Capacitative calcium entry. Glioma C6 as a model of nonexcitable cells

Although the mechanism of the capacitative Ca2+ entry is still a mysterious process, it has been presently accepted that it occurs through plasma membrane channel pores rather than through a carrier mechanism. As it has been proposed by Putney (Cell Calcium, 1986, 7, 1-12), Ca2+ entry is directly dependent on the state of filling of the endoplasmic reticulum Ca2+ stores, i.e. it is activated by the depletion of the endoplasmic reticulum Ca2+ pool. However, the nature of the signal for activation of Ca2+ entry is still unknown. The biphasic capacitative Ca2+ entry involves inositol phosphate system and is ubiquitous in all nonexcitable cells. We have shown that glioma C6 cells belong to such type of cells and are characterized by a typical capacitative Ca2+ entry pathway. The characteristics of this Ca2+ influx is summarized and the hypotheses about its mechanism of activation are discussed.