Does DUSP15 promote activation of ERK MAPK signaling after Hsp90 inhibition in the spinal cord to promote opioid anti‐nociception?

Abstract

The misuse of opioids has become a prevalent problem for chronic pain relief, worsened by numerous side effects such as constipation, tolerance and addiction. Researchers have attempted to optimize opioids to decrease side effects and eliminate dependence by modulating the signal transduction cascades of the mu opioid receptor (MOR). Previous studies from our lab have demonstrated that the chaperone protein Heat shock protein 90 (Hsp90) is an important regulator of the ERK/MAPK pathway which is downstream of MOR. When an Hsp90 inhibitor is administered directly to the spinal cord, there is an increase in opioid antinociception in vivo, signifying that Hsp90 acts to repress the ERK/MAPK signaling pathway and reduce antinociception in the spinal cord. The exact molecular mechanism including the key players in activating opioid anti‐nociception in the spinal cord are still unknown and need to be further investigated. We thus performed quantitative proteomic analysis on the spinal cords of male and female CD‐1 mice treated with the Hsp90 inhibitor 17‐AAG. Network analysis of this data revealed that the phosphatase DUSP15 was upregulated; DUSP15 is known to be a key activator of ERK MAPK, suggesting this molecule could be the mechanism by which spinal Hsp90 inhibition activates ERK MAPK and thus opioid anti‐nociception. To test this hypothesis, we will perform CRISPR/Cas9 gene editing in the spinal cords of adult male and female CD‐1 mice to knock down DUSP15. We will then combine knockdown with Hsp90 inhibitors (17‐AAG, KU‐32) and opioids in the tail flick anti‐nociception assay, to reveal if DUSP15 knockdown will affect the enhanced anti‐nociception caused by spinal Hsp90 inhibition. These studies will thus reveal a key molecular mechanism by which Hsp90 regulates the spinal cord opioid system. Our other studies have shown that spinal Hsp90 inhibition causes enhanced anti‐nociception and decreased side effects like tolerance; these studies will also establish the basic science foundation for the use of Hsp90 inhibitors to improve opioid therapy during chronic pain.Support or Funding InformationThese studies were supported by an Arizona Biomedical Research Commission New Investigator Award (#ADHS18‐198875) and institutional funds from the University of Arizona to JMS. The authors have no other relevant conflicts of interest to declare.