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Originally published In Press as doi:10.1074/jbc.R700022200 on July 2, 2007

J. Biol. Chem., Vol. 282, Issue 34, 24485-24489, August 24, 2007
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A Marriage of Convenience: beta-Subunits and Voltage-dependent K+ Channels*

Yolima P. Torres{ddagger}§, Francisco J. Morera{ddagger}1, Ingrid Carvacho{ddagger}1, and Ramon Latorre{ddagger}2

From the {ddagger}Department of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 5110246, Chile, §Escuela de Ciencias Básicas, Facultad de Salud, Universidad del Valle, Cali, Colombia, and Universidad Austral de Chile, Valdivia 5099200, Chile


    ABSTRACT
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
The movement of ions across cell membranes is essential for a wide variety of fundamental physiological processes, including secretion, muscle contraction, and neuronal excitation. This movement is possible because of the presence in the cell membrane of a class of integral membrane proteins dubbed ion channels. Ion channels, thanks to the presence of aqueous pores in their structure, catalyze the passage of ions across the otherwise ion-impermeable lipid bilayer. Ion conduction across ion channels is highly regulated, and in the case of voltage-dependent K+ channels, the molecular foundations of the voltage-dependent conformational changes leading to the their open (conducting) configuration have provided most of the driving force for research in ion channel biophysics since the pioneering work of Hodgkin and Huxley (Hodgkin, A. L., and Huxley, A. F. (1952) J. Physiol. 117, 500–544). The voltage-dependent K+ channels are the prototypical voltage-gated channels and govern the resting membrane potential. They are responsible for returning the membrane potential to its resting state at the termination of each action potential in excitable membranes. The pore-forming subunits ({alpha}) of many voltage-dependent K+ channels and modulatory beta-subunits exist in the membrane as one component of macromolecular complexes, able to integrate a myriad of cellular signals that regulate ion channel behavior. In this review, we have focused on the modulatory effects of beta-subunits on the voltage-dependent K+ (Kv) channel and on the large conductance Ca2+- and voltage-dependent (BKCa) channel.


    General Properties of Kv and BKCa Channels
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
Voltage-dependent K+ channels are tetrameric channels (reviewed in Ref. 2), with each {alpha}-subunit containing a voltage sensor and contributing to the central pore. This pore is formed by four {alpha}-subunits that encircle a central ion conduction pathway. K+ channels can be recognized by certain common features like the pore-lining P-loops, which have a consensus amino acid sequence, -TXGYGD-, called the K+-channel "signature sequence" (3). The Kv channel {alpha}-subunit contains six transmembrane regions (TM3; S1–S6), with both N and C termini on the intracellular side of the membrane (a tetrameric 6TM architecture). Although conserving the general structure of Kv channels (i.e. they have a voltage sensor (S1–S4) and pore modules (S5-P-S6)), BKCa channels are an exception inside the S4 superfamily of ion channels. BKCa channels contain seven transmembrane segments (S0–S6) with the N terminus facing the extracellular side (reviewed in Ref. 4). The S4 segment of Kv and BKCa channels contains positively charged amino acids (Arg or Lys) at every third position and is part of the voltage sensor responsible for voltage-dependent gating (1) (reviewed in Ref. 5).

Potassium channels may be considered the guardians of the cellular electrical homeostasis, and thus K+ channel diversity is of great importance in determining the variety of electrical responses of cells when subjected to stimuli. The possible mechanisms that originate the immense voltage-dependent K+ channel diversity are: (a) multiple genes, (b) alternative splicing, (c) formation of heteromultimeric channels, and (d) co-expression with accessory subunits.


    beta-Subunits of Kv Channels
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
Kv channel properties can be modified by accessory proteins that regulate their channel gating and/or subcellular distribution (reviewed in Ref. 6). Thebeta-subunits of Kv channels (Kvbeta) are cytoplasmic proteins that have a mass of ~40 kDa. The proteins beta1, beta2, and beta3 are coded by different genes, and additional variability is produced by alternative splicing on the N-terminal region (7, 8). The Kv beta-subunits form a tetrameric structure and are associated in 1:1 ratio with the {alpha}-subunit (9, 10) (Fig. 1A).


