Regulation of the calcium release channel from skeletal muscle by suramin and the disulfonated stilbene derivatives DIDS, DBDS, and DNDS.
Activation of skeletal muscle ryanodine receptors (RyRs) by suramin and disulfonic stilbene derivatives (Diisothiocyanostilbene-2',2'-disulfonic acid (DIDS), 4,4'-dibenzamidostilbene-2,2'-disulfonic acid (DBDS),and 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNDS)) was investigated using planar bilayers. One reversible and two nonreversible mechanisms were identified. K(a) for reversible activation (approximately 100 micro M) depended on cytoplasmic [Ca(2+)] and the bilayer composition. Replacement of neutral lipids by negative phosphatidylserine increased K(a) fourfold, suggesting that reversible binding sites are near the bilayer surface. Suramin and the stilbene derivatives adsorbed to neutral bilayers with maximal mole fractions between 1-8% and with affinities approximately 100 micro M but did not adsorb to negative lipids. DIDS activated RyRs by two nonreversible mechanisms, distinguishable by their disparate DIDS binding rates (10(5) and 60 M(-1) s(-1)) and actions. Both mechanisms activated RyRs via several jumps in open probability, indicating several DIDS binding events. The fast and slow mechanisms are independent of each other, the reversible mechanism and ATP binding. The fast mechanism confers DIDS sensitivity approximately 1000-fold greater than previously reported, increases Ca(2+) activation and increases K(i) for Ca(2+)/Mg(2+) inhibition 10-fold. The slow mechanism activates RyRs in the absence of Ca(2+) and ATP, increases ATP activation without altering K(a), and slightly increases activity at pH < 6.5. These findings explain how different types of DIDS activation are observed under different conditions.
O'Neill
Erin R
ER
School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Callaghan, New South Wales 2308, Australia.
Sakowska
Magdalena M
MM
Laver
Derek R
DR
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008051:Lipid Bilayers / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects* / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D013267:Stilbenes / Q000494:pharmacology*; D013498:Suramin / Q000494:pharmacology*
D008051:Lipid Bilayers; D019837:Ryanodine Receptor Calcium Release Channel; D013267:Stilbenes; D013498:Suramin; D002118:Calcium