Department Of Zoology

Permanent URI for this communityhttps://kr.cup.edu.in/handle/32116/62

Browse

Now showing 1 - 20 of 165

Common geometric basis for apurinic/apyrimidinic endonuclease catalytic activity in structurally non-homologous APE1 and Endonuclease IV.
(2013) Tsutakawa, S.E.; Shin, D.S.; Mol, C.D.; Izumi, T.; Arvai, A.S.; Mantha, Anil K.; Szczesny, B.; Ivanov, I.N.; Hosfield, D.J.; Frankel, K.A.; Hitomi, K; Cunningham, R. P.; Tainer, J. A.
APE1: A Molecule of Focus with Neuroprotective and Anti-Cancer Properties
(OMICS Publishing Group, 2013) Mantha, Anil K.
Apurinic/Apyrimidinic endonuclease (APE1) is a multi-functional, central enzyme of base excision repair (BER) pathway that takes care of oxidized base damage (AP sites and strand breaks) caused by both endogenous and exogenous oxidative DNA damaging agents. In repair function, APE1 exhibits majorly abasic (AP) endonuclease activity and stable interaction(s) with BER-pathway participant proteins. Second function of APE1 is redox activation of various transcription factors (TFs e.g., c-jun, NF-kB, p53 and HIF1α) and also named as redox effector factor 1(Ref-1). In redox function, APE1 reductively activates TFs involved in regulation of gene expression for cell survival mechanisms through stable pair-wise interaction(s). Recent studies have indicated that APE1 also possesses other distinct functions such as RNA metabolism, riboendonuclease activity and protein-protein interaction for maintaining cellular homeostasis. Altered APE1 expression has been reported in various cancers and neurodegenerative diseases. Taken together such findings advocates the necessity to delineate the underlying molecular mechanism(s) for understanding its role in various biological functions, that could be translated to its application in therapeutics against human diseases like cancer, neurodegenerative diseases and other pathologies such as cardiovascular diseases.
Conserved structural chemistry for incision activity in structurally non-homologous apurinic/apyrimidinic endonuclease APE1 and endonuclease IV DNA repair enzymes
(2013) Tsutakawa, Susan E.; Shin, David S.; Mol, Clifford D.; Lzumi, Tadahide; Arwai, Andrew S.; Mantha, Anil K.; Szczesny, Bartosz; Ivanov, Ivaylo N.; Hosfield, David J.; Maiti, Buddhadev; Pique, Mike E.; Frankel, Kenneth A.; Hitomi. Kenichi; Cunnigham, Richard, P.; Mitra, Sankar; Tainer, John A.
Non-coding apurinic/apyrimidinic (AP) sites in DNA form spontaneously and as DNA base excision repair intermediates are the most common toxic and mutagenic in vivo DNA lesion. For repair,APsites must be processed by 5' AP endonucleases in initial stages of base repair. Human APE1 and bacterial Nfo represent the two conserved 5' AP endonuclease families in the biosphere; they both recognize AP sites and incise the phosphodiester backbone 5' to the lesion, yet they lack similar structures and metal ion requirements. Here, we determined and analyzed crystal structures of a 2.4 ? resolution APE1-DNA product complex with Mg2+ and a 0.92 ? Nfo with three metal ions. Structural and biochemical comparisons of these two evolutionarily distinct enzymes characterize keyAPE1catalytic residues that are potentially functionally similar to Nfo active site components, as further tested and supported by computational analyses. We observe a magnesium-water cluster in the APE1 active site, with only Glu-96 forming the direct protein coordination to the Mg2+. Despite differences in structure and metal requirements of APE1 and Nfo, comparison of their active site structures surprisingly reveals strong geometric conservation of the catalytic reaction, with APE1 catalytic side chains positioned analogously to Nfo metal positions, suggesting surprising functional equivalence between Nfo metal ions and APE1 residues. The finding that APE1 residues are positioned to substitute for Nfo metal ions is supported by the impact of mutations on activity. Collectively, the results illuminate the activities of residues, metal ions, and active site features for abasic site endonucleases.
APE1/Ref-1 as an emerging therapeutic target for various human diseases: Phytochemical modulation of its functions
(Nature Publishing Group, 2014) Thakur, Shweta; Sarkar, Bibekananda; Cholia, Ravi P.; Gautam, Nandini; Dhiman, Monisha; Mantha, Anil K.
Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional enzyme involved in the base excision repair (BER) pathway, which repairs oxidative base damage caused by endogenous and exogenous agents. APE1 acts as a reductive activator of many transcription factors (TFs) and has also been named redox effector factor 1, Ref-1. For example, APE1 activates activator protein-1, nuclear factor kappa B, hypoxia-inducible factor 1a, paired box gene 8, signal transducer activator of transcription 3 and p53, which are involved in apoptosis, inflammation, angiogenesis and survival pathways. APE1/Ref-1 maintains cellular homeostasis (redox) via the activation of TFs that regulate various physiological processes and that crosstalk with redox balancing agents (for example, thioredoxin, catalase and superoxide dismutase) by controlling levels of reactive oxygen and nitrogen species. The efficiency of APE1/Ref-1's function(s) depends on pairwise interaction with participant protein(s), the functions regulated by APE1/Ref-1 include the BER pathway, TFs, energy metabolism, cytoskeletal elements and stress-dependent responses. Thus, APE1/Ref-1 acts as a 'hub-protein' that controls pathways that are important for cell survival. In this review, we will discuss APE1/Ref-1's versatile nature in various human etiologies, including neurodegeneration, cancer, cardiovascular and other diseases that have been linked with alterations in the expression, subcellular localization and activities of APE/Ref-1. APE1/Ref-1 can be targeted for therapeutic intervention using natural plant products that modulate the expression and functions of APE1/Ref-1. In addition, studies focusing on translational applications based on APE1/Ref-1-mediated therapeutic interventions are discussed. ? 2014 KSBMB.
DNA Repair and Redox Activities and Inhibitors of Apurinic/ Apyrimidinic Endonuclease 1/Redox Effector Factor 1 (APE1/Ref-1): A Comparative Analysis and Their Scope and Limitations toward Anticancer Drug Development
(ACS Publications, 2014) Kaur, Gagandeep; Cholia, Ravi P.; Mantha, Anil K.; Kumar, Raj
The apurinic/apyrimidinic endonuclease 1/redox effector factor 1 (APE1/Ref-1) is a multifunctional enzyme involved in DNA repair and activation of transcription factors through its redox function. The evolutionarily conserved C- and N-termini are involved in these functions independently. It is also reported that the activity of APE1/Ref-1 abruptly increases several-fold in various human cancers. The control over the outcomes of these two functions is emerging as a new strategy to combine enhanced DNA damage and chemotherapy in order to tackle the major hurdle of increased cancer cell growth and proliferation. Studies have targeted these two domains individually for the design and development of inhibitors for APE1/Ref-1. Here, we have made, for the first time, an attempt at a comparative analysis of APE1/Ref-1 inhibitors that target both DNA repair and redox activities simultaneously. We further discuss their scope and limitations with respect to the development of potential anticancer agents.
A short review on the implications of base excision repair pathway for neurons: Relevance to neurodegenerative diseases
(Elsevier, 2014) Mantha, Anil K.; Sarkar, Bibekananda; Tell, Gianluca
Oxidative DNA damage results from the attack by reactive oxygen and nitrogen species (ROS/RNS) on human genome. This includes base modifications such as oxidized bases, abasic (AP) sites, and single-strand breaks (SSBs), all of which are repaired by the base excision repair (BER) pathway, one among the six known repair pathways. BER-pathway in mammalian cells involves several evolutionarily conserved proteins and is also linked to genome replication and transcription. The BER-pathway enzymes, namely, DNA glycosylases (DGs) and the end-processing proteins such as abasic endonuclease (APE1), form complexes with downstream repair enzymes via protein-protein and DNA-protein interactions. An emerging concept for BER proteins is their involvement in non-canonical functions associated to RNA metabolism, which is opening new interesting perspectives. Various mechanisms that are underlined in maintaining neuronal cell genome integrity are identified, but are inconclusive in providing protection against oxidative damage in neurodegenerative disorders, main emphasis is given towards the role played by the proteins of BER-pathway that is discussed. In addition, mechanisms of action of BER-pathway in nuclear vs. mitochondria as well as the non-canonical functions are discussed in connection to human neurodegenerative diseases. ? 2013 ? Elsevier B.V. and Mitochondria Research Society. All rights reserved.
