Identification of two distinct transcripts for the neuronal apoptosis inhibitory protein gene

NAIP expression increases in a rat model of liver mass restoration

The neuronal apoptosis inhibitory protein (NAIP) is a constituent of the NLRC4 inflammasome, which plays a key role in innate immunity, and an antiapoptotic protein. Recently, we reported the previously undescribed role of NAIP in cell division. The liver is one of the body's most actively regenerative organs. Given the novel mitotic role of NAIP, we examined its expression in hepatic mass restoration. The major liver lobe of Wistar rats was removed, and samples from both newly formed liver tissue, assessed by positive Ki67 immunostaining, and the remnant, intact liver lobes from hepatectomized rats were taken 3 and 7 days after surgery. Naip5 and Naip6 mRNA levels were significantly higher in regenerating hepatic tissue than in intact liver lobe tissue, and this increase was also observed at the protein level. Naip5 and Naip6 mRNA in situ hybridization showed that this increase occurred in the hepatic parenchyma. The histology of the regenerated liver tissue was normal, with the exception of a noticeable deficiency of hepatic lobule central veins. The results of this study suggest the involvement of NAIP in liver mass restoration following partial hepatectomy.

Neuronal apoptosis inhibitory protein is implicated in amyotrophic lateral sclerosis symptoms

The delineation of the molecular pathology underlying amyotrophic lateral sclerosis (ALS) is being hampered by the lack of suitable biomarkers. We have previously reported that bromocriptine upregulates the endogenous antioxidative factor, neuronal apoptosis inhibitory protein (NAIP), sustains motor function and slows disease progression in ALS patients, implying the NAIP's implication in ALS. Here, we aimed to verify a correlation of NAIP level with disease progression in ALS patients. The amount of NAIP in mononuclear cells (MNC) from peripheral blood from ALS patients (n = 18) and the age matched healthy controls (n = 12) was validated by NAIP-Dot blotting. Notably, the MNC-NAIP level in ALS patients (0.62 ± 0.29 ng) was nearly half of that in the healthy controls (1.34 ± 0.61 ng, P = 0.0019). Furthermore, the MNC-NAIP level in ALS patients and their ALS Functional Rating Scale-Revised (ALSFRS-R) score were evaluated through 1 year. Regression analysis of the MNC-NAIP vs ALSFRS-R indicated that a higher amount of MNC-NAIP was associated with a smaller change in ALSFRS-R at 12 months (R2 = 0.799; P = 0.016), suggesting that a progressive increment of the MNC-NAIP led to slower ALS progression. Our present report implies that NAIP will have broad implications for ALS symptoms as a risk factor and a promising prognostic biomarker.

Inhibitor of apoptosis proteins (IAPs) as regulatory factors of hepatic apoptosis

IAPs are a group of regulatory proteins that are structurally related. Their conserved homologues have been identified in various organisms. In human, eight IAP members have been recognized based on baculoviral IAP repeat (BIR) domains. IAPs are key regulators of apoptosis, cytokinesis and signal transduction. The antiapoptotic property of IAPs depends on their professional role for caspases. IAPs are functionally non-equivalent and regulate effector caspases through distinct mechanisms. IAPs impede apoptotic process via membrane receptor-dependent (extrinsic) cascade and mitochondrial dependent (intrinsic) pathway. IAP-mediated apoptosis affects the progression of liver diseases. Therapeutic options of liver diseases may depend on the understanding toward mechanisms of the IAP-mediated apoptosis.

Role of IAPs in prostate cancer progression: immunohistochemical study in normal and pathological (benign hyperplastic, prostatic intraepithelial neoplasia and cancer) human prostate

Background

In this study was investigate IAPs in normal human prostate (NP), benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia (PIN) and prostatic carcinoma (PC), and their involvement in apoptosis/proliferation via NF-kB (TNF-α, IL-1) stimulation.

Methods

Immunohistochemical and Western blot analyses were performed in 10 samples of normal prostates, 35 samples of BPH, 27 samples diagnosis of PIN (with low-grade PIN or high-grade PIN) and 95 samples of PC (with low, medium or high Gleason grades).

Results

In NP, cytoplasm of epithelial cells were positive to c-IAP1/2 (80% of samples), c-IAP-2 (60%), ILP (20%), XIAP (20%); negative to NAIP and survivin. In BPH, epithelial cells were immunostained to c-IAP1/2 (57.57%), c-IAP-2 (57.57%), ILP (66.6%), NAIP (60.6%), XIAP (27.27%), survivin (9.1%). Whereas low-grade PIN showed intermediate results between NP and BPH; results in high-grade PIN were similar to those found in PC. In PC, epithelial cells were immunostained to c-IAP1/2, c-IAP-2, ILP, NAIP, XIAP (no Gleason variation) and survivin (increasing with Gleason).

