title: A variably spliced region in the type 1 ryanodine receptor may participate in an inter-domain interaction.
abstract: The aim of the present study was to examine residues that are variably spliced in the juvenile and adult isoforms of the skeletal-muscle RyR1 (type 1 ryanodine receptor). The juvenile ASI(-) splice variant is less active than the adult ASI(+) variant and is overexpressed in patients with DM (myotonic dystrophy) [Kimura, Nakamori, Lueck, Pouliquin, Aoike, Fujimura, Dirksen, Takahashi, Dulhunty and Sakoda (2005) Hum. Mol. Genet. 14, 2189-2200]. In the present study, we explore the ASI region using synthetic peptides corresponding to rabbit RyR1 residues Thr3471-Gly3500 either containing [PASI(+)] or lacking [PASI(-)] the ASI residues. Both peptides increased [3H]ryanodine binding to rabbit RyR1s, increased Ca2+ release from sarcoplasmic reti-culum vesicles and increased single RyR1 channel activity. The peptide PASI(-) was more active in each case than PASI(+). [3H]Ryanodine binding to recombinant ASI(+)RyR1 or ASI(-)-RyR1 was enhanced more by PASI(-) than PASI(+), with the greatest increase seen when PASI(-) was added to ASI(-)RyR1. The activation of the RyR channels is consistent with the hypo-thesis that the peptides interrupt an inhibitory inter-domain inter-action and that PASI(-) is more effective at interrupting this interaction than PASI(+). We therefore suggest that the ASI(-) sequence interacts more tightly than the ASI(+) sequence with its binding partner, so that the ASI(-)RyR1 is more strongly inhibited (less active) than the ASI(+)RyR1. Thus the affinity of the binding partners in this inter-domain interaction may deter-mine the activities of the mature and juvenile isoforms of RyR1 and the stronger inhibition in the juvenile isoform may contribute to the myopathy in DM.
authors.affiliation: Division of Molecular Bioscience, JCSMR (John Curtin School of Medical Research), Australian National University, P.O. Box 334, Canberra, ACT 2601, Australia. kimura@hyo-med.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Kimura
authors.forename: Suzy M
authors.initials: SM
authors.lastname: Pace
authors.forename: Lan
authors.initials: L
authors.lastname: Wei
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Beard
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dirksen
authors.forename: Angela F
authors.initials: AF
authors.lastname: Dulhunty
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D005091:Exons; D014644:Genetic Variation; D007700:Kinetics; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000502:physiology*; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection
chemical_list: D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel