Generation and characterization of LANP/pp32 null mice

ANP32A represses Wnt signaling across tissues thereby protecting against osteoarthritis and heart disease

OBJECTIVES

To investigate how ANP32A, previously linked to the antioxidant response, regulates Wnt signaling as unraveled by transcriptome analysis of Anp32a-deficient mouse articular cartilage, and its implications for osteoarthritis (OA) and diseases beyond the joint.

METHODS

Anp32a knockdown chondrogenic ATDC5 cells were cultured in micromasses. Wnt target genes, differentiation markers and matrix deposition were quantified. Wnt target genes were determined in articular cartilage from Anp32a-deficient mice and primary human articular chondrocytes upon ANP32A silencing, using qPCR, luciferase assays and immunohistochemistry. Co-immunoprecipitation, immunofluorescence and chromatin-immunoprecipitation quantitative PCR probed the molecular mechanism via which ANP32A regulates Wnt signaling. Anp32a-deficient mice were subjected to the destabilization of the medial meniscus (DMM) OA model and treated with a Wnt inhibitor and an antioxidant. Severity of OA was assessed by cartilage damage and osteophyte formation. Human Protein Atlas data analysis identified additional organs where ANP32A may regulate Wnt signaling. Wnt target genes were determined in heart and hippocampus from Anp32a-deficient mice, and cardiac hypertrophy and fibrosis quantified.

RESULTS

Anp32a loss triggered Wnt signaling hyper-activation in articular cartilage. Mechanistically, ANP32A inhibited target gene expression via histone acetylation masking. Wnt antagonist treatment reduced OA severity in Anp32a-deficient mice by preventing osteophyte formation but not cartilage degradation, contrasting with antioxidant treatment. Dual therapy ameliorated more OA features than individual treatments. Anp32a-deficient mice also showed Wnt hyper-activation in the heart, potentially explaining the cardiac hypertrophy phenotype found.

CONCLUSIONS

ANP32A is a novel translationally relevant repressor of Wnt signaling impacting osteoarthritis and cardiac disease.

Behavioral sensitization induced by methamphetamine causes differential alterations in gene expression and histone acetylation of the prefrontal cortex in rats

Background

Methamphetamine (METH) is one of the most widely abused illicit substances worldwide; unfortunately, its addiction mechanism remains unclear. Based on accumulating evidence, changes in gene expression and chromatin modifications might be related to the persistent effects of METH on the brain. In the present study, we took advantage of METH-induced behavioral sensitization as an animal model that reflects some aspects of drug addiction and examined the changes in gene expression and histone acetylation in the prefrontal cortex (PFC) of adult rats.

Methods

We conducted mRNA microarray and chromatin immunoprecipitation (ChIP) coupled to DNA microarray (ChIP-chip) analyses to screen and identify changes in transcript levels and histone acetylation patterns. Functional enrichment analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, were performed to analyze the differentially expressed genes. We then further identified alterations in ANP32A (acidic leucine-rich nuclear phosphoprotein-32A) and POU3F2 (POU domain, class 3, transcription factor 2) using qPCR and ChIP-PCR assays.

Results

In the rat model of METH-induced behavioral sensitization, METH challenge caused 275 differentially expressed genes and a number of hyperacetylated genes (821 genes with H3 acetylation and 10 genes with H4 acetylation). Based on mRNA microarray and GO and KEGG enrichment analyses, 24 genes may be involved in METH-induced behavioral sensitization, and 7 genes were confirmed using qPCR. We further examined the alterations in the levels of the ANP32A and POU3F2 transcripts and histone acetylation at different periods of METH-induced behavioral sensitization. H4 hyperacetylation contributed to the increased levels of ANP32A mRNA and H3/H4 hyperacetylation contributed to the increased levels of POU3F2 mRNA induced by METH challenge-induced behavioral sensitization, but not by acute METH exposure.

Conclusions

The present results revealed alterations in transcription and histone acetylation in the rat PFC by METH exposure and provided evidence that modifications of histone acetylation contributed to the alterations in gene expression caused by METH-induced behavioral sensitization.

