NR4A orphan nuclear receptors as mediators of CREB-dependent neuroprotection

Abstract

Induced expression of neuroprotective genes is essential for maintaining neuronal integrity after stressful insults to the brain. Here we show that NR4A nuclear orphan receptors are induced after excitotoxic and oxidative stress in neurons, up-regulate neuroprotective genes, and increase neuronal survival. Moreover, we show that NR4A proteins are induced by cAMP response element binding protein (CREB) in neurons exposed to stressful insults and that they function as mediators of CREB-induced neuronal survival. Animals with null mutations in three of six NR4A alleles show increased oxidative damage, blunted induction of neuroprotective genes, and increased vulnerability in the hippocampus after treatment with kainic acid. We also demonstrate that NR4A and the transcriptional coactivator PGC-1α independently regulate distinct CREB-dependent neuroprotective gene programs. These data identify NR4A nuclear orphan receptors as essential mediators of neuroprotection after exposure to neuropathological stress.excitotoxicity | kainic acid | oxidative stress N europathological conditions including stroke, Alzheimer's disease, and Parkinson's disease are associated with excitotoxic and oxidative stress. Transcriptional increases of neuroprotective genes, including antiapoptotic factors and scavengers of reactive oxygen species (ROS), are an important strategy for neuroprotection. Thus, understanding how neuroprotective gene programs are controlled at the transcriptional level is of considerable importance and may contribute to the identification of therapeutic strategies of disorders associated with neurodegeneration. cAMP response element binding protein (CREB) is a transcription factor that is activated in response to stressful stimuli such as hypoxia, oxidative stress, excitotoxicity, and ischemia (1). Evidence from loss-of-function and other types of experiments shows that CREB plays an important role in neuronal survival (2-5) and neuroprotection (6). It is also well established that CREB is required for acquisition of ischemic tolerance, an endogenous neuroprotective mechanism whereby prior exposure to brief ischemia produces resilience to subsequent normally injurious ischemia (7,8).Despite the well-documented neuroprotective effect of CREB, only little is known of how CREB mediates this activity and only few directly regulated neuroprotective target genes have been identified (9-13). In addition to target genes that are directly neuroprotective, CREB-induced transcription factors or cofactors may also contribute to neuron survival by regulating downstream gene batteries controlled by elevated cAMP levels in a transcription factor cascade initiated by activated CREB. Indeed, CREB induces the expression of peroxisome proliferator-activated receptor gamma coactivator-1a (PGC-1α), an important regulator of ROS-detoxifying enzyme gene expression (14). However, how CREB mediates neuroprotective gene cascades via the induction of additional transcriptional regulators remains unexplored.The NR4A orphan nuclear receptor (NR...

Essential role for DNA-PK-mediated phosphorylation of NR4A nuclear orphan receptors in DNA double-strand break repair

“…Such chromatin association has previously been found necessary for efficient activation of related DNA damage-responsive ATM kinases (Kim et al 2009). Finally, it is notable that numerous studies have implicated NR4A transcription factors in gene regulatory responses that counteract stressful insults, including oxidative stress, which often leads to induction of DSBs via the generation of reactive oxygen species (Rassool et al 2007;Volakakis et al 2010). Thus, the results presented here show that NR4A proteins use dual mechanisms that are both dependent on and independent of gene regulatory functions to provide protection against such stressful insults.…”

“…Neurons were derived from mouse embryonic stem cells differentiated as described previously (Volakakis et al 2010). Unless stated otherwise, cells were transfected with Lipofectamine Plus (Invitrogen) according to the manufacturer's instructions.…”

“…Generation of lentiviruses encoding GFP (Lenti-GFP) or NR4A2 (Lenti-NR4A2) has been described elsewhere (Volakakis et al 2010). MEFs were infected with lentiviruses at 5 MOI (multiplicity of infection) in six-well plates.…”

“…Similar results were obtained with viruses made in-house. For in-house virus production, 293FT cells were transfected with packaging plasmids as described in Volakakis et al (2010), including shRNA-encoding plasmid shControl (SHC002) and shmNR4A1 (TRCN0000218931 and TRCN0000234021, Mission System, Sigma). MEFs were infected with in-house-made lentivirus at 10 MOI as described above but without polybrene.…”

Prostaglandin E2 is essential for efficacious skeletal muscle stem-cell function, augmenting regeneration and strength

“…Nurr1 was among the few that were differentially expressed. Nurr1 had also previously been shown to mediate PGE2 signaling through cAMP and phospho-CREB to induce cell proliferation in colorectal cancer and neuronal cells (32,33). To investigate its putative role as a downstream effector of EP4 signaling in MuSCs, we examined its expression in vivo.…”