Analysis of Puff Dynamics in Oocytes: Interdependence of Puff Amplitude and Interpuff Interval

Abstract

Puffs are localized Ca(2+) signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP(3)). They are analogous to the sparks of myocytes and are believed to be the result of the liberation of Ca(2+) from the endoplasmic reticulum through the coordinated opening of IP(3) receptor/channels clustered at a functional release site. In this article, we analyze sequences of puffs that occur at the same site to help elucidate the mechanisms underlying puff dynamics. In particular, we show a dependence of the interpuff time on the amplitude of the preceding puff, and of the amplitude of the following puff on the preceding interval. These relationships can be accounted for by an inhibitory role of the Ca(2+) that is liberated during puffs. We construct a stochastic model for a cluster of IP(3) receptor/channels that quantitatively replicates the observed behavior, and we determine that the characteristic time for a channel to escape from the inhibitory state is of the order of seconds.

Rapid ligand‐regulated gating kinetics of single inositol 1,4,5‐trisphosphate receptor Ca 2+ release channels

“…A refractory period has been invoked to account for mutual annihilation of colliding intracellular Ca 2 þ waves (Lechleiter et al, 1991) and the periodicity of Ca 2 þ oscillations (Parker & Ivorra, 1990), but its molecular basis has remained unknown. The observed latency is in quantitative agreement with the mean refractory periods (B2.5 s) between two successive spontaneous InsP 3 Rmediated elementary Ca 2 þ release events (puffs) observed in the presence of saturating [InsP 3 ] (Fraiman et al, 2006). This result indicates that the latency for channel recovery from Ca 2 þ inhibition, rather than other mechanisms such as lingering high [Ca 2 þ ] i in the vicinity of the Ca 2 þ release sites after a Ca 2 þ release event, is responsible for the refractory behaviour of Ca 2 þ release sites observed in vivo (Ilyin & Parker, 1994).…”

Imaging the quantal substructure of single IP 3 R channel activity during Ca 2+ puffs in intact mammalian cells

“…4D). This is unlikely to result in stochastic recovery of IP 3 R from an inactivated state induced by a preceding puff, because the mean size of the first puffs evoked by photo-released IP 3 is not appreciably greater than subsequent puffs (17), and puff amplitudes show only weak correlations with the amplitude of a preceding puff and with the inter-puff interval (31). Instead, we propose that the rapid cessation of channel openings results from an inhibitory process with kinetics comparable to the regenerative activation.…”

Quantifying calcium fluxes underlying calcium puffs in Xenopus laevis oocytes

“…As done in [27], we assume that the number of channels that open during a puff is equal to the number of IP 3 R’s with IP 3 bound in the cluster and that they all open and close simultaneously (see Supplementary Section). In this way, the distribution of observed currents, f I (I) , depends on the probability that there are N p IP 3 R’s with IP 3 bound in a cluster, P(N p ) , and on the relationship between the current, I , and N p (the number of channels that open during a puff).…”