Distinct regions of the slo subunit determine differential BKCa channel responses to ethanol.
BACKGROUND
Ethanol at clinically relevant concentrations increases BKCa channel activity in dorsal root ganglia neurons, GH3 cells, and neurohypophysial terminals, leading to decreases in cell excitability and peptide release. In contrast, ethanol inhibits BKCa channels from aortic myocytes, which likely contributes to alcohol-induced aortic constriction. The mechanisms that determine differential BKCa channel responses to ethanol are unknown. We hypothesized that nonconserved regions in the BKCa channel-forming subunit (slo) are major contributors to the differential alcohol responses of different BKCa channel phenotypes.


METHODS
We constructed chimeras by interchanging the core and the tail domains of two BKCa channel-forming subunits (mslo and bslo) that, after expression, differentially respond to ethanol (activation and inhibition, respectively), and studied ethanol action on these mbslo and bmslo chimeric channels using single-channel, patch-clamp techniques.


CONCLUSIONS
Data from cell-free membranes patches demonstrate that the activity of channels that share a mslo-type core-linker (wt mslo and the mbslo chimera) is consistently and significantly potentiated by acute exposure to ethanol. Thus, a mslo tail is not necessary for ethanol potentiation of slo channels. In contrast, the activity of channels that share a bslo-type core-linker (wt bslo and the bmslo chimera) display heterogenous responses to ethanol: inhibition (in the majority of cases), refractoriness, or activation. Overall, our data indicate that the slo core-linker is a critical region likely contributing to the differential responses of BKCa channels to ethanol.
Department of Pharmacology, Program in Neuroscience, and Center of Excellence in Cardiovascular Biology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Pengchong
P
Liu
Jianxi
J
Liu
Weihua
W
Huang
Ming D
MD
Li
Alejandro M
AM
Dopico
D000818:Animals; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D021122:Protein Subunits / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D014982:Xenopus laevis
D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D021122:Protein Subunits; D000431:Ethanol