Modulation of skeletal muscle Ca2(+)-release channel activity by sphingosine.
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.
Needleman
D H
DH
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.
Aghdasi
B
B
Seryshev
A B
AB
Schroepfer
G J
GJ
Hamilton
S L
SL
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*
D015220:Calcium Channels; D008051:Lipid Bilayers; D013107:Sphingolipids; D012433:Ryanodine; D013110:Sphingosine