The Alpha Isoform of Heat Shock Protein 90 and the Co-chaperones p23 and Cdc37 Promote Opioid Anti-nociception in the Brain

Abstract

Opioid activation of the mu opioid receptor (MOR) promotes signaling cascades that evoke both analgesic responses to pain and side effects like addiction and dependence. Manipulation of these cascades, such as by biased agonism, has great promise to improve opioid therapy. However, the signaling cascades of the MOR are in general poorly understood, providing few targets for drug development. In our earlier work, we identified Heat shock protein 90 (Hsp90) as a novel and crucial regulator of opioid anti-nociception in the brain by promoting ERK MAPK activation. In this study, we sought to identify the molecular isoforms and co-chaperones by which Hsp90 carried out this role, which could provide specific targets for future clinical intervention. We used novel selective small molecule inhibitors as well as CRISPR/Cas9 gene editing constructs delivered by the intracerebroventricular (icv) route to the brains of adult CD-1 mice to target Hsp90 isoforms (Hsp90α/β, Grp94) and co-chaperones (p23, Cdc37, Aha1). We found that inhibition of the isoform Hsp90α fully blocked morphine anti-nociception in a model of post-surgical paw incision pain, while blocking ERK and JNK MAPK activation, suggesting Hsp90α as the main regulator of opioid response in the brain. We further found that inhibition of the co-chaperones p23 and Cdc37 blocked morphine anti-nociception, suggesting that these co-chaperones assist Hsp90α in promoting opioid anti-nociception. Lastly, we used cycloheximide treatment in the brain to demonstrate that rapid protein translation within 30 min of opioid treatment is required for Hsp90 regulation of opioid response. Together these studies provide insight into the molecular mechanisms by which Hsp90 promotes opioid anti-nociception. These findings thus both improve our basic science knowledge of MOR signal transduction and could provide future targets for clinical intervention to improve opioid therapy.

Inhibiting Spinal Cord-Specific Hsp90 Isoforms Reveals a Novel Strategy to Improve the Therapeutic Index of Opioid Treatment

“…However, these hypotheses only address the slower tolerance seen over time with repeated treatment, they do not explain the tolerance rescue we observed. One potential clue for this rescue mechanism could be our earlier findings that both brain and spinal cord effects of Hsp90 inhibition on anti-nociception require rapid protein translation [14–16]. The translation inhibitor we used had no impact on anti-nociception in Vehicle-treated mice, suggesting that this mechanism is newly activated upon Hsp90 inhibitor treatment.…”

“…One potential avenue is to investigate specific Hsp90 isoforms and co-chaperones active in the spinal cord. In our earlier work, we found that the Hsp90α isoform and the co-chaperones p23 and Cdc37 were responsible for regulating anti-nociception in the brain [22]. If different isoforms and/or co-chaperones regulate opioid antinociception in the spinal cord, then we could use isoform-and co-chaperone-selective inhibitors to selectively inhibit spinal cord Hsp90 even with systemic administration.…”

“…In our work, we've uncovered a role for Hsp90 in opioid signaling and anti-nociception that differs between the brain and spinal cord. In brain, Hsp90 promotes ERK MAPK signaling via the Hsp90α isoform and the cochaperones Cdc37 and p23; Hsp90 inhibitor treatment in the brain thus reduces ERK MAPK signaling and opioid anti-nociception [13][14][15]. In contrast, Hsp90 represses opioid anti-nociception and signaling in the spinal cord, so that Hsp90 inhibitor treatment in the spinal cord promotes an ERK-RSK signaling cascade that results in enhanced opioid anti-nociception [16].This enhanced anti-nociception led us to hypothesize that spinal Hsp90 inhibitor treatment could be used to improve the therapeutic index of opioids and enable a dose-reduction strategy.…”

The Effect of Heat Shock Protein 90 Inhibitor on Pain in Cancer Patients: A Systematic Review and Meta-Analysis

“…Another reason may be related to the activity of Hsp90 inhibitors on pain drugs, such as opioids. Previous studies showed that inhibition of Hsp90 in the mouse brain could diminish the opioid-induced signaling and behavior [ 29 , 30 ]. The increased risk of pain by Hsp90 inhibitors could relate to the attenuation of pain management in the patients.…”

The Potential of Hsp90 in Targeting Pathological Pathways in Cardiac Diseases

“…The Hsp90 chaperone family contains four isoforms in mammalian cells. These isoforms are Hsp90α, Hsp90β, glucose response protein 94 (Grp94), and tumor necrosis factor type 1 receptor-associated protein (TRAP1) [6]. Hsp90α/β operates in the cytosol while Grp94 localizes to the endoplasmic reticulum and TRAP1 to the inner mitochondrial space [7].…”