Conclusions

IAPs could be involved in prostate disorder (BPH, PIN and PC) development since might be provoke inhibition of apoptosis and subsequently cell proliferation. At the same time, different transduction pathway such as IL-1/NIK/NF-kB or TNF/NF-kB (NIK or p38) also promotes proliferation. Inhibitions of IAPs, IL-1α and TNFα might be a possible target for PC treatment since IAPs are the proteins that inhibited apoptosis (favour proliferation) and IL-1α and TNFα would affect all the transduction pathway involucrate in the activation of transcription factors related to survival or proliferation (NF-kB, Elk-1 or ATF-2).

Distribution of neuronal apoptosis inhibitory protein in human tissues

The neuronal apoptosis inhibitory protein (NAIP) gene, also known as the baculovirus inhibitor of apoptosis repeat-containing protein 1 (BIRC1) gene, is a member of the inhibitors of apoptosis (IAP) family and was first characterized as a candidate gene for spinal muscular atrophy (SMA). The expression of NAIP has been thoroughly studied in the central nervous system and overlaps the pattern of neurodegeneration in SMA. Recent studies have pointed to a role for NAIP in non-neuronal cells. We report here the production of a specific anti-NAIP antibody and the profile of NAIP expression in human adult tissues by Western blot and immunohistochemical detection methods. NAIP was detected in a number of tissues by Western blot analysis, but immunohistochemistry revealed that NAIP's presence in certain tissues, such as liver, lung, and spleen, is most likely due to macrophage infiltration. In the small intestine, the expression of NAIP coincides with the expression of p21(WAF1). This observation, coupled with findings from other groups, suggests a role for NAIP in increasing the survival of cells undergoing terminal differentiation as well as the possibility that the protein serves as an intestinal pathogen recognition protein. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

A dopamine D4 receptor antagonist attenuates ischemia-induced neuronal cell damage via upregulation of neuronal apoptosis inhibitory protein

Neuronal apoptosis inhibitory protein (NAIP/BIRC1), the inhibitor of apoptosis protein (IAP) family member, suppresses neuronal cell death induced by a variety of insults, including cell death from ischemia and stroke. The goal of the present study was to develop an efficient method for identification of compounds with the ability to upregulate endogenous NAIP and to determine the effects on these compounds on the cellular response to ischemia. A novel NAIP-enzyme-linked immunosorbent assay (ELISA)-based in vitro drug-screening system is established. Use of this system identified an antagonist of dopamine D4 receptor, termed L-745,870, with a potent NAIP upregulatory effect. L-745,870-mediated NAIP upregulation in neuronal and nonneuronal cultured cells resulted in decreased vulnerability to oxidative stress-induced apoptosis. Reducing NAIP expression via RNA interference techniques resulted in prevention of L-745,870-mediated protection from oxidative stress. Further, systemic administration of L-745,870 attenuated ischemia-induced damage of the hippocampal CA1 neurons and upregulated NAIP expression in the rescued hippocampal CA1 neurons in a gerbil model. These data suggest that the NAIP upregulating compound, L-745,870, has therapeutic potential in acute ischemic disorders and that our NAIP-ELISA-based drug screening may facilitate the discovery of novel neuroprotective compounds.

Cloning and characterization of rat neuronal apoptosis inhibitory protein cDNA

The human neuronal apoptosis inhibitory protein (NAIP) gene was originally discovered because of its deletion in infantile spinal muscular atrophy (SMA), a childhood genetic disorder characterized by motor neuron loss and progressive paralysis with muscular atrophy. Although SMA is now known to be caused by deletions of survival motor neuron (SMN), the fact that NAIP is an anti-apoptotic protein is consistent with the NAIP gene modifying SMA severity. Here we report the cloning of a 1.5 kb rat NAIP cDNA fragment which contains BIR-3 (third baculovirus inhibitory repeat) domain. This fragment shows 78% homology to the human NAIP and 86% homology to the murine counterpart. We have investigated the distribution of NAIP mRNA expressing neurons by in situ RT-PCR technique in the rat central nervous system (CNS). Although all of the neurons appeared to express NAIP mRNA ubiquitously, pronounced elevation of NAIP mRNA expression was observed in the areas innervated by glutamatergic neurons after kainic acid (KA) injection. We have raised an anti-rat NAIP antiserum in rabbits using NAIP cDNA and recombinant rat NAIP, and carried out an immunohistological investigation. We observed highly immunoreactive neuronal subpopulations in the retinal ganglion, cerebral cortex, hippocampus, basal forebrain, thalamus, areas of midbrain, Purkinje cells of the cerebellum, and motor neurons in the spinal cord. Increased immunoreactivity of glutamatergic neurons was also observed broadly in the CNS after KA treatment. This study provides additional evidence that expression of mRNA and gene products of NAIP seem to be regulated in response to excessive stimuli or injuries in rat CNS, and these results are compatible with an anti-apoptotic role of NAIP in acute SMA as well as in brain injuries.

