Spinal SGK1/GRASP-1/Rab4 is involved in complete Freund's adjuvant-induced inflammatory pain via regulating dorsal horn GluR1-containing AMPA receptor trafficking in rats

Hsien Yu Peng, Gin Den Chen, Ming Chun Hsieh, Cheng Yuan Lai, Yi Ping Huang, Tzer Bin Lin

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The elusiveness of the mechanism underlying pain is a major impediment in developing effective clinical treatments. We examined whether the phosphorylation of spinal serum- and glucocorticoid-inducible kinase 1 (SGK1) and downstream glutamate receptor interacting protein (GRIP)-associated protein-1 (GRASP-1)/Rab4-dependent GluR1-containing α-amino-3-hydroxy-5- methyl-4-isoxazolepropionic acid receptor (AMPAR) recycling play a role in inflammatory pain. After intraplantar injection of complete Freund's adjuvant (CFA), we assessed thermal hyperalgesia using the Hargreaves test and analyzed dorsal horn samples (L4-5) using Western blotting, coprecipitation, and immunofluorescence. CFA administration provoked behavioral hyperalgesia along with SGK1 phosphorylation, GluR1 trafficking from the cytosol to the membrane, and phosphorylated SGK1 (pSGK1)-GRASP-1, GRASP-1-Rab4, and Rab4-GluR1 coprecipitation in the ipsilateral dorsal horn. In the dorsal horns of hyperalgesic rats, CFA-enhanced pSGK1 was demonstrated to be colocalized with NeuN, GRASP-1, Rab4, and GluR1 by immunofluorescence. GSK-650394 (an SGK1 activation antagonist, 1, 10, and 30 μM, 10 μL/rat, intrathecally) dose-dependently prevented CFA-induced pain behavior and the associated SGK1 phosphorylation, GluR1 trafficking, and protein-protein interactions at 1 day after CFA administration. Intrathecal 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, an AMPAR antagonist, 1, 3, and 10 μM, 10 μL/rat) attenuated the hyperalgesia and GluR1 trafficking caused by CFA; however, it had no effect on SGK1 phosphorylation. Small interfering RNA targeting Rab4 hindered the CFA-induced hyperalgesia and the associated GluR1 trafficking and Rab4-GluR1 coprecipitation. Our results suggest that spinal SGK1 phosphorylation, which subsequently triggers the GRASP-1/Rab4 cascade, plays a pivotal role in CFA-induced inflammatory pain by regulating GluR1-containing AMPAR recycling in the dorsal horn.

Original languageEnglish
Pages (from-to)2380-2392
Number of pages13
JournalPain
Volume153
Issue number12
DOIs
Publication statusPublished - Dec 2012
Externally publishedYes

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Keywords

  • CFA
  • GluR1
  • GRASP-1
  • Rab4
  • SGK1

ASJC Scopus subject areas

  • Clinical Neurology
  • Anesthesiology and Pain Medicine
  • Neurology
  • Pharmacology

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