PDCD5 interacts with Tip60 and functions as a cooperator in acetyltransferase activity and DNA damage-induced apoptosis

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

Insights into Regulators of p53 Acetylation

The tumor suppressor p53 is a transcription factor that regulates the expression of dozens of target genes and diverse physiological processes. To precisely regulate the p53 network, p53 undergoes various post-translational modifications and alters the selectivity of target genes. Acetylation plays an essential role in cell fate determination through the activation of p53. Although the acetylation of p53 has been examined, the underlying regulatory mechanisms remain unclear and, thus, have attracted the interest of researchers. We herein discuss the role of acetylation in the p53 pathway, with a focus on p53 acetyltransferases and deacetylases. We also review recent findings on the regulators of these enzymes to understand the mode of p53 acetylation from a broader perspective.

Arabidopsis mediator subunit 17 connects transcription with DNA repair after UV-B exposure

Mediator 17 (MED17) is a subunit of the Mediator complex that regulates transcription initiation in eukaryotic organisms. In yeast and humans, MED17 also participates in DNA repair, physically interacting with proteins of the nucleotide excision DNA repair system, but this function in plants has not been investigated. We studied the role of MED17 in Arabidopsis plants exposed to UV-B radiation. Our results demonstrate that med17 and OE MED17 plants have altered responses to UV-B, and that MED17 participates in various aspects of the DNA damage response (DDR). Comparison of the med17 transcriptome with that of wild-type (WT) plants showed that almost one-third of transcripts with altered expression in med17 plants were also changed by UV-B exposure in WT plants. Increased sensitivity to DNA damage after UV-B in med17 plants could result from the altered regulation of UV-B responsive transcripts but MED17 also physically interacts with DNA repair proteins, suggesting a direct role of this Mediator subunit during repair. Finally, we show that MED17 is necessary to regulate the DDR activated by ataxia telangiectasia and Rad3 related (ATR), and that programmed cell death 5 (PDCD5) overexpression reverts the deficiencies in DDR shown in med17 mutants. Our data demonstrate that MED17 is an important regulator of DDR after UV-B irradiation in Arabidopsis.

The role of protein acetylation in carcinogenesis and targeted drug discovery

Protein acetylation is a reversible post-translational modification, and is involved in many biological processes in cells, such as transcriptional regulation, DNA damage repair, and energy metabolism, which is an important molecular event and is associated with a wide range of diseases such as cancers. Protein acetylation is dynamically regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs) in homeostasis. The abnormal acetylation level might lead to the occurrence and deterioration of a cancer, and is closely related to various pathophysiological characteristics of a cancer, such as malignant phenotypes, and promotes cancer cells to adapt to tumor microenvironment. Therapeutic modalities targeting protein acetylation are a potential therapeutic strategy. This article discussed the roles of protein acetylation in tumor pathology and therapeutic drugs targeting protein acetylation, which offers the contributions of protein acetylation in clarification of carcinogenesis, and discovery of therapeutic drugs for cancers, and lays the foundation for precision medicine in oncology.

Programmed cell death 5 improves skeletal muscle insulin resistance by inhibiting IRS-1 ubiquitination through stabilization of MDM2

AIMS

Insulin resistance is defined as the decreased sensitivity of tissues and organs to insulin and it is the main pathological basis of metabolic syndrome. PDCD5 is widely expressed in tissues including skeletal muscle and liver, but its exact function and the role in insulin resistance has not been studied. The present study is to explore the effect of PDCD5 on insulin resistance in skeletal muscle, the largest target organ of insulin, and its mechanism.

MATERIALS AND METHODS

Mice were fed with high-fat diet to establish obesity model. C2C12 myoblasts differentiated into myotubes and then were treated with palmitate to induce insulin resistance. Gain-of-function and loss-of-function experiments were performed by infecting C2C12 with adenovirus containing PDCD5 cDNA or PDCD5 shRNA.

KEY FINDINGS

PDCD5 protein was first increased and then decreased in the skeletal muscle from high-fat diet induced obese mice and consistently in palmitate induced insulin resistance C2C12 myotubes. Overexpression of PDCD5 in C2C12 cells did not affect the sensitivity to insulin but inhibited the palmitate induced insulin resistance, while knockdown of PDCD5 aggravated the insulin resistance. Mechanistically, PDCD5 interacted with ubiquitin ligase MDM2; overexpression of PDCD5 decreased MDM2 protein level, inhibited the increased interaction of MDM2 with IRS-1 and the degradation of IRS-1 by palmitate stimulation.

SIGNIFICANCE

PDCD5 is upregulated during the early stage of insulin resistance in skeletal muscle. The increased PDCD5 inhibits IRS-1 ubiquitination, increases the stability of IRS-1 by interacting with and degrading MDM2, thus providing a protective effect on insulin resistance in skeletal muscle.

OsPDCD5 negatively regulates plant architecture and grain yield in rice

Plant architecture is an important agronomic trait that affects crop yield. Here, we report that a gene involved in programmed cell death, OsPDCD5, negatively regulates plant architecture and grain yield in rice. We used the CRISPR/Cas9 system to introduce loss-of-function mutations into OsPDCD5 in 11 rice cultivars. Targeted mutagenesis of OsPDCD5 enhanced grain yield and improved plant architecture by increasing plant height and optimizing panicle type and grain shape. Transcriptome analysis showed that OsPDCD5 knockout affected auxin biosynthesis, as well as the gibberellin and cytokinin biosynthesis and signaling pathways. OsPDCD5 interacted directly with OsAGAP, and OsAGAP positively regulated plant architecture and grain yield in rice. Collectively, these findings demonstrate that OsPDCD5 is a promising candidate gene for breeding super rice cultivars with increased yield potential and superior quality.

Club cell-specific role of programmed cell death 5 in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) causes progressive fibrosis and worsening pulmonary function. Prognosis is poor and no effective therapies exist. We show that programmed cell death 5 (PDCD5) expression is increased in the lungs of patients with IPF and in mouse models of lung fibrosis. Lung fibrosis is significantly diminished by club cell-specific deletion of Pdcd5 gene. PDCD5 mediates β-catenin/Smad3 complex formation, promoting TGF-β-induced transcriptional activation of matricellular genes. Club cell Pdcd5 knockdown reduces matricellular protein secretion, inhibiting fibroblast proliferation and collagen synthesis. Here, we demonstrate the club cell-specific role of PDCD5 as a mediator of lung fibrosis and potential therapeutic target for IPF.

Idiopathic pulmonary fibrosis (IPF) is a fatal adult lung disease. Here the authors investigate the functional significance of PDCD5 in club cells as a mediator of lung fibrosis and potential therapeutic target for IPF.

Effect of Tiotropium Bromide on Airway Inflammation and Programmed Cell Death 5 in a Mouse Model of Ovalbumin-Induced Allergic Asthma

Rationale

We previously demonstrated increased expression of programmed cell death 5 (PDCD5) in asthmatic patients and ovalbumin-induced allergic asthma. International guidelines (GINA 2019) have included the use of tiotropium bromide for chronic treatment of the most severe and frequently exacerbated asthma in patients ≥6 years old, who do not have good response to inhaled corticosteroids.

