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Schrift GL, Waldron TT, Timmons MA, Ramaswamy S, Kearney WR, Murphy KP. Molecular basis for nucleotide-binding specificity: role of the exocyclic amino group "N2" in recognition by a guanylyl-ribonuclease. J Mol Biol 2005; 355:72-84. [PMID: 16300786 DOI: 10.1016/j.jmb.2005.10.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 10/10/2005] [Accepted: 10/10/2005] [Indexed: 11/18/2022]
Abstract
Proteins interact with nucleotides to perform a multitude of functions within cells. These interactions are highly specific; however, the molecular basis for this specificity is not well understood. To identify factors critical for protein-guanine nucleotide recognition the binding of two closely related ligands, guanosine 3'-monophosphate (3'GMP) and inosine 3'-monophosphate (3'IMP), to Ribonuclease Sa (RNase Sa), a small, guanylyl-endoribonuclease from Streptomyces aureofaciens, was compared using isothermal titration calorimetry, NMR, X-ray crystallography and molecular dynamics simulations. This comparison has allowed for the determination of the contribution of the exocyclic amino group "N2" of the guanine base to nucleotide binding specificity. Calorimetric measurements indicate that RNase Sa has a higher affinity for 3'GMP (K=(1.5+/-0.2)x10(5)) over 3'IMP (K=(3.1+/-0.2)x10(4)) emphasizing the importance of N2 as a key determinant of RNase Sa guanine binding specificity. This result was unexpected as the published structural data for RNase Sa in complex with 3'GMP showed only a potential long-range interaction (>3.3A) between N2 and the side-chain of Glu41 of RNase Sa. The observed difference in affinity is largely due to a reduction in the favorable enthalpy change by 10 kJ/mol for 3'IMP binding as compared to 3'GMP that is accompanied by a significant difference in the heat capacity changes observed for binding the two ligands. To aid interpretation of the calorimetric data, the first crystal structure of a small, guanylyl ribonuclease bound to 3'IMP was determined to 2.0 A resolution. This structure has revealed small yet unexpected changes in the ligand conformation and differences in the conformations of the side-chains contacting the sugar and phosphate moieties as compared to the 3'GMP complex. The structural data suggest the less favorable enthalpy change is due to an overall lengthening of the contacts between RNase Sa and 3'IMP as compared to 3'GMP. The long-range interaction between N2 and Glu41 is critical for positioning of the nucleotide in the binding cleft for optimal contact formation. Thus, combined, the data demonstrate how a long-range interaction can have a significant impact on nucleotide binding affinity and energetics.
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Ramaswamy S. Pubertal augmentation in juvenile rhesus monkey testosterone production induced by invariant gonadotropin stimulation is inhibited by estrogen. J Clin Endocrinol Metab 2005; 90:5866-75. [PMID: 16030161 DOI: 10.1210/jc.2005-0092] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Experimental and epidemiological studies have indicated the adverse impact of changing estrogen [17beta-estradiol (E2)] milieu or of endocrine disrupters on testis development and function. OBJECTIVE This study examines the direct impact of elevated E2 levels on gonadotropin-induced pubertal testis development and function in the primate. DESIGN Juvenile monkeys, which have characteristically little endogenous gonadotropin secretion, were treated with pulsatile infusions of recombinant monkey (rm) FSH (rmFSH) and LH (rmLH) in the presence (experiment 1, approximately 100 pg/ml for about 15-20 wk; experiment 2, approximately 400 pg/ml for about 5 wk) or absence (control group) of elevated E2 in the circulation. Changes in circulating concentrations of E2, gonadotropins, testosterone (T), and inhibin B were monitored throughout the study. The number of Leydig cells per testis was determined after immunohistochemical staining for 3-beta hydroxysteroid dehydrogenase in experiment 2. RESULTS Exogenous gonadotropin treatment produced physiological, episodic, and similar circulating concentrations of FSH and LH in both groups. Exposure to approximately 100 pg/ml of E2 appeared to blunt testicular T production. Exposure to approximately 400 pg/ml of E2 led to a significant (approximately 75%) inhibition of T production together with a marked (approximately 40%) decrease in Leydig cell numbers per testis and a notable inhibition in the growth of the testis. In contrast, E2 exposure had little effect on inhibin B production. CONCLUSIONS The direct testicular impact of elevated E2 is on Leydig cell number, T production, and testicular growth, but not on inhibin B production. This experimental paradigm provides a powerful primate model for the examination of the direct impact of E2 or other endocrine disrupters on pubertal testicular development.
