Properties of two multisubstrate Cl- channels from human syncytiotrophoblast reconstituted on planar lipid bilayers

被引:14
作者
Grosman, C
Mariano, MI
Bozzini, JP
Reisin, IL
机构
[1] UNIV BUENOS AIRES,FAC FARM & BIOQUIM,DEPT QUIM ANALIT & FISICOQUIM,RA-1113 BUENOS AIRES,DF,ARGENTINA
[2] INST NAC MICROBIOL DR CG MALBRAN,SERV MICROSCOPIA ELECTRON,RA-1281 BUENOS AIRES,DF,ARGENTINA
关键词
placenta; apical plasma membrane vesicles; single-channel recording; Cl-; channels; multiple conductance levels; cooperativity;
D O I
10.1007/s002329900218
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We describe the first successful reconstitution of placental ionic channels on planar lipid bilayers. An apical plasma membrane-enriched vesicle fraction from human syncytiotrophoblast at term was prepared by following isotonic agitation, differential centrifugation, and Mg2+-induced selective precipitation of nonapical membranes, and its purity was assessed by biochemical and morphological marker analysis. We have already reported that, unlike previous patch-clamp studies, nonselective cation channels were incorporated in most cases, a result consistent with the higher permeability for cations as compared with C1(-) and with the low apical membrane potential difference at term revealed by fluorescent probe partition studies, and microelectrode techniques. In this paper, we report that C1(-)-selective channels were incorporated in 4% of successful reconstitutions (14 out of 353) and that their analysis revealed two types of activity. One of them was consistent with a voltage-dependent, 100-pS channel while the other was consistent with the lateral association of 47-pS conductive units, giving rise to multibarrelled, DIDS-sensitive channels of variable conductance (300 to 650 pS). The latter displayed a very complex behavior which included cooperative gating of conductive units, long-lived substates, voltage-dependent entry into an apparent inactivated state, and flickering activity. The role of the reported C1(-) channels in transplacental ion transport and/or syncytium homeostasis remains to be determined.
引用
收藏
页码:83 / 95
页数:13
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