Correction: A Ca²⁺-stimulated exosome release pathway in cancer cells is regulated by Munc13-4

Characterization of Ca²⁺- and Munc13-4–dependent released exosomes. (A) Culture media supernatants (as in Fig. 1 B) from untreated or ionomycin-treated MDA-MB-231 cells were pelleted at 100,000 g, floated to the 20%/40% interface of a sucrose block gradient as in Shurtleff et al. (2016), filtered onto nitrocellulose, and immunoblotted for CD63, ALIX, CD9, and GM130. 1% of total cellular lysate was similarly filtered. (B) The 100,000-g pellet fractions from untreated or ionomycin-treated cells were purified on a density block gradient as in Raposo et al. (1996) and Théry et al. (1999) to 1.19 g/ml density, filtered onto nitrocellulose, and immunoblotted for CD63, CD9, ALIX, and GM130. (C) 100,000-g pellet fractions from the media of MDA-MB-231 cells (with indicated treatments) were analyzed by dynamic light scattering for size distribution. (D) The mean diameter determined by dynamic light scattering is shown as mean values ± SE for n = 6. (E) 100,000-g pellet fractions from control (Ctrl) or Munc13-4 KD MDA-MB-231 cells were imaged by electron microscopy. Bar, 100 nm. (F) 100,000-g pellet fractions from control or ionomycin-treated MDA-MB-231 cells or Munc13-4 KD cells were analyzed by SDS-PAGE and stained with SYP​RO Ruby. 0.1% cell lysates were similarly analyzed. Approximate molecular mass markers in kilodaltons are indicated.