The mammalian Hedgehog pathway is modulated by ANP32 proteins

Medulloblastoma (MB) is the most common malignant brain tumor in children. Transcriptional profiling has so far delineated four major MB subgroups of which one is driven by uncontrolled Hedgehog (Hh) signaling (SHH-MB). This pathway is amenable to drug targeting, yet clinically approved compounds exclusively target the transmembrane component Smoothened (SMO). Unfortunately, drug resistance against SMO inhibitors is encountered frequently, making the identification of novel Hh pathway components mandatory, which could serve as novel drug targets in the future. Here, we have used MB as a tool to delineate novel modulators of Hh signaling and have identified the Acidic Nuclear Phosphoprotein 32 (ANP32) family of proteins as novel regulators. The expression of all three family members (ANP32A, ANP32B, ANP32E) is increased in Hh-induced MB and their expression level is negatively associated with overall survival in SHH-MB patients. Mechanistically, we could find that ANP32 proteins function as positive modulators of mammalian Hh signaling upstream of GLI transcription factors. These findings add hitherto unknown regulators to the mammalian Hh signaling cascade and might spur future translational efforts to combat Hh-driven malignancies.

The acidic protein rich in leucines Anp32b is an immunomodulator of inflammation in mice

ANP32B belongs to a family of evolutionary conserved acidic nuclear phosphoproteins (ANP32A-H). Family members have been described as multifunctional regulatory proteins and proto-oncogenic factors affecting embryonic development, cell proliferation, apoptosis, and gene expression at various levels. Involvement of ANP32B in multiple processes of cellular life is reflected by the previous finding that systemic gene knockout (KO) of Anp32b leads to embryonic lethality in mice. Here, we demonstrate that a conditional KO of Anp32b is well tolerated in adult animals. However, after immune activation splenocytes isolated from Anp32b KO mice showed a strong commitment towards Th17 immune responses. Therefore, we further analyzed the respective animals in vivo using an experimental autoimmune encephalomyelitis (EAE) model. Interestingly, an exacerbated clinical score was observed in the Anp32b KO mice. This was accompanied by the finding that animal-derived T lymphocytes were in a more activated state, and RNA sequencing analyses revealed hyperactivation of several T lymphocyte-associated immune modulatory pathways, attended by significant upregulation of Tfh cell numbers that altogether might explain the observed strong autoreactive processes. Therefore, Anp32b appears to fulfill a role in regulating adequate adaptive immune responses and, hence, may be involved in dysregulation of pathways leading to autoimmune disorders and/or immune deficiencies.

ANP32A regulates ATM expression and prevents oxidative stress in cartilage, brain, and bone

Osteoarthritis is the most common joint disorder with increasing global prevalence due to aging of the population. Current therapy is limited to symptom relief, yet there is no cure. Its multifactorial etiology includes oxidative stress and overproduction of reactive oxygen species, but the regulation of these processes in the joint is insufficiently understood. We report that ANP32A protects the cartilage against oxidative stress, preventing osteoarthritis development and disease progression. ANP32A is down-regulated in human and mouse osteoarthritic cartilage. Microarray profiling revealed that ANP32A protects the joint by promoting the expression of ATM, a key regulator of the cellular oxidative defense. Antioxidant treatment reduced the severity of osteoarthritis, osteopenia, and cerebellar ataxia features in Anp32a-deficient mice, revealing that the ANP32A/ATM axis discovered in cartilage is also present in brain and bone. Our findings indicate that modulating ANP32A signaling could help manage oxidative stress in cartilage, brain, and bone with therapeutic implications for osteoarthritis, neurological disease, and osteoporosis.

ANP32A modulates cell growth by regulating p38 and Akt activity in colorectal cancer

Acidic leucine-rich nuclear phosphoprotein-32A (ANP32A) possesses multiple biochemical activities, has been found to be decreased or absent in malignant tumors. However, new findings have shown that it is expressed in greater amounts in advanced cancers than in early-stage tumors. The role and clinical significance of ANP32A in colorectal cancer (CRC) is still unknown. In the present study, the expression of ANP32A was assessed in 68 CRC patients by IHC, and then the correlation of its expression with clinicopathological factors was investigated using the Allred, Klein and immune response scoring system analysis. Western blot and real-time PCR analyses were used to assess ANP32A expression and the activity of Akt and p38 in cancer and normal tissues. These data indicated a significant association between ANP32A expression and the activity of Akt and p38, besides the tumor differentiation status in CRC patients. IHC and western blotting data revealed that ANP32A was overexpressed in CRC patients, and ANP32A levels were higher in poorly differentiated tumors. Protein and mRNA analysis revealed that with a high expression of ANP32A, the activation of Akt was enhanced, while the p-38 phosphorylation level was decreased in CRC tissues. MTT assay and functional studies revealed that knockdown of ANP32A inhibited cell growth and induced p38 phosphorylation and Akt dephosphorylation. The present study indicated that ANP32A promoted CRC proliferation by inhibition of p38 and activation of Akt signaling pathways and suggested that ANP32A may play a potential role in CRC diagnosis and therapy.

