Figure 5

Effects of mutant VAMP2 TMDs on exocytosis measured by membrane capacitance in INS-1 832/13 clonal β-cells. Reconstitution of exocytosis by VAMP2 WT or VAMP2 VV and kinetics of vesicle pools were measured in INS-1 832/13 clonal β-cells expressing VAMP2pHL WT^R or VAMP2pHL VV^R after knock-down of endogenous VAMP2. (a) Representative traces of cumulative increase in membrane capacitance (ΔC in fF) elicited by 10 depolarizations (top panel) from −70 mV to 0 mV applied at 1 Hz. Cells were co-transfected with either shC + eGFP (n = 5, black trace), shV + eGFP (n = 6, red trace), shV + VAMP2pHL WT^R (n = 6, blue trace) or shV + VAMP2pHL VV^R (n = 10, green trace). (b) Quantification of the cumulative increase of capacitance normalized to cell capacitance (ΔC.C⁻¹) at the end of the train. Although presenting a clear trend, the difference in the cumulative exocytosis measured in cells expressing either VAMP2pHL WT^R or VAMP2pHL VV^R did not reach statistical significance (ANOVA and Tukey, p = 0.093, *p < 0.05). However, differences became significantly evident when comparing the kinetics of exocytosis for WT^R or VV^R to those of the reference control shC (ANOVA and Dunnett, +, p < 0.05).