Objective

To explore the role of tiotropium and its effect on PDCD5 level in a mouse model of chronic asthma.

Methods

We divided 12 female mice into 2 groups: untreated asthma (n = 6) and tiotropium-treated asthma (n = 6). The impact of tiotropium was assessed by histology of lung tissue and morphometry. Pulmonary function was tested by using pressure sensors. The number of cells in bronchoalveolar lavage fluid (BALF) was detected. Levels of PDCD5, active caspase-3, and muscarinic acetylcholine receptors M2 (ChRM2) and M3 (ChRM3) were examined.

Results

Tiotropium treatment significantly reduced airway inflammation and remodeling in asthmatic mice and intensified the lung function. PDCD5 level was reduced with tiotropium (p < 0.05). Moreover, active caspase-3 level was decreased with tiotropium (p < 0.001), and ChRM3 level was increased.

Conclusions

Tiotropium treatment may alleviate the pathological changes with asthma by regulating apoptosis.

Effects of Tumor Necrosis Factor Alpha on the Expression of Programmed Cell Death Factor 5 in Arthritis

OBJECTIVE

To investigate the effect of tumor necrosis factor alpha (TNF-α) on the proliferation of fibroblast-like synoviocytes (FLS) and the expression of programmed cell death factor 5 (PDCD5) in an inflammatory microenvironment, for the further understanding of the mechanism of action of TNF-α in promoting the proliferation of synovial cells and the apoptosis of the chondrocytes.

METHODS

Articular carriage specimens were obtained from 21 cases with osteoarthritis and 12 cases with femoral neck fractures as healthy controls during arthroplasties. The expression of PDCD5 was evaluated by immunofluorescence analyzed by mean option density (MOD) detected using the software ImagePro Plus. Real-time PCR was performed to evaluate the transcriptions of PDCD5 and TNF-α in synovium. FLS cells derived from rheumatoid arthritis patients were cultured in vitro and incubated with different concentrations of TNF-α. The effects of TNF-α at different concentrations on the proliferation of FLS cells were detected by Cell Counting Kit-8 (CCK-8) assay to evaluate the cell proliferation rate. After incubation with the absence or presence of recombinant human TNF-α at different concentrations, the FLS cells were isolated for detection of PDCD5 protein and PDCD5 gene. The expression of PDCD5 protein was detected by western-blot and the transcription of PDCD5 gene from the cells was detected by real-time quantitative PCR.

RESULTS

The MOD of PDCD5 as well as TNF-α of osteoarthritis cartilage sections were significantly increased compared with those of the controls, and in synovium there was a positive correlation between transcriptions of their mRNA. When the concentration of TNF-α was 1 ng/mL, the cell proliferation rate was not significantly different from that of the control group (P = 0.592), while the proliferation of FLS cells was significantly promoted when the concentration of TNF-α was 5, 10, 15, or 20 ng/mL, and the proliferation-promoting rates were 35.64% ± 6.96%, 48.72% ± 7.69%, 45.60% ± 8.85%, and 39.32% ± 6.18%, respectively (P < 0.01). The transcription of PDCD5 gene was significantly downregulated, which was 80.44% ± 4.07% and 84.30% ± 5.48%, respectively (P < 0.05), in the FLS cells incubated with TNF-α at the concentration of 10 and 15 ng/mL for 24 h. When the concentration of TNF-α was 1, 5, or 20 ng/mL, the transcription of PDCD5 mRNA in FLS cells was not significantly different from that in the control group (P > 0.05). The expression of PDCD5 protein was only significantly downregulated when the concentration of TNF-α was 10 ng/mL (P < 0.01), while the expression of PDCD5 protein in FLS cells was not significantly different from that in the control group (P > 0.05).

CONCLUSION

The expression of PDCD5 as well as TNF-α in osteoarthritis cartilage and synovium was significantly higher than in healthy tissues, and TNF-α can promote the proliferation of FLS cells in patients with rheumatoid arthritis, and inhibit the expression of PDCD5. PDCD5 may be involved in the abnormal proliferation of synoviocytes and the degeneration of chondrocytes stimulated by TNF-α.

Programmed Cell Death 5 Provides Negative Feedback on Cardiac Hypertrophy Through the Stabilization of Sarco/Endoplasmic Reticulum Ca2+-ATPase 2a Protein

PDCD5 (programmed cell death 5) is ubiquitously expressed in tissues, including the heart; however, the mechanism underlying the cardiac function of PDCD5 has not been understood. We investigated the mechanisms of PDCD5 in the pathogenesis of cardiac hypertrophy. Cardiac-specific PDCD5 knockout mice developed severe cardiac hypertrophy and impaired cardiac function, whereas PDCD5 protein was significantly increased in transverse aortic constriction mouse hearts and phenylephrine-stimulated cardiomyocytes. Overexpression of PDCD5 inhibited phenylephrine-induced cardiomyocyte hypertrophy, and knockdown of PDCD5 induced cardiomyocyte hypertrophy and aggravated phenylephrine-induced hypertrophy. The expression of PDCD5 protein was regulated by NFATc2 (nuclear factor of activated T cells c2) during hypertrophy. SERCA2a (sarco/endoplasmic reticulum Ca²⁺-ATPase 2a) expression was decreased in PDCD5-deficient mouse hearts because of increased ubiquitination. PDCD5-deficient cardiomyocytes displayed decreased calcium uptake rate, slowed decay of Ca²⁺ transients, decreased calcium stores, and diastolic dysfunction. Moreover, reintroduction of PDCD5 in PDCD5-deficient mouse hearts reserved SERCA2a protein, suppressed NFATc2 protein, and rescued the hypertrophy and cardiac dysfunction. Our results revealed that PDCD5 is a novel target of NFATc2 in the hypertrophic heart and provides negative feedback to protect the heart against excessive hypertrophy via the stabilization of SERCA2a protein.

Histone acetyl transferase TIP60 inhibits the replication of influenza a virus by activation the TBK1-IRF3 pathway

Influenza A virus (IAV) is an important pathogen that poses a severe threat to the health of humans. Nucleoprotein (NP) of IAV plays crucial roles in the viral life cycle by interacting with various cellular factors. Histone Acetyl Transferase TIP60 is a key target of several viral proteins during infection, including HIV-1 Tat, HPV E6, HTLV-1 p30^II and HCMV UL27 proteins. However, Whether the interaction between the IAV NP and TIP60, and the role of TIP60 in IAV life cycle are largely unknown. Here, we showed that IAV infection up-regulated TIP60 protein and RNA expression. Overexpression of TIP60 inhibited viral protein and RNA expression and reduced the progeny viral titer. Further study revealed that TIP60 inhibited viral replication through activation of TBK1-IRF3 signaling pathway. Furthermore, we demonstrated that the NP protein of IAV interacted with TIP60. Together, these results indicate that TIP60 play a repressor in IAV infection, and it may be a possible target for antiviral drugs.

