Figure 2.

Examples of U251 GBM cells undergoing methuosis in response to treatment with novel indole-based chalcones. A: The images show representative cells at 24 hours after addition of 10 μmol/L MIPP or MOMIPP. Slight modification of MOMIPP by altering the pyridinyl nitrogen configuration abolishes the formation of vacuoles. B: Electron micrographs show the extreme accumulation of electron-lucent vacuoles in attached (att) and detached (det) cells exposed to MIPP for 48 hours. The detached cells are mostly nonviable (Trypan blue staining), and typically have significant gaps in the plasma membrane (arrows). Nevertheless, the nuclei (N) remain intact, without the characteristic features of apoptosis. C: Vacuoles induced by MIPP in U251 cells expressing GFP-Rab7 are decorated with this late endosomal marker. The same vacuoles contain LAMP1, but not the autophagosome marker, LC3II, or the recycling endosome marker, Rab11. A small subpopulation of the vacuoles contains the early endosome marker, EEA1, possibly representing a transition state between nascent macropinosomes and mature late endosome-like vacuoles. Images in A are reprinted with permission from Overmeyer et al⁴⁶ and Trabbic et al⁵⁰ (copyright 2014 American Chemical Society). Images in B and C are reprinted with permission from Overmeyer et al.⁴⁶ Scale bars: 10 μm (B and C).