Dictyostelium cell death

Abstract

Cell death in the stalk of Dictyostelium discoideum, a prototypic vacuolar cell death, can be studied in vitro using cells differentiating as a monolayer. To identify early events, we examined potentially dying cells at a time when the classical signs of Dictyostelium cell death, such as heavy vacuolization and membrane lesions, were not yet apparent. We observed that most cells proceeded through a stereotyped series of differentiation stages, including the emergence of “paddle” cells showing high motility and strikingly marked subcellular compartmentalization with actin segregation. Paddle cell emergence and subsequent demise with paddle-to-round cell transition may be critical to the cell death process, as they were contemporary with irreversibility assessed through time-lapse videos and clonogenicity tests. Paddle cell demise was not related to formation of the cellulose shell because cells where the cellulose-synthase gene had been inactivated underwent death indistinguishable from that of parental cells. A major subcellular alteration at the paddle-to-round cell transition was the disappearance of F-actin. The Dictyostelium vacuolar cell death pathway thus does not require cellulose synthesis and includes early actin rearrangements (F-actin segregation, then depolymerization), contemporary with irreversibility, corresponding to the emergence and demise of highly polarized paddle cells.

Evaluation of the Roles of Apoptosis, Autophagy, and Mitophagy in the Loss of Plating Efficiency Induced by Bax Expression in Yeast

“…Autophagy has often been observed simultaneously with apoptosis, but data suggest that it might correspond to a survival attempt in apoptotic cells because the inhibition of autophagy induces a stimulation of cell death kinetics (17). Processes of cell death with autophagy have been reported previously in two models of physiological cell death: DIF-induced death in D. discoideum (61) and genetic incompatibility in P. anserina (62). In these two models, death is clearly associated with autophagic markers, FIGURE 5.…”

Developmental Cell Death in Dictyostelium Does Not Require Paracaspase

“…1) was functionally investigated in more detail. Upon induction by starvation and addition of DIF, the morphological stages on the cell death pathway (emergence and demise of paddle cells, cellulose synthesis, paddle-to-round cell transition, actin depolymerization, vacuolization) seen in parent HMX44A cells (14) were also observed in pcpϪ cells (Fig. 5).…”

“…Plates were examined for plaques formed by Dictyostelium cells and for development with a binocular photomicroscope (Zeiss). Monolayer assays, cell fixation and staining, microscopy, and image processing were done as described previously (14).…”

“…The stages of Dictyostelium cell death have been described in detail (13,14) using cells of another strain, HMX44A, as a monolayer. Compared with the in vivo situation or with K-AX3 cell monolayers, this system could permit the detection of more subtle alterations of the cell death process.…”

“…Each of these is made of a mass of spores supported by a stalk where cells are massively vacuolated and dead (10). This developmental cell death can be mimicked and studied in detail in vitro using Dictyostelium HMX44A cells, which upon starvation and addition of the morphogen differentiation-inducing factor (DIF) differentiate as a monolayer from vegetative to "stalk" cells (11), undergoing caspase-independent (12) autophagic vacuolar (13,14) cell death. We obtained paracaspase-null (pcpϪ) clones by homologous recombination in this haploid organism in four distinct Dictyo-stelium strains.…”