Figure 6.

Competition between native Munc18-1 and overexpressed Munc18-2. Munc18-1, Munc18-2, Munc18-2 NV, or Munc18-1 NV were overexpressed in +/+ cells. Ca²⁺ uncaging, Ca²⁺ measurement, membrane capacitance recording, and amperometry was performed as in Figure 5. A, B, Munc18-1 overexpression increased exocytosis. n = 12 untransfected cells; n = 12 Munc18-1 overexpressing cells. C, D, Munc18-2 decreased secretion, whereas Munc18-2 NV had no effect. n = 37 untransfected +/+ cells; n = 33 Munc18-2 and 36 Munc18-2 NV expressing +/+ cells. E, F, Overexpression of Munc18-1 NV increased secretion. In this set of measurements, the effect of Munc18-2 was reconfirmed. n = 30 untransfected cells; n = 25 Munc18-1 NV and 25 Munc18-2 expressing cells. *p < 0.05; **p < 0.01; ***p < 0.001.