    Kv beta-Subunits Modify the Biophysical Properties of Kv Channels
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
Two main types of inactivating Kv channels have been described: 1) delayed rectifiers showing slow (second time scale) inactivation and 2) rapidly inactivating (A-type) Kv channels (reviewed in Ref. 7). The co-expression of some Kv beta-subunits with Kv{alpha} changes the inactivation kinetics in slow inactivating channels, inducing a fast A-type inactivation (11). In addition, these subunits regulate the surface expression and voltage sensitivity of Kv1 channels (reviewed in Ref. 6; see below).

Kvbeta1.1 binds to the N terminus of the Kv1 subfamily but not to Kv2, Kv3, or Kv4, indicating that Kvbeta1 interaction with Kv{alpha} channels is restricted to Kv1 family members. The Kv beta1.1-subunit modifies the rate of inactivation in delayed rectifier channels like Kv1.4, but the voltage dependence of this process remains unchanged (8, 11). Similar to Kvbeta1.1, the Kv beta1.2- and Kvbeta1.3-subunits accelerate inactivation in Kv1.4 (12) and induce inactivation in non-inactivating Kv1.1 and Kv1.5 channels (11). Both Kv beta1.1- and Kvbeta1.2-subunits produce a left-ward shift of the conductance-voltage curves of Kv1.5 channels and increase the rate of inactivation (13). In addition, Kvbeta1.3 slows deactivation and modifies the Kv1.5 response to PKA activation. Kv beta1.3-subunit contains consensus sites for phosphorylation by PKA that induces a response to kinase activation, slowing fast inactivation of the channel. Kvbeta2 is unable to induce N-type inactivation by itself, but it increases the rate of inactivation. This subunit also induces an increase in the rate of activation of Kv1.4 channels without any appreciable change in the voltage dependence of activation gating. When co-expressed with Kv1.5, Kvbeta2 accelerates inactivation and induces a shift in the activation threshold toward hyperpolarizing potentials (14).


Figure 1
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FIGURE 1.
Structural topology of Kv and BKCa channels and their beta-subunits. A, Kv channels have four similar or identical {alpha}-subunits, each of which has six transmembrane segments (S1–S6). Kv1 channels have cytoplasmic beta-subunits that interact with the N-terminal T1 domains. Structure of Kvbeta2 is shown (from Ref. 19). B, proposed topology of {alpha}- and beta-subunits of BKCa. The channel is formed by four {alpha}-subunits and probably four beta-subunits. Structure of ball-and-chain domains of BKCabeta2 is shown (from Ref. 28).

 

    Kv beta-Subunit Pharmacology
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
The {alpha}-dendrotoxin ({alpha}-DTX) block a class of fast inactivating aminopyridine-sensitive K+ channels. By sedimentation analysis of {alpha}-DTX acceptors isolated from bovine cortex, two species are identified: a large subunit ({alpha}) and a "novel" subunit (beta) (9). The Kv beta-subunits have been related with changes in blockade induced by anesthetics. Bupivacaine induces internal and external blockade in the Kv{alpha}1.5 channels. The internal blockade induced by bupivacaine decreases (~4-fold) when Kv{alpha}1.5 is assembled with Kvbeta1.3. Quinidine is also less potent (~8-fold) in blocking channels formed by Kv{alpha}1.5/Kvbeta1.3 than channels consisting only of{alpha}-subunits (15). In dorsal root ganglion neurons, the Kvbeta1-subunit decreased the Kv1.1 sensitivity to the local anesthetic n-butyl-p-aminobenzoate used in treatment of chronic pain (16).


    Structure and Redox Properties of Kv beta-Subunit
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
The structure of the isolated Kvbeta1 N terminus (amino acids 1–62) was solved using NMR spectroscopy (17). The N terminus of Kvbeta1.1 does not exhibit a well defined, unique, three-dimensional structure, indicating a fast conformational equilibrium between weakly structured substrates. The lack of a well defined structure can be an advantage in view of the long trajectory that is followed by the N terminus before reaching its blocking site (10, 18). The crystallization of the Kv beta2-subunit showed that it forms a 4-fold symmetric tetramer composed of four triose-phosphate isomerase barrels, each having eight parallel beta-strands that form a central core and intervening{alpha}-helices encircling the perimeter of the barrel (19). At the front face of each Kv beta2-subunit, there is a tightly bound NADP+ molecule. The crystal structure of the Kv1.2 channel in complex with the Kv beta2-subunit shows that the N terminus of the Kv1.2 {alpha}-subunit forming the T1 domain is like a docking platform for the Kv beta2-subunit (10). As observed in the isolated structure of the Kv beta2-subunit (19), the active site contains an NADP+ cofactor and catalytic residues for the hydride transfer. Therefore, Kv beta-subunits can be important for catalytic function behaving as a redox sensor and allowing direct coupling of membrane electrical activity to the redox state of the cell (2022). Some of the main properties of Kv beta-subunits are summarized in Table 1.


