ROLE OF G PROTEINS IN STIMULATION OF NA-H EXCHANGE BY CELL SHRINKAGE
ROLE OF G PROTEINS IN STIMULATION OF NA-H EXCHANGE BY CELL SHRINKAGE
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DOI：
10.1152/ajpcell.1992.262.2.c533
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发表时间：
1992-02-01
影响因子：
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通讯作者：
BORON, WF
中科院分区：
文献类型：
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作者：
DAVIS, BA;HOGAN, EM;BORON, WF
许多细胞通过刺激特定的离子转运过程（例如，Na-H交换）。 然而，目前尚不清楚细胞如何感知这种体积变化，也不知道这种信号如何被转导到离子转运蛋白。 我们研究了内透析藤壶肌纤维中Na-H交换的活化，用玻璃微电极测量细胞内pH（pH（i））。 当细胞被透析至pH（i）约为7.2时，Na-H交换仅在收缩的细胞中是活跃的。 我们发现，通过将介质渗透压从975 mosmol/kgH 2 O增加到1，600 mosmol/kgH 2 O引起的收缩诱导的Na-H交换刺激，通过在透析液中包含1 mM鸟苷5 '-O-（2-硫代二磷酸）抑制约72%。 后者是G蛋白激活的拮抗剂。 即使在未收缩的细胞中，Na-H交换也通过用1 mM鸟苷5 '-O-（3-硫代三磷酸）透析细胞而被激活，这导致G蛋白的延长激活。 在未萎缩的细胞中，注射霍乱毒素也会引起Na-H交换的激活，这会激活某些G蛋白。 将细胞暴露于100 nM佛波醇12-肉豆蔻酸酯13-乙酸酯或用含有20 μ M腺苷3 '，5'-环一磷酸（cAMP）（或50 μ M二丁酰cAMP）加0.5 mM 3-异丁基-1-甲基黄嘌呤的溶液透析细胞，都不会显著刺激交换剂。 因此，我们的数据表明，G蛋白通过既不涉及蛋白激酶C也不涉及cAMP的途径，在收缩信号到Na-H交换器的转导中起着关键作用。
Many cells respond to shrinkage by stimulating specific ion transport processes (e.g., Na-H exchange). However, it is not known how the cell senses this volume change, nor how this signal is transduced to an ion transporter. We have studied the activation of Na-H exchange in internally dialyzed barnacle muscle fibers, measuring intracellular pH (pH(i)) with glass microelectrodes. When cells are dialyzed to a pH(i) of approximately 7.2, Na-H exchange is active only in shrunken cells. We found that the shrinkage-induced stimulation of Na-H exchange, elicited by increasing medium osmolality from 975 to 1,600 mosmol/kgH2O, is inhibited approximately 72% by including in the dialysis fluid 1 mM guanosine 5'-O-(2-thiodiphosphate). The latter is an antagonist of G protein activation. Even in unshrunken cells, Na-H exchange is activated by dialyzing the cell with 1 mM guanosine 5'-O-(3-thiotriphosphate), which causes the prolonged activation of G proteins. Activation of Na-H exchange is also elicited in unshrunken cells by injecting cholera toxin, which activates certain G proteins. Neither exposing cells to 100 nM phorbol 12-myristate 13-acetate nor dialyzing them with a solution containing 20-mu-M adenosine 3',5'-cyclic monophosphate (cAMP) (or 50-mu-M dibutyryl cAMP) plus 0.5 mM 3-isobutyl-1-methylxanthine substantially stimulates the exchanger. Thus our data suggest that a G protein plays a key role in the transduction of the shrinkage signal to the Na-H exchanger via a pathway that involves neither protein kinase C nor cAMP.