Signalling pathways underlying sensitization of TRPV1 by RET receptors

Here I report that artemin, a member of the glial cell line-derived neurontrophic factor (GDNF) family, can potentiate TRPV1 activity. Analysis of capsaicin-evoked Ca2+ transients in isolated mouse dorsal root ganglion (DRG) neurons and neuro-2a cells revealed a rapid, potent and prolonged sensitization caused by artemin (~60% cells sensitized with ~2-fold increase in peak response to capsaicin). The mechanism of sensitization of TRPV1 by artemin was further investigated by observing the effects of inhibitors of potential members of artemin-activated second messenger signalling pathways. Pharmacological blockade of PKC, PI3K and Src kinase all prevented enhancement of the capsaicin response evoked by artemin, whereas inhibition of PKA, MAPK and Akt had no effect on sensitization. These and other data support the hypothesis that sensitization of TRPV1 by artemin is mediated by two pathways: tyrosine kinase signalling cascades involving PKCδ, PI3K and Src kinase are the major mediators of artemin induced TRPV1 sensitization in sensory neurons, whereas the PLCδ/PKCε signalling pathway has a smaller effect. The cytoskeletal protein β-actin was found to be associated with immunoprecipitated TRPV1 and the interaction between TRPV1 and actin was enhanced after exposure to artemin. The enhancement of membrane expression of TRPV1 can be blocked by the specific actin inhibitor, Latrunculin B (1 μM), both in a biotinylation assay and in calcium imaging, which suggests that β-actin may be involved in artemin-induced TRPV1 translocation. These findings give us a further insight into ongoing molecular events during thermal hyperalgesia and inflammatory pain and may provide a molecular basis for the development of effective drugs in treating such pain.EThOS - Electronic Theses Online ServiceGBUnited Kingdo