Blunted IgE-mediated activation of mast cells in mice lacking the serum- and glucocorticoid-inducible kinase SGK3

Previous studies have shown that pharmacological inhibition of the phosphoinositol-3 (PI3) kinase disrupts the activation of mast cells. Through phosphoinositide-dependent kinase PDK1, PI3 kinase activates the serum- and glucocorticoid-inducible kinase 3 (SGK3). The present study explored the role of SGK3 in mast cell function. Mast cells were isolated and cultured from bone marrow (BMMCs) of gene-targeted mice lacking SGK3 ([sgk3.sup.-/-]) and their wild-type littermates ([sgk3.sup.+/+]). BMMC numbers in the ear conch were similar in both genotypes. Stimulation with IgE and cognate antigen triggered the release of intracellular [Ca.sup.2+] and entry of extracellular [Ca.sup.2+]. Influx of extracellular [Ca.sup.2+] but not [Ca.sup.2+] release from intracellular stores was significantly blunted in [sgk3.sup.-/-] BMMCs compared with [sgk3.sup.+/+] BMMCs. Antigen stimulation further led to a rapid increase of a [K.sup.+]-selective conductance in [sgk3.sup.+/+] BMMCs, an effect again blunted in [sgk3.sup.-/-] BMMCs. In contrast, the [Ca.sup.2+] ionophore ionomycin activated [K.sup.+] currents to a similar extent in [sgk3.sup.-/-] and in [sgk3.sup.+/+] BMMCs. [beta]-Hexosaminidase release, triggered by antigen stimulation, was also significantly decreased in [sgk3.sup.-/-] BMMCs. IgE-dependent anaphylaxis measured as a sharp decrease in body temperature upon injection of DNP-HSA antigen was again significantly blunted in [sgk3.sup.-/-] compared with [sgk3.sup.+/+] mice. Serum histamine levels measured 30 rain after induction of an anaphylactic reaction were significantly lower in [sgk3.sup.-/-] than in [sgk3.sup.+/+] mice. In conclusion, both in vitro and in vivo function of BMMCs are impaired in gene targeted mice lacking SGK3. Thus SGK3 is critical for proper mast cell function. allergy; anaphylaxis; calcium ion channels; degranulation; potassium ion channels; [K.sub.ca] 3.1; phosphoinositol-3 kinase doi: 10.1152/ajpcell.00539.2009.