Nerve Growth Factor (NGF) Regulates Activity of the Transcription Factor NFAT in Neurons via the Phosphatidylinositol-3-Kinase (PI3K)-Akt-Glycogen Synthase Kinase 3{beta} (GSK3{beta}) Pathway [Signal Transduction]

September 17th, 2014 by Kim, M. S., Shutov, L. P., Gnanasekaran, A., Lin, Z., Rysted, J. E., Ulrich, J. D., Usachev, Y. M.

The Ca2+/calcineurin-dependent transcription factor NFAT (nuclear factor of activated T-cells) plays an important role in regulating many neuronal functions, including excitability, axonal growth, synaptogenesis and neuronal survival. NFAT can be activated by action potential firing or depolarization that leads to Ca2+/calcineurin-dependent dephosphorylation of NFAT and its translocation to the nucleus. Recent data suggest that NFAT and NFAT-dependent functions in neurons can also be potently regulated by nerve growth factor (NGF) and other neurotrophins. However, the mechanisms of NFAT regulation by neurotrophins are not well understood. Here, we show that in dorsal root ganglion (DRG) sensory neurons, NGF markedly facilitates NFAT-mediated gene expression induced by mild depolarization. The effects of NGF were not associated with changes in intracellular Ca2+ concentration ([Ca2+]i) and were independent of phospholipase C (PLC) activity. Instead, the facilitatory effect of NGF depended on activation of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway downstream of the TrkA receptor, and on inhibition of glycogen synthase kinase 3β (GSK3β), a protein kinase known to phosphorylate NFAT and promote its nuclear export. Knockdown or knockout of NFATc3 eliminated this facilitatory effect. Simultaneous monitoring of EGFP-NFATc3 nuclear translocation and [Ca2+]i changes in DRG neurons indicated that NGF slowed the rate of NFATc3 nuclear export, but did not affect its nuclear import rate. Collectively, our data suggest that NGF facilitates depolarization-induced NFAT activation by stimulating PI3K/Akt signaling, inactivating GSK3β, and thereby slowing NFATc3 export from the nucleus. We propose that NFAT serves as an integrator of neurotrophin action and depolarization-driven calcium signaling to regulate neuronal gene expression.
  • Posted in Journal of Biological Chemistry, Publications
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