Neuregulin-1β regulates tyrosine kinase receptor expression in cultured dorsal root ganglion neurons with excitotoxicity induced by glutamate

Neuregulin-1 (NRG-1) signaling regulates neuronal development, migration, myelination, and synaptic maintenance. Three members of tyrosine kinase receptor (Trk) family, TrkA, TrkB, and TrkC, have been identified in DRG neurons. Whether NRG-1 beta and its signaling pathways influence the expression of these Trk receptors in DRG neurons is still unclear. In the present study, primary cultured DRG neurons were used to determine the effects of NRG-1 beta on TrkA, TrkB, and TrkC expression in DRG neurons with excitotoxicity induced by glutamate (Glu). The involvement of phosphatidylinositol 3-kinase (PI3K)/Akt and the effects of extracellular signal-regulated protein kinase (ERK1/2) signaling pathways on NRG-1 beta were also determined. DRG neurons were cultured for 48 h and then exposed to Glu, Glu plus NRG-1 beta, LY294002 plus Glu plus NRG-1 beta, PD98059 plus Glu plus NRG-1 beta, and PD98059 plus LY294002 plus Glu plus NAG-1 beta for an additional 24 h. The DRG neurons were continuously exposed to culture media as a control. After that, all cultures were processed for detection of mRNA levels of TrkA, TrkB, and TrkC using real time-PCR analysis. Protein levels of TrkA, TrkB, and TrkC were detected using a Western blot assay. The expression of TrkA, TrkB, and TrkC in situ was determined by a fluorescent labeling technique. The levels of phosphorylated Akt (pAkt), phosphorylated ERK1/2 (pERK1/2), total protein levels of Akt and ERK1/2 were detected using a Western blot assay. The results indicated that in primary cultured DRG neurons with excitotoxicity induced by Glu, NRG-1 beta increased the expression of TrkA and TrkB their mRNAs, but not TrkC and its mRNA. Inhibitors (LY294002, PD98059) either alone or in combination blocked the effects of NRG-1 beta. NRG-1 beta may play an important role in regulating the expression of different Trk receptors in DRG neurons through the PI3K/Akt and ERK1/2 signaling pathways. (C) 2012 Elsevier B.V. All rights reserved.