Issues

Constitutively active Ras induces ‘methuosis’, a non-apoptotic form of cell death involving accumulation of vacuoles derived from macropinosomes. U251 glioblastoma cells, stably expressing myc-H-Ras(G12V) under the control of a tetracycline promoter, were incubated with doxycycline for 4 days to induce the expression of myc-tagged Ras. The confocal image clearly shows that myc-H-Ras(G12V) (red) associates with the membrane surrounding the cytoplasmic vacuoles, which were determined to be enlarged macropinosomes. The vacuoles delineated by Ras are distinct from the autophagic vacuoles, identified by their reactivity with an antibody against endogenous LC3 (green). For details, see the article by Overmeyer and colleagues on page 965.