Ryanodine-sensitive calcium

Peracchia C Possible involvement of caffeine and ryanodine-sensitive calcium stores in low pH-induced regulation of gap junction channels in Peracchia C (ed) Biophysics of Gap Junction Channels. Boca Raton, CRC Press, 1991a, pp 13-28. 

Marengo, J. J., Hidalgo, C., and Bull, R. (1998). Sulfhydryl Oxidation Modifies the Calcium Dependence of Ryanodine-Sensitive Calcium Channels of Excitable Cells. Biophys J 74(3) 1263—77. 

The open probability of ryanodine-sensitive calcium release channels in cardiac and smooth muscle increases with cytoplasmic calcium, and this property of the ryanodine receptor has been referred to as calcium-in-... 

Li Rinzel, 1994). The latter reductions therefore yield a minimal model for Ca oscillations, like the earlier, two-pool minimal model considered below, which takes into account only CICR and not the inhibition of Ca " release at high levels of cytosolic Ca. A one-pool version of this model in which Ca and IP3 behave as co-agonists for Ca " release is presented in section 9.4. A model based on the bellshaped calcium dependence of the ryanodine-sensitive calcium channel was recently proposed for calcium dynamics in cardiac myocytes (Tang Othmer, 1994b). 

Tang, Y. H.G. Othmer. 1994b. A model of calcium dynamics in cardiac myocytes based on the kinetics of ryanodine-sensitive calcium channels. Biophys. J. 67 2223-35. 

Flubendiamide is a novel insecticide possessing potent and selective activity against lepidopterous insects [1], This insecticidal activity has been clarified to be mediated by a ryanodine-sensitive calcium release channel (RyR) [2-3], The stabilization of RyR to open state by the compound induces robust calcium release from intracellular calcium store (Figure 1). This implies a significant impact on components involved in intracellular calcium homeostasis such as the pump, a pivotal component which reuptakes released Ca into SR. In this study, we examined effects on the Ca pump, as a consequence of the calcium mobilization induced by flubendiamide. 

Fig. 31.3. Schematic illustration of the effect of flubendiamide on calcium intracellular homeostasis. RyR Ryanodine sensitive calcium release channel Flu flubendiamide, benzendicarboxamide derivatives.

In this communication, we present evidence that the phthalic acid diamides, a novel chemical class of highly potent insecticides discovered by Nihon Nohyaku Co., Ltd. (14), act on ryanodine-sensitive calcium release channels in insects by a mechanism distinct from that of ryanodine. 

It is known that structurally diverse low-molecular weight compounds modulate the calcium conductance of ryanodine-sensitive calcium release channels (RyR) in mammals. For example, methylxanthines such as caffeine induce RyR-mediated Ca release from the sarcoplasmic reticulum and decrease the apparent dissociation constant of ryanodine ( /7J. 

Martin C, Hyvelin JM, Chapman KE, Marthan R, Ashley RH, Savineau JP 1999 Pregnant rat myometrial cells show heterogeneous ryanodine- and caffeine-sensitive calcium stores. Am J Physiol 277 C243-C252... 

Wayman CP, Gibson A, McFadzean I 1998 Depletion of either ryanodine- or IP3-sensitive calcium stores activates capacitative calcium entry in mouse anococcygeus smooth muscle cells. Pfliiger s Arch 435 231—239... 

Garaschuk 0, Yaari Y, Konnerth A. (1997). Release and sequestration of calcium by ryanodine-sensitive stores in rat hippocampal neurones. J Physiol (London). 502(pt 1) 13-30. 

Ullmer C, Boddeke HG, Schmuck K, Lubbert H. 5-HT2B receptor-mediated calcium release from ryanodine-sensitive intracellular stores in human pulmonary artery endothelial cells. Br J Pharmacol 1996 117 1081-1088. 

New agrochemicals introduced in the past five years include new chemistries with known modes of action, such as the protoporphyrinogen inhibitor bencarba-zone, the phytoene desaturase picolinafen and beflutamid, and sodium channel pyrethroids new chemistries with possibly new modes of action, such as flonic-amid and pyridalyl and new chemistries with established new modes of actions, such as flubendiamide, which activates ryanodine-sensitive intracellular calcium release channels, ryanodine receptors RyR, in insects. 

Ebbinghaus-Kintscher, U., Luemmen, P, Lobitz, N., Schsulte, T., Funke, C., Fischer, R., Masaki, T., Yasokawa, N., and Tohnishi, M., Phthalic acid diamides activate ryanodine-sensitive Ca2+ release channels in insects, Cell Calcium, 39, 21, 2006. 

Calcium Induced Calcium Release in Smooth Muscle Calcium-induced calcium release was first indicated in smooth muscle by experiments demonstrating that caffeine, which is known to bind and activate ryanodine receptors, contracts smooth muscle in calcium free solutions (Endo 1977). Subsequently, experiments demonstrated that ryanodine depletes caffeine-sensitive calcium release (lino et al. 1988 Ito et al. 1991), and CICR was directly measured in permeabilized preparations using a calcium indicator (lino 1989a). These experiments established that the CICR apparatus exists as a potential calcium release mechanism from smooth muscle sarcoplasmic reticulum, but did not establish evi-... 

Figure 18. Current model of mechanisms postulated to participate in generation of calcium transients during stimulation of snake VN neurons with chemoattractants in ESS. Initially ESS activates receptors that trigger IP3 production, mediating an increase in cytosolic Ca through simultaneous release of Ca from intracellular stores and influx through a PLC-dependent channel in the plasma membrane. There is additional Ca release from ryanodine-sensitive stores through a calcium-induced calcium release mechanism. Normal cytosolic levels of Ca are restored by activation of the Na+/ Ca exchanger.

Calcium couples muscle membrane excitation to filament contraction. Important work has focused on the proteins present in the T-tubule/SR junction. One protein, an integral component of the T-tubular membrane, is a form of L-type, dihydropyridine-sensitive, voltage-dependent calcium channel. Another, the ryanodine receptor (RyR), is a large protein associated with the SR membrane in the triad that may couple the conformational changes in the Ca2+ channel protein induced by T-tubular depolarization to the Ca2+ release from the SR (Fig. 43-6). 

Kitazawa T, Kobayashi S, Horiuti K, Somlyo AV, Somlyo AP 1989 Receptor coupled, permeabilized smooth muscle role of the phosphatidylinositol cascade, G proteins and modulation of the contractile response to Ca2+. J Biol Chem 264 5339-5342 Lopez-Lopez JR, Shacklock PS, Balke CW, Wier WG 1995 Local calcium transients triggered by single L-type calcium channel currents in cardiac cells. Science 268 1042-1045 Marks AR, Fleischer S, Tempst P 1990 Surface topography analysis of the ryanodine receptor/ junctional channel complex based on proteolysis sensitivity mapping. J Biol Chem 265 13143-13149... 

Bers, D. M., and Bridge, J. H. (1989). Relaxation of Rabbit Ventricular Muscle by Na-Ca Exchange and Sarcoplasmic Reticulum Calcium Pump. Ryanodine and Voltage Sensitivity. Circ Res 65(2) 334-42. 

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