Pnas4 is a novel regulator for convergence and extension during vertebrate gastrulation

Upregulation of PPPDE1 contributes to anorectal malformations via the mitochondrial apoptosis pathway during hindgut development in rats

Congenital anorectal malformations (ARMs) are among the most prominent deformities of the gastrointestinal tract; however, their precise aetiology remains obscure. Immunohistochemistry demonstrated that, in the ARM group, the PPPDE1-positive cells were widely distributed in the hindgut epithelial tissue from GD13 to GD16. Immunofluorescence revealed that most TUNEL-, Bax-, and Cytochrome C (Cyt C)-positive cells overlapped with PPPDE1-positive cells in the urorectal septum (URS). Western blotting and quantitative real-time RT-PCR revealed that PPPDE1 levels were significantly higher in the ARM group from GD13 to GD14 (p < 0.05). IEC-6 cells were transfected with PPPDE1 overexpression plasmid/NC (negative control) or si-PPPDE1/si-NC. Flow cytometry analysis and CCK-8 assay (used to detect apoptosis and proliferation, respectively), as well as western blotting, showed that the levels of PPPDE1 were positively correlated with the pro-apoptotic molecules Bax and Cyt C. Accordingly, aberrantly high expression of PPPDE1 caused a spatiotemporal imbalance in foetal rats with ARMs during hindgut development. Therefore, the upregulation of PPPDE1 may promote epithelial apoptosis and reduce proliferation in the hindgut via the mitochondrial apoptotic pathway. This could affect the fusion of the URS and cloacal membrane, ultimately inhibiting the hindgut development and resulting in ARMs.

Analysis of transcription profile to reveal altered signaling pathways following the overexpression of human desumoylating isopeptidase 2 in pancreatic cancer cells

Human desumoylating isopeptidase 2 (DESI-2) is a member of the DESI family and contains a conserved PPPDE1 domain. Previous studies have demonstrated that DESI-2 overexpression may induce cell apoptosis. In the present study, differentially expressed genes were analyzed using a transcription microarray in DESI-2 overexpressing PANC-1 pancreatic cancer cells. A total of 45,033 genes were examined by microarray, which identified 1,766 upregulated and 1,643 downregulated genes. A series of altered signaling pathways were analyzed, in which certain essential signaling factors, including retinoid X receptor (RXR), BH3 interacting-domain death agonist, Ras homolog gene family member A (RhoA) and Rho-associated protein kinase, were further investigated at the protein level. The release of cytochrome c and the activation of caspase-3 were also detected by western blot analysis. Immunohistochemistry further revealed the expression features of RXR and RhoA in pancreatic ductal adenocarcinoma tissues with various DESI-2 expression levels. The results serve as a valuable reference for the further elucidation of the functions of DESI-2 in pancreatic cancer.

Implications of PPPDE1 expression in the distribution of plakoglobin and β-catenin in pancreatic ductal adenocarcinoma

Human PPPDE peptidase domain-containing protein 1 (PPPDE1) is a recently identified protein; however, its exact functions remain unclear. In our previous study, the PPPDE1 protein was found to be decreased in certain cancer tissues. In the present study, a total of 96 pancreatic ductal carcinoma tissue samples and 31 normal tissues samples were assessed to investigate the distribution of plakoglobin and β-catenin under the conditions of various PPPDE1 expression levels by means of immunohistochemistry. Generally, the staining of PPPDE1 was strong in normal tissues, but weak in cancer tissues. Plakoglobin was mainly distributed along the membrane and cytoplasm border in normal cells, but was less evident in the membranes of cancer cells. In particular, a greater percentage of cells exhibited low membrane plakoglobin expression in cancer tissue with low PPPDE1 expression (PPPDE1-low cancer) compared with that in cancer tissue with high PPPDE1 expression (PPPDE1-high cancer). The distribution of β-catenin in normal tissues was similar to that of plakoglobin. However, β-catenin was peculiarly prone to invade nucleus in PPPDE1-low cancer compared with PPPDE1-high cancer. Our data suggested potential links between PPPDE1 expression and the distribution of plakoglobin and β-catenin in pancreatic ductal adenocarcinoma, providing insights into the role of PPPDE1 in the progression of pancreatic cancer.

