Cellular proton buffering: Spatio-temporal dynamics

细胞溶质pH的变化影响多种细胞过程，包括基因表达、代谢活性、细胞信号传导、细胞增殖和肿瘤生长。我们几乎不知道质子缓冲的生理过程的动态变化和细胞分布的作用，相反，细胞缓冲的钙，例如，有证据表明，细胞质质子缓冲有几个组件，其中一些可能有助于动态和局部变化的缓冲能力，因此对pH值变化的幅度和动力学。酸/碱偶联膜转运蛋白和碳酸酐酶活性可能会影响pH瞬变细胞内和细胞外;然而，关于快速H+/HCO 3-跨细胞膜转运的相关性和碳酸酐酶用于质子缓冲的细胞分布知之甚少。在本研究中，我们要分析钠-碳酸氢盐协同转运蛋白（NBCe 1，SLC 4A 4），一个总理酸/碱调节细胞中的作用，和细胞溶质碳酸酐酶II的活性和分布，为'明显的'细胞溶质质子缓冲。通过用染料和/或微电极测量培养的星形胶质细胞中的细胞内pH，其中这些蛋白质天然表达，以及在非洲爪蟾卵母细胞中，其中这些转运蛋白将异源表达，酸/碱通量和Na+上升的速率，以及碳酸酐酶II活性将与细胞H+缓冲相关。我们的目标是评估质子缓冲能力的动态和局部变化，这决定了细胞和组织中pH值瞬变的程度，并将尝试使用数学方法对时空质子缓冲进行建模。这些结果对于深入了解pH变化的产生和调节以及pH依赖性细胞过程的调节是重要的。

Changes in cytosolic pH affect multiple cellular processes, including gene expression, metabolic activity, cellular signalling, cell proliferation and tumor growth. We know virtually nothing about the role of dynamic changes and cellular distribution of proton buffering for physiological processes, in contrast to cellular buffering of calcium e.g. There is evidence, however, that cytoplasmic proton buffering has several components, some of which may contribute to dynamic and local changes of buffering capacity, and hence on the amplitude and kinetics of pH changes. Acid-/base-coupled membrane transporters and carbonic anhydrase activity may affect pH transients both intra- and extracellularly; very little is known, however, about the relevance of fast H+/HCO3 - transport across cell membranes and the cellular distribution of carbonic anhydrases for proton buffering. In the present study, we want to analyse the role of the sodium-bicarbonate cotransporter (NBCe1, SLC4A4), a prime acid/base regulator in cells, and the activity and distribution of cytosolic carbonic anhydrase II, for ‘apparent’ cytosolic proton buffering. By measuring intracellular pH with dyes and/or microelectrodes in cultured astrocytes, where these proteins are natively expressed, and in Xenopus oocytes, in which these transport proteins will be heterologously expressed, the rate of acid/base flux and Na+ rise, and the carbonic anhydrase II activity will be correlated with cellular H+ buffering. We aim to evaluate the dynamics and local changes of proton buffer capacity, which determine the extent of pH transients in cells and tissues, and will try to model spatio-temporal proton buffering using mathematical approaches. The results are important for gaining insight into the generation and modulation of pH changes, and into the regulation of pHdependent cellular processes.