Essential oils and their constituents as anticancer agents: A mechanistic view
(Hindawi Publishing Corporation, 2014) Gautam, Nandini; Mantha, Anil K.; Mittal, Sunil
Exploring natural plant products as an option to find new chemical entities as anticancer agents is one of the fastest growing areas of research. Recently, in the last decade, essential oils (EOs) have been under study for their use in cancer therapy and the present review is an attempt to collect and document the available studies indicating EOs and their constituents as anticancer agents. This review enlists nearly 130 studies of EOs from various plant species and their constituents that have been studied so far for their anticancer potential and these studies have been classified as in vitro and in vivo studies for EOs and their constituents. This review also highlights in-depth various mechanisms of action of different EOs and their constituents reported in the treatment strategies for different types of cancer. The current review indicates that EOs and their constituents act by multiple pathways and mechanisms involving apoptosis, cell cycle arrest, antimetastatic and antiangiogenic, increased levels of reactive oxygen and nitrogen species (ROS/RNS), DNA repair modulation, and others to demonstrate their antiproliferative activity in the cancer cell. The effect of EOs and their constituents on tumour suppressor proteins (p53 and Akt), transcription factors (NF-B and AP-1), MAPK-pathway, and detoxification enzymes like SOD, catalase, glutathione peroxidase, and glutathione reductase has also been discussed. ? 2014 Nandini Gautam et al.
Oxidative stress and inflammation in cardiovascular diseases: Two sides of the same coin
(Springer India, 2015) Dhiman, Monisha; Thakur, Shweta; Upadhyay, Shishir; Kaur, Amandeep; Mantha, Anil K.
Globally, the major cause of long- term disability and death is an ?epidemiologic transition? from infectious diseases and malnutrition complications to non-communicable chronic diseases like cardiovascular disease (CVD), cancer and diabetes. CVD accounts for major global mortality. Imbalance due to the generation of reactive oxygen species (ROS) levels above normal baseline levels and decreased antioxidant defence reserve makes the cardiovascular system (cardiac and vascular cells) susceptible to oxidative stress and damage. Growing evidences support the notion that oxidative stress plays a crucial role in the development and progression of CVD by altering normal functions such as inactivation of nitric oxide (NO) leading to endothelial dysfunction, intracellular Ca2+overload and others. Oxidative stress also mediates inflammation through various signalling cascades such as the activation of inflammatory transcription factors (TFs) namely NF-?B, AP-1 and Nrf-1. A vicious cycle of oxidative stress-mediated inflammation and inflammation- induced oxidative stress makes the CVD-related complications worse. Therefore, it is also very important to clearly understand the role of enzymatic sources of RO mechanisms underlying pathological conditions and link between oxidative stress and inflammation during each stage of CVD. The present chapter will elucidate the role of oxidative stress and inflammation in CVD development and progression. It is important to find the remedial measures, to develop the efficient biomarkers and to design the therapeutic strategies for CVD in the near future. ? Springer India 2015.
A review on protein–protein interaction network of APE1/Ref-1 and its associated biological functions
(Wiley, 2015) Thakur, S.; Dhiman, Monisha; Tell, G.; Mantha, Anil K.
Apurinic/apyrimidinic endonuclease 1 (APE1) is a classic example of functionally variable protein. Besides its well-known role in (i) DNA repair of oxidative base damage, APE1 also plays a critical role in (ii) redox regulation of transcription factors controlling gene expression for cell survival pathways, for which it is also known as redox effector factor 1 (Ref-1), and recent evidences advocates for (iii) coordinated control of other non-canonical protein–protein interaction(s) responsible for significant biological functions in mammalian cells. The diverse functions of APE1 can be ascribed to its ability to interact with different protein partners, owing to the attainment of unfolded domains during evolution. Association of dysregulation of APE1 with various human pathologies, such as cancer, cardiovascular diseases and neurodegeneration, is attributable to its multifunctional nature, and this makes APE1 a potential therapeutic target. This review covers the important aspects of APE1 in terms of its significant protein–protein interaction(s), and this knowledge is required to understand the onset and development of human pathologies and to design or improve the strategies to target such interactions for treatment and management of various human diseases. Copyright © 2015 John Wiley & Sons, Ltd.
