Targeted ablation of Par-4 reveals a cell type-specific susceptibility to apoptosis-inducing agents.
The prostate apoptosis response-4 (Par-4) protein has been shown to function as an effector of cell death in response to various apoptotic stimuli, and down-regulation of this protein has been suggested to be a key event during tumorigenesis. Several studies suggest an essential function for the COOH-terminal leucine repeats/death domain of Par-4 in mediating apoptosis. We investigated the biological role of this domain in vivo by generating knock-out mice expressing a Par-4 mutant protein lacking the COOH terminus domain. We found that the Par-4 mutant mice are viable and fertile with no overt phenotype, thus excluding an essential role for the COOH terminus domain of Par-4 in embryogenesis and developmental apoptosis. To determine the requirement of Par-4 for apoptosis, we treated primary fibroblasts with various stimuli that trigger mitochondria and membrane receptor cell death pathways. Fibroblasts isolated from Par-4 mutant mice are as sensitive as the wild-type cells to these apoptosis-inducing agents. Similar effects were observed following RNA interference (RNAi)-mediated knockdown of Par-4 in these cells. In contrast, RNAi-mediated depletion of Par-4 in HeLa cells resulted in a significant inhibition of apoptosis induced by various proapoptotic agents. Taken together, our findings provide strong genetic evidence that the proapoptotic function of Par-4 is dependent on the cellular context and raise the possibility that alterations of Par-4 function may occur during carcinogenesis.
Department of Pathology, Harvard Medical School, 77 Louis Pasteur Avenue, Boston, MA 02115, USA.
El Bachir
el B
Affar
Margaret Po-shan
MP
Luke
Frédérique
F
Gay
Dominica
D
Calvo
Guangchao
G
Sui
Robert S
RS
Weiss
En
E
Li
Yang
Y
Shi
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000172:deficiency* / Q000235:genetics / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D019311:Staurosporine / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; C101296:prostate apoptosis response-4 protein; D000001:Calcimycin; D015759:Ionomycin; D005047:Etoposide; D004317:Doxorubicin; D019311:Staurosporine