Cellular proton buffering: Spatio-temporal dynamics

点击翻译按钮获取中文摘要

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.