A mysterious channel: new insights into proton channel functioning raise new questions

摘要

Voltage-gated proton channels were described for the first time in snail neurons more than 25 years ago (Thomas & Meech, 1982). They have been found subsequently in a wide variety of mammalian cells, including epithelial cells, oocytes, skeletal muscle cells, lymphocytes and various phagocytes. Proton channels of all cell preparations are characterized by high proton selectivity, strong pH and voltage dependence, and high sensitivity to Zn2+. Proton channels open only when the electrochemical gradient for protons is outward, so they carry only outward current in the steady state. Depending on the cell type studied, proton channel currents differ to some extent with respect to their activation and deactivation time constants and their Ca2+ dependence (for review, see DeCoursey, 2003). To date, it remains unclear whether all proton channels are encoded by the same genes, while the observed differences in proton currents reflect channel modulation due to the specific microenvironment in certain cell types, or whether different proton channel types exist which are encoded by different genes.