Comprehensive analysis of expression profile reveals the ubiquitous distribution of PPPDE peptidase domain 1, a Golgi apparatus component, and its implications in clinical cancer

PPPDE peptidase domain 1 (PPPDE1) is a recently identified gene; however, its expression regulation and biological function are unclear. Previous studies have indicated that PPPDE1 is involved in embryogenesis, apoptosis induction and cell cycle regulation. In the present study, we first used an anti-PPPDE1 antibody to determine that endogenous PPPDE1 is located in the Golgi apparatus. Immunohistochemistry (IHC) of mouse embryos indicated that PPPDE1 was markedly distributed in liver, skin, intestinal villi, and muscles, whereas Western blot analysis of mouse mature organs revealed its ubiquitous expression, without an appreciable distinction in protein abundance. Surprisingly, another potential isoform of PPPDE1 with a molecular weight of 18 kD (rather than its predicted molecular weight of 21 kD) was detected in the mouse kidney, testis, and intestine. Moreover, microarrays that were derived from twelve tumor types revealed that PPPDE1 expression was significantly lower in pancreas, stomach, and skin tumors compared with normal tissue from these organs. We specifically and extensively analyzed PPPDE1 expression in clinical samples and observed strong associations between PPPDE1 expression and (i) differentiation grade in pancreatic ductal adenocarcinoma and (ii) T stage in skin squamous cell carcinoma. Our data are the first to reveal the expression profile of PPPDE1 protein and its implications in cancer. These results will contribute to the understanding of the expression regulation and biological functions of PPPDE1 in development and carcinogenesis.

PNAS-4 expression and its relationship to p53 in colorectal cancer

PNAS-4 is a novel pro-apoptotic protein activated during the early response to DNA damage; however, the molecular mechanisms and pathways regulating PNAS-4 expression in tumors are not well understood. We hypothesized that PNAS-4 is a p53 down-stream target gene and designed this study. We searched online for putative p53-binding sites in the entire PNAS-4 gene and did not find any corresponding information. In HCT116 colon cancer cells, after being transfected with small interfering RNA to silence p53, the expressions of PNAS-4 and other known p53 target gene (Apaf1, Bax, Fas and Dr5) were determined by real-time PCR. We found that PNAS-4 was up-regulated while Apaf1, Bax, Fas and Dr5 were down-regulated. We then examined the expression of PNAS-4 and p53 mutation in colorectal cancer patients. PNAS-4 expressed both in colorectal cancers and normal tissues, but compared with paired control, PNAS-4 was up-regulated in cancers (P=0.018). PNAS-4 overexpression ratios were correlated to the p53 mutant status (P=0.001). The mean PNAS-4 expression levels of p53 mutant homozygote group and heterozygote group were higher than that of p53 wild type group (P=0.013). The expression ratios of PNAS-4 (every sample in relative to its paired normal mucosa) were different between negative lymph node metastasis (66% up-regulated, 34% down-regulated) and positive metastasis (42% up-regulated, 58% down-regulated). Taken together, these findings suggested that PNAS-4 was not a p53 target, but overexpression of PNAS-4 was correlated to p53 inactivity in colorectal cancer.

PNAS4 knockout does not induce obviously neurocytes apoptosis and abnormal development in mice brain

Apoptosis is one kind of programmed cell death and contributes to development of a variety of organs such as brain. PNAS4 has been reported to be a novel apoptosis-related gene. Overexpression and knocking down of PNAS4 would cause zebrafish and Xenopus lavis developmental abnormalities. But its function and apoptotic mechanism in mammals are still unknown. Here, we first reported that established PNAS4 CKO (conditional knock out) mice using recombineering technology. We prepared its polyclonal antibodies which recognized both myc-PNAS4 overexpression protein and WT and CKO mice brain tissue and MEFS cells with high titre and specificity. Further we detected that PNAS4 was highly expressed in the embryonic period. However, we observed neither neural structural abnormality nor apoptosis signal in PNAS4 CKO mice brain. Our data suggested that PNAS4 was not involved in mice brain development and apoptosis.

Kzp controls canonical Wnt8 signaling to modulate dorsoventral patterning during zebrafish gastrulation

During vertebrate embryonic development, the body axis formation requires the action of Wnt signals and their antagonists. Zygotic canonical wnt8 expression appears exclusively at the ventrolateral margin and mediates Wnt/β-catenin activities to promote posterior and ventral cell fate. However, the mechanisms involved in the initiation of zygotic wnt8 signals are poorly understood. Here, we identify a novel, maternally derived transcription factor, Kzp (Kaiso zinc finger-containing protein), as an important determinant for the initiation of zygotic Wnt signals in zebrafish. Kzp is a DNA-binding transcription factor that recognizes specific consensus DNA sequences, 5'-(t/a/g)t(a/t/g)nctgcca-3', through zinc fingers and controls the initiation of zygotic wnt8 expression by directly binding to the wnt8 promoter during zebrafish embryonic development. Depletion of Kzp strongly dorsalized embryos, which was characterized by the expansion of dorsal gene expression. Overexpression of Kzp caused posteriorization. These phenotypes were highly similar to ones induced by wnt8 depletion or overexpression and were rescued by alteration of wnt8 activity. Thus, our results provide the first insight into the mechanism involved in the initiation of zygotic canonical Wnt signals by a maternally derived transcription factor.

