Abstract: |
The cloning of the Mu opioid receptor has led to the identification of a large series of splice variants. The gene is complex, with two independent promoters responsible for two distinct sets of splice variants. The primary promoter, associated with exon 1, encodes the majority of the variants, while a second promoter upstream of the first is associated with exon 11 (E11). The majority of the variants generated by the exon 1 promoter involve splicing at the C-terminus of the receptor, without any changes in the transmembrane domains or binding pocket. Most of the variants produced by the E11 promoter have unusual structures with six transmembrane domains. However, both sets of variants are functionally important, as shown by the actions of opioids in their respective knockout mice, providing a new perspective on understanding complex Mu opioid actions in animals and humans. |