeability followed by a transient rise in potassium ion permeability The technique is especially valuable for studying kinetic properties of voltage-gated channels as well as voltage-dependent channels. See Membrane Potential Patch Clamp Methods... 

Available evidence suggests that a single unifying mechanism does not exist but rather that various vasodilators may act at different places in the series of processes that couple excitation of vascular smooth muscle cells with contraction. For example, the vasodilators known as calcium channel antagonists block or limit the entry of calcium through voltage-dependent channels in the membrane of vascular smooth muscle cells. In this way, the calcium channel blockers limit the amount of free intracellular calcium available to interact with smooth muscle contractile proteins (see Chapter 14). 

Figure 7. Schematic representation for the formation of supramolecular channel 4 from lipid units 2. A relatively hydrophilic synthetic lipid component of oligoether structure 2a-d is combined with appropriate counter ion having two hydrophobic alkyl chains 2e-g to make doubly amphiphilic synthetic lipid 2. Combinations 2c-2e and 2d-2g afforded voltage dependent channels as will be described later.

Potassium ion channels are a veiy diverse family of membrane proteins, with numerous sub-types both in the CNS and peripheral tissues, in particular in the heart. On the basis of the amino acid sequence of the pore-forming a sub-unit, they are classified into two main super-families, the inward rectifier superfamily (which includes receptor-coupled, adenosine 5 -triphosphate (ATP)-sensitive and voltage-dependent channels) and the Sha/cer-related superfamily (which includes Ca2-H-dependent channels). 

The existence of voltage-gated ion channels in bilayers are not limited to nerve membranes. They are present to some extent in all cell membranes. Even the paramecium has at least seven kinds of Na+, K+, and Ca2+ channels.483 Channels may also be formed by many peptide antibiotics. Among them are the human defensins (Chapter 31) and the 20-residue alamethi-cin. Six to eleven of the mostly helical monomers of that antibiotic assemble to form a single voltage-dependent channel.4844843 The bacterial toxin colicin El (Box 8-D) forms voltage-dependent channels within bacterial membranes.485... 

G402S- TS near complete loss of voltage-dependent channel inactivation (Splawski... 

Serum withdrawal affects the expression of plasma membrane calcium channels in diverse ways. Voltage-dependent calcium channels have their expression increased in the absence of serum in the culture medium (Ihara, et al., 2002, Kushmerick, et al., 2001, Patel, et al., 2005), whereas non voltage-dependent channels are down regulated (Golovina, 1999, Golovina, et al., 2001, Sweeney, et al., 2002, Yu, et al., 2004, Yu, et al., 2003). 

Trautmann, A., Delaporte, C., and Marty, A., 1986, Voltage-dependent channels of human muscle cultures, Pflugers Arch, 406, pp 163-172. 

Amphotericin B Voltage-dependent channel maker in cell membrane... 

In the calyx of Held synapse in the auditory brainstem of rats the 5-HTib receptor inhibition of glutamate release was fully explained by inhibition of Ca2+ entry through voltage-dependent channels (Mizutani et al. 2006). In rat nucleus accumbens, in contrast, the analogous 5-HTib effect did not involve inhibition of Ca2+ channels (Muramatsu et al. 1998). In rat amygdala, the 5-HTia inhibition operated via a cyclic AMP pathway and apparently inhibition of Ca2+ entry an unexplained observation was the failure of pertussis toxin to abolish the 5-HTia inhibition (Cheng et al. 1998). 

Na K -ATPase Voltage Dependent Channel Ligand Gated Channel... 

Depolarization of vascular smooth muscle activates the L-type calcium channels, which results in increased cytosolic concentrations of calcium and hence increased tone. Calcium channel blockers (e.g., verapamil and diltiazem) block the influx of calcium through the L-type voltage-dependent channels located on vascular smooth muscle and cardiac muscle cells as well as cardiac nodal cells. Therefore, they are used in the treatment of angina, hypertension, and certain arrhythmias. 

Modulatory effects may be postsynaptically mediated by interactions within the spiny projection neurons, or involve presynaptic regulation of neurotransmitter release from corticostriatal terminals. Postsynaptic effects may be mediated by direct actions of intracellular signaling pathways (cAMP, calcineurin) on receptor status (phosphorylation/ dephosphorylation of receptor proteins), and actions on voltage-dependent channels, which may amplify or attenuate the electrical response of the cell to synaptic currents. 

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