Aims: The pathophysiological mechanism for neuropathic pain (NP), one of the most common types of intractable pain, remains largely unknown. We previously reported that pituitary adenylate-cyclase activating polypeptide (PACAP) is required for the development of spinal sensitization and induction of NP. Previous in vitro studies suggest that PACAP transcription unit has two RE1-like elements and that the transcriptional repressor REST controls expression of PACAP gene. However the regulation of PACAP gene through its RE1 sites in vivo has not been studied. We have analyzed the functional role of PACAP gene RE1 element following nerve injury.
Main methods: An L5-spinal nerve transection (L5-SNT) in mice was used as a model of spinal injury. DRGs after the L5-SNT were studied.
Key findings: PACAP mRNA increased in the DRG following spinal nerve injury. REST4, an alternatively spliced isoform of REST was shown to be regulated by the splicing activator (nSR100) and nSR100 itself also increased. Overexpression of either REST4 or nSR100 in vitro increased PACAP expression, while overexpression of REST repressed PACAP mRNA production. Reporter gene analysis showed that a novel RE1 previously predicted by in silica analysis was indeed functional. ChIP analysis showed that REST bound significantly to this RE1 in the DRG of naive mice, while REST binding to this RE1 was decreased following spinal nerve injury. The expression of REST was decreased by nSR100-dependent alternative splicing of the REST gene, leading to derepression of PACAP.
Significance: PACAP expression in the DRG following spinal nerve injury is controlled through a novel RE1 by REST. (C) 2015 Elsevier Inc. All rights reserved.