Toponomics analysis of drug-induced changes in arachidonic acid-dependent signaling pathways during spinal nociceptive processing.

Multi-Epitope-Ligand-Carthography (MELC) allows consecutive immunohistochemical visualization of up to 100 proteins on the same tissue sample. Subsequent biomathematical analysis of these images allows a quantitative description of changes in protein networks. We used the MELC technology to study the effect of the nonopioid analgesic drug dipyrone on protein network profiles associated with arachidonic acid-dependent signaling pathways. MELC analysis with 31 different fluorescence-labeled tags was used to compare the effect of dipyrone on protein networks in spinal cords of mice with zymosan-induced hyperalgesia, a common model for inflammatory pain. We found that the number of motifs which describe the colocalization of 5-lipoxygenase (5-LO) or 12-LO with other proteins increased disproportionally after dipyrone treatment. Activation of 5-LO and 12-LO induces their translocation to membrane compartments which was also reflected by MELC results. Although no changes in 5-LO or 12-LO expression were seen by Western blot analysis or by immunohistochemistry in spinal cords of dipyrone-treated mice, the activation of both enzymes was verified by determining LO-products. Spinal amounts of 5(S)-hydroxyeicosatetraenoic acid (HETE) and 12(S)-HETE, which are generated by 5-LO and 12-LO, respectively, were significantly increased in spinal cords of dipyrone-treated animals. In primary spinal cord neurons, dipyrone selectively and dose-dependently increased 5(S)-(HETE) and 12(S)-HETE synthesis. Thus, we show for the first time that monitoring protein network profiles by topological proteomic analysis is a useful tool to identify mechanisms of drug actions.

Toponomics analysis of functional interactions of the ubiquitin ligase PAM (Protein Associated with Myc) during spinal nociceptive processing.

Protein associated with Myc (PAM) is a giant E3 ubiquitin ligase of 510 kDa. Although the role of PAM during neuronal development is well established, very little is known about its function in the regulation of synaptic strength. Here we used multiepitope ligand cartography (MELC) to study protein network profiles associated with PAM during the modulation of synaptic strength. MELC is a novel imaging technology that utilizes biomathematical tools to describe protein networks after consecutive immunohistochemical visualization of up to 100 proteins on the same sample. As an in vivo model to modulate synaptic strength we used the formalin test, a common model for acute and inflammatory pain. MELC analysis was performed with 37 different antibodies or fluorescence tags on spinal cord slices and led to the identification of 1390 PAM-related motifs that distinguish untreated and formalin-treated spinal cords. The majority of these motifs related to ubiquitin-dependent processes and/or the actin cytoskeleton. We detected an intermittent colocalization of PAM and ubiquitin with TSC2, a known substrate of PAM, and the glutamate receptors mGluR5 and GLUR1. Importantly these complexes were detected exclusively in the presence of F-actin. A direct PAM/F-actin interaction was confirmed by colocalization and cosedimentation. The binding of PAM toward F-actin varied strongly between the PAM splice forms found in rat spinal cords. PAM did not ubiquitylate actin or alter actin polymerization and depolymerization. However, F-actin decreased the ubiquitin ligase activity of purified PAM. Because PAM activation is known to involve its translocation, the binding of PAM to F-actin may serve to control its subcellular localization as well as its activity. Taken together we show that defining protein network profiles by topological proteomics analysis is a useful tool to identify previously unknown protein/protein interactions that underlie synaptic processes.