The deacetylation of Foxk2 by Sirt1 reduces chemosensitivity to cisplatin.

In multiple types of cancer, decreased tumour cell apoptosis during chemotherapy is indicative of decreased chemosensitivity. Forkhead box K2 (FOXK2), which is essential for cell fate, regulates cancer cell apoptosis through several post-translational modifications. However, FOXK2 acetylation has not been extensively studied. Here, we evaluated the effects of sirtiun 1 (SIRT1) on FOXK2 deacetylation. Our findings demonstrated that SIRT1 inhibition increased FOXK2-induced chemosensitivity to cisplatin and that K223 in FOXK2 was acetylated. Furthermore, FOXK2 K223 deacetylation reduced chemosensitivity to cisplatin in vitro and in vivo. Mechanistically, FOXK2 was acetylated by the acetyltransferase cAMP response element binding protein and deacetylated by SIRT1. Furthermore, cisplatin attenuated the interaction between FOXK2 and SIRT1. Cisplatin or SIRT1 inhibition enhanced FOXK2 acetylation, thereby reducing the nuclear distribution of FOXK2. Additionally, FOXK2 K223 acetylation significantly affected the expression of cell cycle-related and apoptosis-related genes in cisplatin-stimulated cancer cells, and FOXK2 K223 hyperacetylation promoted mitotic catastrophe, which enhanced chemosensitivity to cisplatin. Overall, our results provided insights into the mechanisms of SIRT1-mediated FOXK2 deacetylation, which was involved in chemosensitivity to cisplatin.

ATM-CHK2-Beclin 1 axis promotes autophagy to maintain ROS homeostasis under oxidative stress.

The homeostatic link between oxidative stress and autophagy plays an important role in cellular responses to a wide variety of physiological and pathological conditions. However, the regulatory pathway and outcomes remain incompletely understood. Here, we show that reactive oxygen species (ROS) function as signaling molecules that regulate autophagy through ataxia-telangiectasia mutated (ATM) and cell cycle checkpoint kinase 2 (CHK2), a DNA damage response (DDR) pathway activated during metabolic and hypoxic stress. We report that CHK2 binds to and phosphorylates Beclin 1 at Ser90/Ser93, thereby impairing Beclin 1-Bcl-2 autophagy-regulatory complex formation in a ROS-dependent fashion. We further demonstrate that CHK2-mediated autophagy has an unexpected role in reducing ROS levels via the removal of damaged mitochondria, which is required for cell survival under stress conditions. Finally, CHK2-/- mice display aggravated infarct phenotypes and reduced Beclin 1 p-Ser90/Ser93 in a cerebral stroke model, suggesting an in vivo role of CHK2-induced autophagy in cell survival. Taken together, these results indicate that the ROS-ATM-CHK2-Beclin 1-autophagy axis serves as a physiological adaptation pathway that protects cells exposed to pathological conditions from stress-induced tissue damage.

Corrigendum: Digital Gene Expression Analysis of Populus simonii × P. nigra Pollen Germination and Tube Growth.

[This corrects the article on p. 825 in vol. 7, PMID: 27379121.].

Digital Gene Expression Analysis of Populus simonii × P. nigra Pollen Germination and Tube Growth.

Pollen tubes are an ideal model for the study of cell growth and morphogenesis because of their extreme elongation without cell division; however, the genetic basis of pollen germination and tube growth remains largely unknown. Using the Illumina/Solexa digital gene expression system, we identified 13,017 genes (representing 28.3% of the unigenes on the reference genes) at three stages, including mature pollen, hydrated pollen, and pollen tubes of Populus simonii × P. nigra. Comprehensive analysis of P. simonii × P. nigra pollen revealed dynamic changes in the transcriptome during pollen germination and pollen tube growth (PTG). Gene ontology analysis of differentially expressed genes showed that genes involved in functional categories such as catalytic activity, binding, transporter activity, and enzyme regulator activity were overrepresented during pollen germination and PTG. Some highly dynamic genes involved in pollen germination and PTG were detected by clustering analysis. Genes related to some key pathways such as the mitogen-activated protein kinase signaling pathway, regulation of the actin cytoskeleton, calcium signaling, and ubiquitin-mediated proteolysis were significantly changed during pollen germination and PTG. These data provide comprehensive molecular information toward further understanding molecular mechanisms underlying pollen germination and PTG.

