Hypoxia inhibits human recombinant large conductance, Ca2+-activated K+ (maxi-K) channels by a mechanism which is membrane delimited and Ca2+ sensitive

被引:65
作者
Lewis, A
Peers, C
Ashford, MLJ
Kemp, PJ
机构
[1] Univ Leeds, Sch Biomed Sci, Leeds LS2 9JT, W Yorkshire, England
[2] Univ Leeds, Inst Cardiovasc Res, Leeds LS2 9JT, W Yorkshire, England
[3] Univ Dundee, Ninewells Hosp & Med Sch, Dept Pharmacol & Neurosci, Dundee DD1 9SY, Scotland
来源
JOURNAL OF PHYSIOLOGY-LONDON | 2002年 / 540卷 / 03期
关键词
D O I
10.1113/jphysiol.2001.013888
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Large conductance, Ca2+-activated K+ (maxi-K) channel activity was recorded in excised, inside-out patches from HEK 293 cells stably co-expressing the alpha- and beta-subunits of human brain maxi-K channels. At +50 mV, and in the presence of 300 nM Ca-i(2+), single channel activity was acutely and reversibly suppressed upon reducing Pot from 150 to > 40 mmHg by over 30 %. The hypoxia-evoked reduction in current was due predominantly to suppression in NPo, although a minor component was attributable to reduced unitary conductance of 8-12 %. Hypoxia caused an approximate doubling of the time constant for activation but was without effect on deactivation. At lower levels of Ca-i(2+) (30 and 100 rim), hypoxic inhibition did not reach significance. In contrast, 300 nm and 1 muM Ca-i(2+) both sustained significant hypoxic suppression of activity over the entire activating voltage range. At these two Ca-i(2+) levels, hypoxia evoked a positive shift in the activating voltage (by similar to10 mV at 300 nM and similar to25 mV at 1 muM). At saturating [Ca2+]; (100 muM), hypoxic inhibition was absent. Distinguishing between hypoxia-evoked changes in voltage- and/or Ca-i(2+)-sensitivity was achieved by evoking maximal channel activity using high depolarising potentials (up to +200 mV) in the presence of 300 muM or 100 muM Ca-i(2+) or in its virtual absence (> 1 nM). Under these experimental conditions, hypoxia caused significant channel inhibition only in the presence of 300 nm Ca-i(2+). Thus, since regulation was observed in excised patches, maxi-K channel inhibition by hypoxia does not require soluble intracellular components and, mechanistically, is voltage independent and Ca-i(2+) sensitive.
引用
收藏
页码:771 / 780
页数:10
相关论文
共 46 条
[1]   Stable expression of the human large-conductance Ca2+-activated K+ channel alpha- and beta-subunits in HEK293 cells [J].
Ahring, PK ;
Strobaek, D ;
Christophersen, P ;
Olesen, SP ;
Johansen, TE .
FEBS LETTERS, 1997, 415 (01) :67-70
[2]   Vasoregulation by the β1 subunit of the calcium-activated potassium channel [J].
Brenner, R ;
Peréz, GJ ;
Bonev, AD ;
Eckman, DM ;
Kosek, JC ;
Wiler, SW ;
Patterson, AJ ;
Nelson, MT ;
Aldrich, RW .
NATURE, 2000, 407 (6806) :870-876
[3]   An oxygen-, acid- and anaesthetic-sensitive TASK-like background potassium channel in rat arterial chemoreceptor cells [J].
Buckler, KJ ;
Williams, BA ;
Honore, E .
JOURNAL OF PHYSIOLOGY-LONDON, 2000, 525 (01) :135-142
[4]   Cellular oxygen sensing by mitochondria: old questions, new insight [J].
Chandel, NS ;
Schumacker, PT .
JOURNAL OF APPLIED PHYSIOLOGY, 2000, 88 (05) :1880-1889
[5]   Molecular basis of hypoxia-induced pulmonary vasoconstriction:: role of voltage-gated K+ channels [J].
Coppock, EA ;
Martens, JR ;
Tamkun, MM .
AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY, 2001, 281 (01) :L1-L12
[6]   Oxygen causes fetal pulmonary vasodilation through activation of a calcium-dependent potassium channel [J].
Cornfield, DN ;
Reeve, HL ;
Tolarova, S ;
Weir, EK ;
Archer, S .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 1996, 93 (15) :8089-8094
[7]   Neuroepithelial bodies as airway oxygen sensors [J].
Cutz, E ;
Jackson, A .
RESPIRATION PHYSIOLOGY, 1999, 115 (02) :201-214
[8]  
Friedman JE, 1998, NEUROSCIENCE, V82, P421
[9]   NADPH oxidase is an O2 sensor in airway chemoreceptors:: Evidence from K+ current modulation in wild-type and oxidase-deficient mice [J].
Fu, XW ;
Wang, DS ;
Nurse, CA ;
Dinauer, MC ;
Cutz, E .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2000, 97 (08) :4374-4379
[10]   Potassium channels underlying the resting potential of pulmonary artery smooth muscle cells [J].
Gurney, AM ;
Osipenko, ON ;
MacMillan, D ;
Kempsill, FE .
CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, 2002, 29 (04) :330-333