SGK3 Regulates Ca²⁺Entry and Migration of Dendritic Cells

Abstract

Background/Aims: Dendritic cells (DCs) are antigen-presenting cells linking innate and adaptive immunity. DC maturation and migration are governed by alterations of cytosolic Ca²⁺ concentrations ([Ca²⁺]_i). Ca²⁺ entry is in part accomplished by store-operated Ca²⁺ (SOC) channels consisting of the membrane pore-forming subunit Orai and the ER Ca²⁺ sensing subunit STIM. Moreover, DC functions are under powerful regulation of the phosphatidylinositol-3-kinase (PI3K) pathway, which suppresses proinflammatory cytokine production but supports DC migration. Downstream targets of PI3K include serum- and glucocorticoid-inducible kinase isoform SGK3. The present study explored, whether SGK3 participates in the regulation of [Ca²⁺]_i and Ca²⁺-dependent functions of DCs, such as maturation and migration. Methods/ Results: Experiments were performed with bone marrow derived DCs from gene targeted mice lacking SGK3 (sgk3^-/-) and DCs from their wild type littermates (sgk3^+/+). Maturation, phagocytosis and cytokine production were similar in sgk3^-/- and sgk3^+/+ DCs. However, SOC entry triggered by intracellular Ca²⁺ store depletion with the endosomal Ca²⁺ ATPase inhibitor thapsigargin (1 µM) was significantly reduced in sgk3^-/- compared to sgk3^+/+ DCs. Similarly, bacterial lipopolysaccharide (LPS, 1 µg/ml)- and chemokine CXCL12 (300 ng/ml)- induced increase in [Ca²⁺]_i was impaired in sgk3^-/- DCs. Moreover, currents through SOC channels were reduced in sgk3^-/- DCs. STIM2 transcript levels and protein abundance were significantly lower in sgk3^-/- DCs than in sgk3^+/+ DCs, whereas Orai1, Orai2, STIM1 and TRPC1 transcript levels and/or protein abundance were similar in sgk3-/- and sgk3^+/+ DCs. Migration of both, immature DCs towards CXCL12 and LPS-matured DCs towards CCL21 was reduced in sgk3^-/- as compared to sgk3^+/+ DCs. Migration of sgk3^+/+ DCs was further sensitive to SOC channel inhibitor 2-APB (50 µM) and to STIM1/STIM2 knock-down. Conclusion: SGK3 contributes to the regulation of store-operated Ca²⁺ entry into and migration of dendritic cells, effects at least partially mediated through SGK3-dependent upregulation of STIM2 expression.

SGK3 sustains ERα signaling and drives acquired aromatase inhibitor resistance through maintaining endoplasmic reticulum homeostasis

“…Here we showed that SERCA2b is required for ERα expression, and SGK3 preserves SERCA2b function in AIresistant cells, although the detailed mechanism still needs to be resolved. Recently, Schmid et al reported that SGK3 regulates Ca 2+ entry in dendritic cells through up-regulation of STIM2 expression (44). Our study suggests SGK3 maintains EnR Ca 2+ homeostasis through preserving SERCA2b function, and thus protects against excessive EnR stress, which results in ERα depletion and cell death in AI-resistant cells.…”

Energy-sensitive regulation of Na+/K+-ATPase by Janus kinase 2

“…Ouabain-sensitive K ϩ -induced currents (Ipump) reflecting Na ϩ /K ϩ -ATPase activity were determined by whole cell patch-clamp recording in human Jurkat T cells before and following energy depletion with 2 mM DNP for 4 h in the presence and absence of JAK2 inhibitor AG490 (40 M) (preincubation 1 h before addition of DNP). Alternatively, Jurkat cells were pretreated with AG490 (40 M) alone for 4 h. Patch-clamp experiments were performed at room temperature in voltage-clamp, fast whole cell mode (35,70,79). Cells were continuously superfused through a flow system inserted into the dish.…”

Down-Regulation of Store-Operated Ca2+ Entry and Na+ Ca2+ Exchange in MCF-7 Breast Cancer Cells by Pharmacological JAK3 Inhibition

“…Orai and NCX dependent Ca 2+ oscillations are further instrumental in the stimulation of cell migration [52][53][54]. Accordingly, Orai1, 2, or 3 [6][7][8][9], their regulators STIM 1 or 2 [12,13,15] and Na + /Ca 2+ exchangers [55] are involved in the regulation of survival, proliferation, and migration of tumor cells [56][57][58][59][60][61][62][63][64][65][66][67][68][69].…”