Comparative characterization of two intracellular Ca(2+)-release channels from the red flour beetle, Tribolium castaneum

Ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are members of a family of tetrameric intracellular Ca(2+)-release channels (CRCs). While it is well known in mammals that RyRs and IP(3)Rs modulate multiple physiological processes, the roles of these two CRCs in the development and physiology of insects remain poorly understood. In this study, we cloned and functionally characterized RyR and IP(3)R cDNAs (named TcRyR and TcIP(3)R) from the red flour beetle, Tribolium castaneum. The composite TcRyR gene contains an ORF of 15,285 bp encoding a protein of 5,094 amino acid residues. The TcIP(3)R contains an 8,175 bp ORF encoding a protein of 2,724 amino acids. Expression analysis of TcRyR and TcIP(3)R revealed significant differences in mRNA expression levels among T. castaneum during different developmental stages. When the transcript levels of TcRyR were suppressed by RNA interference (RNAi), an abnormal folding of the adult hind wings was observed, while the RNAi-mediated knockdown of TcIP(3)R resulted in defective larval–pupal and pupal–adult metamorphosis. These results suggested that TcRyR is required for muscle excitation-contraction (E-C) coupling in T. castaneum, and that calcium release via IP(3)R might play an important role in regulating ecdysone synthesis and release during molting and metamorphosis in insects.