Altered protein-expressing profile in hPNAS4-induced apoptosis in A549 human lung adenocarcinoma cells

Human PNAS4 (hPNAS4) is a recently identified pro-apoptosis gene, which is able to induce apoptosis in A549 human lung adenocarcinoma cells following its overexpression. In this work, we investigated the changes of protein profile in hPNAS4-induced apoptosis in A549 cells through proteomic strategy consisting of two-dimensional electrophoresis (2-DE) coupled with MALDI-Q-TOF mass spectrometry. A total of 20 different proteins with more than 3.0-fold change in expression, including 5 up-regulated and 15 down-regulated proteins were successfully identified by database search. The mRNA transcription levels of the different proteins were further examined by RT-PCT. Functional analyses showed these different proteins are involved in diverse biological processes including metabolism, proteolysis, signal transduction, apoptosis, and redox regulation. Two essential apoptosis-associated protein, annexin A1 and prothymosin alpha, were confirmed by Western blot and showed consistent changes with proteomic detection. Our data provide molecular evidence and possible associated pathway in hPNAS4-induced apoptosis through proteomic strategy, which should be contributed to further investigation on biological function of hPNAS4.

Wnt11 patterns a myocardial electrical gradient through regulation of the L-type Ca(2+) channel

Electrical gradients are critical for many biological processes, including the normal function of excitable tissues, left-right patterning, organogenesis and wound healing. The fundamental mechanisms that regulate the establishment and maintenance of such electrical polarities are poorly understood. Here we identify a gradient of electrical coupling across the developing ventricular myocardium using high-speed optical mapping of transmembrane potentials and calcium concentrations in the zebrafish heart. We excluded a role for differences in cellular excitability, connexin localization, tissue geometry and mechanical inputs, but in contrast we were able to demonstrate that non-canonical Wnt11 signals are required for the genesis of this myocardial electrical gradient. Although the traditional planar cell polarity pathway is not involved, we obtained evidence that Wnt11 acts to set up this gradient of electrical coupling through effects on transmembrane Ca(2+) conductance mediated by the L-type calcium channel. These data reveal a previously unrecognized role for Wnt/Ca(2+) signalling in establishing an electrical gradient in the plane of the developing cardiac epithelium through modulation of ion-channel function. The regulation of cellular coupling through such mechanisms may be a general property of non-canonical Wnt signals.

Identification, characterization, and effects of Xenopus laevis PNAS-4 gene on embryonic development

Apoptosis plays an important role in embryonic development. PNAS-4 has been demonstrated to induce apoptosis in several cancer cells. In this study, we cloned Xenopus laevis PNAS-4 (xPNAS-4), which is homologous to the human PNAS-4 gene. Bioinformatics analysis for PNAS-4 indicated that xPNAS-4 shared 87.6% identity with human PNAS-4 and 85.5% with mouse PNAS-4. The phylogenetic tree of PNAS-4 protein was also summarized. An analysis of cellular localization using an EGFP-fused protein demonstrated that xPNAS-4 was localized in the perinuclear region of the cytoplasm. RT-PCR analysis revealed that xPNAS-4, as a maternally expressed gene, was present in all stages of early embryo development. Whole-mount in situ hybridization showed that xPNAS-4 was mainly expressed in ectoderm and mesoderm. Furthermore, microinjection of xPNAS-4 mRNA in vivo caused developmental defects manifesting as a small eye phenotype in the Xenopous embryos, and as a small eye or one-eye phenotype in developing zebrafish embryos. In addition, embryos microinjected with xPNAS-4 antisense morpholino oligonucleotides (MOs) exhibited a failure of head development and shortened axis.

Prokaryotic expression, purification and characterization of a novel pro-apoptosis protein hPNAS-4

Recently, hPNAS-4 [human PNAS-4; also known as C1orf121 (Genbank accession number NP-057160)] was reported to be a novel pro-apoptotic protein in mammalian cells. However, at present there is little information about hPNAS-4 and its molecular mechanisms. In our present studies, the hPNAS-4 gene was first cloned into the pGEX-6p-1 vector with a GST (glutathione transferase) tag to express in soluble form in Escherichia coli induced with 0.5 mM IPTG (isopropyl beta-D-thiogalactoside) at 25 degrees C, and the recombinant hPNAS-4 was purified to near homogeneity with 96% purity by affinity chromatography and anion-exchange chromatography. The purified hPNAS-4 protein was further identified by liquid chromatography-ESI (electrospray ionization)-MS analysis and used to raise polyclonal antibodies that could specifically recognize the hPNAS-4 protein. In addition, hPNAS-4 is localized to the cytoplasm and the perinuclear compartment. Furthermore, the overexpression of hPNAS-4 in human A549 lung cancer cells resulted in decrease of cell viability via apoptosis. This study represented an important step to investigate the characterization for the new pro-apoptosis protein hPNAS-4, which should aid the discovery of new drug targets for the development of effective therapeutic approaches to cancer in the future.