Ginkgolide B Revamps Neuroprotective Role of Apurinic/Apyrimidinic Endonuclease 1 and Mitochondrial Oxidative Phosphorylation Against Ab 25–35 -Induced Neurotoxicity in Human Neuroblastoma Cells
(Wiley, 2015) Kaur, Navrattan; Dhiman, Monisha; Perez-Polo, J. Regino; Mantha, Anil K.
Accumulating evidence points to roles for oxidative stress, amyloid beta (Aβ), and mitochondrial dysfunction in the pathogenesis of Alzheimer's disease (AD). In neurons, the base excision repair pathway is the predominant DNA repair (BER) pathway for repairing oxidized base lesions. Apurinic/apyrimidinic endonuclease 1 (APE1), a multifunctional enzyme with DNA repair and reduction–oxidation activities, has been shown to enhance neuronal survival after oxidative stress. This study seeks to determine 1) the effect of Aβ25–35 on reactive oxygen species (ROS)/reactive nitrogen species (RNS) levels, 2) the activities of respiratory complexes (I, III, and IV), 3) the role of APE1 by ectopic expression, and 4) the neuromodulatory role of ginkgolide B (GB; from the leaves of Ginkgo biloba). The pro-oxidant Aβ25–35 peptide treatment increased the levels of ROS/RNS in human neuroblastoma IMR-32 and SH-SY5Y cells, which were decreased after pretreatment with GB. Furthermore, the mitochondrial APE1 level was found to be decreased after treatment with Aβ25–35 up to 48 hr, and the level was increased significantly in cells pretreated with GB. The oxidative phosphorylation (OXPHOS; activities of complexes I, III, and IV) indicated that Aβ25–35 treatment decreased activities of complexes I and IV, and pretreatment with GB and ectopic APE1 expression enhanced these activities significantly compared with Aβ25–35 treatment. Our results indicate that ectopic expression of APE1 potentiates neuronal cells to overcome the oxidative damage caused by Aβ25–35. In addition, GB has been shown to modulate the mitochondrial OXPHOS against Aβ25–35-induced oxidative stress and also to regulate the levels of ROS/RNS in the presence of ectopic APE1. This study presents findings from a new point of view to improve therapeutic potential for AD via the synergistic neuroprotective role played by APE1 in combination with the phytochemical GB. © 2015 Wiley Periodicals, Inc.
Investigating regulatory signatures of human autophagy related gene 5 (ATG5) through functional in silico analysis
(Elsevier B.V., 2016) Vij, Avni; Randhawa, Rohit; Parkash, Jyoti; Changotra, Harish; Vij, A.; Randhawa, R.; Parkash, J.; Changotra, H.
Autophagy is an essential, homeostatic process which removes damaged cellular proteins and organelles for cellular renewal. ATG5, a part of E3 ubiquitin ligase-like complex (Atg12-Atg5/Atg16L1), is a key regulator involved in autophagosome formation - a crucial phase of autophagy. In this study, we used different in silico methods for comprehensive analysis of ATG5 to investigate its less explored regulatory activity. We have predicted various physico-chemical parameters and two possible transmembrane models that helped in exposing its functional regions. Twenty four PTM sites and 44 TFBS were identified which could be targeted to modulate the autophagy pathway. Furthermore, LD analysis identified 3 blocks of genotyped SNPs and 2 deleterious nsSNPs that may have damaging impact on protein function and thus could be employed for carrying genome-wide association studies. In conclusion, the information obtained in this study could be helpful for better understanding of regulatory roles of ATG5 and provides a base for its implication in population-based studies. ? 2016 Elsevier B.V.
Regulation of limited N-terminal proteolysis of APE1 in tumor via acetylation and its role in cell proliferation
(Impact Journals, 2016) Bhakat, K. K.; Sengupta, S.; Adeniyi, V. F.; Roychoudhury, S; . Nath, S.; Bellot, L. J.; Luxon, B. A.
