Quantifying and monitoring functional photosystem II and the stoichiometry of the two photosystems in leaf segments: approaches and approximations.

Chow, Wah Soon,Fan, Da-Yong,Oguchi, Riichi,Jia, Husen,Losciale, Pasquale,Park, Youn-Il,He, Jie,Oquist, Gunnar,Shen, Yun-Gang,Anderson, Jan M W. Junk ; Kluwer Academic Publishers 2012 Photosynthesis research Vol.113 No.1

<P>Given its unique function in light-induced water oxidation and its susceptibility to photoinactivation during photosynthesis, photosystem II (PS II) is often the focus of studies of photosynthetic structure and function, particularly in environmental stress conditions. Here we review four approaches for quantifying or monitoring PS II functionality or the stoichiometry of the two photosystems in leaf segments, scrutinizing the approximations in each approach. (1) Chlorophyll fluorescence parameters are convenient to derive, but the information-rich signal suffers from the localized nature of its detection in leaf tissue. (2) The gross O(2) yield per single-turnover flash in CO(2)-enriched air is a more direct measurement of the functional content, assuming that each functional PS II evolves one O(2) molecule after four flashes. However, the gross O(2) yield per single-turnover flash (multiplied by four) could over-estimate the content of functional PS II if mitochondrial respiration is lower in flash illumination than in darkness. (3) The cumulative delivery of electrons from PS II to P700(+) (oxidized primary donor in PS I) after a flash is added to steady background far-red light is a whole-tissue measurement, such that a single linear correlation with functional PS II applies to leaves of all plant species investigated so far. However, the magnitude obtained in a simple analysis (with the signal normalized to the maximum photo-oxidizable P700 signal), which should equal the ratio of PS II to PS I centers, was too small to match the independently-obtained photosystem stoichiometry. Further, an under-estimation of functional PS II content could occur if some electrons were intercepted before reaching PS I. (4) The electrochromic signal from leaf segments appears to reliably quantify the photosystem stoichiometry, either by progressively photoinactivating PS II or suppressing PS I via photo-oxidation of a known fraction of the P700 with steady far-red light. Together, these approaches have the potential for quantitatively probing PS II in vivo in leaf segments, with prospects for application of the latter two approaches in the field.</P>

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.

Najafpour, Mohammad Mahdi,Moghaddam, Atefeh Nemati,Yang, Young Nam,Aro, Eva-Mari,Carpentier, Robert,Eaton-Rye, Julian J,Lee, Choon-Hwan,Allakhverdiev, Suleyman I W. Junk ; Kluwer Academic Publishers 2012 Photosynthesis research Vol.114 No.1

<P>The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster.</P>

Effect of estrogen on expression of prohibitin in white adipose tissue and liver of diet-induced obese rats.

Choi, Minji,Chaudhari, Harmesh N,Ji, Young Rae,Ryoo, Zae Young,Kim, Sang Woo,Yun, Jong Won Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2015 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.407 No.1

<P>Prohibitin (PHB) is a ubiquitously expressed and highly conserved protein that participates in diverse cellular processes, and its functions are linked to a variety of diseases. In the present study, to explore transcriptional activation and signaling pathways involved in PHB regulation in response to sex hormone treatment, we investigated the effects of estrogen (17-β-estradiol, E2) on regulation of PHB in several metabolic tissues from male and female rats. Elevated expression of PHB was prominent in white adipose tissue (WAT) and the liver, and E2 stimulated PHB expression in both ND and HFD-fed rats. To further confirm the expression of PHB which was increased in WAT and the liver, we analyzed PHB expression levels in 3T3-L1 and C9 cells after the treatment of E2. Transcription and protein levels of PHB were dose-dependently increased by E2 treatment in both cell types, supporting our in vivo data. To further evaluate the possible role of E2 in elevation of PHB via estrogen receptors (ER), the potent ER inhibitor fulvestrant was treated to 3T3-L1 and C9 cells. Fulvestrant markedly suppressed both transcription and protein levels of PHB, suggesting that PHB expression in both tissues may be regulated through ERs. GeneMANIA, a predictive web interface, was used to show that Phb is regulated via the intracellular steroid hormone receptor signaling pathway, suggesting a role for ERs in expression of Phb as well as other metabolically important genes. Based on these results, we expect that targeting PHB would be a useful therapeutic approach for treatment of obesity.</P>

Radicicol, an inhibitor of Hsp90, enhances TRAIL-induced apoptosis in human epithelial ovarian carcinoma cells by promoting activation of apoptosis-related proteins.