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TABLE 1
Summary of principal functions and tissue expression of Kvbeta and BKCabeta subunits

 

    beta-Subunits of BKCa Channels
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
Regulatory beta-subunits of BKCa channels (BKCabeta) contain 191–235 amino acids sharing a predicted membrane topology, with the N and C termini oriented toward the cytoplasm (Fig. 1B). They have two putative TM segments connected by a 112–123-residue extracellular "loop" that contains three or four putative glycosylation sites and disulfide linkages arising from conserved cysteine residues (23). At present, four BKCa beta-subunits have been cloned in mammals (beta1–beta4, coded by genes KCNMB1–4) (Reviewed in Ref. 23). The BKCabeta3 family comprises four distinct subunits (beta3a–d) that arise as a consequence of alternative splicing of a single gene.


    Changes in Biophysical Properties of BKCa Channels Induced by BKCa beta-Subunits
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
The BKCa beta1-subunits induce an increase of the apparent Ca2+ sensitivity, a decrease of the voltage dependence of the channel, and slowing of the macroscopic kinetics (reviewed in Refs. 4 and 23). The BKCabeta1 effects seem to result from a stabilization of voltage sensor activation both when the channel is closed and when open. Ca2+ sensitivity in these channels is increased because, at all voltages, less Ca2+-binding energy is necessary to open the channel (24).

BKCa beta2 increases the Ca2+ and voltage sensitivity of BKCa channels and slows the kinetics of the channel (25, 26). Moreover, this subunit induces fast and complete inactivation (27). The N terminus of the BKCa beta2-subunit (residues 1–45, BKCabeta2N) blocks the BKCa channel via interaction with a receptor site in the {alpha}-subunit, which becomes accessible once the channel is in the open state. BKCabeta2N structure was studied by NMR spectroscopy and consists of two domains connected by a flexible linker (Glu17–Arg19) (28) (Fig. 1B). Orio et al. (29) suggested that N- and C-terminal domains from BKCabeta1 and BKCa beta2-subunits modulate the steady-state and kinetic parameters of BKCa channels.

BKCabeta3a–c induce channel inactivation to BKCa currents and also produce an outward rectification of the open channel currents. The inactivation process is faster than BKCabeta2-induced inactivation albeit incomplete (25). BKCa beta3b-subunit induces a small and consistent decrease in activation time constants at all Ca2+ concentrations, and it does not affect channel deactivation (25). beta3b-Subunit confers a non-linearity on instantaneous current-voltage properties that is regulated by extracellular segment of this beta-subunit (30).

The human BKCa beta4-subunit has a complex Ca2+ concentration-dependent effect on BKCa channel current. This subunit decreases apparent Ca2+ sensitivity at low Ca2+ concentrations but induces an increase in the apparent sensitivity at high Ca2+ concentrations (25, 31, 32). Human BKCabeta4 also slows down activation and deactivation kinetics (25, 31).


