title: Modulation of skeletal muscle Ca2(+)-release channel activity by sphingosine.
abstract: The effect of D-erythro-C18-sphingosine (sphingosine) and related compounds on the Ca(2+)-release channel (ryanodine binding protein) was examined on rabbit skeletal muscle membranes, on the purified ryanodine binding protein, and on the channel reconstituted into planar lipid bilayers. Sphingosine inhibited [3H]ryanodine binding to sarcoplasmic reticulum (SR) membranes in a dose-dependent manner similar to published results (R. A. Sabbadini, R. Betto, A. Teresi, G. Fachechi-Cassano, and G. Salviati. J. Biol. Chem. 267: 15475-15484, 1992). The sphingolipid also inhibited [3H]ryanodine binding to the purified ryanodine binding protein. Our results demonstrate that the inhibition of [3H]ryanodine binding by sphingosine is due to an increased rate of dissociation of bound [3H]ryanodine from SR membranes and a decreased rate of association of [3H]ryanodine to the high-affinity site. Unlike other modulators of the Ca(2+)-release channel, sphingosine can remove bound [3H]ryanodine from the high-affinity site within minutes. Sphingosine increased the rate of dissociation of [3H]ryanodine bound to a solubilized proteolytic fragment derived from the carboxy terminus of the ryanodine binding protein (cleavage at Arg4475). Sphingosine also inhibited the activity of the Ca(2+)-release channel incorporated into planar lipid bilayers. Taken together, the data provide evidence for a direct effect of sphingosine on the Ca(2+)-release channel. Sphingosine is a noncompetitive inhibitor at the high-affinity ryanodine binding site, and it interacts with a site between Arg4475 and the carboxy terminus of the Ca(2+)-release channel.
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Needleman
authors.forename: B
authors.initials: B
authors.lastname: Aghdasi
authors.forename: A B
authors.initials: AB
authors.lastname: Seryshev
authors.forename: G J
authors.initials: GJ
authors.lastname: Schroepfer
authors.forename: S L
authors.initials: SL
authors.lastname: Hamilton
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D011817:Rabbits; D012433:Ryanodine / Q000037:antagonists & inhibitors / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013107:Sphingolipids / Q000494:pharmacology; D013110:Sphingosine / Q000494:pharmacology*
chemical_list: D015220:Calcium Channels; D008051:Lipid Bilayers; D013107:Sphingolipids; D012433:Ryanodine; D013110:Sphingosine