A calcium switch for the functional coupling between α (hslo) and β subunits (KV, Caβ) of maxi K channels

Meera, Pratap; Wallner, Martín; Jiang, Zhiming; Toro, Ligia

doi:10.1016/0014-5793(96)00151-2

Cited by 228 publications

(224 citation statements)

References 13 publications

Supporting

Mentioning

189

Contrasting

Order By: Relevance

“…1F) document the shifts to the left in channel gating along the voltage axis with increasing free intracellular calcium. These observations are thus similar to those recently reported by others (33)(34)(35)(36)(37)(38)(39) for heterologous expression of mammalian Slo genes encoding BK Ca channels.…”

Section: Resultssupporting

confidence: 92%

Enhanced Activity of a Large Conductance, Calcium-sensitive K+ Channel in the Presence of Src Tyrosine Kinase

Ling

Woronuk

et al. 2000

Journal of Biological Chemistry

View full text Add to dashboard Cite

Large conductance, calcium-sensitive K ؉ channels (BK Ca channels) contribute to the control of membrane potential in a variety of tissues, including smooth muscle, where they act as the target effector for intracellular "calcium sparks" and the endothelium-derived vasodilator nitric oxide. Various signal transduction pathways, including protein phosphorylation can regulate the activity of BK Ca channels, along with many other membrane ion channels. In our study, we have examined the regulation of BK Ca channels by the cellular Src gene product (cSrc), a soluble tyrosine kinase that has been implicated in the regulation of both voltage-and ligand-gated ion channels. Using a heterologous expression system, we observed that co-expression of murine BK Ca channel and the human cSrc tyrosine kinase in HEK 293 cells led to a calcium-sensitive enhancement of BK Ca channel activity in excised membrane patches. In contrast, co-expression with a catalytically inactive cSrc mutant produced no change in BK Ca channel activity, demonstrating the requirement for a functional cSrc molecule. Furthermore, we observed that BK Ca channels underwent direct tyrosine phosphorylation in cells co-transfected with BK Ca channels and active cSrc but not in cells co-transfected with the kinase inactive form of the enzyme. A single Tyr to Phe substitution in the C-terminal half of the channel largely prevented this observed phosphorylation. Given that cSrc may become activated by receptor tyrosine kinases or G-protein-coupled receptors, these findings suggest that cSrc-dependent tyrosine phosphorylation of BK Ca channels in situ may represent a novel regulatory mechanism for altering membrane potential and calcium entry.In the large family of voltage-gated K ϩ channels, large conductance, calcium-sensitive potassium (maxi-K or BK Ca ) 1 channels represent a unique class whose gating depends primarily on membrane voltage but which can be shifted in the negative direction by intracellular free calcium. A direct physiologic consequence of this behavior is that BK Ca channels act as "coincidence detectors" and regulate, in a feedback fashion, cellular processes stimulated by close temporal changes in membrane potential and intracellular calcium. That BK Ca channels indeed play such a role is evidenced by the fact that blocking these channels increases the degree of myogenic tone observed in arterial smooth muscle (1-3) and enhances the presynaptic calcium-dependent release of neurotransmitter at neuromuscular junctions (4, 5).Given their potential to influence cellular processes, it is not surprising that BK Ca channels are also targets of cellular signaling pathways, including phosphorylation and dephosphorylation reactions (6 -11), heterotrimeric GTP-binding proteins (12, 13), and the endothelium-derived vasodilator nitric oxide (14). To date, however, many of the molecular aspects of these regulatory events remain poorly understood.Of these various cellular pathways, protein phosphorylation remains as one of the most common forms of intrace...

show abstract

Section: Resultssupporting

confidence: 92%

Enhanced Activity of a Large Conductance, Calcium-sensitive K+ Channel in the Presence of Src Tyrosine Kinase

Ling

Woronuk

et al. 2000

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…The voltage-and calcium-dependence of both hSlo and hSlo-N200A (Fig. 3B) were in reasonable agreement to those for hSlo expressed alone, without a regulatory ␤-subunit, in oocytes (40).…”

Section: Overexpressed Hslo Is Efficiently Transported To the Cell Susupporting

confidence: 73%

“…For the bath solution, CaCl 2 was replaced by 5 mM EGTA. Ca 2ϩ concentration, adjusted by adding concentrated CaCl 2 , was measured with a Ca 2ϩ electrode (World Precision Instruments, Sarasota, FL) (40). The current signal was digitized to a frequency equal to 5-fold the filter cutoff frequency.…”

Section: Transfection and Assessment Of Protein Expression Polaritymentioning

confidence: 99%

Apical sorting of a voltage- and Ca ²⁺ -activated K ⁺ channel α-subunit in Madin-Darby canine kidney cells is independent of N-glycosylation