Kim, Yun Jeong,Lee, Seon Ae,Myung, Soon Chul,Kim, Wonyong,Lee, Chung Soo Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2012 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.359 No.1

<P>Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in various cancer cells. Hsp90 is known to be involved in cell survival and growth in tumor cells. Nevertheless, Hsp90 inhibitors exhibit a variable effect on the cytotoxicity of anticancer drugs. Furthermore, the combined effect of Hsp90 inhibitors on TRAIL-induced apoptosis in epithelial ovarian cancer cells has not been determined. To assess the ability of an inhibitor of Hsp90 inhibitor radicicol to promote apoptosis, we investigated the effect of radicicol on TRAIL-induced apoptosis in the human epithelial ovarian carcinoma cell lines OVCAR-3 and SK-OV-3. TRAIL induced a decrease in Bid, Bcl-2, Bcl-xL, and survivin protein levels, increase in Bax levels, loss of the mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-8, -9, and -3), cleavage of PARP-1 and an increase in the tumor suppressor p53 levels. Radicicol enhanced TRAIL-induced apoptosis-related protein activation, nuclear damage and cell death. These results suggest that radicicol may potentiate the apoptotic effect of TRAIL on ovarian carcinoma cell lines by increasing the activation of the caspase-8- and Bid-dependent pathway and the mitochondria-mediated apoptotic pathway, leading to caspase activation. Radicicol may confer a benefit in the TRAIL treatment of epithelial ovarian adenocarcinoma.</P>

RC3/neurogranin negatively regulates extracellular signal-regulated kinase pathway through its interaction with Ras.

Ryoo, Kanghyun,Hwang, Sang-Gil,Kim, Kwang Je,Choi, Eui-Ju Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2015 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.402 No.1

<P>RC3/neurogranin is a postsynaptic protein and plays pivotal roles in spatial learning and emotional anxiety as well as synaptic plasticity. The expression level of RC3 is dynamically changed during developmental stages, but the function of RC3 in brain development is not well understood yet. Neurotrophins interact with tropomyosin-related kinase receptors to activate Ras-extracellular signal-regulated kinase (ERK) pathway and can also induce neuronal differentiation. In this study, we demonstrate that RC3 inhibits Ras-ERK pathway by interaction with Ras and controls neurite outgrowth induced by neurotrophins. In PC12 cells, RC3 inhibits nerve growth factor (NGF)-induced activation of Ras and thereby ERK1/2 signaling cascade as well as neurite outgrowth induced by NGF. We found Ras is the target of the inhibitory function of RC3, because RC3 interacts with Ras and suppresses the elevated affinity of Ras to Ras-binding domain of Raf-1. Meanwhile, already activated Raf-1 by Ras activity is not affected by RC3. Furthermore, depletion of RC3 by RNA interference drastically enhances the stimulation of ERK1/2 and neurite outgrowth induced by brain-derived neurotrophic factor in hippocampal neurons. These findings suggest that RC3 is a novel natural inhibitor of Ras-ERK1/2 signaling axis, leading to negatively regulate neuronal differentiation induced by neurotrophins.</P>

Biogenesis of Epstein-Barr virus microRNAs.