PDCD5 regulates iNKT cell terminal maturation and iNKT1 fate decision

Invariant natural killer T1 (iNKT1) cells are characterized by the preferential expression of T-box transcription factor T-bet (encoded by Tbx21) and the production of cytokine IFN-γ, but the relationship between the developmental process and iNKT1 lineage diversification in the thymus remains elusive. We report in the present study a crucial role of programmed cell death 5 (PDCD5) in iNKT cell terminal maturation and iNKT1 fate determination. Mice with T cell-specific deletion of PDCD5 had decreased numbers of thymic and peripheral iNKT cells with a predominantly immature phenotype and defects in response to α-galactosylceramide. Loss of PDCD5 also selectively abolished the iNKT1 lineage by reducing T-bet expression in iNKT cells at an early thymic developmental stage (before CD44 upregulation). We further demonstrated that TOX2, one of the high mobility group proteins that was highly expressed in iNKT cells at stage 1 and could be stabilized by PDCD5, promoted the permissive histone H3K4me3 modification in the promoter region of Tbx21. These data indicate a pivotal and unique role of PDCD5/TOX2 in iNKT1 lineage determination. They also suggest that the fate of iNKT1 may be programmed at the developmental stage of iNKT cells in the thymus.

Programmed cell death 5 transgenic mice attenuates adjuvant induced arthritis by 2 modifying the T lymphocytes balance

BACKGROUND

Programmed cell death 5 (PDCD5) is an apoptosis-related gene cloned from TF-1 cells whose primary biological functions are to promote apoptosis and immune regulation. The effects and mechanisms exerted by key mediators of arthritic inflammation remain unclear in PDCD5 transgenic (PDCD5 tg) mice.

RESULTS

In the current study, PDCD5 tg mice inhibited the progression of adjuvant-induced arthritis, specifically decreasing clinical signs and histological damage, compared with arthritis control mice. Additionally, the ratio of CD4⁺IFN-γ⁺ cells (Th1) and CD4⁺IL-17A⁺ cells (Th17), as well as the mRNA expression of the pro-inflammatory mediators IFN-γ, IL-6, IL-17A and TNF-α, were decreased in PDCD5 tg mice, while CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells and the anti-inflammatory mediators IL-4 and IL-10 were increased. Furthermore, PDCD5 tg mice demonstrated reduced serum levels of IFN-γ, IL-6, IL-17A and TNF-α and increased levels of IL-4.

CONCLUSIONS

Based on our data, PDCD5 exerts anti-inflammatory effects by modifying the T lymphocytes balance, inhibiting the production of pro-inflammatory mediators and promoting the secretion of anti-inflammatory cytokines, validating PDCD5 protein as a possible treatment for RA.

PDCD5 regulates cell proliferation, cell cycle progression and apoptosis

Programmed cell death (PDCD)5 is cloned from human leukemia cell line TF-1. PDCD5 is one of the members of the programmed cell death protein family that is frequently involved in tumor growth and apoptosis. To investigate the molecular and cellular functions of PDCD5, the present study established a PDCD5 stably overexpressing A431 cell line and examined the role of PDCD5 in cell proliferation, cell cycle progression and apoptosis. The data demonstrated that overexpression of PDCD5 significantly inhibited cell proliferation, induced cell cycle arrest at G2/M phase and apoptosis in A431 cells. The expression profiles of certain key regulators of these cellular events were further investigated, including P53, B cell lymphoma (BCL)-2, BCL-2 associated X protein (BAX) and caspase (CASP)3. The data demonstrated that at the transcript and protein levels, P53, BAX and CASP3 were all upregulated in the PDCD5 stably overexpressing A431 cells whereas BCL-2 was downregulated, indicating that PDCD5 acts as an important upstream regulator of P53, BCL-2, BAX and CASP3. The data suggest that PDCD5 regulates cell proliferation, cell cycle progression and apoptosis in A431 cells. PDCD5 may be a novel tumor suppressor gene, and may be potentially used for cancer treatment in the future.

Deletion of Pdcd5 in mice led to the deficiency of placenta development and embryonic lethality

Programmed cell death 5 (PDCD5) is an apoptosis promoter molecule that displays multiple biological activities. However, the function of PDCD5 in vivo has not yet been investigated. Here, we generated a Pdcd5 knockout mouse model to study the physiological role of PDCD5 in vivo. Knockout of the Pdcd5 gene resulted in embryonic lethality at mid-gestation. Histopathological analysis revealed dysplasia in both the LZs and JZs in Pdcd5^–/– placentas with defects in spongiotrophoblasts and trophoblast giant cells. Furthermore, Pdcd5^–/– embryos had impaired transplacental passage capacity. We also found that Pdcd5^–/– embryos exhibited cardiac abnormalities and defective liver development. The growth defect is linked to impaired placental development and may be caused by insufficient oxygen and nutrient transfer across the placenta. These findings were verified in vitro in Pdcd5 knockout mouse embryonic fibroblasts, which showed increased apoptosis and G0/G1 phase cell cycle arrest. Pdcd5 knockout decreased the Vegf and hepatocyte growth factor (Hgf) levels, downregulated the downstream Pik3ca–Akt–Mtor signal pathway and decreased cell survival. Collectively, our studies demonstrated that Pdcd5 knockout in mouse embryos results in placental defects and embryonic lethality.

Overexpression of programmed cell death 5 in a mouse model of ovalbumin-induced allergic asthma

Background

Programmed cell death 5 (PDCD5) was first identified as an apoptosis-promoting protein and involved in some autoimmune diseases and inflammatory processes. Our previous study demonstrated greater expression of serum PDCD5 in asthmatic patients than controls. This study aimed to further explore the significance of PDCD5 in mice with induced allergic asthma.

Methods

We divided 16 female mice into 2 groups: control (n = 8) and allergen (ovalbumin, OVA)-challenged mice (n = 8). The modified ovalbumin inhalation method was used to generate the allergic asthma mouse model, and the impact of OVA was assessed by histology of lung tissue and morphometry. The number of cells in bronchoalveolar lavage fluid (BALF) was detected. Pulmonary function was measured by pressure sensors. PDCD5 and active caspase-3 levels were detected.

Results

The expression of PDCD5 was higher with OVA challenge than for controls (p < 0.05). PDCD5 level was correlated with number of inflammatory cells in BALF and lung function. Moreover, active caspase-3 level was increased in the OVA-challenged mice (p < 0.001) and correlated with PDCD5 level (p = 0.000).

Conclusions

These data demonstrate an association between level of PDCD5 and asthma severity and indicate that PDCD5 may play a role in allergic asthma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-016-0317-y) contains supplementary material, which is available to authorized users.

Plant programmed cell death from a chromatin point of view

Programmed cell death (PCD) is a ubiquitous genetically regulated process consisting of the activation of finely controlled signalling pathways that lead to cellular suicide. PCD can be part of a developmental programme (dPCD) or be triggered by environmental conditions (ePCD). In plant cells, as in animal cells, extensive chromatin condensation and degradation of the nuclear DNA are among the most conspicuous features of cells undergoing PCD. Changes in chromatin condensation could either reflect the structural changes required for internucleosomal fragmentation of nuclear DNA or relate to large-scale chromatin rearrangements associated with a major transcriptional switch occurring during cell death. The aim of this review is to give an update on plant PCD processes from a chromatin point of view. The first part will be dedicated to chromatin conformational changes associated with cell death observed in various developmental and physiological conditions, whereas the second part will be devoted to histone dynamics and DNA modifications associated with critical changes in genome expression during the cell death process.

