Dynamin-2 Regulates Fusion Pore Expansion and Quantal Release through a Mechanism that Involves Actin Dynamics in Neuroendocrine Chromaffin Cells
Figure 2
Endogenous dynamin-2 regulates the quantal release and expansion of the fusion pore.
Exocytosis was evoked with 10 µM of the nicotinic agonist DMPP and monitored using amperometry. A: A typical amperometry trace in a single control chromaffin cell stimulated with 10 µM DMPP. B: Scheme of an amperometric spike with the analyzed parameters: quantal size (Q), half width (t1/2) and foot duration. C: Typical amperometric spikes induced by 10 µM DMPP in cells transfected with pEGFP, Dyn2WT, Dyn2K44A or iRNADyn2. D–F: Data show average values ± SEM of Q (C), t1/2 (D) and foot duration (E) of amperometric events in cells transfected with pEGFP (n = 35), iRNA-UnR (n = 28), Dyn2WT (n = 15) in white bars, and cells transfected with iRNADyn2 (n = 29) or Dyn2K44A (n = 18) in gray bars. All amperometric parameter values correspond to the median values of the events from individual cells, which were subsequently averaged per treatment group. Thus, n corresponds to the number of cells in each treatment group. Note that the down-regulation of dynamin-2 (iRNADyn2) or the inhibition of its GTP-ase activity (Dyn2K44A) significantly increased Q, t1/2 and foot duration of the exocytotic events evoked by 10 µM DMPP. *p<0.05 (Kruskal-Wallis test).