Kim, Do Nyun,Lee, Suk Kyeong Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2012 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.365 No.1

<P>Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus implicated in lymphomas, such as Burkitt's lymphoma, Hodgkin's lymphoma, and NK/T cell lymphoma. MicroRNAs (miRNAs) are 19-25 nucleotide long single-stranded RNAs involved in post-transcriptional gene regulation. miRNAs are mainly transcribed by RNA polymerase II (pol II) to have stem-loop structures and subsequently processed by Drosha and Dicer. EBV miRNAs are expressed in B cells, nasopharyngeal carcinoma cells, and gastric carcinoma cells infected with EBV. EBV miRNAs can be divided into two groups: BHRF1 miRNAs and BART miRNAs. In this study, we investigated the biogenesis of EBV miRNAs. Treatment of the SNU-719 EBV-positive gastric cancer cell line with 관-amanitin at a concentration that selectively inhibits RNA polymerase II activity decreased the expression levels of BART miRNAs. The expression levels of BART miRNAs were also reduced by RNA interference targeting Drosha and Dicer. Two of each C/EBP관 and c-Myc binding sites are located upstream of the proposed initiation sites for primary BART miRNA transcripts. Knockdown of C/EBP관 but not c-Myc using siRNAs reduced BART miRNA expression by 25-55% compared with the control. These results suggest that BART miRNAs are transcribed by pol II and undergo a similar biogenesis process with cellular miRNAs.</P>

Cytotoxic effect of gambogic acid on SH-SY5Y neuroblastoma cells is mediated by intrinsic caspase-dependent signaling pathway.

Rahman, Md Ataur,Kim, Nam-Ho,Huh, Sung-Oh Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2013 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.377 No.1

<P>Gambogic acid (GA) is the dry resin of Garcinia hanburyi (Guttiferae) with potent anti-tumor activity, various bioactivities, including detoxification, homeostasis, anti-inflammatory, and parasiticide, whereas the effect of this natural compound on cancer cells has not been clearly clarified. Here, we examined cellular cytotoxicity by cell viability assay and DNA fragmentation by DNA-ladder assay. Activation of different protein expressions were detected by western blot analyses. We first demonstrated that GA reduces the human SH-SY5Y neuroblastoma cell viability with IC50 of 1.28 μM at 6 h which has less toxicity in fibroblast cells. However, lower concentration GA significantly downregulated the expression of anti-apoptotic protein including Bcl-2, Bcl-xL, and Mcl-1, which also dramatically activated cleaved caspase-9 and -3 in a dose- and time-dependent manner. Consequently, GA-induced cytotoxicity was not mediated by the Fas/FasL and PI3 K/AKT/GSK-3β signaling pathway. In addition, GA-induced cells showed damage morphology which had become cell rounding, neurite retraction, membrane blebbing and shrunken in a dose- and time-dependent manner that clearly indicates this morphological change might be due to the process of apoptosis which shows fragmented DNA. Therefore, the findings presented in this study demonstrate that apoptotic effects of GA on SH-SY5Y cells are mediated by intrinsic mitochondrion-dependent caspase pathway which suggests this natural compound might be effective as an anti-cancer agent for neuroblastoma malignancies.</P>

Benzyl isothiocyanate inhibits basal and hepatocyte growth factor-stimulated migration of breast cancer cells.

Kim, Eun Ji,Eom, Soon Ju,Hong, Ji Eun,Lee, Jae-Yong,Choi, Myung-Sook,Park, Jung Han Yoon Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2012 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.359 No.1

<P>Benzyl isothiocyanate (BITC), which is found in cruciferous vegetables, has been shown to have anti-carcinogenic properties. Hepatocyte growth factor (HGF) has the ability to stimulate dissociation, migration, and invasion in various tumor cells, and abnormally increased expressions of HGF and its transmembrane tyrosine kinase receptor, c-Met, have previously been detected in human breast cancer, and are associated with high tumor grade and poor prognosis. In this study, in order to assess the mechanisms relevant to the BITC-induced regulation of breast cancer cell migration and invasion, MDA-MB-231 human breast cancer cells and 4T1 murine mammary carcinoma cells were cultured in the presence of 0-4?μmol/l BITC with or without 10?μg/l of HGF. BITC inhibited both the basal and HGF-induced migration of MDA-MB-231 and 4T1 cells in a dose-dependent manner. In MDA-MB-231 cells, BITC reduced both basal and HGF-induced secretion and activity of urokinase-type plasminogen activator (uPA). In addition, BITC increased the protein levels of plasminogen activator inhibitor-1. HGF stimulated c-Met and Akt phosphorylation, but did not affect the phosphorylation of extracellular signal-regulated kinase-1/2 or stress-activated protein/c-jun N-terminal kinase. BITC suppressed NF-κB activity and reduced the HGF-induced phosphorylation of c-Met and Akt in a dose-dependent manner. LY294002, a specific Akt inhibitor, reduced both basal and HGF-induced uPA secretion and migration of MDA-MB-231 cells. In this study, we demonstrated that BITC profoundly inhibits the migration and invasion of MDA-MB-231 cells, which is associated with reduced uPA activity, and also that these phenomena are accompanied by the suppression of Akt signaling.</P>