Roles of programmed cell death protein 5 in inflammation and cancer (Review)

PDCD5 (programmed cell death 5) is an apoptosis related gene cloned in 1999 from a human leukemic cell line. PDCD5 protein containing 125 amino acid (aa) residues sharing significant homology to the corresponding proteins of species. Decreased expression of PDCD5 has been found in many human tumors, including breast, gastric cancer, astrocytic glioma, chronic myelogenous leukemia and hepatocellular carcinoma. In recent years, increased number of studies have shown the functions and mechanisms of PDCD5 protein in cancer cells, such as paraptosis, cell cycle and immunoregulation. In the present review, we provide a comprehensive review on the role of PDCD5 in cancer tissues and cells. This review summarizes the recent studies of the roles of PDCD5 in inflammation and cancer. We mainly focus on discoveries related to molecular mechanisms of PDCD5 protein. We also discuss some discrepancies between the current studies. Overall, the current available data will open new perspectives for a better understanding of PDCD5 in cancer.

The reduced PDCD5 protein is correlated with the degree of tumor differentiation in endometrioid endometrial carcinoma

Endometrial cancer is one of the most common malignancies in the female genital tract. Programmed cell death 5 (PDCD5) is a newly identified apoptosis related gene and plays an important role in the development of some human tumors. However, the expression and clinical significance of PDCD5 in endometrial cancer have not been fully elucidated. Here, we evaluated the expression of PDCD5 in endometrioid endometrial carcinoma and control endometrium by qRT-PCR, western blot and immunohistochemistry, and analyzed the associations of PDCD5 expression with clinicopathological parameters of patients. In addition, we detected the expression of PDCD5 in control endometrial glandular epithelial cells and endometrioid endometrial carcinoma-derived cell line KLE by immunocytochemistry. The results showed that PDCD5 protein mainly expressed in the cytoplasm of glandular epithelial cells and endometrial carcinoma cells, and there was a low level of PDCD5 expression in the nuclei of the above cells. Furthermore, PDCD5 protein level was significantly lower in endometrial carcinoma samples than that in control endometrium. The decreased PDCD5 expression was correlated with the tumor differentiation degree. It is clear that PDCD5 protein expression was lower in middle and low differentiated endometrial carcinoma compared with control endometrium and high differentiated endometrial carcinoma. However, there were no significant differences of PDCD5 expression between the proliferative phase and the secretory phase of control endometrium, as well as between high differentiated endometrial carcinoma and controls. The results were verified in control glandular epithelial cells and KLE cells by immunocytochemistry. Therefore, PDCD5 may play a key role in the pathogenesis of endometrial cancer and may be a novel target for diagnosis and treatment of endometrial cancer.

Diagnostic investigations of DKK-1 and PDCD5 expression levels as independent prognostic markers of human chondrosarcoma

In this study, we investigated the expression levels of Dickkopf-1 (DKK-1) and programmed cell death 5 (PDCD5) by using quantitative real-time PCR and immunohistochemistry in patients with chondrosarcoma. The DKK-1 mRNA levels were significantly higher in chondrosarcoma when compared with the corresponding nontumor tissues (mean ± SD: 4.23 ± 1.54; 1.54 ± 0.87; P = 0.001). PDCD5 mRNA levels were remarkably deceased in tumor tissues when compared with corresponding nontumor tissues (mean ± SD: 1.94 ± 0.73; 5.42 ± 1.73; P = 0.001). The high and moderate DKK-1 expressions were observed for 60% of chondrosarcoma samples in comparison with 27.5% of corresponding nontumor tissues (P  =  0.001). Moreover, low expression of PDCD5 was found in 67.5% of the tumor tissues when compared with the nontumor tissues (32.5%; P = 0.002). The results of this study showed that high DKK-1 expression levels were strongly related to MSTS stage (P = 0.011) and the advancement of histological grade (P < 0.001). Furthermore, the PDCD5 expression levels were correlated with histological grade (P < 0.001), MSTS stage (P = 0.016), and distant metastasis (P = 0.001). Kaplan-Meier survival and log-rank survival showed that patients with high DKK-1 levels and low PDCD5 levels were correlated with shorter overall survival (log-rank test P < 0.001). PDCD5 levels, histological grade, and tumor stage were independent predictors of overall survival. In conclusion, DKK-1 and PDCD5 can be independent predictors of overall survival in patients suffering from chondrosarcoma. © 2016 IUBMB Life, 68(7):597-601, 2016.

AtPDCD5 Plays a Role in Programmed Cell Death after UV-B Exposure in Arabidopsis

DNA damage responses have evolved to sense and react to DNA damage; the induction of DNA repair mechanisms can lead to genomic restoration or, if the damaged DNA cannot be adequately repaired, to the execution of a cell death program. In this work, we investigated the role of an Arabidopsis (Arabidopsis thaliana) protein, AtPDCD5, which is highly similar to the human PDCD5 protein; it is induced by ultraviolet (UV)-B radiation and participates in programmed cell death in the UV-B DNA damage response. Transgenic plants expressing AtPDCD5 fused to GREEN FLUORESCENT PROTEIN indicate that AtPDCD5 is localized both in the nucleus and the cytosol. By use of pdcd5 mutants, we here demonstrate that these plants have an altered antioxidant metabolism and accumulate higher levels of DNA damage after UV-B exposure, similar to levels in ham1ham2 RNA interference transgenic lines with decreased expression of acetyltransferases from the MYST family. By coimmunoprecipitation and pull-down assays, we provide evidence that AtPDCD5 interacts with HAM proteins, suggesting that both proteins participate in the same pathway of DNA damage responses. Plants overexpressing AtPDCD5 show less DNA damage but more cell death in root tips upon UV-B exposure. Finally, we here show that AtPDCD5 also participates in age-induced programmed cell death. Together, the data presented here demonstrate that AtPDCD5 plays an important role during DNA damage responses induced by UV-B radiation in Arabidopsis and also participates in programmed cell death programs.

Cellular functions of programmed cell death 5

Programmed cell death 5 (PDCD5) was originally identified as an apoptosis-accelerating protein that is widely expressed and has been well conserved during the process of evolution. PDCD5 has complex biological functions, including programmed cell death and immune regulation. It can accelerate apoptosis in different type of cells in response to different stimuli. During this process, PDCD5 rapidly translocates from the cytoplasm to the nucleus. PDCD5 regulates the activities of TIP60, HDAC3, MDM2 and TP53 transcription factors. These proteins form part of a signaling network that is disrupted in most, if not all, cancer cells. Recent evidence suggests that PDCD5 participates in immune regulation by promoting regulatory T cell function via the PDCD5-TIP60-FOXP3 pathway. The stability and expression of PDCD5 are finely regulated by other molecules, such as NF-κB p65, OTUD5, YAF2 and DNAJB1. PDCD5 is phosphorylated by CK2 at Ser119, which is required for nuclear translocation in response to genotoxic stress. In this review, we describe what is known about PDCD5 and its cellular functions.

