The long term aim of this work is to understand the functional and structural properties of an inactivating form of a large-conductance voltage-and calcium (Ca 2+)-activated potassium (K+) channel (termed BK channel). BK channels are a widely distributed family of ion channel proteins found in neurons, skeletal muscle, smooth muscle, endocrine cells, and other tissues. The physiological roles of BK channels remain unclear, although BK channels are typically thought to act as passive sensors of membrane voltage and submembrane Ca2+. In some cases, BK channels may play a role in rapid repolarization after action potentials. In contrast to most previously described BK channels, which exhibit sustained activation during depolarization or elevation of Ca2+ (BKs channels). BK channels found in rat chromaffin cells and the PC12 clonal cell line exhibit rapid inactivation (BKi channels). This inactivation shares a number of features with an N-terminal inactivation exhibited by members of the voltage-dependent K+ channel family suggesting that the mechanism of inactivation may be similar. Using single channel and whole-cell electrophysiological methods, this project will address three issues about the functional properties of BKi channels. First, the mechanism of inactivation of BKi will be determined and compared to inactivation of other voltage-dependent channels. Second, the Ca- and voltage-dependence of activation of BKi channels will be compared to BKs channels. Third, using cells which express either BKi or BKs channels, the physiological roles of BKi and BKs channels will be compared. Because of the widespread distribution of BK channels among cells, the potential importance of this ion channel to normal cellular physiology and health is apparent. This proposal will contribute significantly to our understanding of the functional properties and physiological role of an important class of K+ channel.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK046564-01
Application #
3247967
Study Section
Physiology Study Section (PHY)
Project Start
1993-05-21
Project End
1997-04-30
Budget Start
1993-05-21
Budget End
1994-04-30
Support Year
1
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Washington University
Department
Type
Schools of Medicine
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Zeng, Xu-Hui; Benzinger, G Richard; Xia, Xiao-Ming et al. (2007) BK channels with beta3a subunits generate use-dependent slow afterhyperpolarizing currents by an inactivation-coupled mechanism. J Neurosci 27:4707-15
Zhang, Zhe; Zhou, Yu; Ding, Jiu-Ping et al. (2006) A limited access compartment between the pore domain and cytosolic domain of the BK channel. J Neurosci 26:11833-43
Benzinger, G Richard; Xia, Xiao-Ming; Lingle, Christopher J (2006) Direct observation of a preinactivated, open state in BK channels with beta2 subunits. J Gen Physiol 127:119-31
Chen, Xiao-Ke; Wang, Lie-Cheng; Zhou, Yang et al. (2005) Activation of GPCRs modulates quantal size in chromaffin cells through G(betagamma) and PKC. Nat Neurosci 8:1160-8
Xia, Xiao-Ming; Ding, J P; Lingle, Christopher J (2003) Inactivation of BK channels by the NH2 terminus of the beta2 auxiliary subunit: an essential role of a terminal peptide segment of three hydrophobic residues. J Gen Physiol 121:125-48
Wang, Ying-Wei; Ding, Jiu Ping; Xia, Xiao-Ming et al. (2002) Consequences of the stoichiometry of Slo1 alpha and auxiliary beta subunits on functional properties of large-conductance Ca2+-activated K+ channels. J Neurosci 22:1550-61
Ding, Jiu Ping; Lingle, Christopher J (2002) Steady-state and closed-state inactivation properties of inactivating BK channels. Biophys J 82:2448-65
Zhang, X; Solaro, C R; Lingle, C J (2001) Allosteric regulation of BK channel gating by Ca(2+) and Mg(2+) through a nonselective, low affinity divalent cation site. J Gen Physiol 118:607-36
Zeng, X H; Ding, J P; Xia, X M et al. (2001) Gating properties conferred on BK channels by the beta3b auxiliary subunit in the absence of its NH(2)- and COOH termini. J Gen Physiol 117:607-28
Lingle, C J; Zeng, X H; Ding, J P et al. (2001) Inactivation of BK channels mediated by the NH(2) terminus of the beta3b auxiliary subunit involves a two-step mechanism: possible separation of binding and blockade. J Gen Physiol 117:583-606

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