Ion Channels Modulating Mouse Dendritic Cell Functions

Ca(2+)-mediated signal transduction pathways play a central regulatory role in dendritic cell (DC) responses to diverse Ags. However, the mechanisms leading to increased [Ca(2+)](i) upon DC activation remained ill-defined. In the present study, LPS treatment (100 ng/ml) of mouse DCs resulted in a rapid increase in [Ca(2+)](i), which was due to Ca(2+) release from intracellular stores and influx of extracellular Ca(2+) across the cell membrane. In whole-cell voltage-clamp experiments, LPS-induced currents exhibited properties similar to the currents through the Ca(2+) release-activated Ca(2+) channels (CRAC). These currents were highly selective for Ca(2+), exhibited a prominent inward rectification of the current-voltage relationship, and showed an anomalous mole fraction and a fast Ca(2+)-dependent inactivation. In addition, the LPS-induced increase of [Ca(2+)](i) was sensitive to margatoxin and ICAGEN-4, both inhibitors of voltage-gated K(+) (Kv) channels Kv1.3 and Kv1.5, respectively. MHC class II expression, CCL21-dependent migration, and TNF-alpha and IL-6 production decreased, whereas phagocytic capacity increased in LPS-stimulated DCs in the presence of both Kv channel inhibitors as well as the I(CRAC) inhibitor SKF-96365. Taken together, our results demonstrate that Ca(2+) influx in LPS-stimulated DCs occurs via Ca(2+) release-activated Ca(2+) channels, is sensitive to Kv channel activity, and is in turn critically important for DC maturation and functions.