Modulation of frog skeletal muscle Ca2+ release channel gating by anion channel blockers

Abstract

Effects of niflumic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) on frog skeletal muscle ryanodine receptors have been studied by incorporating sarcoplasmic reticulum vesicles into planar lipid bilayers. Niflumic acid increased the mean open probability (Po) at 10 microM and decreased Po at 100 microM with no change in open time constants, unitary conductance, and reversal potential. The Po was augmented by DIDS at 5-200 microM without affecting either unitary conductance or reversal potential. DIDS induced a new third open time constant, probably contributing to a long-lived open state. Channels modified by niflumic acid or DIDS still responded to Ca2+ release channel modulators. These results provide evidence that niflumic acid and DIDS modify the gating mechanism of ryanodine receptors without affecting binding sites to the modulators and the physical pathway of the conducting pore. p-Chloromercuriphenyl sulfonic acid (pCMPS) transiently increased the Po. The channel modified by DIDS responded to pCMPS, whereas that by ryanodine did not. The long open state of the channel induced by DIDS is produced by a quite different mechanism(s) from that by ryanodine. Contrary to cardiac ryanodine receptors, Po of skeletal muscle channels was independent of voltage after DIDS modification.

Identification of 30 kDa calsequestrin-binding protein, which regulates calcium release from sarcoplasmic reticulum of rabbit skeletal muscle

“…The stilbene derivative DIDS has been shown by planar lipidbilayer measurement and ion-flux measurement in the skeletal and cardiac muscle SR to activate RyRs [19,[21][22][23], and in a previous paper [19], we found that DIDS bound not to RyRs but to the 30 kDa protein in the skeletal muscle SR. Furthermore, the 30 kDa protein was also found to bind to CSQ [19], which had been already reported to regulate RyRs in the SR [11][12][13].…”

“…As described above, we identified independently the SR 30 kDa protein as a CSQ-binding protein and found that it was a receptor of 4,4h-di-isothiocyanostilbene-2,2h-disulphonic acid (DIDS) [19]. Because DIDS was known as an activator of RyRs [19,[21][22][23], the 30 kDa protein was thought to possibly regulate RyRs through CSQ. Furthermore, we found that the 30 kDa protein also binds to the CSQ-binding 26 kDa protein, probably junctin [20] ; thus we concluded that CSQ, junctin and the 30 kDa protein form a protein complex, which regulates RyRs.…”

Mechanisms underlying phosphate‐induced failure of Ca2+ release in single skinned skeletal muscle fibres of the rat

“…Retardation of P i exit from the SR by any of the drugs should have been manifested as an impairment in the rate of recovery of the caffeine response. None of the tested compounds had this effect (Table 1), In fact, the response to caffeine after washout of P i in the presence of DIDS was actually greater than the force response obtained after washout under standard myoplasmic conditions ( P < 0.01), an effect which may be due to DIDS ability to increase the open probability of the ryanodine receptor/SR Ca 2+ release channels (Oba et al 1996). Overall, these results suggest that neither Cl − channels nor the VDACs are primarily responsible for the passage of P i from the SR lumen to the myoplasm.…”

“…Similarly, both 9‐AC (100 μ m ) and DIDS (100 μ m ) failed to attenuate the rate of P i exit, indicating that the pathway involved is not a 9‐AC‐sensitive Cl − channel nor is it the VDAC/porin in the SR membrane. The reason for the significant speeding up of recovery in the presence of DIDS (Table 1) is not known, but could involve some type of residual effect of DIDS on either the SR Ca 2+ release channel (Oba et al 1996) or the contractile proteins.…”

Restitution of the bullfrog gastric mucosa is dependent on a DIDS-inhibitable pathway not related to \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{HCO}_{3}^{-}\) \end{document} ion transport

“…It is more likely that both SITS and DIDS, a stilbene compound similar to SITS that was shown in this study to completely block restitution, may influence restitution by a mechanism independent of their action on ion transport. DIDS, in addition to blocking ion transport, inhibits ryanodine receptors (12,13,19,24), purino(ATP) receptors (20), ATP-dependent K channels (17), and monocarboxylate transporters (MCTs) (9). The later are involved in H ϩ -coupled lactate transport, a proton efflux pathway in white skeletal muscle, red blood cells, and many tumor cells that utilize glycolysis to generate ATP.…”