A systemic proteomic analysis of Populus chloroplast by using shotgun method.

The chloroplast is one of the most important organelles in plants. Proteomic investigations of chloroplasts have been undertaken for many herb plant species, but to date no such investigation has been reported for woody plant chloroplasts. In the present study we initiated a systematic proteomic study of Populus chloroplasts using a shotgun proteomic method. After isolation of chloroplasts and tryptic digestion of the proteins, the protein fragments were separated via HPLC using an SCX column, and the peptides were analyzed by LC-MS/MS; 119 proteins were successfully identified. Based on annotation information in the UniProtKB/Swiss-Prot database, these proteins were identified as being localized in the chloroplast thylakoid membrane, chloroplast stroma, chloroplast thylakoid lumen, and plastoglobules. Over 50% of all identified proteins were confirmed as chloroplast thylakoid proteins, and 85 are encoded by the chloroplast genome with the remaining proteins encoded by the nuclear genome. Based on functional annotation, these proteins were classified into four functional categories, including photosynthesis, redox regulation and stress, primary and secondary metabolism, transport and signaling. These data provide a valuable basis for further studies on photosynthesis in poplar species.

[The effect of urokinase on hepatic fibrogenesis in rats].

OBJECTIVE: To investigate the effect of urokinase on hepatic fibrogenesis in rats. METHODS: Hepatic fibrosis was induced in rats by complex pathogenic factors including subcutaneous injections of carbon tetrachloride, alcohol and cholesterol feeding. Animals were randomly divided into 3 groups: normal control group, hepatic fibrosis group (complex pathogenic factors for 6 weeks), UK prevention group (complex pathogenic factors+UK for 6 weeks). The animals were sacrificed at the end of week 6. The expression of alpha-SMA, uPA, PAI-1, TGFb1, TIMP-1, collagen type I and type III proteins in hepatic fibrosis tissue was detected by immunohistochemistry, the expression of PAI-1 and TGFb1 mRNA in the hepatic fibrosis tissue was quantified by real time RT-PCR. The serum levels of hyaluronicacid (HA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin (TBil) and the content of liver hydroxyproline (Hyp) were detected using ELISA kits. RESULTS: The serum ALT, AST, TBil, HA and the content of liver Hyp were (46.66+/-6.30) U/L, (126.26+/-31.65) U/L, (31.11+/-4.20) micromol/L, (109.70+/-18.81) microg/L and (0.98+/-0.09) mg/(g liver), respectively, in UK prevention group, which were significantly lower than those [(101.57+/-11.97) U/L, (205.89+/-56.26) U/L, (67.75+/-2.75) micromol/L, (184.43+/-32.36) microg/L and (1.65+/-0.16) mg/(g liver), respectively] in hepatic fibrosis group (q = 3.3801-20.0061, P < 0.01). The levels of a-SMA, collagen type I, type III, TIMP-1, PAI-1, TGFb1 proteins were (299.27+/-37.36), (210.05+/-27.17), (192.94+/-24.48), (213.70+/-32.21), (204.25+/-17.92), (205.97+/-23.81), respectively, in UK prevention group, which were significantly lower than those [(418.83+/-30.21), (323.77+/-21.53), (302.37+/-31.43), (376.63+/-25.19), (313.53+/-26.67) and (327.42+/-36.75), respectively] in hepatic fibrosis group. The level of uPA protein was increased, and the expression of PAI-1, TGFb1 mRNA in hepatic fibrosis tissue was decreased in UK prevention group. CONCLUSION: In the early stage of hepatic fibrogenesis, urokinase can attenuate the progression of rat hepatic fibrosis via upregulation of uPA, downregulation of TGFb1, and inhibition of HSC activation.

