Regulatory, Integrative and Comparative Physiology

Molecular cloning and characterization of ryanodine receptor from unfertilized sea urchin eggs

Mieko Shiwa, Takashi Murayama, Yasuo Ogawa


Unfertilized eggs of sea urchins (Hemicentrotus pulcherrimus) demonstrated cyclic ADP-ribose (cADPR)-induced Ca2+ release and caffeine-induced Ca2+ release, both of which were considered to be mediated through the ryanodine receptor (RyR). We cloned cDNAs for sea urchin egg RyR (suRyR), which encode a 597-kDa protein of 5,317 amino acids. suRyR shares common structural features with known RyRs: the well-conserved COOH-terminal domain, which forms a functional Ca2+ channel, and a large hydrophilic NH2-terminal domain. suRyR shows amino acid sequence identity (43–45%) similar to the three mammalian RyR isoforms. Phylogenetic analysis indicates that suRyR branched from three isoforms of vertebrates before they diverged, suggesting that suRyR may be the only RyR isoform in the sea urchin. Four in-frame insertions were found in suRyR cDNAs, one of which was novel and unique, in that it had a cluster of serine residues. The transcripts with and without these insertions were found in the egg RNA. These results suggest that suRyR may be expressed as a functional Ca2+-induced Ca2+ release channel, which might also be involved in cADPR-induced Ca2+ release.

  • cyclic adenosine 5′-diphosphate-ribose
  • calcium release channel
  • endoplasmic reticulum
  • fertilization


  • This work was supported in part by the Scientific Research Promotion Fund from Promotion and Mutual Aid for Private Schools of Japan Grant 131025 and by the High Technology Research Center Grant from the Ministry of Education, Science, Sports, Culture, and Technology, Japan.

  • The nucleotide sequence data reported here will appear in the DDBJ, EMBL, and GenBank nucleotide sequence databases with accession numberAB051576.

  • Address for reprint requests and other correspondence: T. Murayama, Dept. of Pharmacology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan (E-mail:takashim{at}

  • The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

  • 10.1152/ajpregu.00519.2001

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