Cloning of the Vanilloid-like Receptor VR-L and investigation of its interaction with members of the transient receptor potential family of receptors

Early pharmacological studies (Szolcsanyi and Jancso-Gabor, 1975, Wood, 1988) showed that capsaicin, the pungent ingredient of chilli peppers and other vanilloids, can specifically stimulate the C unmyelinated fibres which transmit nociceptive information i.e. information about noxious thermal, chemical and mechanical stimuli. The specific action of capsaicin on this subset of sensory neurons led researchers to postulate the existence of a capsaicin receptor. Caterina et al (1997) cloned Vanilloid Receptor 1 (VR1) from dorsal root ganglia, where the somata of C fibres reside. VR1 responds to capsaicin, heat, protons and to the cannabinoid ligand, anandamide (Zygmunt et al., 1999). Discrepancies between the pharmacological profile of VR1 and native vanilloid responses fuelled research for the identification of other vanilloid receptors. In this thesis, the cloning of a new member of the vanilloid receptor family is described using bioinformatics tools. The novel receptor was named Vanilloid Receptor-like (VR-L) and was found to share 49% identity with VR1 and 20% with members of the Transient Receptor Potential (TRP) family. VR-L transcripts were identified in a wide range of tissues including the capsaicin insensitive dorsal root ganglia neurons. The expression of the channel in these neurons can be upregulated by Nerve Growth Factor, as it was established with semi-quantitative RT- PCR. Co-immunoprecipitation studies were carried out to investigate the possibility that VR-L interacts with VR1 and other members of the TRP family to regulate indirectly vanilloid and other responses. VR1 and VR-L were found to form homomultimers and also to interact with each other and with members of the TRP family. A VR-L stable cell line was generated to study the functional significance of the interactions identified