PMID- 26009545 OWN - NLM STAT- MEDLINE DCOM- 20160219 LR - 20181113 IS - 1540-7748 (Electronic) IS - 0022-1295 (Print) IS - 0022-1295 (Linking) VI - 145 IP - 6 DP - 2015 Jun TI - Molecular basis for differential modulation of BK channel voltage-dependent gating by auxiliary gamma subunits. PG - 543-54 LID - 10.1085/jgp.201511356 [doi] AB - Large conductance Ca(2+)- and voltage-activated potassium (BK) channels are comprised of pore-forming alpha subunits and various regulatory auxiliary subunits. The BK channel auxiliary gamma (BKgamma) subunits are a newly identified class of proteins containing an extracellular leucine-rich repeat domain (LRRD), a single transmembrane (TM) segment, and a short cytoplasmic C-terminal tail (C-tail). Although each of the four BKgamma proteins shifts the voltage dependence of BK channel activation in a hyperpolarizing direction, they show markedly different efficacies, mediating shifts over a range of 15-145 mV. Analyses of chimeric BKgamma subunits created by swapping individual structural elements, and of BKgamma deletion and substitution mutants, revealed that differential modulation of BK gating by the four BKgamma subunits depends on a small region consisting of the TM segment and the adjacent intracellular cluster of positively charged amino acids. The gamma1 and gamma2 TM segments contributed approximately -100 mV, and the gamma1 and gamma3 C-tails contributed approximately -40 mV, to shifting the voltage dependence of BK channel activation, whereas the gamma3 and gamma4 TM segments and the gamma2 and gamma4 C-tails contributed much less. The large extracellular LRRDs were mainly functionally interchangeable, although the gamma1 LRRD was slightly less effective at enhancing (or slightly more effective at attenuating) the shift in BK channel voltage-dependent gating toward hyperpolarizing potentials than those of the other BKgamma subunits. Analysis of mutated BKgamma subunits revealed that juxta-membrane clusters of positively charged amino acids determine the functions of the gamma1 and gamma3 C-tails. Therefore, the modulatory functions of BKgamma subunits are coarse- and fine-tuned, respectively, through variations in their TM segments and in the adjacent intracellular positively charged regions. Our results suggest that BK channel modulation by auxiliary gamma subunits depends on intra- and/or juxta-membrane mechanisms. CI - (c) 2015 Li et al. FAU - Li, Qin AU - Li Q AD - Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030. FAU - Fan, Fei AU - Fan F AD - Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030. FAU - Kwak, Ha Rim AU - Kwak HR AD - Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030. FAU - Yan, Jiusheng AU - Yan J AD - Department of Anesthesiology and Perioperative Medicine, Center for Neuroscience and Pain Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 Program in Neuroscience, University of Texas Graduate School of Biomedical Sciences, Houston, TX 77225 jyan1@mdanderson.org. LA - eng GR - R01 NS078152/NS/NINDS NIH HHS/United States GR - R21 NS075118/NS/NINDS NIH HHS/United States GR - NS075118/NS/NINDS NIH HHS/United States GR - NS078152/NS/NINDS NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PL - United States TA - J Gen Physiol JT - The Journal of general physiology JID - 2985110R RN - 0 (KCNMA1 protein, human) RN - 0 (LRRC26 protein, human) RN - 0 (LRRC38 protein, human) RN - 0 (LRRC52 protein, human) RN - 0 (LRRC55 protein, human) RN - 0 (Large-Conductance Calcium-Activated Potassium Channel alpha Subunits) RN - 0 (Membrane Proteins) RN - 0 (Neoplasm Proteins) RN - 0 (Protein Subunits) RN - RWP5GA015D (Potassium) SB - IM CIN - J Gen Physiol. 2015 Jun;145(6):457-8. PMID: 26009540 MH - Amino Acid Sequence MH - Cell Membrane/*metabolism MH - HEK293 Cells MH - Humans MH - *Ion Channel Gating MH - Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/chemistry/genetics/*metabolism MH - Membrane Potentials MH - Membrane Proteins/chemistry/genetics/*metabolism MH - Models, Molecular MH - Molecular Sequence Data MH - Mutation MH - Neoplasm Proteins/chemistry/genetics/*metabolism MH - Potassium/*metabolism MH - Protein Conformation MH - Protein Subunits MH - Structure-Activity Relationship MH - Transfection PMC - PMC4442785 EDAT- 2015/05/27 06:00 MHDA- 2016/02/20 06:00 PMCR- 2015/12/01 CRDT- 2015/05/27 06:00 PHST- 2015/05/27 06:00 [entrez] PHST- 2015/05/27 06:00 [pubmed] PHST- 2016/02/20 06:00 [medline] PHST- 2015/12/01 00:00 [pmc-release] AID - jgp.201511356 [pii] AID - 201511356 [pii] AID - 10.1085/jgp.201511356 [doi] PST - ppublish SO - J Gen Physiol. 2015 Jun;145(6):543-54. doi: 10.1085/jgp.201511356.