Expression of the human erythroid Rh glycoprotein (RhAG) enhances both NH3 and NH4+ transport in HeLa cells

被引:52
作者
Benjelloun, F
Bakouh, N
Fritsch, J
Hulin, P
Lipecka, J
Edelman, A
Planelles, G
Thomas, SR
Chérif-Zahar, B
机构
[1] Univ Paris 05, INSERM, U467, F-75015 Paris, France
[2] CNRS, UPR 1524, F-75674 Paris, France
来源
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY | 2005年 / 450卷 / 03期
关键词
Rh proteins; ammonium; intracellular pH;
D O I
10.1007/s00424-005-1381-y
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
The erythroid Rh-associated glycoprotein (RhAG) is strictly required for the expression of the Rh blood group antigens carried by Rh (D,CE) proteins. A biological function for RhAG in ammonium transport has been suggested by its ability to improve survival of an ammonium-uptake-deficient yeast. We investigated the function of RhAG by studying the entry of NH3/NH4+ in HeLa cells transiently expressing the green fluorescent protein (GFP)-RhAG fusion protein and using a fluorescent proton probe to measure intracellular pH (pH(i)). Under experimental conditions that reduce the intrinsic Na/H exchanger activity, exposure of control cells to a 10 mM NH4Cl-containing solution induces the classic pHi response profile of cells having a high permeability to NH3 (P-NH3) but relatively low permeability to NH4+ (P-NH4). In contrast, under the same conditions, the pHi profile of cells expressing RhAG clearly indicated an increased P-NH4, as evidenced by secondary reacidification during NH4Cl exposure and a pHi undershoot below the initial resting value upon its removal. Measurements of pHi during methylamonium exposure showed that RhAG expression enhances the influx of both the unprotonated and ionic forms of methylammonium. Using a mathematical model to adjust passive permeabilities for a fit to the pHi profiles, we found that RhAG expression resulted in a threefold increase Of P-NH4 and a twofold increase Of P-NH3. Our results are the first evidence that the human erythroid RhAG increases the transport of both NH3 and NH4+.
引用
收藏
页码:155 / 167
页数:13
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