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Parales RE, Huang R, Yu CL, Parales JV, Lee FKN, Lessner DJ, Ivkovic-Jensen MM, Liu W, Friemann R, Ramaswamy S, Gibson DT. Purification, characterization, and crystallization of the components of the nitrobenzene and 2-nitrotoluene dioxygenase enzyme systems. Appl Environ Microbiol 2005; 71:3806-14. [PMID: 16000792 PMCID: PMC1169052 DOI: 10.1128/aem.71.7.3806-3814.2005] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein components of the 2-nitrotoluene (2NT) and nitrobenzene dioxygenase enzyme systems from Acidovorax sp. strain JS42 and Comamonas sp. strain JS765, respectively, were purified and characterized. These enzymes catalyze the initial step in the degradation of 2-nitrotoluene and nitrobenzene. The identical shared reductase and ferredoxin components were monomers of 35 and 11.5 kDa, respectively. The reductase component contained 1.86 g-atoms iron, 2.01 g-atoms sulfur, and one molecule of flavin adenine dinucleotide per monomer. Spectral properties of the reductase indicated the presence of a plant-type [2Fe-2S] center and a flavin. The reductase catalyzed the reduction of cytochrome c, ferricyanide, and 2,6-dichlorophenol indophenol. The ferredoxin contained 2.20 g-atoms iron and 1.99 g-atoms sulfur per monomer and had spectral properties indicative of a Rieske [2Fe-2S] center. The ferredoxin component could be effectively replaced by the ferredoxin from the Pseudomonas sp. strain NCIB 9816-4 naphthalene dioxygenase system but not by that from the Burkholderia sp. strain LB400 biphenyl or Pseudomonas putida F1 toluene dioxygenase system. The oxygenases from the 2-nitrotoluene and nitrobenzene dioxygenase systems each had spectral properties indicating the presence of a Rieske [2Fe-2S] center, and the subunit composition of each oxygenase was an alpha(3)beta(3) hexamer. The apparent K(m) of 2-nitrotoluene dioxygenase for 2NT was 20 muM, and that for naphthalene was 121 muM. The specificity constants were 7.0 muM(-1) min(-1) for 2NT and 1.2 muM(-1) min(-1) for naphthalene, indicating that the enzyme is more efficient with 2NT as a substrate. Diffraction-quality crystals of the two oxygenases were obtained.
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Ferraro DJ, Gakhar L, Ramaswamy S. Rieske business: structure-function of Rieske non-heme oxygenases. Biochem Biophys Res Commun 2005; 338:175-90. [PMID: 16168954 DOI: 10.1016/j.bbrc.2005.08.222] [Citation(s) in RCA: 249] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2005] [Accepted: 08/30/2005] [Indexed: 11/20/2022]
Abstract
Rieske non-heme iron oxygenases (RO) catalyze stereo- and regiospecific reactions. Recently, an explosion of structural information on this class of enzymes has occurred in the literature. ROs are two/three component systems: a reductase component that obtains electrons from NAD(P)H, often a Rieske ferredoxin component that shuttles the electrons and an oxygenase component that performs catalysis. The oxygenase component structures have all shown to be of the alpha3 or alpha3beta3 types. The transfer of electrons happens from the Rieske center to the mononuclear iron of the neighboring subunit via a conserved aspartate, which is shown to be involved in gating electron transport. Molecular oxygen has been shown to bind side-on in naphthalene dioxygenase and a concerted mechanism of oxygen activation and hydroxylation of the ring has been proposed. The orientation of binding of the substrate to the enzyme is hypothesized to control the substrate selectivity and regio-specificity of product formation.
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Gupta PB, Kuperwasser C, Brunet JP, Ramaswamy S, Kuo WL, Gray JW, Naber SP, Weinberg RA. The melanocyte differentiation program predisposes to metastasis after neoplastic transformation. Nat Genet 2005; 37:1047-54. [PMID: 16142232 PMCID: PMC1694635 DOI: 10.1038/ng1634] [Citation(s) in RCA: 339] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Accepted: 07/12/2005] [Indexed: 11/09/2022]
Abstract
The aggressive clinical behavior of melanoma suggests that the developmental origins of melanocytes in the neural crest might be relevant to their metastatic propensity. Here we show that primary human melanocytes, transformed using a specific set of introduced genes, form melanomas that frequently metastasize to multiple secondary sites, whereas human fibroblasts and epithelial cells transformed using an identical set of genes generate primary tumors that rarely do so. Notably, these melanomas have a metastasis spectrum similar to that observed in humans with melanoma. These observations indicate that part of the metastatic proclivity of melanoma is attributable to lineage-specific factors expressed in melanocytes and not in other cell types analyzed. Analysis of microarray data from human nevi shows that the expression pattern of Slug, a master regulator of neural crest cell specification and migration, correlates with those of other genes that are important for neural crest cell migrations during development. Moreover, Slug is required for the metastasis of the transformed melanoma cells. These findings indicate that melanocyte-specific factors present before neoplastic transformation can have a pivotal role in governing melanoma progression.