    BKCa beta-Subunit Pharmacology
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
Charybdotoxin (ChTX), a toxin isolated from the scorpion Leiurus quinquestratus (33), made possible the isolation and purification of the first BKCa beta-subunit reported (reviewed in Ref. 34). By the inhibition of 125I-ChTX binding to BKCa channels, a natural product identified as dehydrosoyasaponin was discovered. Dehydrosoyasaponin is a triterpene glycoside that increases the mean open time of BKCa channels but only when it is added into the intracellular face of the channel and when the beta-subunit is present (35). Iberiotoxin (IbTx), a scorpion toxin isolated from the scorpion Buthus tamulus, is another potent BKCa channel blocker with the advantage of being highly selective for BKCa (34). BKCa beta1-, beta2-, and beta4-subunits altered ChTx and IbTx binding in electrophysiological and biochemical studies (3638). BKCa channels are modulated by external binding of 17 beta-estradiol. The presence of 17 beta-estradiol elicits an increase in the currents recorded in patches expressing {alpha}- and beta-subunits but not in those expressing only the {alpha}-subunit (39). The chemotherapeutic xenoestrogen tamoxifen also increased the BKCa probability of opening only in the BKCa beta1-subunit presence (40). Cells expressing BKCa{alpha}beta4 channels confer particular sensitivity to the adrenal glucocorticoids cortisol and corticosterone and are potentiated to a lesser degree by other sex and stress steroids (41). Fatty acids such as arachidonic acid (AA) alter BKCa beta-subunit modulation of BKCa channel inactivation. Currents induced by channels formed by {alpha}+beta2 and {alpha}+beta3 were affected by AA (42). BKCa channel inactivation may be a specific mechanism by which AA and other unsaturated fatty acids influence neuronal death/survival in neuropathological conditions (42). Recently, the fluorescent dye voltage-sensitive DiBAC4 (3) was reported as a BKCa channel selective activator only when the regulatory rBKCabeta1 or rBKCabeta4, but not rBKCabeta2, were co-expressed with rBKCa{alpha} in HEK293 cells (43). Some of the main properties of BKCa beta-subunits are summarized in Table 1.


    beta-Subunit Kv and BKCa Channel Trafficking
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
beta-Subunits of Kv channels, in addition to modulating the channel activity at the cell surface, control the surface expression of the {alpha}-subunit (44). The interaction of Kv1 {alpha}-subunit and Kv beta-subunit polypeptides is an early event in Kv1 biosynthesis, occurring in the endoplasmic reticulum (ER) (44, 45) (Fig. 2A). Despite dramatic differences in their effects on channel gating, each of the Kv beta-subunits displays robust trafficking effects. Kv beta1.1-, beta1.2-, beta2-, and beta3-subunits increase the membrane expression and the mature form of Kv1.2 when they are co-expressed (44, 4648). The interaction with Kv beta2-subunits results in increased stability of Kv1.2 {alpha}-subunits. There is a dramatic difference in the degradation rates of the free Kv1.2 pool (non-bonded to Kv beta2-subunit, t1/2 ~3 h) and the Kv1.2 associated with Kvbeta2 (t1/2 ~15 h) (44). Therefore, although some cytoplasmic Kv1 channel beta-subunits affect the inactivation kinetics of {alpha}-subunits, a more general and perhaps more fundamental role is to mediate the biosynthetic maturation and surface expression of voltage-gated K+ channel complexes.


Figure 2
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FIGURE 2.
beta-Subunits and Kv and BKCa channel trafficking. A, the interaction between the T1 tetramerization domains in the N terminus of the channel with Kvbeta is necessary for surface expression and axonal targeting of Kv. At the level of the ER, the ER chaperone, calnexin, promotes forward trafficking of Kv (modified from Ref. 49). B, beta1-subunit of the BKCa channel enhances the internalization of the {alpha}-subunit (50). The beta1-subunit (circled inset) contains functional endocytic trafficking signals.

 
The Kv beta-subunits (Kvbeta1.1, Kvbeta1.2, Kvbeta2, and Kvbeta3) can also induce the targeting of Kv1.2 to axons in cultured hippocampal neurons, recapitulating the subcellular localization of Kv1.2 observed in mammalian central and peripheral neurons (46). Axonal targeting of Kv1 channels (reviewed in Ref. 49) is affected by mutations that disrupt the NADP+ binding site but not by mutations in the putative catalytic active site (46). Regarding BKCa beta-subunit trafficking, two reports have appeared indicating that BKCabeta1 and BKCabeta2 are able to reach the plasma membrane when they are expressed alone in HEK293 cells (50, 51). Co-expressing BKCabeta1 with BKCa {alpha}-subunit reduces steady-state BKCa channels surface expression levels by means of an endocytic mechanism. This result shows that BKCabeta1 can also regulate BKCa surface expression levels (50) (Fig. 2B). In addition, the co-expression of BKCa beta1-subunit with BKCa {alpha}-subunit splice variant SV1 (that is retained in ER) exhibits dominant-negative properties on BKCa beta1 surface expression. This study provides important insights into BKCa subunit assembly and suggests the early assembly of BKCa and beta1-subunits in the ER (52).