Knockdown of pp32 Increases Histone Acetylation and Ameliorates Cognitive Deficits

Aging is a cause of cognitive decline in the elderly and the major risk factor for Alzheimer's disease, however, aging people are not all destined to develop into cognitive deficits, the molecular mechanisms underlying this difference in cognition of aging people are obscure. Epigenetic modifications, particularly histone acetylation in the nervous system, play a critical role in regulation of gene expression for learning and memory. An inhibitor of acetyltransferases (INHAT) is reported to suppress histone acetylation via a histone-masking mechanism, and pp32 is a key component of INHAT complex. In the present study, we divided ~18 m-old aged mice into the cognitive-normal and the cognitive-impaired group by Morris water maze, and found that pp32 level was significantly increased in the hippocampus of cognitive-impaired aged mice. The mRNA and protein levels of synaptic-associated proteins decreased with reduced dendrite complexity and histone acetylation. Knockdown of pp32 rescued cognitive decline in cognitive-impaired aged mice with restoration of synaptic-associated proteins, the increase of spine density and elevation of histone acetylation. Our study reveals a novel mechanism underlying the aging-associated cognitive disturbance, indicating that suppression of pp32 might represent a promising therapeutic approach for learning and memory impairments.

ANP32B deficiency impairs proliferation and suppresses tumor progression by regulating AKT phosphorylation

The acidic leucine-rich nuclear phosphoprotein 32B (ANP32B) is reported to impact normal development, with Anp32b-knockout mice exhibiting smaller size and premature aging. However, its cellular and molecular mechanisms, especially its potential roles in tumorigenesis, remain largely unclear. Here, we utilize 'knockout' models, RNAi silencing and clinical cohorts to more closely investigate the role of this enigmatic factor in cell proliferation and cancer phenotypes. We report that, compared with Anp32b wild-type (Anp32b^+/+) littermates, a broad panel of tissues in Anp32b-deficient (Anp32b^−/−) mice are demonstrated hypoplasia. Anp32b^−/− mouse embryo fibroblast cell has a slower proliferation, even after oncogenic immortalization. ANP32B knockdown also significantly inhibits in vitro and in vivo growth of cancer cells by inducing G₁ arrest. In line with this, ANP32B protein has higher expression in malignant tissues than adjacent normal tissues from a cohort of breast cancer patients, and its expression level positively correlates with their histopathological grades. Moreover, ANP32B deficiency downregulates AKT phosphorylation, which involves its regulating effect on cell growth. Collectively, our findings suggest that ANP32B is an oncogene and a potential therapeutic target for breast cancer treatment.

BALB/c-congenic ANP32B-deficient mice reveal a modifying locus that determines viability

We previously found that deletion of the multifunctional factor ANP32B (a.k.a. SSP29, APRIL, PAL31, PHAPI2) resulted in a severe but strain-specific defect resulting in perinatal lethality. The difficulty in generating an adult cohort of ANP32B-deficient animals limited our ability to examine adult phenotypes, particularly cancer-related phenotypes. We bred the Anp32b-null allele into the BALB/c and FVB/N genetic background. The BALB/c, but not the FVB/N, background provided sufficient frequency of adult Anp32b-null (Anp32b^−/−) animals. From these, we found no apparent oncogenic role for this protein in mammary tumorigenesis contrary to what was predicted based on human data. We also found runtism, pathologies in various organ systems, and an unusual clinical chemistry signature in the adult Anp32b^−/− mice. Intriguingly, genome-wide single-nucleotide polymorphism analysis suggested that our colony retained an unlinked C57BL/6J locus at high frequency. Breeding this locus to homozygosity demonstrated that it had a strong effect on Anp32b^−/− viability indicating that this locus contains a modifier gene of Anp32b with respect to development. This suggests a functionally important genetic interaction with one of a limited number of candidate genes, foremost among them being the variant histone gene H2afv. Using congenic breeding strategies, we have generated a viable ANP32B-deficient animal in a mostly pure background. We have used this animal to reliably exclude mouse ANP32B as an important oncogene in mammary tumorigenesis. Our further phenotyping strengthens the evidence that ANP32B is a widespread regulator of gene expression. These studies may also impact the choice of subsequent groups with respect to congenic breeding versus de novo zygote targeting strategies for background analyses in mouse genetics.