Anti-inflammatory effects of recombinant human PDCD5 (rhPDCD5) in a rat collagen-induced model of arthritis

Programmed cell death 5 (PDCD5) was first identified as a gene upregulated in cells undergoing apoptosis. We recently demonstrated the inhibitory effect of PDCD5 on experimentally induced autoimmune encephalomyelitis. In this study, we investigated the anti-inflammatory effects of recombinant human PDCD5 (rhPDCD5) in a rat collagen-induced arthritis (CIA) model. We find that vaccination of collagen II (CII) induced CIA rats with rhPDCD5 significantly delayed the occurrence and reduced the severity of CIA rats. rhPDCD5 also restored the loss of Foxp3⁺ regulatory T (Treg) cells and decreased the population of Th1 and Th17 in CIA rats. Simultaneously, rhPDCD5 treatment suppressed the production of pro-inflammatory cytokines (interleukin (IL)-6, IL-17A, tumor necrosis factor-α (TNF-α), and interferon gamma (IFN-γ)) and increased the secretion of anti-inflammatory cytokines (transforming growth factor beta 1 (TGF-β1) and IL-10) in CIA rats. In addition, rhPDCD5 inhibited the ability of CII to induce proliferation of splenocytes and lymph node cells (LNCs) and promoted the CII-activated CD4⁺ cell apoptosis. These results of rhPDCD5-treated CIA rats were similar with those of recombinant human TNF-α receptor IgG Fc (rhTNFR:Fc). Thus, to our knowledge, we provide the first evidence that rhPDCD5 may be an efficient approach to diminishing exacerbated immune responses in CIA, indicating its therapeutic potential in the treatment of rheumatoid arthritis and other autoimmune diseases.

Bifurcation analysis and potential landscapes of the p53-Mdm2 module regulated by the co-activator programmed cell death 5

The dynamics of p53 play important roles in the regulation of cell fate decisions in response to various stresses, and programmed cell death 5 (PDCD5) functions as a co-activator of p53 that modulates p53 dynamics. In the present paper, we investigated how p53 dynamics are modulated by PDCD5 during the deoxyribose nucleic acid damage response using methods of bifurcation analysis and potential landscape. Our results revealed that p53 activities display rich dynamics under different PDCD5 levels, including monostability, bistability with two stable steady states, oscillations, and the coexistence of a stable steady state (or two states) and an oscillatory state. The physical properties of the p53 oscillations were further demonstrated by the potential landscape in which the potential force attracts the system state to the limit cycle attractor, and the curl flux force drives coherent oscillation along the cyclic trajectory. We also investigated the efficiency with which PDCD5 induced p53 oscillations. We show that Hopf bifurcation can be induced by increasing the PDCD5 efficiency and that the system dynamics exhibited clear transition features in both barrier height and energy dissipation when the efficiency was close to the bifurcation point.

Low programmed cell death 5 expression is a prognostic factor in ovarian cancer

Background:

Ovarian cancer is a leading gynecological malignancy. We investigated the prognostic value of programmed cell death 5 (PDCD5) in patients with ovarian cancer.

Methods:

Expression levels of PDCD5 mRNA and protein were examined in six ovarian cancer cell lines (SKOV3, CAOV3, ES2, OV1, 3AO, and HOC1A) and one normal ovarian epithelial cell line (T29) using reverse transcription polymerase chain reaction, Western blotting, and flow cytometry. After inducing PDCD5 induction in SKOV3 cells or treating this cell line with taxol or doxorubicin (either alone or combined), apoptosis was measured by Annexin V-FITC/propidium iodide staining. Correlations between PDCD5 protein expression and pathological features, histological grade, FIGO stage, effective cytoreductive surgery, and serum cancer antigen-125 values were evaluated in patients with ovarian cancer.

Results:

PDCD5 mRNA and protein expression were downregulated in ovarian cancer cells. Recombinant human PDCD5 increased doxorubicin-induced apoptosis in SKOV3 cells (15.96 ± 2.07%, vs. 3.17 ± 1.45% in controls). In patients with ovarian cancer, PDCD5 expression was inversely correlated with FIGO stage, pathological grade, and patient survival (P < 0.05, R = 0.7139 for survival).

Conclusions:

PDCD5 expression is negatively correlated with disease progression and stage in ovarian cancer. Therefore, measuring PDCD5 expression may be a good method of determining the prognosis of ovarian cancer patients.

In silico identification of genetically attenuated vaccine candidate genes for Plasmodium liver stage

Genetically attenuated parasites (GAPs) that lack genes essential for the liver stage of the malaria parasite, and therefore cause developmental arrest, have been developed as live vaccines in rodent malaria models and recently been tested in humans. The genes targeted for deletion were often identified by trial and error. Here we present a systematic gene - protein and transcript - expression analyses of several Plasmodium species with the aim to identify candidate genes for the generation of novel GAPs. With a lack of liver stage expression data for human malaria parasites, we used data available for liver stage development of Plasmodium yoelii, a rodent malaria model, to identify proteins expressed in the liver stage but absent from blood stage parasites. An orthology-based search was then employed to identify orthologous proteins in the human malaria parasite Plasmodium falciparum resulting in a total of 310 genes expressed in the liver stage but lacking evidence of protein expression in blood stage parasites. Among these 310 possible GAP candidates, we further studied Plasmodium liver stage proteins by phyletic distribution and functional domain analyses and shortlisted twenty GAP-candidates; these are: fabB/F, fabI, arp, 3 genes encoding subunits of the PDH complex, dnaJ, urm1, rS5, ancp, mcp, arh, gk, lisp2, valS, palm, and four conserved Plasmodium proteins of unknown function. Parasites lacking one or several of these genes might yield new attenuated malaria parasites for experimental vaccination studies.

Programmed cell death 5 mediates HDAC3 decay to promote genotoxic stress response

The inhibition of p53 activity by histone deacetylase 3 (HDAC3) has been reported, but the precise molecular mechanism is unknown. Here we show that programmed cell death 5 (PDCD5) selectively mediates HDAC3 dissociation from p53, which induces HDAC3 cleavage and ubiquitin-dependent proteasomal degradation. Casein kinase 2 alpha phosphorylates PDCD5 at Ser-119 to enhance its stability and importin 13-mediated nuclear translocation of PDCD5. Genetic deletion of PDCD5 abrogates etoposide (ET)-induced p53 stabilization and HDAC3 cleavage, indicating an essential role of PDCD5 in p53 activation. Restoration of PDCD5^WT in PDCD5^−/− MEFs restores ET-induced HDAC3 cleavage. Reduction of both PDCD5 and p53, but not reduction of either protein alone, significantly enhances in vivo tumorigenicity of AGS gastric cancer cells and correlates with poor prognosis in gastric cancer patients. Our results define a mechanism for p53 activation via PDCD5-dependent HDAC3 decay under genotoxic stress conditions.

The tumour suppressor p53 is known to be inhibited by histone deacetylase 3 but the molecular mechanism is poorly understood. Here Choi et al. show regulation by programmed cell death 5 and an essential role in activating p53 following DNA damage.