Mammalian apurinic/apyrimidinic (AP) endonuclease 1 (APE1), a ubiquitous and multifunctional protein, plays an essential role in the repair of both endogenous and drug-induced DNA damages in the genome. Unlike its E.coli counterpart Xth, mammalian APE1 has a unique N-terminal domain and possesses both DNA damage repair and transcriptional regulatory functions. Although the overexpression of APE1 in diverse cancer types and the association of APE1 expression with chemotherapy resistance and poor prognosis are well documented, the cellular and molecular mechanisms that alter APE1 functions during tumorigenesis are largely unknown. Here, we show the presence of full-length APE1 and N-terminal truncated isoforms of APE1 in tumor tissue samples of various cancer types. However, primary tumor tissue has higher levels of acetylated APE1 (AcAPE1) as well as full-length APE1 compared to adjacent non-tumor tissue. We found that APE1 is proteolytically cleaved by an unknown serine protease at its N-terminus following residue lysine (Lys) Lys6 and/or Lys7 and after Lys27 and Lys31 or Lys32. Acetylation of these Lys residues in APE1 prevents this proteolysis. The N-terminal domain of APE1 and its acetylation are required for modulation of the expression of hundreds of genes. Importantly, we found that AcAPE1 is essential for sustained cell proliferation. Together, our study demonstrates that increased acetylation levels of APE1 in tumor cells inhibit the limited N-terminal proteolysis of APE1 and thereby maintain the functions of APE1 to promote tumor cells' sustained proliferation and survival.
Recent developments on the structure–activity relationship studies of MAO inhibitors and their role in different neurological disorders
(Royal Society of Chemistry, 2016) Kumar, Bhupinder; Sheetal; Mantha, Anil K.; Kumar, Vinod
Monoamine oxidase (MAO) enzyme catalyzes the oxidative deamination of xenobiotic and endogenous amines including many neurotransmitters. The MAO enzyme exists in two isoforms; MAO-A and MAO-B and these isoforms display considerable sequence similarity but differ in tissue distribution, inhibitor selectivity and specificity towards ligands. The altered concentration of the neurotransmitters in the brain is linked with the biochemical pathology of various neurological disorders including depression, Alzheimer's disease and Parkinson's disease. MAO inhibitors were the first antidepressants discovered but their irreversible binding to the enzyme resulted in a number of side effects including fatal food–drug interactions. The new generation MAO inhibitors, especially reversible and selective inhibitors, were less toxic and found to be effective against various neurological disorders. Now the MAO enzyme has been recognised as an important drug target and MAO-A selective inhibitors are being developed as drug candidates for the management of depression and anxiety disorders, whereas MAO-B selective inhibitors are found to be effective for the treatment of Parkinson's disease and Alzheimer's disease with a better safety profile as compared to nonselective MAO inhibitors. The current review article describes recent developments on the design, synthesis and screening of MAO inhibitors, structure–activity relationship studies, and their role in the etiology and treatment of various neurological disorders.
Elevated level of acetylation of APE1 in tumor cells modulates DNA damage repair
(Impact Journals LLC, 2016) Sengupta, S.; Mantha, Anil K.; Song, H.; Roychoudhury, S.; Nath, S.; Ray, S.; Bhakat, K.K.
Apurinic/apyrimidinic (AP) sites are frequently generated in the genome by spontaneous depurination/depyrimidination or after removal of oxidized/modified bases by DNA glycosylases during the base excision repair (BER) pathway. Unrepaired AP sites are mutagenic and block DNA replication and transcription. The primary enzyme to repair AP sites in mammalian cells is AP endonuclease (APE1), which plays a key role in this repair pathway. Although overexpression of APE1 in diverse cancer types and its association with chemotherapeutic resistance are well documented, alteration of posttranslational modification of APE1 and modulation of its functions during tumorigenesis are largely unknown. Here, we show that both classical histone deacetylase HDAC1 and NAD+-dependent deacetylase SIRT1 regulate acetylation level of APE1 and acetylation of APE1 enhances its AP-endonuclease activity both in vitro and in cells. Modulation of APE1 acetylation level in cells alters AP site repair capacity of the cell extracts in vitro. Primary tumor tissues of diverse cancer types have higher level of acetylated APE1 (AcAPE1) compared to adjacent non-tumor tissue and exhibit enhanced AP site repair capacity. Importantly, in the absence of APE1 acetylation, cells accumulate AP sites in the genome and show increased sensitivity to DNA damaging agents. Together, our study demonstrates that elevation of acetylation level of APE1 in tumor could be a novel mechanism by which cells handle the elevated levels of DNA damages in response to genotoxic stress and maintain sustained proliferation.
Human apurinic/apyrimidinic endonuclease (APE1) is acetylated at DNA damage sites in chromatin, and acetylation modulates its DNA repair activity
(American Society for Microbiology, 2016) Roychoudhury, S.; Nath, S.; Song, H.; Hegde, M.L.; Bellot, L.J.; Mantha, Anil K.; Sengupta, S.; Ray, S.; Natarajan, A.; Bhakat, K.K.
