Abstract
Functional large-conductance Ca2+- and voltage-activated K+ (BK) channels can be assembled from four α subunits (Slo1) alone, or together with four auxiliary β1 subunits to greatly increase the apparent Ca2+ sensitivity of the channel. We examined the structural features involved in this modulation with two types of experiments. In the first, the tail domain of the α subunit, which includes the RCK2 (regulator of K+ conductance) domain and Ca2+ bowl, was replaced with the tail domain of Slo3, a BK-related channel that lacks both a Ca2+ bowl and high affinity Ca2+ sensitivity. In the second, the Ca2+ bowl was disrupted by mutations that greatly reduce the apparent Ca2+ sensitivity. We found that the β1 subunit increased the apparent Ca2+ sensitivity of Slo1 channels, independently of whether the α subunits were expressed as separate cores (S0-S8) and tails (S9-S10) or full length, and this increase was still observed after the Ca2+ bowl was mutated. In contrast, β1 subunits no longer increased Ca2+ sensitivity when Slo1 tails were replaced by Slo3 tails. The β1 subunits were still functionally coupled to channels with Slo3 tails, as DHS-I and 17β-estradiol activated these channels in the presence of β1 subunits, but not in their absence. These findings indicate that the increase in apparent Ca2+ sensitivity induced by the β1 subunit does not require either the Ca2+ bowl or the linker between the RCK1 and RCK2 domains, and that Slo3 tails cannot substitute for Slo1 tails. The β1 subunit also induced a decrease in voltage sensitivity that occurred with either Slo1 or Slo3 tails. In contrast, the β1 subunit-induced increase in apparent Ca2+ sensitivity required Slo1 tails. This suggests that the allosteric activation pathways for these two types of actions of the β1 subunit may be different.
| Original language | English |
|---|---|
| Pages (from-to) | 829-843 |
| Number of pages | 15 |
| Journal | Journal of General Physiology |
| Volume | 120 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 1 2002 |
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Keywords
- Ca-activated K channel
- DHS-I
- Estrogen
- RCK domain
- Slo3
ASJC Scopus subject areas
- Physiology
Cite this
Slo1 tail domains, but not the Ca2+ bowl, are required for the β1 subunit to increase the apparent Ca2+ sensitivity of BK channels. / Qian, Xiang; Nimigean, Crina M.; Niu, Xiaowei; Moss, Brenda L.; Magleby, Karl.
In: Journal of General Physiology, Vol. 120, No. 6, 01.12.2002, p. 829-843.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Slo1 tail domains, but not the Ca2+ bowl, are required for the β1 subunit to increase the apparent Ca2+ sensitivity of BK channels
AU - Qian, Xiang
AU - Nimigean, Crina M.
AU - Niu, Xiaowei
AU - Moss, Brenda L.
AU - Magleby, Karl
PY - 2002/12/1
Y1 - 2002/12/1
N2 - Functional large-conductance Ca2+- and voltage-activated K+ (BK) channels can be assembled from four α subunits (Slo1) alone, or together with four auxiliary β1 subunits to greatly increase the apparent Ca2+ sensitivity of the channel. We examined the structural features involved in this modulation with two types of experiments. In the first, the tail domain of the α subunit, which includes the RCK2 (regulator of K+ conductance) domain and Ca2+ bowl, was replaced with the tail domain of Slo3, a BK-related channel that lacks both a Ca2+ bowl and high affinity Ca2+ sensitivity. In the second, the Ca2+ bowl was disrupted by mutations that greatly reduce the apparent Ca2+ sensitivity. We found that the β1 subunit increased the apparent Ca2+ sensitivity of Slo1 channels, independently of whether the α subunits were expressed as separate cores (S0-S8) and tails (S9-S10) or full length, and this increase was still observed after the Ca2+ bowl was mutated. In contrast, β1 subunits no longer increased Ca2+ sensitivity when Slo1 tails were replaced by Slo3 tails. The β1 subunits were still functionally coupled to channels with Slo3 tails, as DHS-I and 17β-estradiol activated these channels in the presence of β1 subunits, but not in their absence. These findings indicate that the increase in apparent Ca2+ sensitivity induced by the β1 subunit does not require either the Ca2+ bowl or the linker between the RCK1 and RCK2 domains, and that Slo3 tails cannot substitute for Slo1 tails. The β1 subunit also induced a decrease in voltage sensitivity that occurred with either Slo1 or Slo3 tails. In contrast, the β1 subunit-induced increase in apparent Ca2+ sensitivity required Slo1 tails. This suggests that the allosteric activation pathways for these two types of actions of the β1 subunit may be different.
AB - Functional large-conductance Ca2+- and voltage-activated K+ (BK) channels can be assembled from four α subunits (Slo1) alone, or together with four auxiliary β1 subunits to greatly increase the apparent Ca2+ sensitivity of the channel. We examined the structural features involved in this modulation with two types of experiments. In the first, the tail domain of the α subunit, which includes the RCK2 (regulator of K+ conductance) domain and Ca2+ bowl, was replaced with the tail domain of Slo3, a BK-related channel that lacks both a Ca2+ bowl and high affinity Ca2+ sensitivity. In the second, the Ca2+ bowl was disrupted by mutations that greatly reduce the apparent Ca2+ sensitivity. We found that the β1 subunit increased the apparent Ca2+ sensitivity of Slo1 channels, independently of whether the α subunits were expressed as separate cores (S0-S8) and tails (S9-S10) or full length, and this increase was still observed after the Ca2+ bowl was mutated. In contrast, β1 subunits no longer increased Ca2+ sensitivity when Slo1 tails were replaced by Slo3 tails. The β1 subunits were still functionally coupled to channels with Slo3 tails, as DHS-I and 17β-estradiol activated these channels in the presence of β1 subunits, but not in their absence. These findings indicate that the increase in apparent Ca2+ sensitivity induced by the β1 subunit does not require either the Ca2+ bowl or the linker between the RCK1 and RCK2 domains, and that Slo3 tails cannot substitute for Slo1 tails. The β1 subunit also induced a decrease in voltage sensitivity that occurred with either Slo1 or Slo3 tails. In contrast, the β1 subunit-induced increase in apparent Ca2+ sensitivity required Slo1 tails. This suggests that the allosteric activation pathways for these two types of actions of the β1 subunit may be different.
KW - Ca-activated K channel
KW - DHS-I
KW - Estrogen
KW - RCK domain
KW - Slo3
UR - http://www.scopus.com/inward/record.url?scp=0036900726&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036900726&partnerID=8YFLogxK
U2 - 10.1085/jgp.20028692
DO - 10.1085/jgp.20028692
M3 - Article
C2 - 12451052
AN - SCOPUS:0036900726
VL - 120
SP - 829
EP - 843
JO - Journal of General Physiology
JF - Journal of General Physiology
SN - 0022-1295
IS - 6
ER -