Characterization of the BMP signaling pathways that produce nociceptor sensitization in Drosophila

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 DESCRIPTION (provided by applicant): Normal pain promotes health by warning us of potential tissue damage, but abnormal pain compromises the quality of life for millions around the world. The impact of pain on the US economy has been estimated at over $600B. Pain sensitization, an increase in pain signaling after tissue damage, also promotes health by preventing re-injury during healing. Some types of abnormal pain, including types of chronic pain, result from dysregulation of the pain sensitization system. Available treatment for chronic pain is inadequate, in part because the deleterious side effects of our best analgesics, the opioids, are accentuated with longer use. Better treatments for abnormal pain are badly needed. We propose to reveal novel targets for pain medications by exploiting the powerful genetic toolkit of the Drosophila model. When the epidermis of the fly larva is damaged by a controlled dose of ultraviolet (UV) light, the fly exhibits allodynia, a type of nociceptive sensitization. Ths means that the damaged fly will react, with a nocifensive avoidance behavior in the form of an unmistakable corkscrew roll, to a thermal stimulus that most undamaged flies find innocuous. This damage induced sensitization paradigm has previously been used to demonstrate that the nociceptor neuron requires signaling by the Bone Morphogenetic Proteins (BMP) pathway in order to produce allodynia. Many BMP signaling components in the fly are very similar to their mammalian orthologs. Our preliminary results show that one of the three known BMPs in the fly, dpp, and its receptor put are necessary in the nociceptor neurons for allodynia following UV damage. Aim 1 will examine the necessity of the other BMP ligands gbb and scw, and the other BMP receptors tkv, sax, wit and babo. This will be accomplished by targeting an RNAi silencing allele of each gene specifically to the nociceptor neurons by the Gal4/UAS system. Aim 2 will examine the intracellular relay components mad, med, smox, R-SMAD, shn and brk, again using Gal4/UAS and RNAi tools. Aim 3 will describe the transcriptional output of the BMP signaling pathway in the nociceptor neuron by magnetic bead- assisted cell sorting and RNA sequencing. This procedure will identify the target genes regulated by the pathway in the nociceptor neurons. Finally, the necessity for the expression of these target genes will be tested by analyzing RNAi mutants in the UV sensitization paradigm. The proposed studies will identify the components of the BMP signaling pathway that are required for allodynia. Because of the high degree of functional conservation between fly and mammalian BMPs, components identified by these experiments represent targets for novel medications for the treatment of abnormal pain in humans.