Extended JAK activation and delayed STAT1 dephosphorylation contribute to the distinct signaling profile of CNS neurons exposed to interferon-gamma

Although interferon-gamma (IFN-gamma) plays a critical role in the noncytolytic elimination of many neurotropic viral infections, the signaling response to this cytokine has not been extensively characterized in primary CNS neurons. We previously demonstrated that the IFN-gamma response at the signaling and gene expression levels is temporally extended in primary mouse hippocampal neurons, as compared to the transient response of primary mouse embryonic fibroblasts (MEF). We hypothesize that the protracted kinetics of STAT1 phosphorylation in IFN-gamma-treated neurons are due to extended receptor activation and/or delayed STAT1 dephosphorylation in the nucleus. Here, we show that in response to IFN-gamma, the Janus kinases (JAK1/JAK2) associated with the neuronal IFN-gamma receptor complex remain active for an extended period as compared to MEF. Experimental inactivation of JAK1/JAK2 in neurons after IFN-gamma treatment did not reverse the extended STAT1 phosphorylation phenotype. These results suggest that the extended kinetics of neuronal IFN-gamma signaling are a product of distinct negative feedback mechanisms operating at both the receptor and within the nucleus. (C) 2012 Elsevier B.V. All rights reserved.