Xestospongin C empties the ER calcium store but does not inhibit InsP3-induced Ca2+ release in cultured dorsal root ganglia neurones

School of Biological Sciences, The University of Manchester, 1.124 Stopford Building, Oxford Road, Manchester, UK.
Cell Calcium (Impact Factor: 3.51). 08/2002; 32(1):49-52. DOI: 10.1016/S0143-4160(02)00094-5
Source: PubMed


The action of Xestospongin C (XeC) on calcium concentration in the cytosol ([Ca2+]i) and within the lumen of endoplasmic reticulum (ER) ([Ca2+]L) was studied using cultured dorsal root ganglia (DRG) neurones. Application of 2.5 microM of XeC triggered a slow [Ca2+]i transient as measured by Fura-2 video-imaging. The kinetics and amplitude of XeC-induced [Ca2+]i response was similar to that triggered by 1 microM thapsigargin (TG). The [Ca2+]L was monitored in cells loaded with low-affinity Ca2+ indicator Mag-Fura-2. The cytosolic portion of Mag-Fura-2 was removed by permeabilisation of the plasmalemma with saponin. Application of XeC to these permeabilised neurones resulted in a slow depletion of the ER Ca2+ store. XeC, however, failed to inhibit inositol 1,4,5-trisphosphate (InsP3)-induced [Ca2+]L responses. We conclude that XeC is a potent inhibitor of sarco(endo)plasmic reticulum calcium ATPase, and it cannot be regarded as a specific inhibitor of InsP3 receptors in cultured DRG neurones.

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Available from: Alexei Verkhratsky
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    • "By inhibiting the SERCA pump with thapsigargin or by activating the ryanodine receptor with caffeine, it is possible to induce the release of Ca 2þ specifically from the ER. In our studies of vagal dissociated neurons, thapsigargin evoked a Ca 2þ transient, consistent with numerous reports of a functional ER within the soma of sensory neurons (Cohen and Moore, 1997; Cordoba-Rodriguez et al., 1999; Gover et al., 2007; Nicolson et al., 2002; Solovyova et al., 2002; Taylor-Clark et al., 2005). Fig. 4 – Representative data of single neuron RT-PCR detection of Orai channels. "
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    • "Xestospongin C also blocked the adverse effect of a presenilin-1 mutation in rendering neurons vulnerable to being damaged by the volatile anesthetic isoflurane (Liang et al., 2008). However, additional actions of xestospongin C on ER Ca 2ϩ handling have been reported, including inhibition of SERCA pumps and depletion of Ca 2ϩ stores without inhibiting IP 3 -induced Ca 2ϩ release in sensory neurons (Solovyova et al., 2002a). Another antagonist at IP 3 R that has been widely used to elucidate the involvement of Ca 2ϩ release from IP 3 sensitive ER stores in experimental models is 2-amino- ethoxydiphenyl borate (2-APB). "
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    • "A screen of 2-APB analogues with selectivity for store-operated Ca 2þ entry may yet also provide IP 3 R-selective antagonists (Goto et al. 2010). Xestospongins, isolated from an Australian sponge, are high-affinity membrane-permeant inhibitors of IP 3 -evoked Ca 2þ release that do not affect IP 3 binding (Gafni et al. 1997), but they, too, have side effects (Solovyova et al. 2002). High concentrations of caffeine inhibit IP 3 -evoked Ca 2þ release (Parker and Ivorra 1991) without affecting IP 3 binding (Worley et al. 1987), but caffeine also stimulates RyR, inhibits cyclic nucleotide phosphodiesterases, and interferes with many Ca 2þ indicators. "
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