The expression and distributions of ANP32A in the developing brain

Acidic (leucine-rich) nuclear phosphoprotein 32 family, member A (ANP32A), has multiple functions involved in neuritogenesis, transcriptional regulation, and apoptosis. However, whether ANP32A has an effect on the mammalian developing brain is still in question. In this study, it was shown that brain was the organ that expressed the most abundant ANP32A by human multiple tissue expression (MTE) array. The distribution of ANP32A in the different adult brain areas was diverse dramatically, with high expression in cerebellum, temporal lobe, and cerebral cortex and with low expression in pons, medulla oblongata, and spinal cord. The expression of ANP32A was higher in the adult brain than in the fetal brain of not only humans but also mice in a time-dependent manner. ANP32A signals were dispersed accordantly in embryonic mouse brain. However, ANP32A was abundant in the granular layer of the cerebellum and the cerebral cortex when the mice were growing up, as well as in the Purkinje cells of the cerebellum. The variation of expression levels and distribution of ANP32A in the developing brain would imply that ANP32A may play an important role in mammalian brain development, especially in the differentiation and function of neurons in the cerebellum and the cerebral cortex.

Caspase-3-resistant uncleavable form of acidic leucine-rich nuclear phosphoprotein 32B potentiates leukemic cell apoptosis

One member of the highly conserved acidic leucine‑rich nuclear phosphoprotein 32 kDa (ANP32) family of proteins, ANP32B, is critical for normal development, as demonstrated by a study in ANP32B‑deficient mice. Another study indicated that ANP32B was a direct substrate of caspase‑3, and was primarily cleaved at the sequence Ala‑Glu‑Val‑Asp, following Asp‑163. To investigate the significance of ANP32B cleavage in apoptosis, leukemic U937T cell lines were generated with inducible expression of ANP32B(wild type; WT), the uncleavable mutant ANP32B(D163A) and the N‑terminal fragment ANP32B(1‑163). Notably, overexpression of ANP32B(WT) and ANP32B(D163A) moderately increased and significantly enhanced etoposide‑induced apoptosis and caspase‑3 activation, whereas expression of ANP32B(1‑163) produced no effect. Two hypotheses have been generated, which may explain the distinct roles of the various ANP32B forms: i) ANP32B(WT) and ANP32B(D163A) localize in the nucleus while ANP32B(1‑163) mainly resides in the cytosol; or ii) ANP32B(WT) and ANP32B(D163A), but not ANP32B(1‑163), inhibit the expression of the anti‑apoptotic protein Bcl‑2. Based on these observations, caspase‑3‑resistant uncleavable ANP32B(D163A) is hypothesized to be pro‑apoptotic in leukemic cells.

Cracking the ANP32 whips: important functions, unequal requirement, and hints at disease implications

The acidic (leucine-rich) nuclear phosphoprotein 32 kDa (ANP32) family is composed of small, evolutionarily conserved proteins characterized by an N-terminal leucine-rich repeat domain and a C-terminal low-complexity acidic region. The mammalian family members (ANP32A, ANP32B, and ANP32E) are ascribed physiologically diverse functions including chromatin modification and remodelling, apoptotic caspase modulation, protein phosphatase inhibition, as well as regulation of intracellular transport. In addition to reviewing the widespread literature on the topic, we present a concept of the ANP32s as having a whip-like structure. We also present hypotheses that ANP32C and other intronless sequences should not currently be considered bona fide family members, that their disparate necessity in development may be due to compensatory mechanisms, that their contrasting roles in cancer are likely context-dependent, along with an underlying hypothesis that ANP32s represent an important node of physiological regulation by virtue of their diverse biochemical activities.