Apurinic/apyrimidinic (AP) sites, the most frequently formed DNA lesions in the genome, inhibit transcription and block replication. The primary enzyme that repairs AP sites in mammalian cells is the AP endonuclease (APE1), which functions through the base excision repair (BER) pathway. Although the mechanism by which APE1 repairs AP sites in vitro has been extensively investigated, it is largely unknown how APE1 repairs AP sites in cells. Here, we show that APE1 is acetylated (AcAPE1) after binding to the AP sites in chromatin and that AcAPE1 is exclusively present on chromatin throughout the cell cycle. Positive charges of acetylable lysine residues in the N-terminal domain of APE1 are essential for chromatin association. Acetylation-mediated neutralization of the positive charges of the lysine residues in the N-terminal domain of APE1 induces a conformational change; this in turn enhances the AP endonuclease activity of APE1. In the absence of APE1 acetylation, cells accumulated AP sites in the genome and showed higher sensitivity to DNA-damaging agents. Thus, mammalian cells, unlike Saccharomyces cerevisiae or Escherichia coli cells, require acetylation of APE1 for the efficient repair of AP sites and base damage in the genome. Our study reveals that APE1 acetylation is an integral part of the BER pathway for maintaining genomic integrity. ? 2017 Roychoudhury et al.
Indian herbs and their therapeutic potential against Alzheimer’s disease: What makes them special? Neuroprotective Effects of Phytochemicals in Neurological Disorders.
(2016) Kaur, Navrattan; Sarkar, Bibekananda; Gill, Iqbal; Kaur, S; Mittal, Sunil; Dhiman, Monisha; Padala, Prasad R; Perez-Polo ,Regino; Mantha, Anil K.
Scaffold attachment factor A (SAF-A) and Ku temporally regulate repair of radiation-induced clustered genome lesions
(Impact Journals LLC, 2016) Hegde, M.L.; Dutta, A.; Yang, C.; Mantha, Anil K.; Hegde, P.M.; Pandey, A.; Sengupta, S.; Yu, Y.; Calsou, P.; Chen, D.; Lees-Miller, S.P.; Mitra, S.
Ionizing radiation (IR) induces highly cytotoxic double-strand breaks (DSBs) and also clustered oxidized bases in mammalian genomes. Base excision repair (BER) of bi-stranded oxidized bases could generate additional DSBs as repair intermediates in the vicinity of direct DSBs, leading to loss of DNA fragments. This could be avoided if DSB repair via DNA-PK-mediated nonhomologous end joining (NHEJ) precedes BER initiated by NEIL1 and other DNA glycosylases (DGs). Here we show that DNAPK subunit Ku inhibits DGs via direct interaction. The scaffold attachment factor (SAF)-A, (also called hnRNP-U), phosphorylated at Ser59 by DNA-PK early after IR treatment, is linked to transient release of chromatin-bound NEIL1, thus preventing BER. SAF-A is subsequently dephosphorylated. Ku inhibition of DGs in vitro is relieved by unphosphorylated SAF-A, but not by the phosphomimetic Asp59 mutant. We thus propose that SAF-A, in concert with Ku, temporally regulates base damage repair in irradiated cell genome.
Cloning and characterization of a riboflavin-binding hexamerin from the larval fat body of a lepidopteran stored grain pest, Corcyra cephalonica
(Elsevier Inc., 2016) Rao, V. Venkat; Ningshen, Thuirei Jacob; Chaitanya, R. K.; Senthilkumaran, B.; Dutta-Gupta, Aparna; Rao, V.V.; Ningshen, T.J.; Chaitanya, R.K.; Senthilkumaran, B.; Dutta-Gupta, A.
In the present study, a riboflavin-binding hexamerin (RbHex) was cloned and characterized from the larval fat body of Corcyra cephalonica. The complete cDNA (2121 bp) encodes a 706-amino acid protein with a molecular mass ~ 82 kDa. Expression of RbHex 82 was predominant in fat body among larval tissues. Further, it is prominently expressed during the last instar larval development. Homology modeling and docking studies predicted riboflavin binding site of the hexamerin. Spectrofluorimetric analysis further confirmed riboflavin release from the hexamerin fraction. Quantitative RT-PCR studies demonstrated hormonal regulation of RbHex 82. 20-Hydroxyecdysone (20HE) had a stimulatory effect on its transcription whereas JH alone did not show any effect. However, JH in the presence of 20HE maintains the RbHex 82 expression which indicates the JH's role as a status quo factor. This study is the first to report the characterization of riboflavin-binding hexamerin in a lepidopteran pest. Further, the possibility of RbHex 82 as a pest control target is discussed. ? 2016 Elsevier Inc.
