Characterisation, localisation and expression of porcine TACR1, TACR2 and TACR3 genes

Substance P is involved in many physiological and pathophysiological processes. This functional diversity is mediated by three neurokinin receptor subtypes (NK1R, NK2R and NK3R) encoded by the TACR1, TACR2 and TACR3 genes, respectively. Despite the increasing interest in using pigs (Sus scrofa) to study human disease mechanisms, the sequences of these receptors are still unconfirmed or in the case of the NK1 receptor, not yet even unpredicted. We employed in silico analysis to define the localisation of the porcine tachykinin receptor genes, and to predict the structures and amino acid sequences of the respective proteins. A reverse transcription polymerase chain reaction (RT-PCR) assay was performed to analyse the expression of tachykinin receptor genes in different porcine tissues. The data show that the TACR1 gene is located on chromosome 3, TACR2 on chromosome 14 and TACR3 on chromosome 8. All three genes encode proteins with structures that incorporate features of G-protein-coupled receptors with sizes of 407, 381 and 464 amino acids, respectively. The receptors display a high degree of similarity to other mammalian neurokinin receptors. The NK1R subtype is expressed in both the central nervous system and peripheral tissues, while NK2R expression seems to be localised mostly to peripheral tissues. The expression of NK3R is found mainly in the central nervous system. This report provides for the first time the results of a comprehensive analysis of the structure and distribution of porcine NK1R, as well as other porcine neurokinin receptors and their genes. We hope that our data may offer an invaluable foundation for the future studies on the function of diverse tachykinin peptides in the central nervous system and peripheral tissues.