Overexpression of the pp32r1 (ANP32C) oncogene or its functional mutant pp32r1Y140H confers enhanced resistance to FTY720 (Finguimod)

pp32r1 (ANP32C) is oncogenic and has been shown to be overexpressed in tumors of the breast, prostate, and pancreas. In this work we show that pp32 family proteins are able to bind to the sphingosine analog FTY720 (Finguimod). Molecular docking studies highlight that a conserved residue F136 is likely to be a key determinant of the FTY720 binding site on the pp32 leucine-rich repeat domain. Transduction of the renal carcinoma cell line ACHN or cervical cancer cell line HeLa with lentivirus expressing the oncogenic family member pp32r1 or a pp32r1Y140H functional mutant illustrated an enhanced resistance to FTY720 induced apoptosis. These findings highlight that certain cancers overexpressing pp32r1 or pp32r1 mutants are likely to demonstrate enhanced resistance to FTY720 treatment.

Glycomimetic affinity-enrichment proteomics identifies partners for a clinically-utilized iminosugar

Widescale evaluation of interacting partners for carbohydrates is an underexploited area. Probing of the 'glyco-interactome' has particular relevance given the lack of direct genetic control of glycoconjugate biosynthesis. Here we design, create and utilize a natural product-derived glycomimetic iminosugar probe in a Glycomimetic Affinity-enrichment Proteomics (glyco-AeP) strategy to elucidate key interactions directly from mammalian tissue. The binding partners discovered here and the associated genomic analysis implicate a subset of chaperone and junctional proteins as important in male fertility. Such repurposing of existing therapeutics thus creates direct routes to probing in vivo function. The success of this strategy suggests a general approach to discovering 'carbohydrate-active' partners in biology.

Dysregulation of cell cycle control caused by overexpression of the oncogene pp32r1 (ANP32C) and the Tyr>His mutant pp32r1Y140H

The pp32 (ANP32A) gene acts as a tumor suppressor while its closely related homologue pp32r1 (ANP32C) is oncogenic and is overexpressed in breast, prostate and pancreatic tumors. The transduction of p53wt cell lines (ACHN and HeLa) with pp32r1 or pp32r1Y140H lentivirus increased the proliferation of p53wt cell lines compared to the untransduced control cells while transduction of the p53(R248W) MiaPaCa2 cell line had no effect. Cell cycle analysis of transduced ACHN cells by PI staining and BrdU incorporation illustrated a pronounced shift toward the S-phase of the cell cycle in cells overexpressing the pp32r1 and pp32r1Y140H proteins. Confocal microscopy and western blotting demonstrated that pp32r1 and the pp32r1Y140H mutant protein reside predominantly in the cytoplasm in constrast to pp32 which is a nuclear/cytoplasmic shuttling protein. To determine the effects of pp32r1 or pp32r1Y140H overexpression at the proteomic level we performed a comprehensive proteome analysis on ACHN, ACHN-pp32r1 and ACHN-pp32r1Y140H cell lysates using the isotope-coded protein label (ICPL) method. Among those proteins with >40% regulation were Macrophage Capping protein (CAPG) and Chromodomain Helicase DNA binding protein 4 (CHD4) proteins which were significantly upregulated by pp32r1 and pp32r1Y140H overexpression. This increase in CHD4 also appears to influence a number of cell cycle regulator genes including; p53, p21 and cyclinD1 as judged by western blotting. Silencing of CHD4 in ACHN-pp32r1Y140H cells using specific shRNA reverted the cell cycle dysregulation caused by pp32r1Y140H expression to that of the untransduced ACHN cell line, suggesting that CHD4 is the prominent effector of the pp32r1/pp32r1Y140H phenotype.

LANP mediates neuritic pathology in Spinocerebellar ataxia type 1

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disease that results from a pathogenic glutamine-repeat expansion in the protein ataxin-1 (ATXN1). Although the functions of ATXN1 are still largely unknown, there is evidence to suggest that ATXN1 plays a role in regulating gene expression, the earliest process known to go awry in SCA1 mouse models. In this study, we show that ATXN1 reduces histone acetylation, a post-translational modification of histones associated with enhanced transcription, and represses histone acetyl transferase-mediated transcription. In addition, we find that depleting the Leucine-rich Acidic Nuclear Protein (LANP)-an ATXN1 binding inhibitor of histone acetylation-reverses aspects of SCA1 neuritic pathology.

