Functional Role of Alternative Splicing in Pituitary P2X2 Receptor-Channel Activation and Desensitization

作者：Taka‐aki Koshimizu · 发表于：Molecular Endocrinology · 年份：1998 · DOI：10.1210/me.12.7.901 · 被引用次数：24 · 研究领域：Adenosine and Purinergic Signaling、Reproductive System and Pregnancy、Neonatal Respiratory Health Research

Although ATP-gated ion channel (P2XR) expression is high among anterior pituitary cells, identification of the receptor subtypes and their selective expression within subpopulations of cell types, as well as their physiological role(s), are incompletely characterized. In this study, we focused on the expression and activity of the P2X2R subtype in anterior pituitary cells. Our results indicate that the primary P2X2R gene transcript in pituitary cells undergoes extensive alternative splicing, with generation of six isoforms. Two of these isoforms encode functional channels when expressed in GT1 or HEK293 cells: the wild-type P2X2R and the spliced isoform P2X2−2R, which lacks a stretch of carboxyl-terminal amino acids (Val370-Gln438). Four other clones showed different alterations, including an interfered reading frame starting in the first transmembrane domain and a 27-amino acid deletion in the large extracellular loop. When expressed separately or in combination with wild-type channels, these clones were nonfunctional. In single cell Ca2+ current and cytosolic Ca2+ concentration ([Ca2+]i) measurements, the P2X2R and P2X2−2R had similar EC50 values for ATP and time courses for activation and recovery from desensitization but differed significantly in their desensitization rates. The spliced isoform exhibited rapid and complete desensitization, whereas the wild-type channel desensitized slowly and incompletely. The mRNAs for wild-type and spliced channels were identified in en...