An abnormal ketamine response in mutants defective in the ryanodine receptor gene ryr-1 (unc-68) of Caenorhabditis elegans.

To characterize excitation-contraction coupling in Caenorhabditis elegans, we applied two approaches. First, we isolated a mutant having abnormal responses to ketamine, an anesthetic in vertebrates. The novel mutation unc-68(kh30) (isolated as kra-1(kh30)), exhibited strict ketamine-dependent convulsions followed by paralysis. Second, we cloned the C. elegans ryanodine receptor gene ryr-1 that is located near the center of chromosome V. ryr-1 consists of 46 exons, which encode a predicted protein of 5071 amino acid residues that is homologous to Drosophila and vertebrate ryanodine receptors. ryr-1 promoter/lacZ plasmids were expressed in body-wall and pharyngeal muscles. Non-muscle cell expression may be seen with a truncated promoter. In addition, we show that the unc-68/kra-1(kh30) mutation is a Ser1444 Asn substitution at a putative protein kinase C phosphorylation site in ryr-1, and that unc-68(e540) contains a splice acceptor mutation that creates a premature stop codon in the ryr-1 gene. We confirmed that unc-68(e540) is a mutation in ryr-1 by injecting the complete ryr-1 gene into unc-68(e540) animals and recovering wild-type progeny. Results presented here will be useful in studying the structure and function of ryanodine receptors in excitation-contraction coupling and in understanding the evolution of ryanodine receptor tissue specificity.