Acidic nuclear phosphoprotein 32kDa (ANP32)B-deficient mouse reveals a hierarchy of ANP32 importance in mammalian development

The highly conserved ANP32 proteins are proposed to function in a broad array of physiological activities through molecular mechanisms as diverse as phosphatase inhibition, chromatin regulation, caspase activation, and intracellular transport. On the basis of previous analyses of mice bearing targeted mutations of Anp32a or Anp32e, there has been speculation that all ANP32 proteins play redundant roles and are dispensable for normal development. However, more recent work has suggested that ANP32B may in fact have functions that are not shared by other ANP32 family members. Here we report that ANP32B expression is associated with a poor prognosis in human breast cancer, consistent with the increased levels of Anp32b mRNA present in proliferating wild-type (WT) murine embryonic fibroblasts and stimulated WT B and T lymphocytes. Moreover, we show that, contrary to previous assumptions, Anp32b is very important for murine embryogenesis. In a mixed genetic background, ANP32B-deficient mice displayed a partially penetrant perinatal lethality that became fully penetrant in a pure C57BL/6 background. Surviving ANP32B-deficient mice showed reduced viability due to variable defects in various organ systems. Study of compound mutants lacking ANP32A, ANP32B, and/or ANP32E revealed previously hidden roles for ANP32A in mouse development that became apparent only in the complete absence of ANP32B. Our data demonstrate a hierarchy of importance for the mammalian Anp32 genes, with Anp32b being the most critical for normal development.

Generation and characterization of the Anp32e-deficient mouse

Background

Accumulated literature suggests that the acidic nuclear phosphoprotein 32 kilodalton (Anp32) proteins control multiple cellular activities through different molecular mechanisms. Like other Anp32 family members, Anp32e (a.k.a. Cpd1, PhapIII) has been conserved throughout vertebrate evolution, suggesting that it has an important function in organismal survival.

Principal Findings

Here, we demonstrate that the Anp32e gene can be deleted in mice without any apparent effect on their wellbeing. No defects in thymocyte apoptosis in response to various stresses, fibroblast growth, gross behaviour, physical ability, or pathogenesis were defined. Furthermore, combined deletion of Anp32a and Anp32e also resulted in a viable and apparently healthy mouse.

Significance

These results provide evidence that significant functional redundancy exists among Anp32 family members.

Cpd-1 null mice display a subtle neurological phenotype

Background

CPD1 (also known as ANP32-E) belongs to a family of evolutionarily conserved acidic proteins with leucine rich repeats implicated in a variety of cellular processes regulating gene expression, vesicular trafficking, intracellular signaling and apoptosis. Because of its spatiotemporal expression pattern, CPD1 has been proposed to play an important role in brain morphogenesis and synaptic development.

Methodology/Principal Findings

We have generated CPD1 knock-out mice that we have subsequently characterized. These mice are viable and fertile. However, they display a subtle neurological clasping phenotype and mild motor deficits.

Conclusions/Significance

CPD1 is not essential for normal development; however, it appears to play a role in the regulation of fine motor functions. The minimal phenotype suggests compensatory biological mechanisms.

Hepatopoietin Cn suppresses apoptosis of human hepatocellular carcinoma cells by up-regulating myeloid cell leukemia-1

AIM: To investigate the role of hepatopoietin Cn (HPPCn) in apoptosis of hepatocellular carcinoma (HCC) cells and its mechanism.

METHODS: Two human HCC cell lines, SMMC7721 and HepG2, were used in this study. Immunostaining, Western blotting and enzyme linked immunosorbent assay were conducted to identify the expression of HPPCn and the existence of an autocrine loop of HPPCn/HPPCn receptor in SMMC7721 and HepG2. Apoptotic cells were detected using fluorescein isothiocyanate (FITC)-conjugated Annexin V and propidium iodide.

RESULTS: The HPPCn was highly expressed in human HCC cells and secreted into culture medium (CM). FITC-labeled recombinant human protein (rhHPPCn) could specifically bind to its receptor on HepaG2 cells. Treatment with 400 ng/mL rhHPPCn dramatically increased the viability of HCC-derived cells from 48.1% and 36.9% to 85.6% and 88.4%, respectively (P < 0.05). HPPCn silenced by small-interfering RNA reduced the expression and secretion of HPPCn and increased the apoptosis induced by trichostatin A. Additionally, HPPCn could up-regulate the expression of myeloid cell leukemia-1 (Mcl-1) in HCC cells via mitogen-activated protein kinase (MAPK) and sphingosine kinase-1.

