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Comment
. 2011 Oct 12;478(7368):E1-2; discussion E2-3.
doi: 10.1038/nature10493.

InsP3R channel gating altered by clustering?

Horia Vais  1 , J Kevin Foskett, Don-On Daniel Mak
Affiliations
Comment

InsP3R channel gating altered by clustering?

Horia Vais et al. Nature. .
No abstract available

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Figures

Figure 1
Figure 1. InsP3R channels are clustered before exposure to InsP3, with gating properties unaltered by clustering
a, NA in nuclear membrane patches with no pre-exposure to InsP3 obtained from InsP3R3 expressing DT40-KO cells. Note nonlinear square-root scale for frequency axis. b, Po observed under saturating [InsP3] and sub-optimal [Ca2+]i in multi- and apparent single-channel current records for recombinant rat InsP3R3 (r-3) channels expressed in DT40-KO (DK) cells or Xenopus oocytes (Xo), endogenous Xenopus InsP3R1 (X-1) channels from Xenopus oocytes (Xo), and endogenous insect InsP3R (iR) channels from Sf9 cells. Concentrations of free ATP4− ([ATP]f) in the pipette solutions used are indicated. Mean Po with s.e.m. (as error bars) and Po for individual current records are shown, together with mean Po from Rahman et al. c, Po of r-3 channels in DK cells in optimal [Ca2+]i and sub-saturating [InsP3], ligand conditions not investigated in Rahman et al.. Same symbols as in b are used.
Figure 2
Figure 2. Distribution of cooperativity index for two-channel current records of different InsP3R channels in various systems in optimal and sub-optimal [Ca2+]i
Filled and open circles represent records with two channels exhibiting identical and independent, or non-binomial gating, respectively. Non-binomial records with cooperativity index, (P2+P1/2)2−P2, significantly greater than 0 (in yellow shaded region) had two channels gating with different Po, and those with cooperativity index significantly smaller than 0 (in blue shaded region) had two channels gating with positive cooperativity. The cooperativity indices have no correlation with the durations of the current records (data not shown) and therefore are unlikely to be significantly affected by current record durations limited by channel inactivation.
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Comment on

References

    1. Rahman TU, Skupin A, Falcke M, Taylor CW. Clustering of InsP3 receptors by InsP3 retunes their regulation by InsP3 and Ca2+ Nature. 2009;458:655–659. - PMC - PubMed
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    1. Mak D-OD, Foskett JK. Single-channel kinetics, inactivation, and spatial distribution of inositol trisphosphate (IP3) receptors in Xenopus oocyte nucleus. J. Gen. Physiol. 1997;109:571–587. - PMC - PubMed
    1. Mak D-OD, et al. Single-channel properties in endoplasmic reticulum membrane of recombinant type 3 inositol trisphosphate receptor. J. Gen. Physiol. 2000;115:241–256. - PMC - PubMed
    1. Ionescu L, et al. Graded recruitment and inactivation of single InsP3 receptor Ca2+-release channels: implications for quantal Ca2+ release. J. Physiol. (Lond.) 2006;573:645–662. - PMC - PubMed

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