Disease relevance of Apaf1

• We also show that the Apaf1+ but not the Rb+ allele is retained in pituitary tumors arising in Rb+/-:Apaf1+/- double heterozygous mice [1].
• Gene knockout of Apaf1 in mice leads to late embryonic lethality with malformations such as the persistence of interdigital webs and hyperplasia of brain and retina [2].
• Adeno-associated virus (AAV) vector delivery of an Apaf-1-dominant negative inhibitor was tested for its antiapoptotic effect on degenerating nigrostriatal neurons in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease [3].
• An AAV-derived Apaf-1 dominant negative inhibitor prevents MPTP toxicity as antiapoptotic gene therapy for Parkinson's disease [3].
• Adult Apaf-1-deficient mice exhibit male infertility [4].

High impact information on Apaf1

• These studies indicate the existence of a Cyt c- and apoptosome-independent but Apaf-1-dependent mechanism(s) for caspase activation [5].
• Specific ablation of the apoptotic functions of cytochrome C reveals a differential requirement for cytochrome C and Apaf-1 in apoptosis [5].
• Although fibroblasts from the KA/KA mice were resistant to apoptosis, their thymocytes were markedly more sensitive to death stimuli than Apaf-1(-/-) thymocytes [5].
• However, both Apaf1-/- thymocytes and activated T lymphocytes were sensitive to Fas-induced killing, showing that Fas-mediated apoptosis in these cells is independent of Apaf1 [6].
• Mammalian caspase-9 and its activator Apaf-1 were thought to be essential, because mice lacking either of them display neuronal hyperplasia and their lymphocytes and fibroblasts seem resistant to certain apoptotic stimuli [7].

Biological context of Apaf1

• AIF-dependent cell death displays structural features of apoptosis, and can be genetically uncoupled from Apaf1 and caspase-9 expression [8].
• There are, however, mitochondrially regulated cell death pathways that are independent of Apaf1/caspase-9 [8].
• In contrast to wild-type cells, Apaf1-deficient neurons exhibit delayed DNA fragmentation and only peripheral chromatin condensation [9].
• Using DNA microarray analysis of total RNA isolated from neurons undergoing p53-induced apoptosis a 5-6-fold upregulation of Apaf1 mRNA was detected [10].
• Apaf1-dependent programmed cell death is required for inner ear morphogenesis and growth [11].

Anatomical context of Apaf1

• Here, we report that in response to cytotoxic drugs, Apaf1(-/-) primary myoblasts but not fibroblasts undergo bona fide apoptosis [12].
• Inactivation of the tumor suppressor Rb in the mouse induces cell death, which depends entirely (in lens, CNS) and only partly (PNS, skeletal muscles) on Apaf1/Ced4, an apoptosomal factor thought to be required for processing procaspase-9 following mitochondrial permeabilization [12].
• Processing of procaspase-9 occurred in Apaf1(-/-) myoblasts but not fibroblasts, and ablation of Casp9 prevented drug-induced apoptosis in both cell types [12].
• In Apaf1(-/-)/Bcl2l(-/-) double mutant embryos, no cell death could be detected in the otic epithelium, demonstrating that the cell death regulated by the anti-apoptotic Bcl2l isoform, Bcl-X(L) in the otic epithelium is Apaf1-dependent [11].
• In this study, we investigated the role of apoptotic protease-activating factor 1 (Apaf1), a mammalian homologue of CED-4, in programmed cell death during the negative selection in thymus [13].

Associations of Apaf1 with chemical compounds

• Of 1176 different human cDNA transcripts in cisplatin-treated TTSC-3, three genes (tumour necrosis factor receptor 1, caspase 8 and Apaf1), which are associated with apoptosis, were expressed markedly more than after saline injection [14].
• In this study, we found that NPCs deficient in Apaf-1, or both the pro-apoptotic multidomain Bcl-2 family members Bax and Bak, were resistant to cytosine arabinoside and gamma-irradiation-induced apoptosis [15].
• Here, we studied cell death induced by the methylating agents methyl methanesulfonate (MMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in mouse fibroblasts wild-type (wt) and deficient for Apaf-1 (apaf-1 knockout cells) [16].
• Apaf-1 deficient mouse fibroblasts are resistant to MNNG and MMS-induced apoptotic death without attenuation of Bcl-2 decline [16].
• Furthermore, in the kidneys of Apaf-1-deficient mice, apoptosis induced by in vivo administration of tunicamycin was remarkably suppressed as compared with wild type mice [17].

Regulatory relationships of Apaf1

• Microinjection of neutralizing antibodies against AIF significantly decreased injury-induced neuronal cell death in Apaf1-deficient neurons, indicating its importance in caspase-independent apoptosis [9].
• In the present study, we demonstrate that p53 directly upregulates Apaf1 transcription as a critical step in the induction of neuronal cell death [10].
• Loss of Apaf-1 specifically suppressed apoptosis but not the proliferation and differentiation defects in Rb-mutant embryos [1].
• Apaf-1 is an essential component of the apoptosome complex that becomes activated upon cytochrome c release from mitochondria [16].
• Hsp72 inhibits apoptosis upstream of the mitochondria and not through interactions with Apaf-1 [18].

Other interactions of Apaf1

• We also show that during retinal development apoptotic protease activating factor (Apaf-1) protein levels are markedly decreased and this is associated with the inability to activate the mitochondrial caspase cascade in the mature retina [19].
• Caspase-independent photoreceptor apoptosis in vivo and differential expression of apoptotic protease activating factor-1 and caspase-3 during retinal development [19].
• Together, these results demonstrate that Apaf1 is a key transcriptional target for p53 that plays a pivotal role in the regulation of apoptosis after neuronal injury [10].
• Our results show, that gene expression for Apaf1 first occurs within the embryo between day 7 and 9 of development, becoming more widespread toward day 12 and then includes structures, such as yolk sac, mesenchyme, cartilage, heart anlage, otic vesicle, peridermis, and anlagen of the spinal ganglia and vertebral bodies [2].
• Apoptotic protease-activating factor-1 (Apaf-1), dATP, and procaspase-9 form a multimeric complex that triggers programmed cell death through the activation of caspases upon release of cytochrome c from the mitochondria into the cytosol [20].

Analytical, diagnostic and therapeutic context of Apaf1

• Localization of Apaf1 gene expression in the early development of the mouse by means of in situ reverse transcriptase-polymerase chain reaction [2].
• Moreover, Western blot analysis of procaspase-3 processing, a principal downstream event set in motion by activated Apaf-1, indicated that healthy granulosa cells possess almost exclusively the inactive (pro-) form of the enzyme whereas granulosa cells deprived of hormonal support rapidly process procaspase-3 to the active enzyme [21].
• Immunocytochemistry revealed that pro-apoptosis factor (BAX, Apaf-1 and Caspase 9) are predominantly expressed in the basophilic cytoplasm (infected muscle cell origin) and anti-apoptosis factor (PKB) in the eosinophilic cytoplasm (satellite cell origin) of the nurse cell [22].
• Northern blot and reverse transcription-PCR analysis show that Apaf-1 mRNA is aberrantly processed, resulting in greatly reduced expression levels of normal Apaf-1 mRNA [23].
• METHODS: SDS-polyacrylamide gel electrophoresis and semiquantitative PCR were used to examine Apaf-1 and caspase 3 expression levels during development [24].

References