REGULATION BY NA+ AND CA2+ OF RENAL EPITHELIAL NA+ CHANNELS RECONSTITUTED INTO PLANAR LIPID BILAYERS

被引:28
作者
ISMAILOV, II
BERDIEV, BK
BENOS, DJ
机构
[1] Department of Physiology and Biophysics, The University of Alabama at Birmingham, Birmingham, AL
关键词
D O I
10.1085/jgp.106.3.445
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Purified bovine renal epithelial Na+ channels when reconstituted into planar lipid bilayers displayed a specific orientation when the membrane was clamped to -40 mV (cis-side) during incorporation. The trans-facing portion of the channel was extracellular (i.e., amiloride-sensitive), whereas the cis-facing side was intracellular (i.e., protein kinase A-sensitive). Single channels had a main state unitary conductance of 40 pS and displayed two subconductive states each of 12-13 pS, or one of 12-13 pS and the second of 24-26 pS. Elevation of the [Na+] gradient from the trans-side increased single-channel open probability (P-o) only when the cis-side was bathed with a solution containing low [Na+] (<30 mM) and 10-100 mu M [Ca2+]. Under these conditions, P-o saturated with increasing [Na+](trans). Buffering of the cis compartment [Ca2+] to nearly zero (<1 nM) with 10 mM EGTA increased the initial level of channel activity (P-o = 0.12 +/- 0.02 vs 0.02 +/- 0.01 in control), but markedly reduced the influence of both cis- and trans-[Na+] on P-o. Elevating [Ca2+](cis) at constant [Na+] resulted in inhibition of channel activity with an apparent [K-i(ca2+)] of 10-100 mu M Protein kinase C-induced phosphorylation shifted the dependence of channel P-o on [Ca2+](cis) to 1-3 mu M at stationary [Na+]. The direct modulation of single-channel P-o by Na+ and Ca2+ demonstrates that the gating of amiloride-sensitive Na+ channels is indeed dependent upon the specific ionic environment surrounding the channels.
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收藏
页码:445 / 466
页数:22
相关论文
共 46 条
[1]  
ALVAREZ O, 1985, J ELECTROPHYSIOL TEC, V12, P159
[2]  
BENOS DJ, 1995, J MEMBRANE BIOL, V143, P1
[4]   Gramicidin forms multi-state rectifying channels [J].
Busath, David ;
Szabo, Gabor .
NATURE, 1981, 294 (5839) :371-373
[5]   AMILORIDE-SENSITIVE EPITHELIAL NA+ CHANNEL IS MADE OF 3 HOMOLOGOUS SUBUNITS [J].
CANESSA, CM ;
SCHILD, L ;
BUELL, G ;
THORENS, B ;
GAUTSCHI, I ;
HORISBERGER, JD ;
ROSSIER, BC .
NATURE, 1994, 367 (6462) :463-467
[6]   EPITHELIAL SODIUM-CHANNEL RELATED TO PROTEINS INVOLVED IN NEURODEGENERATION [J].
CANESSA, CM ;
HORISBERGER, JD ;
ROSSIER, BC .
NATURE, 1993, 361 (6411) :467-470
[7]   DOES CALCIUM COUPLE THE APICAL AND BASOLATERAL MEMBRANE PERMEABILITIES IN EPITHELIA [J].
CHASE, HS .
AMERICAN JOURNAL OF PHYSIOLOGY, 1984, 247 (06) :F869-F876
[8]   DOES INTRACELLULAR SODIUM MODIFY MEMBRANE-PERMEABILITY TO SODIUM IONS [J].
CUTHBERT, AW ;
SHUM, WK .
NATURE, 1977, 266 (5601) :468-469
[9]   ACTIVATION OF EPITHELIAL NA CHANNELS BY HORMONAL AND AUTOREGULATORY MECHANISMS OF ACTION [J].
ELS, WJ ;
HELMAN, SI .
JOURNAL OF GENERAL PHYSIOLOGY, 1991, 98 (06) :1197-1220
[10]   SODIUM UPTAKE BY FROG SKIN AND ITS MODIFICATION BY INHIBITORS OF TRANSEPITHELIAL SODIUM-TRANSPORT [J].
ERLIJ, D ;
SMITH, MW .
JOURNAL OF PHYSIOLOGY-LONDON, 1973, 228 (01) :221-239