Mohebbi Nilufar, Benabbas Chahira, Vidal Solange, Daryadel Arezoo, Bourgeois Soline, Velic Ana, Ludwig Marie-Gabrielle, Seuwen Klaus, Wagner Carsten A
Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
Cell Physiol Biochem. 2012;29(3-4):313-24. doi: 10.1159/000338486. Epub 2012 Apr 3.
The Ovarian cancer G protein-coupled Receptor 1 (OGR1; GPR68) is proton-sensitive in the pH range of 6.8 - 7.8. However, its physiological function is not defined to date. OGR1 signals via inositol trisphosphate and intracellular calcium, albeit downstream events are unclear. To elucidate OGR1 function further, we transfected HEK293 cells with active OGR1 receptor or a mutant lacking 5 histidine residues (H5Phe-OGR1). An acute switch of extracellular pH from 8 to 7.1 (10 nmol/l vs 90 nmol/l protons) stimulated NHE and H(+)-ATPase activity in OGR1-transfected cells, but not in H5Phe-OGR1-transfected cells. ZnCl(2) and CuCl(2) that both inhibit OGR1 reduced the stimulatory effect. The activity was blocked by chelerythrine, whereas the ERK1/2 inhibitor PD 098059 had no inhibitory effect. OGR1 activation increased intracellular calcium in transfected HEK293 cells. We next isolated proximal tubules from kidneys of wild-type and OGR1-deficient mice and measured the effect of extracellular pH on NHE activity in vitro. Deletion of OGR1 affected the pH-dependent proton extrusion, however, in the opposite direction as expected from cell culture experiments. Upregulated expression of the pH-sensitive kinase Pyk2 in OGR1 KO mouse proximal tubule cells may compensate for the loss of OGR1. Thus, we present the first evidence that OGR1 modulates the activity of two major plasma membrane proton transport systems. OGR1 may be involved in the regulation of plasma membrane transport proteins and intra- and/or extracellular pH.
卵巢癌G蛋白偶联受体1（OGR1；GPR68）在pH值6.8 - 7.8范围内对质子敏感。然而，其生理功能至今尚未明确。OGR1通过肌醇三磷酸和细胞内钙进行信号传导，尽管下游事件尚不清楚。为了进一步阐明OGR1的功能，我们用活性OGR1受体或缺失5个组氨酸残基的突变体（H5Phe - OGR1）转染HEK293细胞。细胞外pH从8急性切换到7.1（10 nmol/l对90 nmol/l质子）刺激了OGR1转染细胞中的NHE和H(+) - ATP酶活性，但在H5Phe - OGR1转染细胞中未出现这种情况。抑制OGR1的ZnCl(2)和CuCl(2)降低了这种刺激作用。该活性被白屈菜红碱阻断，而ERK1/2抑制剂PD 098059没有抑制作用。OGR1激活增加了转染的HEK293细胞内的钙含量。接下来，我们从野生型和OGR1缺陷型小鼠的肾脏中分离出近端小管，并在体外测量细胞外pH对NHE活性的影响。OGR1的缺失影响了pH依赖性质子外排，然而，其方向与细胞培养实验预期的相反。OGR1基因敲除小鼠近端小管细胞中pH敏感激酶Pyk2的表达上调可能补偿了OGR1的缺失。因此，我们首次证明OGR1调节两种主要质膜质子转运系统的活性。OGR1可能参与质膜转运蛋白以及细胞内和/或细胞外pH的调节。
