Fundamental Ca Signaling Mechanisms in Mouse Dendritic Cells: CRAC Is the Major Ca Entry Pathway

Although Ca-signaling processes are thought to underlie many dendritic cell (DC) functions, the Ca entry pathways are unknown. Therefore, we investigated Ca-signaling in mouse myeloid DC using Ca imaging and electrophysiological techniques. Neither Ca currents nor changes in intracellular Ca were detected following membrane depolarization, ruling out the presence of functional voltage-dependent Ca channels. ATP, a purinergic receptor ligand, and 1–4 dihydropyridines, previously suggested to activate a plasma membrane Ca channel in human myeloid DC, both elicited Ca rises in murine DC. However, in this study these responses were found to be due to mobilization from intracellular stores rather than by Ca entry. In contrast, Ca influx was activated by depletion of intracellular Ca stores with thapsigargin, or inositol trisphosphate. This Ca influx was enhanced by membrane hyperpolarization, inhibited by SKF 96365, and exhibited a cation permeability similar to the Ca release-activated Ca channel (CRAC) found in T lymphocytes. Furthermore, ATP, a putative DC chemotactic and maturation factor, induced a delayed Ca entry with a voltage dependence similar to CRAC. Moreover, the level of phenotypic DC maturation was correlated with the extracellular Ca concentration and enhanced by thapsigargin treatment. These results suggest that CRAC is a major pathway for Ca entry in mouse myeloid DC and support the proposal that CRAC participates in DC maturation and migration. The Journal of Immunology, 2001, 166: 6126–6133.