DIFFERENTIAL EXPRESSION AND REGULATION OF RYANODINE RECEPTOR AND MYOINOSITOL 1,4,5-TRISPHOSPHATE RECEPTOR CA2-TISSUES AND CELL-LINES( RELEASE CHANNELS IN MAMMALIAN)

Ryanodine receptors (RyRs) and Ins(1,4,5)P-3 receptors (Ins(1,4,5)P(3) Rs) represent two multigene families of channel proteins that mediate the release of Ca2+ ions from intracellular stores. In the present stu dy, the expression patterns of these channel proteins in mammalian cel l lines and tissues were investigated by using isoform-specific antibo dies. All cell lines examined expressed two or more Ins(1,4,5)P3R isof orms, with the type 1 Ins(1,4,5)P3R being ubiquitous. RyR isoforms wer e detected in only six out of eight cell lines studied. Similarly, of the nine rabbit tissues examined, RyR protein expression was detected only in brain, heart, skeletal muscle and uterus. Specific [H-3]ryanod ine binding was found in a number of rabbit tissues, although it was n ot detected in mammalian cell lines. Subcellular fractionation of SH-S Y5Y human neuroblastomas revealed that the type 2 RyR and type I Ins(1 ,4,5)P3R co-localize among the fractions of a sucrose-cushion separati on of crude microsomal membrane fractions. Manipulation of SH-SY5Y cel ls by chronic stimulation of muscarinic acetylcholine receptor (mAChR) results in a decrease in their type 1 Ins(1,4,5)P3R levels but not in the abundance of the type 2 RyR. Differentiation of these neuroblasto mas by using retinoic acid did not detectably alter their expression o f Ca2+-release channel proteins. Finally, differentiation of BC(3)H1 c ells affects the expression of their Ca2+-release channel proteins in an isoform-specific manner. In summary, this study demonstrates that m ammalian cell lines display distinct patterns of Ca2+-release channel protein expression. The abundance of these proteins is differentially regulated during phenotypic modifications of a cell, such as different iation or chronic stimulation of mAChR.