NAIP-deltaEx10-11: a novel splice variant of the apoptosis inhibitor NAIP differently expressed in drug-sensitive and multidrug-resistant HL60 leukemia cells

Alterations of neuronal apoptosis inhibitory protein (NAIP), a member of the inhibitory of apoptosis protein (IAP) family of inhibitors of apoptosis, have been previously associated with different neurodegenerative disorders. This study indicated the existence of a novel NAIP splice variant. This isoform, NAIP-deltaEx10-11, was found in tumor cell lines of different origin and in normal adult brain. Analysis of the putative protein predicted that the NAIP variant lacks part of the third BIR domain as well as the COOH-terminal tail of regular NAIP. This might suggest that it is endowed with a reduced antiapoptotic activity. This view is supported by the fact that NAIP-deltaEx10-11 mRNA and protein were much less expressed in the multidrug- and apoptosis-resistant HL60R leukemia than in its parental counterpart HL60. The opposite occurred for regular NAIP. Overall, the NAIP transcripts might be involved in tumor resistance to chemotherapeutic agents.

Functional human NAIP promoter transcription regulatory elements for the NAIP and PsiNAIP genes

Neuronal apoptosis inhibitory protein (NAIP) has been shown to inhibit apoptosis in vitro and in vivo with an expression which is regulated in a variety of cells and tissues and may be modulated by a variety of external stimuli. To understand the molecular basis of the transcriptional regulation of the NAIP gene, we have analyzed the 5'-flanking region and transcription of the human NAIP gene. The functional promoter and silencer elements were identified by luciferase reporter constructs in transient transfection experiments using four different human cells. Although the location of the functional elements were shared among the different cells used, the activities for the NAIP promoter varied. Further, cell type-specific protein binding activities were observed by an electrophoretic mobility shift assay (EMSA). EMSA analysis with specific antibodies and DNA sequence analysis identified the POU domain transcription factor Brn-2 as a candidate transcriptional regulator of the NAIP gene. The DNA sequence of the promoter region of the PsiNAIP gene, a copy gene for NAIP, was nearly identical to that of the NAIP gene, indicating a common regulatory mechanism for transcription of the NAIP and PsiNAIP genes. Indeed, the transcript of the PsiNAIP gene was identified. These results provided the first evidence for the functional promoter and candidate transcriptional factor for the NAIP gene and transcription of the PsiNAIP gene.

Two kinds of BIR-containing protein - inhibitors of apoptosis, or required for mitosis

The baculoviral IAP repeat (BIR) is a zinc-binding fold. Some BIR-containing proteins (BIRCs), including several from insect viruses, insects and vertebrates, are inhibitors of cell death and act by binding to active caspases. Their ability to do so can be antagonized by pro-apoptotic insect proteins such as Grim, HID and Reaper, or the mammalian protein Diablo/Smac. Members of one structurally distinct subgroup of BIR-containing proteins, which are present in yeasts and Caenorhabditis elegans as well as insects and vertebrates, do not act as caspase inhibitors; instead, they are required for chromosome segregation and cytokinesis, and act in concert with inner centromere protein (INCENP) homologues and aurora kinase homologues.

Inhibitor of apoptosis proteins and their relatives: IAPs and other BIRPs

SUMMARY

Apoptosis is a physiological cell death process important for development, homeostasis and the immune defence of multicellular animals. The key effectors of apoptosis are caspases, cysteine proteases that cleave after aspartate residues. The inhibitor of apoptosis (IAP) family of proteins prevent cell death by binding to and inhibiting active caspases and are negatively regulated by IAP-binding proteins, such as the mammalian protein DIABLO/Smac. IAPs are characterized by the presence of one to three domains known as baculoviral IAP repeat (BIR) domains and many also have a RING-finger domain at their carboxyl terminus. More recently, a second group of BIR-domain-containing proteins (BIRPs) have been identified that includes the mammalian proteins Bruce and Survivin as well as BIR-containing proteins in yeasts and Caenorhabditis elegans. These Survivin-like BIRPs regulate cytokinesis and mitotic spindle formation. In this review, we describe the IAPs and other BIRPs, their evolutionary relationships and their subcellular and tissue localizations.