Complete overlap of interleukin-31 receptor A and oncostatin M receptor β in the adult dorsal root ganglia with distinct developmental expression patterns

Interleukin-31 receptor A (IL-31 RA) is a newly identified type I cytokine receptor, that is related to gp130, the common receptor of the interleukin (IL)-6 family cytokines. Recent studies have shown that IL-31RA forms a functional receptor complex for IL-31 together with the beta subunit of oncostatin M receptor (OSMR beta). However, little is known about the target cells of IL-31 because it remains unclear which types of cells express IL-31 RA. In our previous reports, we demonstrated that OSMR beta is expressed in a subset of small-sized nociceptive neurons of adult dorsal root ganglia (DRGs). In the present study, we investigated the IL-31RA expression in the adult and developing DRGs. From a northern blot analysis and in situ hybridization histochemistry, IL-31RA mRNA was found to be expressed in the adult DRGs. According to reverse-transcriptase polymerase chain reaction, IL-31RA mRNA was detected in the DRGs and trigeminal ganglia, while no expression of IL-31 RA mRNA was observed in the CNS. Double immunofluorescence staining revealed IL-31RA to be expressed in a subset of small-sized neurons, all of which colocalized with OSMR beta. In addition, the expression of IL-31 RA was detected in afferent fibers in the spinal cord and the dermis of the skin. We also found that the developmental expression pattern of IL-31RA was different from that of OSMR beta; IL31RA-positive neurons in DRGs first appeared at postnatal day (PN) 10 and reached the adult level at PN14, whereas OSMR beta-positive neurons were observed at PN0 for the first time. We previously demonstrated OSMR beta-expressing neurons to decrease, however, they were not found to disappear in oncostatin M (OSM)-deficient mice. These findings suggest that IL-31 and OSM may thus have redundant-functions in the development of OSMR beta-expressing neurons. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.