Glycogen Synthase Kinase-3β Indirectly Facilitates Interferon-γ-Induced Nuclear Factor-κB Activation and Nitric Oxide Biosynthesis

Either glycogen synthase kinase (GSK)-3 beta or nuclear factor (NF)-kappa B regulates interferon (IFN)-gamma-induced nitric oxide (NO) biosynthesis; however, the inter-regulation between GSK-3 beta and NF-kappa B is unknown. We have previously shown that IFN-gamma-activated GSK-3 beta negatively regulates Src homology-2 domain-containing phosphatase (SHP) 2 to facilitate Janus kinase (Jak) 2-signal transducer and activator of transcription (STAT) 1 activation. Because Jaks-IFN-inducible dsRNA-activated serine-threonine protein kinase (PKR) axis signaling is essential for IFN-gamma-activation of NF-kappa B, in this study we investigate the potential mechanism for GSK-3 beta-facilitated NF-kappa B activation in IFN-gamma-stimulated RAW264.7 murine macrophages. Pharmacological inhibitors of GSK-3 beta or NF-kappa B signaling, such as the inhibitor of kappa B (I kappa B) kinase beta (IKK beta) and I kappa B alpha, inhibited IFN-gamma-induced inducible NO synthase (iNOS) and thus NO biosynthesis. Inhibiting GSK-3 beta decreased IFN-gamma-induced NF-kappa B phosphorylation (Ser536) and activation. The upstream regulators for GSK-3 beta activation, including okadaic acid-sensitive protein phosphatase and proline-rich tyrosine kinase 2, were also important for IFN-gamma-induced I kappa B alpha phosphorylation (Ser32) and degradation. Under IFN-gamma stimulation, Jak2-PKR axis signaling induced I kappa B alpha inactivation as well as iNOS/NO biosynthesis. It is notable that inhibiting GSK-3 beta caused SHP2-mediated dephosphorylation of PKR (Thr446), IKK beta (Ser180), and NF-kappa B (Ser536). Taken together, we provide the first evidence to demonstrate that GSK-3 beta indirectly facilitates IFN-gamma-induced NF-kappa B activation by inhibiting