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Spatial Distribution of IP3 Receptors in Calcium Puffs

Study on the number and organization of IP3 receptors during calcium puffs in cells. Analysis of channel dynamics and cluster width. Investigation of trigger events and channel distribution within clusters.

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Spatial Distribution of IP3 Receptors in Calcium Puffs

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  1. Number and Spatial Distributionof IP3 Receptors UnderlyingCalcium Puffs Jianwei Shuai, Sheila L. Dargan, Heather J. Rose and Ian Parker Department of Neurobiology and Behavior University of California, Irvine NIH Grant Long Beach, Feb. 14, 2005

  2. Hierarchical Organization of Ca2+ Signals blip puff z x Two Basic Questions: How many IP3R channels open during a puff? <10 ? <300 nm ? How large is the width of an IP3R channel cluster?

  3. Puff Initiation with a Trigger Event Space Time Averaged Trigger: Duration = 12 msec, Spatial width at half peak = 0.6 mm. Averaged Puff: Rising Time = 18 msec, Spatial width at half peak = 1.6mm, Duration at half peak = 30 msec. Peak Ratio = Puff peak / Trigger peak = 6.7 (DF/F0) / 1.1 (DF/F0) = 6.1.

  4. Possible Channel Dynamics during a Puff Average number of open Channels Puff Rise T=18 ms Trigger T=12 ms N=1 N=? L=? N=0

  5. Puff Model 6mm L Immobile Buffer L : Cluster width N : Total number of open channels during a puff Free Ca2+ EGTA Fluo4 Dextran 6mm 6mm

  6. Modeling a Puff L L=? N=? L=760 nm N=30 FluoCa (mM) Free Ca2+ (mM)

  7. Confocal Image of a Model Puff Spatial Profile 1.6mm 0.6 Time Trace

  8. Estimating the number of open channels,and their distribution within a Cluster Average Peak Ratio R0 = 6.0 , Average Puff Width W0=1600nm R=6.0, W=1600 Number of open channels during a puff Cluster Width (nm)

  9. Conclusion 1. Data Experiment Model Trigger 610 Width at Half Peak (nm) 600 Puff 1600 30 1600 32 Width at Half Peak (nm) Duration at Half Peak (ms) Ratio 6.1 5.9 Puff Peak / Trigger Peak 2. Prediction 760 (400 - 1000) 30 (20 - 45) Cluster Width (nm) Open Channel No. during a Puff <300? <10 ?

  10. Simulation of Confocal Image Scan line [Fluo4Ca]

  11. Channel Current

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