Recombinant human PDCD5 (rhPDCD5) protein is protective in a mouse model of multiple sclerosis

Background

In multiple sclerosis (MS) and its widely used animal model, experimental autoimmune encephalomyelitis (EAE), autoreactive T cells contribute importantly to central nervous system (CNS) tissue damage and disease progression. Promoting apoptosis of autoreactive T cells may help eliminate cells responsible for inflammation and may delay disease progression and decrease the frequency and severity of relapse. Programmed cell death 5 (PDCD5) is a protein known to accelerate apoptosis in response to various stimuli. However, the effects of recombinant human PDCD5 (rhPDCD5) on encephalitogenic T cell-mediated inflammation remain unknown.

Methods

We examined the effects of intraperitoneal injection of rhPDCD5 (10 mg/kg) on EAE both prophylactically (started on day 0 post-EAE induction) and therapeutically (started on the onset of EAE disease at day 8), with both of the treatment paradigms being given every other day until day 25. Repeated measures two-way analysis of variance was used for statistical analysis.

Results

We showed that the anti-inflammatory effects of rhPDCD5 were due to a decrease in Th1/Th17 cell frequency, accompanied by a reduction of proinflammatory cytokines, including IFN-γ and IL-17A, and were observed in both prophylactic and therapeutic regimens of rhPDCD5 treatment in EAE mice. Moreover, rhPDCD5-induced apoptosis of myelin-reactive CD4⁺ T cells, along with the upregulation of Bax and downregulation of Bcl-2, and with activated caspase 3.

Conclusions

Our data demonstrate that rhPDCD5 ameliorates the autoimmune CNS disease by inhibiting Th1/Th17 differentiation and inducing apoptosis of predominantly pathogenic T cells. This study provides a novel mechanism to explain the effects of rhPDCD5 on neural inflammation. The work represents a translational demonstration that rhPDCD5 has prophylactic and therapeutic properties in a model of multiple sclerosis.

The p53 binding protein PDCD5 is not rate-limiting in DNA damage induced cell death

The tumour suppressor p53 is an important mediator of cell cycle arrest and apoptosis in response to DNA damage, acting mainly by transcriptional regulation of specific target genes. The exact details how p53 modulates this decision on a molecular basis is still incompletely understood. One mechanism of regulation is acetylation of p53 on lysine K120 by the histone-acetyltransferase Tip60, resulting in preferential transcription of proapoptotic target genes. PDCD5, a protein with reported pro-apoptotic function, has recently been identified as regulator of Tip60-dependent p53-acetylation. In an effort to clarify the role of PDCD5 upon DNA damage, we generated cell lines in which PDCD5 expression was conditionally ablated by shRNAs and investigated their response to genotoxic stress. Surprisingly, we failed to note a rate-limiting role of PDCD5 in the DNA damage response. PDCD5 was dispensable for DNA damage induced apoptosis and cell cycle arrest and we observed no significant changes in p53 target gene transcription. While we were able to confirm interaction of PDCD5 with p53, we failed to do so for Tip60. Altogether, our results suggest a role of PDCD5 in the regulation of p53 function but unrelated to cell cycle arrest or apoptosis, at least in the cell types investigated.

Staphylococcus aureus induces hypoxia and cellular damage in porcine dermal explants

We developed a porcine dermal explant model to determine the extent to which Staphylococcus aureus biofilm communities deplete oxygen, change pH, and produce damage in underlying tissue. Microelectrode measurements demonstrated that dissolved oxygen (DO) in biofilm-free dermal tissue was 4.45 ± 1.17 mg/liter, while DO levels for biofilm-infected tissue declined sharply from the surface, with no measurable oxygen detectable in the underlying dermal tissue. Magnetic resonance imaging demonstrated that biofilm-free dermal tissue had a significantly lower relative effective diffusion coefficient (0.26 ± 0.09 to 0.30 ± 0.12) than biofilm-infected dermal tissue (0.40 ± 0.12 to 0.48 ± 0.12; P < 0.0001). Thus, the difference in DO level was attributable to biofilm-induced oxygen demand rather than changes in oxygen diffusivity. Microelectrode measures showed that pH within biofilm-infected explants was more alkaline than in biofilm-free explants (8.0 ± 0.17 versus 7.5 ± 0.15, respectively; P < 0.002). Cellular and nuclear details were lost in the infected explants, consistent with cell death. Quantitative label-free shotgun proteomics demonstrated that both proapoptotic programmed cell death protein 5 and antiapoptotic macrophage migration inhibitory factor accumulated in the infected-explant spent medium, compared with uninfected-explant spent media (1,351-fold and 58-fold, respectively), consistent with the cooccurrence of apoptosis and necrosis in the explants. Biofilm-origin proteins reflected an extracellular matrix-adapted lifestyle of S. aureus. S. aureus biofilms deplete oxygen, increase pH, and induce cell death, all factors that contribute to impede wound healing.

p53 Acetylation: Regulation and Consequences

Post-translational modifications of p53 are critical in modulating its tumor suppressive functions. Ubiquitylation, for example, plays a major role in dictating p53 stability, subcellular localization and transcriptional vs. non-transcriptional activities. Less is known about p53 acetylation. It has been shown to govern p53 transcriptional activity, selection of growth inhibitory vs. apoptotic gene targets, and biological outcomes in response to diverse cellular insults. Yet recent in vivo evidence from mouse models questions the importance of p53 acetylation (at least at certain sites) as well as canonical p53 functions (cell cycle arrest, senescence and apoptosis) to tumor suppression. This review discusses the cumulative findings regarding p53 acetylation, with a focus on the acetyltransferases that modify p53 and the mechanisms regulating their activity. We also evaluate what is known regarding the influence of other post-translational modifications of p53 on its acetylation, and conclude with the current outlook on how p53 acetylation affects tumor suppression. Due to redundancies in p53 control and growing understanding that individual modifications largely fine-tune p53 activity rather than switch it on or off, many questions still remain about the physiological importance of p53 acetylation to its role in preventing cancer.

Deubiquitinase OTUD5 mediates the sequential activation of PDCD5 and p53 in response to genotoxic stress

Programmed cell death 5 (PDCD5) positively regulates p53-mediated apoptosis and rapidly accumulates upon DNA damage. However, the underlying mechanism of PDCD5 upregulation during the DNA damage response remains unknown. Here, we found that OTU deubiquitinase 5 (OTUD5) was bound to PDCD5 in response to etoposide treatment and increased the stability of PDCD5 by mediating deubiquitination of PDCD5 at Lys-97/98. Overexpression of OTUD5 efficiently enhanced the activation of both PDCD5 and p53. Conversely, PDCD5 knockdown greatly attenuated the effect of OTUD5 on p53 activation. In addition, when OTUD5 was depleted, PDCD5 failed to facilitate p53 activation, demonstrating an essential role for the PDCD5-OTUD5 network in p53 activation. Importantly, we found that OTUD5-dependent PDCD5 stabilization was required for sequential activation of p53 in response to genotoxic stress. The sequential activation of PDCD5 and p53 was abrogated by knockdown of OTUD5. Finally, impairment of the genotoxic stress response upon PDCD5 ablation was substantially rescued by reintroducing PDCD5(WT) but not PDCD5(E94D) (defective for OTUD5 interaction) or PDCD5(E16D) (defective for p53 interaction). Together, our findings have uncovered an apoptotic signaling cascade linking PDCD5, OTUD5, and p53 during genotoxic stress responses.

