Gain-of-function of poly(ADP-ribose) polymerase-1 upon cleavage by apoptotic proteases: implications for apoptosis

Abstract

Poly(ADP-ribosyl)ation is an important mechanism for the maintenance of genomic integrity in response to DNA damage. The enzyme responsible for poly(ADP-ribose) synthesis, poly(ADP-ribose) polymerase 1 (PARP-1), has been implicated in two distinct modes of cell death induced by DNA damage, namely apoptosis and necrosis. During the execution phase of apoptosis, PARP-1 is specifically proteolyzed by caspases to produce an N-terminal DNA-binding domain (DBD) and a C-terminal catalytic fragment. The functional consequence of this proteolytic event is not known. However, it has recently been shown that overactivation of full-length PARP-1 can result in energy depletion and necrosis in dying cells. Here, we investigate the molecular basis for the differential involvement of PARP-1 in these two types of cellular demise. We show that the C-terminal apoptotic fragment of PARP-1 loses its DNA-dependent catalytic activity upon cleavage with caspase 3. However, the N-terminal apoptotic fragment, retains a strong DNA-binding activity and totally inhibits the catalytic activity of uncleaved PARP-1. This dominant-negative behavior was confirmed and extended in cellular extracts where DNA repair was completely inhibited by nanomolar concentrations of the N-terminal fragment. Furthermore, overexpression of the apoptotic DBD in mouse fibroblast inhibits endogenous PARP-1 activity very efficiently in vivo, thereby confirming our biochemical observations. Taken together, these experiments indicate that the apoptotic DBD of PARP-1 acts cooperatively with the proteolytic inactivation of the enzyme to trans-inhibit NAD hydrolysis and to maintain the energy levels of the cell. These results are consistent with a model in which cleavage of PARP-1 promotes apoptosis by preventing DNA repair-induced survival and by blocking energy depletion-induced necrosis.

Genetic Suppressor Element 1 (GSE1) Promotes the Oncogenic and Recurrent Phenotypes of Castration-Resistant Prostate Cancer by Targeting Tumor-Associated Calcium Signal Transducer 2 (TACSTD2)

“…The ensuing conundrum is that, even in the presence of mild DNA damage, cleaved PARP1 quells necrosis/necroptosis, promotes apoptosis, and prevents cell survival [24]. Thus, in the context of [23,24], the induction or overexpression of TACSTD2 would elicit cell death, consistent with the position of the current study. Aligned with the therapeutic context hypothesis, although PARP1 participates in the DNA repair process, excessive chemotherapeutic-and/or radiation-induced DNA damage prompts PARP1 (and, by inference, TACSTD2) overactivation, adenosine triphosphate (ATP) depletion, and cell death, secondary to bio-energetic collapse [25,26].…”

“…We cannot fully explain this contradiction; however, we cautiously attribute this to the tumor heterogeneity, mutational status, and/or therapeutic context. We find it intriguing that it was posited that the oncogenic activity of TACTSD2 was mediated by the upregulation of PARP1 [23], considering that the overactivation of the full-length PARP1 induces rapid cellular energy depletion, eliciting a shift in the cell death continuum from apoptosis to necrosis or necroptosis in the presence of enhanced DNA damage [24]. The ensuing conundrum is that, even in the presence of mild DNA damage, cleaved PARP1 quells necrosis/necroptosis, promotes apoptosis, and prevents cell survival [24].…”

“…We find it intriguing that it was posited that the oncogenic activity of TACTSD2 was mediated by the upregulation of PARP1 [23], considering that the overactivation of the full-length PARP1 induces rapid cellular energy depletion, eliciting a shift in the cell death continuum from apoptosis to necrosis or necroptosis in the presence of enhanced DNA damage [24]. The ensuing conundrum is that, even in the presence of mild DNA damage, cleaved PARP1 quells necrosis/necroptosis, promotes apoptosis, and prevents cell survival [24]. Thus, in the context of [23,24], the induction or overexpression of TACSTD2 would elicit cell death, consistent with the position of the current study.…”

Computational Approaches for Cancer-Fighting: From Gene Expression to Functional Foods

“…CENPB encodes for the major centromere autoantigen B that facilitates centromere formation [68]. Interestingly, investigating on CENPB protein interactors (Figure 2), the results associated not only with other proteins involved in centromere formation, but also with PARP1 which is known to be involved in programmed cell deaths [69][70][71], in cancer [72], and in the cellular response to DNA damage [73]. CENPB interacts also with TRIM21, an E3 ubiquitin ligase, involved in innate immunity, associated to cancer proliferation, as well as in systemic lupus erythematosus and in Sjögren's syndrome [74].…”

Cytocidal Antitumor Effects against Human Ovarian Cancer Cells Induced by B-Lactam Steroid Alkylators with Targeted Activity against Poly (ADP-Ribose) Polymerase (PARP) Enzymes in a Cell-Free Assay

“…Nevertheless, PARP overactivation depletes its substrate, NAD+, slowing the rate of glycolysis, electron transport and ATP formation, eventually leading to the functional cell impairment or a PARP-mediated induction of cell and tissue necrosis by extensive depletion of the intracellular NAD pool [10,11]. The cleavage of PARP-1 promotes apoptosis by preventing DNA repair-induced survival and by blocking energy depletion-induced necrosis [12].…”