CONCLUSION: HPPCn is a novel hepatic growth factor that can be secreted to CM and suppresses apoptosis of HCC cells by up-regulating Mcl-1 expression.

Neuronal differentiation is regulated by leucine-rich acidic nuclear protein (LANP), a member of the inhibitor of histone acetyltransferase complex

Neuronal differentiation is a tightly regulated process characterized by temporal and spatial alterations in gene expression. A number of studies indicate a significant role for histone acetylation in the regulation of genes involved in development. Histone acetylation is regulated by histone deacetylases and histone acetyltransferases. Recent findings suggest that these catalytic activities, in turn, are modulated by yet another set of regulators. Of considerable interest in this context is the possible role of the INHAT (inhibitor of histone acetyltransferase) complex, comprised of a group of acidic proteins that suppress histone acetylation by a novel "histone-masking" mechanism. In this study, we specifically examined the role of the leucine-rich acidic nuclear protein (LANP), a defining member of the INHAT complex whose expression is tightly regulated in neuronal development. We report that depleting LANP in neuronal cell lines promotes neurite outgrowth by inducing changes in gene expression. In addition, we show that LANP directly regulates expression of the neurofilament light chain, an important neuron-specific cytoskeletal gene, by binding to the promoter of this gene and modulating histone acetylation levels. Finally, we corroborated our findings in vivo by demonstrating increased neurite outgrowth in primary neurons obtained from LANP null mice, which is also accompanied by increased histone acetylation at the NF-L promoter. Taken together, these results implicate INHATs as a distinct class of developmental regulators involved in the epigenetic modulation of neuronal differentiation.

Isolation and functional identification of a novel human hepatic growth factor: hepatopoietin Cn

Hepatic stimulating substance (HSS) was first isolated from weanling rat liver in 1975 and found to stimulate hepatic DNA synthesis both in vitro and in vivo. Since then, mammalian and human HSS have been investigated for their potential to treat hepatic diseases. However, the essential nature in composition and structure of HSS remain puzzling because HSS has not been completely purified. Heating, ethanol precipitation, and ion-exchange chromatographies had been carried out to isolate the protein with specific stimulating activity from newborn calf liver, and [(3)H]thymidine deoxyribose (TdR)/bromodeoxyuridine (BrdU) incorporation and carboxyfluorescein diacetate succinimidyl ester (CFSE)-based proliferation assay to determine the bioactivity in vitro and in vivo. We report the purification of a novel 30-kDa protein from a crude extract of calf liver HSS. This protein is a member of the leucine-rich acidic nuclear protein family (LANP) and has been named hepatopoietin Cn (HPPCn). Studies of partially hepatectomized (PH) mice show that levels of HPPCn messenger RNA (mRNA) increase after liver injury. Furthermore, the recombinant human protein (rhHPPCn) was shown to stimulate hepatic DNA synthesis and activate signaling pathways involved in hepatocyte proliferation in vitro and in vivo.

CONCLUSION

HPPCn is a novel hepatic growth factor that plays a role in liver regeneration.

pp32/PHAPI determines the apoptosis response of non-small-cell lung cancer

During malignant transformation, cancer cells have to evade cell-intrinsic tumor suppressor mechanisms including apoptosis, thus acquiring a phenotype that is relatively resistant to clinically applied anticancer therapies. Molecular characterization of apoptotic signal transduction defects may help to identify prognostic markers and to develop novel therapeutic strategies. To this end we have undertaken functional analyses of drug-induced apoptosis in human non-small cell-lung cancer (NSCLC) cells. We found that primary drug resistance correlated with defects in apoptosome-dependent caspase activation in vitro. While cytochrome c-induced apoptosome formation was maintained, the subsequent activation of caspase-9 and -3 was abolished in resistant NSCLC. The addition of recombinant pp32/putative human HLA class II-associated protein (pp32/PHAPI), described as a putative tumor suppressor in prostate cancer, successfully restored defective cytochrome c-induced caspase activation in vitro. Conditional expression of pp32/PHAPI sensitized NSCLC cells to apoptosis in vitro and in a murine tumor model in vivo. Immunohistochemical analyses of tumor samples from NSCLC patients revealed that the expression of pp32/PHAPI correlated with an improved outcome following chemotherapy. These results identify pp32/PHAPI as regulator of the apoptosis response of cancer cells in vitro and in vivo, and as a predictor of survival following chemotherapy for advanced NSCLC.

