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 epithe lial tissue (stria vascularis) of the cochlea using RT-PCR of solid-ph ase cDNA libraries. PCR products corresponding to the P2xR1 purinocept or subunit (1) were obtained from vas deferens, brain and microdissect ed cochlear sensory epithelial tissues including organ of Corti, saccu lus and crista ampullaris. Cloning and sequencing revealed that the P2 xR1-2 product included an 85-bp insertion in a region correponding to a novel C-terminal end of the second membrane spanning domain and cont inuing as the cytoplasmic domain. A stop condon sequence after the fir st 51 bp of the insert effectively truncates this subunit, reducing th e final cytoplasmic domain by 90% compared with the previously publish ed P2xR1(-1) sequence, thereby reducing the overall peptide by approxi mately 25%. The region of the receptor lost in the truncated version c oded for a number of serine/proline rich regions which may act as pote ntial intracellular regulatory sites. (C) 1995 Academic Press, Inc.