Identification of a Short Form of the P2xR1-Purinoceptor Subunit Produced by Alternative Splicing in the Pituitary and Cochlea

A truncated form of the P2xR1 purinoceptor subunit (which we designate P2xR1-2) was detected in rat pituitary gland and the secretory epithelial tissue (stria vascularis) of the cochlea using RT-PCR of solid-phase cDNA libraries. PCR products corresponding to the P2xR1 purinoceptor subunit (1) were obtained from vas deferens, brain and microdissected cochlear sensory epithelial tissues including organ of Corti, sacculus and crista ampullaris. Cloning and sequencing revealed that the P2xR1-2 product included an 85 - bp insertion in a region correponding to a novel C-terminal end of the second membrane spanning domain and continuing as the cytoplasmic domain. A stop condon sequence after the first 51 bp of the insert effectively truncates this subunit, reducing the final cytoplasmic domain by 90% compared with the previously published P2xR1(−1) sequence, thereby reducing the overall peptide by approximately 25%. The region of the receptor lost in the truncated version coded for a number of serine/proline rich regions which may act as potential intracellular regulatory sites.