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Regulation of Slack K Na Channel Trafficking by p38 MAP Kinase
Author(s) -
Gururaj Sushmitha,
Bhattacharjee Arin,
Fleites John
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.975.2
Subject(s) - dorsal root ganglion , neuropathic pain , neuroscience , context (archaeology) , mapk/erk pathway , sodium channel , sensitization , protein kinase a , nociception , allodynia , p38 mitogen activated protein kinases , microbiology and biotechnology , hyperalgesia , phosphorylation , chemistry , sensory system , medicine , biology , sodium , receptor , paleontology , organic chemistry
Nociceptive sensitization is a central component of neuropathic pain, involving an alteration in the membrane properties of the sensory neurons of the Dorsal Root Ganglion (DRG) such that they have a lowered threshold for activation and hence, increased spontaneous activity. This DRG hyperexcitability manifests as the painful physiological symptoms of hyperalgesia and allodynia in patients of neuropathic pain, in whom there is as yet a large unmet need for medical treatment due to a lack of proper understanding of the precise molecular mechanisms involved. The key role of sodium activated potassium (K Na ) channels in the maintenance of firing accommodation in DRG neurons makes them important targets to study in the context of DRG excitability, which then deems mechanisms of K Na channel regulation as potential ways to regulate DRG hyperexcitability. In this context, we examined the K Na channel Slack's extensive intracellular C‐terminus for possible sites of regulatory protein interactions and found that it contains two putative p38 MAPK phosphorylation sites that are highly conserved across species. While there is no direct link between p38 MAPK and K Na channels, there is evidence for p38 MAPK's role in facilitating neuronal regeneration after nerve crush of the sciatic nerve, indicating that the kinase could be an important player in neuropathy and potentially, in nociceptive sensitization. To answer the question of whether p38 MAPK regulates Slack channels via phosphorylation of the C‐terminus, we have performed electrophysiology experiments to demonstrate that Slack current is subject to modulation by p38 MAPK, and biochemical experiments to show that Slack is basally phosphorylated by p38 MAPK. Site‐directed mutagenesis of the p38 MAPK phosphorylation sites indicates that modulation occurs via phosphorylation at both the sites. Finally, biotinylation assays suggest that the mechanism of modulation of Slack current by p38 MAPK is likely at the membrane via a trafficking mechanism. Together, these results are the first direct demonstration of Slack as a p38 MAPK substrate, and provide evidence for p38 phosphorylation playing a role in Slack channel trafficking and hence, DRG membrane excitability. Support or Funding Information This work is supported by Grant NS078184 from the National Institute of Health.