Morphine Regulated Synaptic Networks Revealed by Integrated Proteomics and Network Analysis

Mol Cell Proteomics. 2015 Oct;14(10):2564-76. doi: 10.1074/mcp.M115.047977. Epub 2015 Jul 6.


Despite its efficacy, the use of morphine for the treatment of chronic pain remains limited because of the rapid development of tolerance, dependence and ultimately addiction. These undesired effects are thought to be because of alterations in synaptic transmission and neuroplasticity within the reward circuitry including the striatum. In this study we used subcellular fractionation and quantitative proteomics combined with computational approaches to investigate the morphine-induced protein profile changes at the striatal postsynaptic density. Over 2,600 proteins were identified by mass spectrometry analysis of subcellular fractions enriched in postsynaptic density associated proteins from saline or morphine-treated striata. Among these, the levels of 34 proteins were differentially altered in response to morphine. These include proteins involved in G-protein coupled receptor signaling, regulation of transcription and translation, chaperones, and protein degradation pathways. The altered expression levels of several of these proteins was validated by Western blotting analysis. Using Genes2Fans software suite we connected the differentially expressed proteins with proteins identified within the known background protein-protein interaction network. This led to the generation of a network consisting of 116 proteins with 40 significant intermediates. To validate this, we confirmed the presence of three proteins predicted to be significant intermediates: caspase-3, receptor-interacting serine/threonine protein kinase 3 and NEDD4 (an E3-ubiquitin ligase identified as a neural precursor cell expressed developmentally down-regulated protein 4). Because this morphine-regulated network predicted alterations in proteasomal degradation, we examined the global ubiquitination state of postsynaptic density proteins and found it to be substantially altered. Together, these findings suggest a role for protein degradation and for the ubiquitin/proteasomal system in the etiology of opiate dependence and addiction.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Analgesics, Opioid / pharmacology*
  • Animals
  • Caspase 3 / metabolism
  • Corpus Striatum / drug effects
  • Corpus Striatum / metabolism
  • Endosomal Sorting Complexes Required for Transport / metabolism
  • Male
  • Morphine / pharmacology*
  • Nedd4 Ubiquitin Protein Ligases
  • Nerve Tissue Proteins / metabolism*
  • Proteolysis
  • Proteomics
  • Rats, Sprague-Dawley
  • Receptor-Interacting Protein Serine-Threonine Kinases / metabolism
  • Synaptic Transmission / drug effects
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitination / drug effects


  • Analgesics, Opioid
  • Endosomal Sorting Complexes Required for Transport
  • Nerve Tissue Proteins
  • postsynaptic density proteins
  • Morphine
  • NEDD4L protein, rat
  • Nedd4 Ubiquitin Protein Ligases
  • Nedd4 protein, rat
  • Ubiquitin-Protein Ligases
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Casp3 protein, rat
  • Caspase 3