Enhanced Ca2+entry and Na+/Ca2+exchanger activity in dendritic cells from AMP‐activated protein kinase‐deficient mice

In dendritic cells (DCs), chemotactic chemokines, such as CXCL12, rapidly increase cytosolic Ca2+ concentrations ([Ca2+]i) by triggering Ca2+ release from intracellular stores followed by store-operated Ca2+ (SOC) entry. Increase of [Ca2+]i is blunted and terminated by Ca2+ extrusion, accomplished by K+independent Na+/Ca2+ exchangers (NCXs) and K+-dependent Na+/Ca2+ exchangers (NCKXs). Increased [Ca2+]i activates energy-sensing AMP-activated protein kinase (AMPK), which suppresses proinflammatory responses of DCs and macrophages. The present study explored whether AMPK participates in the regulation of DC [Ca2+]i and migration. DCs were isolated from AMPKα1-deficient (ampk–/–) mice and, as control, from their wild-type (ampk+/+) littermates. AMPKα1, Orai1-2, STIM1-2, and mitochondrial calcium uniporter protein expression was determined by Western blotting, [Ca2+]i by Fura-2 fluorescence, SOC entry by inhibition of endosomal Ca2+ ATPase with thapsigargin (1 μM), Na+/Ca2+ exchanger activity from increase of [Ca2+]i, and respective whole-cell current in patch clamp following removal of extracellular Na+. Migration was quantified utilizing transwell chambers. AMPKα1 protein is expressed in ampk+/+ DCs but not in ampk–/– DCs. CXCL12 (300 ng/ml)-induced increase of [Ca2+]i, SOC entry, Orai 1 protein abundance, NCX, and NCKX were all significantly higher in ampk–/– DCs than in ampk+/+ DCs. NCX and NCKX currents were similarly increased in ampk–/– DCs. Moreover, CXCL12 (50 ng/ml)-induced DC migration was enhanced in ampk–/– DCs. AMPK thus inhibits SOC entry, Na+/Ca2+ exchangers, and migration of DCs.—Nurbaeva, M. K., Schmid, E., Szteyn, K., Yang, W., Viollet, B., Shumilina, E., Lang, F. Enhanced Ca2+ entry and Na+/Ca2+ exchanger activity in dendritic cells from AMP-activated protein kinase-deficient mice. FASEB J. 26, 3049–3058 (2012). www.fasebj.org