Modulation of calcium signalling by dominant negative splice variant of ryanodine receptor subtype 3 in native smooth muscle cells

Abstract The ryanodine receptor subtype 3 (RYR3) is expressed ubiquitously but its physiological function varies from cell to cell. Here, we investigated the role of a dominant negative RYR3 isoform in Ca 2+ signalling in native smooth muscle cells. We used intranuclear injection of antisense oligonucleotides to specifically inhibit endogenous RYR3 isoform expression. In mouse duodenum myocytes expressing RYR2 subtype and both spliced and non-spliced RYR3 isoforms, RYR2 and non-spliced RYR3 were activated by caffeine whereas the spliced RYR3 was not. Only RYR2 was responsible for the Ca 2+ -induced Ca 2+ release mechanism that amplified Ca 2+ influx- or inositol 1,4,5-trisphosphate-induced Ca 2+ signals. However, the spliced RYR3 negatively regulated RYR2 leading to the decrease of amplitude and upstroke velocity of Ca 2+ signals. Immunostaining in injected cells showed that the spliced RYR3 was principally expressed near the plasma membrane whilst the non-spliced isoform was revealed around the nucleus. This study shows for the first time that the short isoform of RYR3 controls Ca 2+ release through RYR2 in native smooth muscle cells.