Effect of the modulation of leucine zipper tumor suppressor 2 expression on proliferation of various cancer cells functions as a tumor suppressor.

Kim, Jong Myung,Song, Ji Sun,Cho, Hyun Hwa,Shin, Keun Koo,Bae, Yong Chan,Lee, Byung Ju,Jung, Jin Sup Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2011 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.346 No.1

<P>β-catenin is a component of the adhesion complex linking cadherin and actin cytoskeleton, as well as a major mediator of the Wnt pathway, which is a critical signal cascade regulating embryonic development, cell polarity, carcinogenesis, and stem cell function. NF-κB functions as a key regulator of immune responses and apoptosis, and mutations in NF-κB signaling can lead to immune diseases and cancers. We previously showed that NF-κB-mediated modulation of β-catenin/Tcf signaling is mediated by leucine zipper tumor suppressor 2 (Lzts2) and that lzts2 expression is differentially regulated in various cancer cells. Its functional significances, however, are poorly understood. We showed that NF-κB-induced modulation of β-catenin/Tcf pathway is regulated by lzts2 expression in mesenchymal stem cells (MSCs) and several cancer cells, and that NF-κB-induced lzts2 expression is differentially regulated among cancer cell types. Here, using a promoter-reporter assay and EMSA, we demonstrate that NF-κB regulates lzts2 transcription by directly binding to the lzts2 promoter, and that NF-κB-induced lzts2 transcription differs by cell types. Modulation of lzts2 expression by lentiviral techniques affected proliferation and tumorigenicity of several cancer cell lines such as breast, colon, prostate cancer, and glioma, but did not affect cisplatin sensitivity or cell migration. Our data indicate that lzts2 expression is transcriptionally regulated by NF-κB activities, and the modulation of lzts2 expression affects cell proliferation and tumor growth through the Wnt/β-catenin pathway in various cancer cell lines.</P>

Molecular characterization and transcriptional analysis of the olive flounder (Paralichthys olivaceus) YGHL1 gene in response to hypoxia and infection.

Kim, Young-Ok,Park, Eun-Mi,Moon, Ji Young,Kong, Hee Jeong,Nam, Bo-Hye,Kim, Woo-Jin,Lee, Jeong-Ho,Kim, Kyung-Kil,Lee, Sang-Jun Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2011 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.357 No.1

<P>The hypoxia-inducible gene 1, YGHL1 from olive flounder (Paralichthys olivaceus) (fYGHL1) was cloned, and its structural organization and expression profiles were determined. A 1,400?kb full-length cDNA encoding a predicted polypeptide of 91 amino acids was sequenced. The fYGHL1 gene comprises three introns, four exons, and several transcriptional elements upstream of the transcriptional start site. The mRNA transcript is expressed in almost all tissues, with high expression in the intestine and brain of normal-conditioned fish, and is expressed constitutively in early developmental stages after hatching. The mRNA expression of fYGHL1 is highly regulated by hypoxia and E. tarda infection. The expression of fYGHL1 mRNA was down regulated in the gill, spleen, intestine, and stomach of flounder under hypoxic conditions, whereas the expression level was increased in flounder embryonic cells treated with the hypoxia-mimic CoCl(2) (a HIF-1 inducer). Pathogen challenge induced fYGHL1 expression in the spleen of juvenile fish. Taken together, these results suggest that fYGHL1 is a hypoxia-related gene with potential roles in the hypoxia response mechanism as well as in defense, immune responses, growth, and regulation of reproduction.</P>