ERK1/2 Mitogen-Activated Protein Kinase Phosphorylates Sodium Channel Na(v)1.7 and Alters Its Gating Properties

Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 02/2010; 30(5):1637-47. DOI: 10.1523/JNEUROSCI.4872-09.2010
Source: PubMed


Na(v)1.7 sodium channels can amplify weak stimuli in neurons and act as threshold channels for firing action potentials. Neurotrophic factors and pro-nociceptive cytokines that are released during development and under pathological conditions activate mitogen-activated protein kinases (MAPKs). Previous studies have shown that MAPKs can transduce developmental or pathological signals by regulating transcription factors that initiate a gene expression response, a long-term effect, and directly modulate neuronal ion channels including sodium channels, thus acutely regulating dorsal root ganglion (DRG) neuron excitability. For example, neurotrophic growth factor activates (phosphorylates) ERK1/2 MAPK (pERK1/2) in DRG neurons, an effect that has been implicated in injury-induced hyperalgesia. However, the acute effects of pERK1/2 on sodium channels are not known. We have shown previously that activated p38 MAPK (pp38) directly phosphorylates Na(v)1.6 and Na(v)1.8 sodium channels and regulates their current densities without altering their gating properties. We now report that acute inhibition of pERK1/2 regulates resting membrane potential and firing properties of DRG neurons. We also show that pERK1 phosphorylates specific residues within L1 of Na(v)1.7, inhibition of pERK1/2 causes a depolarizing shift of activation and fast inactivation of Na(v)1.7 without altering current density, and mutation of these L1 phosphoacceptor sites abrogates the effect of pERK1/2 on this channel. Together, these data are consistent with direct phosphorylation and modulation of Na(v)1.7 by pERK1/2, which unlike the modulation of Na(v)1.6 and Na(v)1.8 by pp38, regulates gating properties of this channel but not its current density and contributes to the effects of MAPKs on DRG neuron excitability.

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    • "The expression of the high-affinity NGF receptor TrkA in adult DRG is restricted to nociceptors [8]. After NGF binds to TrkA on nociceptors, mitogen-activated protein kinases are activated [17] and then phosphorylate voltage-gated sodium channels to make nociceptors hyperexcitable without de novo protein synthesis [19] [50]. NGF, as well as other neurotrophins, did not significantly alter the number of TrkA(+) DRG neurons at day 3 after intrathecal injection to naive rats [35]. "
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    ABSTRACT: Mirror-image pain is characterized by mechanical hypersensitivity on the uninjured mirror-image side. Recent reports favor central mechanisms, but whether peripheral mechanisms are involved remains unclear. We used unilateral spinal nerve ligation (SNL) to induce mirror-image pain in rats. On the mirror-image (contralateral) side, we found that satellite glia in the dorsal root ganglion (DRG) were activated, whereas macrophages/Schwann cells in the DRG and astrocytes/oligodendrocytes/microglia in the dorsal spinal cord were not. Subsequently, a rise of nerve growth factor (NGF) was detected in the contralateral DRG, and NGF immunoreactivity was concentrated in activated satellite glia. These phenomena were abolished if fluorocitrate (a glial inhibitor) was intrathecally injected before SNL. Electrophysiological recordings in cultured small DRG neurons showed that exogenous NGF enhanced nociceptor excitability. Intrathecal injection of NGF into naïve rats induced long-lasting mechanical hypersensitivity, similar to SNL-evoked mirror-image pain. Anti-NGF effectively relieved SNL-evoked mirror-image pain. In the contralateral DRG, SNL-evoked tumor necrosis factor alpha (TNFα) increase, which was started later than that in the ipsilateral DRG and cerebrospinal fluid, occurred earlier than satellite glial activation and NGF rise. Intrathecal injection of TNFα into naïve rats not only activated satellite glia to produce extra NGF in the DRG but also evoked mechanical hypersensitivity, which could be attenuated by anti-NGF injection. These results suggest that after SNL, satellite glia in the contralateral DRG are activated by TNFα diffused from the injured side via cerebrospinal fluid, and then activated satellite glia produce extra NGF to enhance nociceptor excitability, which induces mirror-image pain.
    Pain 01/2014; DOI:10.1016/j.pain.2014.01.010 · 5.21 Impact Factor
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    • "Retrograde transport of NGF via the peripheral terminals of abnormally sprouting sensory nerve fibres to the cell bodies of primary sensory neurons in the dorsal root ganglia (DRGs) likely contributes to first-order sensory neuron hyperexcitability via multiple mechanisms. Such mechanisms include upregulated synthesis of pro-nociceptive mediators (Mantyh et al. 2011), activation of p38 mitogenactivated protein kinase (MAPK) (Ji et al. 2002) and p44/ p42 MAPK (Averill et al. 2001)-induced sensitization (phosphorylation) of the TRPV1 (Ji et al. 2002) as well as voltage-gated sodium (Hudmon et al. 2008; Stamboulian et al. 2010) and calcium channels (Martin et al. 2006). Together, these observations strongly implicate a role for NGF/TrkA signalling in the maintenance of PCIBP. "
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    ABSTRACT: Prostate cancer (PCa) has a high propensity for metastasis to bone. Despite the availability of multiple treatment options for relief of PCa-induced bone pain (PCIBP), satisfactory relief of intractable pain in patients with advanced bony metastases is challenging for the clinicians because currently available analgesic drugs are often limited by poor efficacy and/or dose-limiting side effects. Rodent models developed in the past decade show that the pathobiology of PCIBP comprises elements of inflammatory, neuropathic and ischemic pain arising from ectopic sprouting and sensitization of sensory nerve fibres within PCa-invaded bones. In addition, at the cellular level, PCIBP is underpinned by dynamic cross talk between metastatic PCa cells, cellular components of the bone matrix, factors associated with the bone microenvironment as well as peripheral components of the somatosensory system. These insights are aligned with the clinical management of PCIBP involving use of a multimodal treatment approach comprising analgesic agents (opioids, NSAIDs), radiotherapy, radioisotopes, cancer chemotherapy agents and bisphosphonates. However, a major drawback of most rodent models of PCIBP is their short-term applicability due to ethical concerns. Thus, it has been difficult to gain insight into the mal(adaptive) neuroplastic changes occurring at multiple levels of the somatosensory system that likely contribute to intractable pain at the advanced stages of metastatic disease. Specifically, the functional responsiveness of noxious circuitry as well as the neurochemical signature of a broad array of pro-hyperalgesic mediators in the dorsal root ganglia and spinal cord of rodent models of PCIBP is relatively poorly characterized. Hence, recent work from our laboratory to develop a protocol for an optimized rat model of PCIBP will enable these knowledge gaps to be addressed as well as identification of novel targets for drug discovery programs aimed at producing new analgesics for the improved relief of intractable PCIBP.
    Inflammopharmacology 08/2013; 21(5). DOI:10.1007/s10787-013-0183-7
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    • "Nav1.7 has been shown to accumulate in the blind-ending axons of painful human neuromas [45-47]. Interestingly, the MAP kinase, ERK1/2, which phophorylates Nav1.7 and enhances its activation [48], also accumulates in painful human neuromas [47], and has recently been shown in experimental neuromas to co-localize within individual axons with Nav1.7 [49]. "
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    Molecular Pain 11/2012; 8(1):82. DOI:10.1186/1744-8069-8-82 · 3.65 Impact Factor
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