Ryanodine receptor expression in the kidney and a non-excitable kidney epithelial cell

An oligonucleotide probe to a conserved 3' region within the three identified ryanodine receptor-calcium release channel isoforms hybridized to a single clone from a rabbit kidney cDNA library. The kidney clone encoded the carboxyl-terminal 338 amino acids within the putative transmembrane domain of the type 2 ryanodine receptor sequence. Reverse transcriptase-polymerase chain reaction with isoform-specific oligonucleotide primers demonstrated the presence of the type 2 ryanodine receptor transcript in rabbit kidney, as well as in a non-excitable cell line, LLC-RK1, derived from rabbit kidney epithelial cells. Amplification by rapid amplification of 5' cDNA ends indicated the kidney type 2 ryanodine receptor transcript extended >7000 base pairs from the stop codon and is therefore not homologous to the short RyR-1 transcript of approximately 2500 base pairs previously observed in rabbit brain. [3H]Ryanodine binding and immunoblot analysis with a type 2 ryanodine receptor-specific antibody demonstrated that the native type 2 ryanodine receptor protein is expressed in the kidney. These observations suggest that the type 2 ryanodine receptor isoform may play a functional role in regulating intracellular calcium homeostasis in non-excitable cells.