The von Hippel-Lindau tumor suppressor regulates programmed cell death 5-mediated degradation of Mdm2

Functional loss of the von Hippel-Lindau (VHL) tumor suppressor protein (pVHL), which is part of an E3-ubiquitin ligase complex, initiates most inherited and sporadic clear-cell renal cell carcinomas (ccRCC). Genetic inactivation of the TP53 gene in ccRCC is rare, suggesting that an alternate mechanism alleviates the selective pressure for TP53 mutations in ccRCC. Here we use a zebrafish model to describe the functional consequences of pVHL loss on the p53/Mdm2 pathway. We show that p53 is stabilized in the absence of pVHL and becomes hyperstabilized upon DNA damage, which we propose is because of a novel in vivo interaction revealed between human pVHL and a negative regulator of Mdm2, the programmed cell death 5 (PDCD5) protein. PDCD5 is normally localized at the plasma membrane and in the cytoplasm. However, upon hypoxia or loss of pVHL, PDCD5 relocalizes to the nucleus, an event that is coupled to the degradation of Mdm2. Despite the subsequent hyperstabilization and normal transcriptional activity of p53, we find that zebrafish vhl(-/-) cells are still as highly resistant to DNA damage-induced cell cycle arrest and apoptosis as human ccRCC cells. We suggest this is because of a marked increase in expression of birc5a, the zebrafish homolog of Survivin. Accordingly, when we knock down Survivin in human ccRCC cells we are able to restore caspase activity in response to DNA damage. Taken together, our study describes a new mechanism for p53 stabilization through PDCD5 upon hypoxia or pVHL loss, and reveals new clinical potential for the treatment of pathobiological disorders linked to hypoxic stress.

Programmed cell death protein 5 interacts with the cytosolic chaperonin containing tailless complex polypeptide 1 (CCT) to regulate β-tubulin folding

Programmed cell death protein 5 (PDCD5) has been proposed to act as a pro-apoptotic factor and tumor suppressor. However, the mechanisms underlying its apoptotic function are largely unknown. A proteomics search for binding partners of phosducin-like protein, a co-chaperone for the cytosolic chaperonin containing tailless complex polypeptide 1 (CCT), revealed a robust interaction between PDCD5 and CCT. PDCD5 formed a complex with CCT and β-tubulin, a key CCT-folding substrate, and specifically inhibited β-tubulin folding. Cryo-electron microscopy studies of the PDCD5·CCT complex suggested a possible mechanism of inhibition of β-tubulin folding. PDCD5 bound the apical domain of the CCTβ subunit, projecting above the folding cavity without entering it. Like PDCD5, β-tubulin also interacts with the CCTβ apical domain, but a second site is found at the sensor loop deep within the folding cavity. These orientations of PDCD5 and β-tubulin suggest that PDCD5 sterically interferes with β-tubulin binding to the CCTβ apical domain and inhibits β-tubulin folding. Given the importance of tubulins in cell division and proliferation, PDCD5 might exert its apoptotic function at least in part through inhibition of β-tubulin folding.

Serum programmed cell death protein 5 (PDCD5) levels is upregulated in liver diseases

Intracellular protein molecules are detected in the blood following release from damaged cells. PDCD5 is widely expressed in most types of normal human tissue and is unregulated in cells undergoing apoptosis. It is therefore hypothesized that release of PDCD5 into the circulation might be a specific marker of apoptosis. In this study, a sandwich ELISA was developed for quantification of soluble PDCD5 protein and used to investigate serum PDCD5 levels in liver diseases. The highest levels of PDCD5 were detected in acute icteric hepatitis (AIH) patients compared with normal subjects and other detected liver diseases, such as chronic active hepatitis B (CAHB), chronic persistent hepatitis B (CPHB) and and liver cirrhosis (LC). Increased PDCD5 levels correlated well with ALT and AST in AIH and CAHB patients. In patients with CPHB, increased PDCD5 levels correlated well with AST, TBI, DBIL, and IBIL. In LC patients, PDCD5 levels correlated well with AST/ALT and DBIL. More importantly, increased PDCD5 levels were also observed in patients with normal ALT or AST levels. These data demonstrate a correlation between increased levels of PDCD5 in serum and liver disease progression and indicate the potential utility of serum PDCD5 as a biomarker for monitoring liver injury.

Recombinant human PDCD5 protein enhances chemosensitivity of breast cancer in vitro and in vivo

Resistance to paclitaxel is common for treatment of breast cancer. Programmed cell death 5 (PDCD5) accelerates apoptosis in different cell types in response to various stimuli; moreover PDCD5 has been shown to be down-regulated in many tumors. In this study, protein levels of PDCD5 were found to be up-regulated in paclitaxel-treated MDA-MB-231 breast cancer cells. MTT, CCK-8, and clonogenic assays have shown that recombinant human PDCD5 (rhPDCD5) alone could not produce an obvious growth inhibition. However, upon paclitaxel triggering apoptosis, rhPDCD5 protein potentiated chemotherapeutic drugs-induced growth arrest in MDA-MB-231, SK-BR-3, and ZR-75-1 breast cancer cells. In vivo, we use a human breast cancer xenograft model to study. We found that rhPDCD5 dramatically improves the antitumor effects of paclitaxel treatment by intraperitoneal administration. These data suggest that rhPDCD5 has the potential to use as a therapeutic agent to enhance the paclitaxel sensitivity of breast cancer cells.

PDCD5 negatively regulates autoimmunity by upregulating FOXP3(+) regulatory T cells and suppressing Th17 and Th1 responses

Maintenance of FOXP3 protein expression is crucial for differentiation and maturation of regulatory T (Treg) cells, which play important roles in immune homeostasis and immune tolerance. We demonstrate here that PDCD5 interacts with FOXP3, increases acetylation of FOXP3 in synergy with Tip60 and enhances the repressive function of FOXP3. In PDCD5 transgenic (PDCD5tg) mice, overexpression of PDCD5 enhanced the level of FOXP3 protein and percentage of CD4(+)CD25(+)FOXP3(+) cells. Naïve CD4(+) T cells from PDCD5tg mice were more sensitive to TGF-β-induced Treg polarization and expansion. These induced Tregs retained normal suppressive function in vitro. Severity of experimentally-induced autoimmune encephalomyelitis (EAE) in PDCD5tg mice was significantly reduced relative to that of wild-type mice. The beneficial effect of PDCD5 likely resulted from increases of Treg cell frequency, accompanied by a reduction of the predominant pathogenic Th17/Th1 response. Activation-induced cell death enhanced by PDCD5 was also linked to this process. This is the first report revealing that PDCD5 activity in T cells suppresses autoimmunity by modulating Tregs. This study suggests that PDCD5 serves as a guardian of immunological functions and that the PDCD5-FOXP3-Treg axis may be a therapeutic target for autoimmunity.