Improved therapeutic efficacy against murine carcinoma by combining honokiol with gene therapy of PNAS-4, a novel pro-apoptotic gene

PNAS-4, a novel pro-apoptotic gene activated during the early response to DNA damage, can inhibit proliferation via apoptosis when overexpressed in some tumor cells. Recent studies have indicated that honokiol can induce apoptosis, inhibit angiogenesis, and suppress tumor growth. In the present study, we investigated whether mouse PNAS-4 (mPNAS-4) could augment the apoptosis of tumor cells induced by honokiol in vitro, and whether the antiangiogenic activity of honokiol and induction of apoptosis by mPNAS-4 could work cooperatively to improve the antitumor efficacy in vivo. In vitro, mPNAS-4 inhibited proliferation of murine colorectal carcinoma CT26 and Lewis lung carcinoma LL2 cells through induction of apoptosis, and significantly augmented the apoptosis of CT26 and LL2 cells induced by honokiol. Compared with treatment with mPNAS-4 or honokiol alone, in vivo systemic administration of an expression plasmid encoding mPNAS-4 and low-dose honokiol significantly suppressed tumor growth through the enhanced induction of apoptosis and the augmented inhibition of angiogenesis. Our data suggest that the combined treatment with mPNAS-4 plus honokiol augments antitumor effects in vitro and in vivo, and that the improved antitumor activity in vivo may be associated with enhanced induction of apoptosis and augmented inhibition of angiogenesis. The present study may provide a novel and effective method for the treatment of cancer.

PNAS-4, a novel pro-apoptotic gene, can potentiate antineoplastic effects of cisplatin

PURPOSE

PNAS-4, a novel pro-apoptotic gene activated during the early response to DNA damage, can inhibit proliferation via apoptosis when overexpressed in some tumor cells. The objectives of this study were to determine whether PNAS-4 could enhance apoptosis induced by cisplatin besides its induction of apoptosis, and to evaluate the usefulness of combined treatment with mouse PNAS-4 (mPNAS-4) gene therapy and low-dose cisplatin chemotherapy in the inhibition of tumor growth in colon carcinoma (CT26) and Lewis lung carcinoma (LL/2) murine models.

METHODS

In this study, the in vitro growth-inhibitory and pro-apoptotic effects of PNAS-4 and/or cisplatin on CT26, LL/2, and SKOV3 cancer cells were assessed by MTT assay, flow cytometric analysis, DNA fragmentation, and morphological analysis, respectively. The in vivo antitumor activity of combined treatment with mPNAS-4 gene therapy and low-dose cisplatin were evaluated in the inhibition of tumor growth in colon carcinoma (CT26) and Lewis lung carcinoma (LL/2) murine models. Tumor volume and survival time were observed. Induction of apoptosis was also assessed in tumor tissues.

RESULTS

In vitro, PNAS-4 inhibited proliferation of colon carcinoma (CT26), Lewis lung carcinoma (LL/2) and human ovarian cancer (SKOV3) cell lines via apoptosis, and significantly enhanced the apoptosis of CT26, LL/2, and SKOV3 cells induced by cisplatin. In vivo systemic administration of expression plasmid encoding mPNAS-4 (pcDNA3.1-mPS) and cisplatin, significantly decreased tumor growth through increased tumor cell apoptosis compared to treatment with mPNAS-4 or cisplatin alone.

CONCLUSIONS

Our data suggests that the combined treatment with mPNAS-4 plus cisplatin may augment the induction of apoptosis in tumor cells in vitro and in vivo, and that the augmented antitumor activity in vivo may result from the increased induction of apoptosis. The present study may provide a novel way to augment the antitumor efficacy of cytotoxic chemotherapy.

A novel pro-apoptosis gene PNAS4 that induces apoptosis in A549 human lung adenocarcinoma cells and inhibits tumor growth in mice

The gene PNAS4 is a high conservative gene that shares high homology of sequence in various organisms from plants to animals. We found overexpression of human PNAS4 induced apoptosis and arrested cell cycle in S phase in A549 human lung adenocarcinoma cells. In C57BL/6 mice model of Lewis lung carcinoma, overexpression of mouse PNAS4 significantly suppressed tumor growth and prolonged survival time through induction of tumor cell apoptosis, exhibiting effective antitumor. Our original investigations in vitro and vivo indicated PNAS4 is a novel pro-apoptosis gene, which could be used as a potential target of cancer biotherapy in future.