[The plasma levels of transforming growth factor beta1 and the protein expressions of alpha-SMA, urokinase plasminogen activator and plasminogen activator inhibitor-1 in liver of patients with different grades of hepatic fibrosis].

OBJECTIVE: To measure the plasma levels of transforming growth factor beta1 (TGFbeta1), the protein expression of alpha-SMA in hepatic stellate cells and urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1), and study on the relationships between the plasma levels of TGFbeta1, the protein expression and the serum hyaluronic acid (HA) in patients with different grades of hepatic fibrosis. METHODS: Thirty seven cases with hepatic fibrosis of different grades were classified according to HE and VG staining categories from 0 to 4, in which there were 8 cases in grade 1, 9 cases in grade 2, 7 cases in grade 3, 13 cases in grade 4. The plasma levels of TGFbeta1 and the serum levels of HA were detected by ELISA. The protein expressions of a-SMA, uPA and PAI-1 in fibrotic liver tissue were observed by immunohistochemistry. RESULTS: With the progression of hepatic fibrosis, the plasma levels of TGFbeta1 and the protein expression of a-SMA, uPA and PAI-1 in fibrotic liver tissue were increased. In grade 3 and 4, the plasma levels of TGFbeta and the protein expression of a-SMA and PAI-1 in fibrotic liver tissue were significantly increased, but the protein expression of uPA in cirrhosis liver tissue did not increased. CONCLUSION: TGFbeta1, a-SMA, uPA and PAI-1 play an important role in the progression of hepatic fibrosis. Inhibiting the early activation of latent TGFbeta1 or increasing uPA and inhibiting PAI-1 over express may contribute to matrix degradation and retard the progression of hepatic fibrosis.

[The plasma levels of urokinase plasminogen activator and urokinase plasminogen activator receptor and plasminogen activator inhibitor-1 in patients with different stages of liver cirrhosis following chronic hepatitis B].

OBJECTIVES: To measure the plasma levels of urokinase plasminogen activator (uPA), urokinase plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1), and study the relationship between the plasma levels of uPA, PAI-1 and the serum albumin (Alb), collagen type IV (CIV), the serum hyaluronic acid (HA), prothrombin time (PT) and prothrombin activity (PTA) in patients with different stages of liver cirrhosis following chronic hepatitis B. METHODS: 72 cases with liver cirrhosis of different stages were classified according to child-pugh's categories A, B, C, in which there were 23 cases in child A, 29 cases in child B, and 20 cases in child C. The plasma levels of uPA, uPAR, PAI-1 and the serum levels of HA, CIV were detected by ELISA. The serum PCIII concentration was determined by radioimmunoassay. RESULTS: With the progression of hepatic fibrosis, the plasma levels of uPA, uPAR and PAI-1 were (1.36+/-0.43) microg/L, (3.03+/-1.48) microg/L and (24.09+/-7.14) microg/L respectively in group A, (1.79+/-0.62) microg/L, (4.80+/-2.22) microg/L and (41.40+/-17.52) microg/L respectively in group B. The highest levels were in child C, whose levels were (1.88+/-0.64) microg/L, (4.82+/-2.02) microg/L and (52.60+/-16.87) microg/L respectively, compared with group A and group B, t value were from 2.81 to 7.38, all of P value were less than 0.01. There was negative correlation between the plasma levels of uPA and the serum PCIII (r=-0.4785, P<0.05) in child A, but, positive correlation between the plasma PAI-1 and the serum HA (r=0.5447, P<0.01) in child C. The value of PAI-1/uPA was significantly decreased in child A, but increased in child B and child C. CONCLUSION: In the late of liver cirrhosis, increased PAI-1 together with uPA, uPAR are associated with overall inhibition of matrix degradation. The plasma levels of uPA and PAI-1 were correlation to the progression of liver cirrhosis.