The crystal structure of the tumor suppressor protein pp32 (Anp32a): structural insights into Anp32 family of proteins

The tumor suppressor protein pp32 is highly overexpressed in many cancers of the breast and prostate, and has also been implicated in the neurodegenerative disease spinocerebellar ataxias type 1 (SCA1). Pp32 is a multifunctional protein that is involved in the regulation of transcription, apoptosis, phosphorylation, and cell cycle progression, the latter through its association with the hyperphosphorylated form of the retinoblastoma tumor suppressor. We have determined the structure of an N-terminal pp32 fragment comprising a capped leucine-rich repeat (LRR) domain, which provides insight into the structural and biochemical properties of the pp32 (Anp32) family of proteins.

The role of LANP and ataxin 1 in E4F-mediated transcriptional repression

The leucine-rich acidic nuclear protein (LANP) belongs to the INHAT family of corepressors that inhibits histone acetyltransferases. The mechanism by which LANP restricts its repression to specific genes is unknown. Here, we report that LANP forms a complex with transcriptional repressor E4F and modulates its activity. As LANP interacts with ataxin 1--a protein mutated in the neurodegenerative disease spinocerebellar ataxia type 1 (SCA1)--we tested whether ataxin 1 can alter the E4F-LANP interaction. We show that ataxin 1 relieves the transcriptional repression induced by the LANP-E4F complex by competing with E4F for LANP. These results provide the first functional link, to our knowledge, between LANP and ataxin 1, and indicate a potential mechanism for the transcriptional aberrations observed in SCA1.

Proliferation related acidic leucine-rich protein PAL31 functions as a caspase-3 inhibitor

Proliferation related acidic leucine-rich protein PAL31 (PAL31) is expressed in proliferating cells and consists of 272 amino acids with a tandem structure of leucine-rich repeats in the N-terminus and a highly acidic region with a putative nuclear localization signal in the C-terminus. We previously reported that PAL31 is required for cell cycle progression. In the present study, we found that the antisense oligonucleotide of PAL31 induced apoptosis to the transfected Nb2 cells. Stable transfectants, in which PAL31 was regulated by an inducible promoter, were generated to gain further insight into the signaling role of PAL31 in the regulation of apoptosis. Expression of PAL31 resulted in the marked rescue of Rat1 cells from etoposide and UV radiation-induced apoptosis and the cytoprotection was correlated with the levels of PAL31 protein. Thus, cytoprotection from apoptosis is a physiological function of PAL31. PAL31 can suppress caspase-3 activity but not cytochrome c release in vitro, indicating that PAL31 is a direct caspase-3 inhibitor. In conclusion, PAL31 is a multifunctional protein working as a cell cycle progression factor as well as a cell survival factor.

Tumor suppressor pp32 represses cell growth through inhibition of transcription by blocking acetylation and phosphorylation of histone H3 and initiating its proapoptotic activity

pp32 belongs to a family of leucine-rich acidic nuclear proteins, which play important roles in many cellular processes including regulation of chromatin remodeling, transcription, RNA transport, transformation and apoptosis. pp32 is described as a new tumor suppressor. It is unknown as to how pp32 works in tumor suppression. We found that overexpression of pp32 in human Jurkat T cells inhibits cell growth, and silenced pp32 promotes growth. We first showed that hyperacetylation and hyperphosphorylation of histone H3 are required for T-cell activation. Phosphorylation of histone H3 precedes acetylation during T-cell activation. pp32 specifically binds to histone H3 and blocks its acetylation and phosphorylation. pp32 directly initiates caspase activity and also promotes granzyme A-mediated caspase-independent cell death. Taken together, pp32 plays a repressive role by inhibiting transcription and triggering apoptosis.

pp32/ I-1(PP2A) negatively regulates the Raf-1/MEK/ERK pathway

In this study, we focus on the potential interaction of pp32/I-1(PP2A) (pp32) with the Raf-MEK-ERK signaling pathway. We show that overexpressed pp32 suppresses Raf-1 activation, thereby downregulating the level of ERK activation. This suppression of Raf-1 requires the C-terminal half of pp32. Conversely, knock-down of PP32 by siRNA enhances ERK and MEK activations. Taken together, we propose that tumor-suppression by pp32 is, at least in part, mediated by downregulation of the Raf-MEK-ERK signaling pathway.