    Knock-out Models
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
Mouse genetic models have played an important role in the elucidation of molecular pathways underlying human disease; gene deletions have also underscored the physiological relevance of Kv and BKCa channel beta-subunits. This approach has been used to determine the effects of Kvbeta1 (53) and Kvbeta2 (54) removal on Kv1 family Kv currents. Kvbeta1.1-deficient mice show normal synaptic plasticity, but they show impaired learning, indicating that the Kv beta1.1-subunit contributes to certain types of learning and memory (53). In aged mice, the deletion of the auxiliary potassium channel subunit Kvbeta1.1 resulted in increased neuronal excitability, synaptic plasticity, and learning (55). The phenotype of Kvbeta2-null mice includes reduced life spans, occasional seizures, and cold swim-induced tremors similar to that observed in Kv1.1-null mice (54).

Regarding BKCa channels, deletion of the smooth muscle BKCa beta1-subunit causes slight hypertension and increased contractile response to vasoactive agonists (56, 57). BKCabeta4 knock-out mice, on the other hand, display abnormal neuronal firing properties and temporal lobe seizures, indicating that the gating properties conferred by the beta4-subunits are essential to normal neuronal function (58).


    Coda
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 
The properties of native Kv and BKCa channels are profoundly influenced by associated beta-subunits controlling their subcellular distribution and channel gating. Here we have reviewed the most important examples of Kv beta- and BKCa beta-subunit modulation of channel gating, pharmacological properties, and channel trafficking. beta-Subunits are expressed in many tissues, and in some cases, they are tissue-specific, allowing the involvement of K+ channels in a variety of different physiological processes. Three different genes that code for Kvbeta (KCNAB1–3) and four genes that code for BKCabeta (KCNMB1–4) have been reported. Additional diversity of beta-subunits is produced by alternative splicing. beta-Subunits are, however, only one piece of a protein network that is associated with ion channels. The pore-forming subunits of Kv and BKCa channels are components of large protein complexes in the plasma membrane. It is very important to know the changes in Kv and BKCa channel function induced by partners sharing the same protein complex. Identification of these partners and determination of their influence in channel properties will not only provide us with new insights about channel function but can also lead us to unravel new disguises of these molecular machines in cell physiology and pathophysiology.


    FOOTNOTES
 
* This minireview will be reprinted in the 2007 Minireview Compendium, which will be available in January, 2008. Work on ion channels in the Latorre laboratory was supported by FONDECYT Grants 1030830 and 1070049 (to R. L.) and DID-UACH Grants D-2006-10 (to F. J. M.) and D-2005-18 (to I. C.). Back

1 Supported by CONICYT doctoral fellowships. Back

2 To whom correspondence should be addressed. Tel.: 56-63-234501; Fax: 56-63-234515; E-mail: rlatorre{at}cecs.cl.

3 The abbreviations used are: TM, transmembrane; Kv, voltage-dependent K+ channel; BKCa, large conductance Ca2+- and voltage-dependent K+ channel; Kvbeta, beta-subunits of Kv channels; {alpha}-DTX, {alpha}-dendrotoxin; BKCabeta, beta-subunits of BKCa channels; BKCabeta2N, N terminus of the BKCa beta2-subunit; ChTX, charybdotoxin; IbTx, iberiotoxin; AA, arachidonic acid; ER, endoplasmic reticulum; PKA, cAMP-dependent protein kinase. Back


    ACKNOWLEDGMENTS
 
We thank Dr. Cristian Zaelzer for assistance with figures and Drs. Jimmy Ou and Eduardo Rosenmann for comments on the manuscript. The Centro de Estudios Científicos is funded in part by grants from Fundación Andes and The Tinker Foundation and hosts a Millenium Science Institute (MIDEPLAN, Chilean government).



    REFERENCES
 TOP
 ABSTRACT
 General Properties of Kv...
 beta-Subunits of Kv Channels
 Kv beta-Subunits Modify the...
 Kv beta-Subunit Pharmacology
 Structure and Redox Properties...
 beta-Subunits of BKCa Channels
 Changes in Biophysical...
 BKCa beta-Subunit Pharmacology
 beta-Subunit Kv and BKCa...
 Knock-out Models
 Coda
 REFERENCES
 

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