ING5 is a Tip60 cofactor that acetylates p53 in response to DNA damage

Posttranslational modification of p53 is a critical event in regulating the expression of its target genes. p53 is acetylated at lysine 120 (K120) by acetyltranferases Tip60 (KAT5) and hMOF (KAT8) in response to DNA damage. Identification of cofactors for these two enzymes will shed light on the mechanism by which cells make a choice between cell-cycle arrest and apoptosis. It has been reported that ING5, a member of the inhibitor of growth (ING) family, is involved in p53-dependent pathways, but its exact role is unknown. In this study, we found that ING5 expression was significantly increased and that ING5 assisted Tip60, but not hMOF, in acetylating p53 at K120 in response to DNA damage. ING5 had no effect on acetylation of p53 at K373/382, but it formed a complex with p53 and Tip60. ING5 was required for acetylation of p53 at K120, and p53 acetylated at K120 subsequently bound to the promoters of its target apoptotic genes, BAX and GADD45, to promote their expression and lead to apoptosis. Mutation of K120 to K120R abolished the effects of ING5 on p53-induced gene expression. Thus, we conclude that ING5 functions as a cofactor of Tip60 in the acetylation of p53 at K120 in response to DNA damage.

The involvement of programmed cell death 5 (PDCD5) in the regulation of apoptosis in cerebral ischemia/reperfusion injury

AIMS

Programmed Cell Death 5 (PDCD5) is a protein that accelerates apoptosis in different types of cells in response to various stimuli and is down-regulated in many cancer tissues. We hypothesized in this study that down-regulating PDCD5 can protect the brain from ischemic damage by inhibiting PDCD5-induced apoptotic pathway.

METHODS

One hundred and sixty male Sprague-Dawley rats were randomly assigned to five groups: Sham surgery (n = 25), MCAO (n = 45), MCAO+rhPDCD5 (RhPDCD5) (n = 30), MCAO+control siRNA (n = 30), and MCAO+PDCD5 siRNA (n = 30). At 24 h following MCAO, immunohistochemistry and Western blot were performed.

RESULTS

PDCD5 siRNA reduced the infarct volume, improved neurological deficits, improved cerebral blood flow (CBF), and reduced Evans blue extravasation. Meanwhile, over-expression of PDCD5 protein with recombinant human PDCD5 (rhPDCD5) had an opposite effect. Immunohistochemistry and Western blot demonstrated PDCD5 siRNA decreased the expressions of key proapoptotic proteins such as p53, Bax/Bcl-2, and cleaved caspase-3 in the penumbra areas, whereas rhPDCD5 increased cell apoptosis. Double fluorescence labeling showed the positive immunoreactive materials of PDCD5 were partly colocalized with MAP2, GFAP, CD34, p53, and caspase-3 in the penumbra areas in brain.

CONCLUSIONS

PDCD5-induced apoptosis and over-expression of PDCD5 are harmful to the ischemic neurons in vivo. Meanwhile, the inhibition of PDCD5 may be protective via reducing the apoptotic-related protein such as p53, Bax, and caspase-3. This observation may have potential for the treatment of ischemic cerebral stroke.

Targeted delivery of biodegradable nanoparticles with ultrasound-targeted microbubble destruction-mediated hVEGF-siRNA transfection in human PC-3 cells in vitro

A potentially viable approach for treating late-stage prostate cancer is gene therapy. Successful gene therapy requires safe and efficient delivery systems. In this study, we report the efficient delivery of small interfering RNA (siRNA) via the use of biodegradable nanoparticles (NPs) made from monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly-l-lysine (mPEG-PLGA-PLL) triblock copolymers. On the basis of previous findings, cyclic Arg-Gly-Asp (cRGD) peptides were conjugated to NPs to recognize the target site, integrin αvβ3, expressed in high levels in PC-3 prostate cancer cells. The suppression of angiogenesis by the downregulation of vascular endothelial growth factor (VEGF) expression has been widely used to inhibit the growth of malignant tumors. In our study, human VEGF (hVEGF)-siRNA was encapsulated in NPs to inhibit VEGF expression in PC-3 cells. Concurrently, sonoporation induced by ultrasound-targeted microbubble destruction (UTMD) was utilized for the delivery of siRNA-loaded NPs. Our results showed low cytotoxicity and high gene transfection efficiency, demonstrating that the targeted delivery of biodegradable NPs with UTMD may be potentially applied as new vector system for gene delivery.

Tip60 HAT activity mediates APP induced lethality and apoptotic cell death in the CNS of a Drosophila Alzheimer's disease model

Histone acetylation of chromatin promotes dynamic transcriptional responses in neurons that influence neuroplasticity critical for cognitive ability. It has been demonstrated that Tip60 histone acetyltransferase (HAT) activity is involved in the transcriptional regulation of genes enriched for neuronal function as well as the control of synaptic plasticity. Accordingly, Tip60 has been implicated in the neurodegenerative disorder Alzheimer's disease (AD) via transcriptional regulatory complex formation with the AD linked amyloid precursor protein (APP) intracellular domain (AICD). As such, inappropriate complex formation may contribute to AD-linked neurodegeneration by misregulation of target genes involved in neurogenesis; however, a direct and causative epigenetic based role for Tip60 HAT activity in this process during neuronal development in vivo remains unclear. Here, we demonstrate that nervous system specific loss of Tip60 HAT activity enhances APP mediated lethality and neuronal apoptotic cell death in the central nervous system (CNS) of a transgenic AD fly model while remarkably, overexpression of Tip60 diminishes these defects. Notably, all of these effects are dependent upon the C-terminus of APP that is required for transcriptional regulatory complex formation with Tip60. Importantly, we show that the expression of certain AD linked Tip60 gene targets critical for regulating apoptotic pathways are modified in the presence of APP. Our results are the first to demonstrate a functional interaction between Tip60 and APP in mediating nervous system development and apoptotic neuronal cell death in the CNS of an AD fly model in vivo, and support a novel neuroprotective role for Tip60 HAT activity in AD neurodegenerative pathology.

PDCD5 promotes cisplatin-induced apoptosis of glioma cells via activating mitochondrial apoptotic pathway

Glioma is one of the most common primary brain tumors. Despite surgical resection, radiotherapy, and chemotherapy, the prognosis of patients with malignant glioma remains poor. Programmed cell death 5 (PDCD5) is a newly described pro-apoptotic protein. Our previous study showed that PDCD5 downregulation in gliomas was associated with higher pathological grade. Here, we investigated the effect of PDCD5 on chemosensitivity of glioma cells and its mechanism. We demonstrated that overexpression or knockdown of PDCD5 had no significant effect on the proliferation of glioma cell lines (U87, U251, and T98G) in the absence of chemotherapeutic agents. However, PDCD5 overexpression effectively sensitized U87 cells to chemotherapeutic drugs (cisplatin, carboplatin, and vincristine) in a concentration-dependent manner, while its knockdown resulted in decreased chemosensitivity in U251, T98G, and U87 cells. Importantly, expression of PDCD5 also markedly inhibited tumor cell proliferation and colony formation in the presence of low doses of cisplatin. Furthermore, we found that PDCD5 expression promoted cisplatin-induced apoptosis, increased markedly the activation of caspase-3 and caspase-9, and decreased significantly the ratio of Bcl-2/Bax proteins, but had no effect on the activation of caspase-8. Taken together, our findings indicate that PDCD5 promotes chemosensitivity by activating mitochondria-related apoptotic pathway, and that the combination of PDCD5 and chemotherapeutic drugs such as cisplatin, is expected to be an effective therapeutic strategy for the malignant glioma.