A microRNA switch regulates the rise in hypothalamic GnRH production before puberty
(Nature Publishing Group, 2016) Messina, Andrea; Langlet, Fanny; Chachlaki, Konstantina; Roa, Juan; Rasika, Sowmyalakshmi; Jouy, Nathalie; Gallet, Sarah; Gaytan, Francisco; Parkash, Jyoti; Tena-Sempere, Manuel; Giacobini, Paolo; Prevot, Vincent; Messina, A.; Langlet, F.; Chachlaki, K.; Roa, J.; Rasika, S.; Jouy, N.; Gallet, S.; Gaytan, F.; Parkash, J.; Tena-Sempere, M.; Giacobini, P.; Prevot, V.
A sparse population of a few hundred primarily hypothalamic neurons forms the hub of a complex neuroglial network that controls reproduction in mammals by secreting the 'master molecule' gonadotropin-releasing hormone (GnRH). Timely postnatal changes in GnRH expression are essential for puberty and adult fertility. Here we report that a multilayered microRNA-operated switch with built-in feedback governs increased GnRH expression during the infantile-to-juvenile transition and that impairing microRNA synthesis in GnRH neurons leads to hypogonadotropic hypogonadism and infertility in mice. Two essential components of this switch, miR-200 and miR-155, respectively regulate Zeb1, a repressor of Gnrh transcriptional activators and Gnrh itself, and Cebpb, a nitric oxide-mediated repressor of Gnrh that acts both directly and through Zeb1, in GnRH neurons. This alteration in the delicate balance between inductive and repressive signals induces the normal GnRH-fuelled run-up to correct puberty initiation, and interfering with this process disrupts the neuroendocrine control of reproduction. ? 2016 Nature Publishing Group. All rights reserved.
Phytochemical Ginkgolide B Attenuates Amyloid-␤ 1 - 42 Induced Oxidative Damage and Altered Cellular Responses in Human Neuroblastoma SH-SY5Y Cells
(IOS Press, 2017) Gill, Iqbal; Kaur, Sukhchain; Kaur, Navrattan; Dhiman, Monisha; Mantha, Anil K.
Oxidative stress is an upsurge in reactive oxygen/nitrogen species (ROS/RNS), which aggravates damage to cellular components viz. lipids, proteins, and nucleic acids resulting in impaired cellular functions and neurological pathologies including Alzheimer's disease (AD). In the present study, we have examined amyloid-β (Aβ)-induced oxidative stress responses, a major cause for AD, in the undifferentiated and differentiated human neuroblastoma SH-SY5Y cells. Aβ1-42-induced oxidative damage was evaluated on lipids by lipid peroxidation; proteins by protein carbonyls; antioxidant status by SOD and GSH enzyme activities; and DNA and RNA damage levels by evaluating the number of AP sites and 8-OHG base damages produced. In addition, the neuro-protective role of the phytochemical ginkgolide B (GB) in countering Aβ1-42-induced oxidative stress was assessed. We report that the differentiated cells are highly vulnerable to Aβ1-42-induced oxidative stress events as exerted by the deposition of Aβ in AD. Results of the current study suggest that the pre-treatment of GB, followed by Aβ1-42 treatment for 24 h, displayed neuro-protective potential, which countered Aβ1-42-induced oxidative stress responses in both undifferentiated and differentiated SH-SY5Y neuronal cells by: 1) hampering production of ROS and RNS; 2) reducing lipid peroxidation; 3) decreasing protein carbonyl content; 4) restoring antioxidant activities of SOD and GSH enzymes; and 5) maintaining genome integrity by reducing the oxidative DNA and RNA base damages. In conclusion, Aβ1-42 induces oxidative damage to the cellular biomolecules, which are associated with AD pathology, and are protected by the pre-treatment of GB against Aβ-toxicity. Taken together, this study advocates for phytochemical-based therapeutic interventions against AD.