Bravo‐Zehnder

Orio

Norambuena

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

100

View full text Add to dashboard Cite

The voltage-and Ca 2؉ -activated K ؉ (KV,Ca) channel is expressed in a variety of polarized epithelial cells seemingly displaying a tissuedependent apical-to-basolateral regionalization, as revealed by electrophysiology. Using domain-specific biotinylation and immunofluorescence we show that the human channel KV,Ca ␣-subunit (human Slowpoke channel, hSlo) is predominantly found in the apical plasma membrane domain of permanently transfected Madin-Darby canine kidney cells. Both the wild-type and a mutant hSlo protein lacking its only potential N-glycosylation site were efficiently transported to the cell surface and concentrated in the apical domain even when they were overexpressed to levels 200-to 300-fold higher than the density of intrinsic Slo channels. Furthermore, tunicamycin treatment did not prevent apical segregation of hSlo, indicating that endogenous glycosylated proteins (e.g., KV,Ca ␤-subunits) were not required. hSlo seems to display properties for lipid-raft targeting, as judged by its buoyant distribution in sucrose gradients after extraction with either detergent or sodium carbonate. The evidence indicates that the hSlo protein possesses intrinsic information for transport to the apical cell surface through a mechanism that may involve association with lipid rafts and that is independent of glycosylation of the channel itself or an associated protein. Thus, this particular polytopic model protein shows that glycosylation-independent apical pathways exist for endogenous membrane proteins in Madin-Darby canine kidney cells.human Slowpoke channel ͉ epithelial polarity

show abstract

“…It would be interesting to test for the possibility that the low Ca 2+ affinity of these putative Ca 2+ and Mg 2+ sites is determined by the close proximity of the histidine residues. Despite the fact that it contains an S4 domain, the molecular nature of the BK channel voltage-dependence remained unclear until it was unequivocally demonstrated that depolarizing voltages are able to activate the BK channel in the absence of Ca 2+ (Pallota, 1985;Meera et al, 1996;Cui et al, 1997;Cox et al, 1997;Stefani et al, 1997;Rothberg and Magleby, 2000;Nimigean and Magleby, 2000;Taludker and Aldrich, 2000). One of the first observations in support of the presence of an integral voltage sensor in the BK channel-forming protein is depicted in Figure 4B.…”

Section: Sensing Elementsmentioning

confidence: 99%

Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage

2006

View full text Add to dashboard Cite

Large conductance Ca 2+ -activated K + (BK) channels belong to the S4 superfamily of K + channels that include voltage-dependent K + (Kv) channels characterized by having six (S1-S6) transmembrane domains and a positively charged S4 domain. As Kv channels, BK channels contain a S4 domain, but they have an extra (S0) transmembrane domain that leads to an external NH 2 -terminus. The BK channel is activated by internal Ca 2+ , and using chimeric channels and mutagenesis, three distinct Ca 2+ -dependent regulatory mechanisms with different divalent cation selectivity have been identified in its large COOH-terminus. Two of these putative Ca 2+ -binding domains activate the BK channel when cytoplasmic Ca 2+ reaches micromolar concentrations, and a low Ca 2+ affinity mechanism may be involved in the physiological regulation by Mg 2+ . The presence in the BK channel of multiple Ca 2+ -binding sites explains the huge Ca 2+ concentration range (0.1 μM-100 μM) in which the divalent cation influences channel gating. BK channels are also voltage-dependent, and all the experimental evidence points toward the S4 domain as the domain in charge of sensing the voltage. Calcium can open BK channels when all the voltage sensors are in their resting configuration, and voltage is able to activate channels in the complete absence of Ca 2+ . Therefore, Ca 2+ and voltage act independently to enhance channel opening, and this behavior can be explained using a two-tiered allosteric gating mechanism.

show abstract

A calcium switch for the functional coupling between α (hslo) and β subunits (K_V, _Caβ) of maxi K channels

Cited by 228 publications

References 13 publications

Enhanced Activity of a Large Conductance, Calcium-sensitive K+ Channel in the Presence of Src Tyrosine Kinase

Enhanced Activity of a Large Conductance, Calcium-sensitive K+ Channel in the Presence of Src Tyrosine Kinase

Apical sorting of a voltage- and Ca ²⁺ -activated K ⁺ channel α-subunit in Madin-Darby canine kidney cells is independent of N-glycosylation

Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage

Contact Info

Product

Resources

About

A calcium switch for the functional coupling between α (hslo) and β subunits (KV, Caβ) of maxi K channels

Cited by 228 publications

References 13 publications

Enhanced Activity of a Large Conductance, Calcium-sensitive K+ Channel in the Presence of Src Tyrosine Kinase

Enhanced Activity of a Large Conductance, Calcium-sensitive K+ Channel in the Presence of Src Tyrosine Kinase

Apical sorting of a voltage- and Ca 2+ -activated K + channel α-subunit in Madin-Darby canine kidney cells is independent of N-glycosylation

Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage

Contact Info

Product

Resources

About

A calcium switch for the functional coupling between α (hslo) and β subunits (K_V, _Caβ) of maxi K channels

Apical sorting of a voltage- and Ca ²⁺ -activated K ⁺ channel α-subunit in Madin-Darby canine kidney cells is independent of N-glycosylation