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206
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Lee K, Friemann R, Parales JV, Gibson DT, Ramaswamy S. Purification, crystallization and preliminary X-ray diffraction studies of the three components of the toluene 2,3-dioxygenase enzyme system. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:669-72. [PMID: 16511124 PMCID: PMC1952458 DOI: 10.1107/s1744309105017549] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 06/03/2005] [Indexed: 05/06/2023]
Abstract
Pseudomonas putida F1 can grow with toluene as its sole source of carbon and energy. The initial reaction of the degradation of toluene is catalyzed by a three-component toluene dioxygenase enzyme system consisting of a reductase (ReductaseTOL), a ferredoxin (FerredoxinTOL) and a Rieske non-heme iron dioxygenase (OxygenaseTOL). The three components and the apoenzyme of the dioxygenase (apo-OxygenaseTOL) were overexpressed, purified and crystallized. ReductaseTOL diffracts to 1.8 A and belongs to space group P4(1)2(1)2, with unit-cell parameters a = b = 77.1, c = 156.3 A. Ferredoxin(TOL) diffracts to 1.2 A and belongs to space group P2(1), with unit-cell parameters a = 30.5, b = 52.0, c = 30.95 A, beta = 113.7 degrees. Apo-OxygenaseTOL and OxygenaseTOL diffract to 3.2 A and belong to space group P4(3)32, with unit-cell parameters a = 235.9 A and a = 234.5 A, respectively.
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Garraway LA, Widlund HR, Rubin MA, Getz G, Berger AJ, Ramaswamy S, Beroukhim R, Milner DA, Granter SR, Du J, Lee C, Wagner SN, Li C, Golub TR, Rimm DL, Meyerson ML, Fisher DE, Sellers WR. Integrative genomic analyses identify MITF as a lineage survival oncogene amplified in malignant melanoma. Nature 2005; 436:117-22. [PMID: 16001072 DOI: 10.1038/nature03664] [Citation(s) in RCA: 1087] [Impact Index Per Article: 57.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Accepted: 04/19/2005] [Indexed: 11/09/2022]
Abstract
Systematic analyses of cancer genomes promise to unveil patterns of genetic alterations linked to the genesis and spread of human cancers. High-density single-nucleotide polymorphism (SNP) arrays enable detailed and genome-wide identification of both loss-of-heterozygosity events and copy-number alterations in cancer. Here, by integrating SNP array-based genetic maps with gene expression signatures derived from NCI60 cell lines, we identified the melanocyte master regulator MITF (microphthalmia-associated transcription factor) as the target of a novel melanoma amplification. We found that MITF amplification was more prevalent in metastatic disease and correlated with decreased overall patient survival. BRAF mutation and p16 inactivation accompanied MITF amplification in melanoma cell lines. Ectopic MITF expression in conjunction with the BRAF(V600E) mutant transformed primary human melanocytes, and thus MITF can function as a melanoma oncogene. Reduction of MITF activity sensitizes melanoma cells to chemotherapeutic agents. Targeting MITF in combination with BRAF or cyclin-dependent kinase inhibitors may offer a rational therapeutic avenue into melanoma, a highly chemotherapy-resistant neoplasm. Together, these data suggest that MITF represents a distinct class of 'lineage survival' or 'lineage addiction' oncogenes required for both tissue-specific cancer development and tumour progression.
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209
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Alvarez JV, Febbo PG, Ramaswamy S, Loda M, Richardson A, Frank DA. Identification of a genetic signature of activated signal transducer and activator of transcription 3 in human tumors. Cancer Res 2005; 65:5054-62. [PMID: 15958548 DOI: 10.1158/0008-5472.can-04-4281] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that is activated in diverse human tumors and may play a direct role in malignant transformation. However, the full complement of target genes that STAT3 regulates to promote oncogenesis is not known. We created a system to express a constitutively active form of STAT3, STAT3-C, in mouse fibroblasts and used it to identify STAT3 targets. We showed that a subset of these targets, which include transcription factors regulating cell growth, survival, and differentiation, are coexpressed in a range of human tumors. Using immunohistochemical staining of tissue microarrays, we showed that these targets are enriched in breast and prostate tumors harboring activated STAT3. Finally, we showed that STAT3 is required for the expression of these genes in a breast cancer cell line. Taken together, these results identify a cohort of STAT3 targets that may mediate its role in oncogenesis.
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210
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Karlsson A, Parales JV, Parales RE, Gibson DT, Eklund H, Ramaswamy S. NO binding to naphthalene dioxygenase. J Biol Inorg Chem 2005; 10:483-9. [PMID: 15942729 DOI: 10.1007/s00775-005-0657-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Accepted: 04/26/2005] [Indexed: 11/28/2022]
Abstract
Nitric oxide (NO) is commonly used as an analogue for dioxygen in structural and spectroscopic studies of oxygen binding and oxygen activation. In this study, crystallographic structures of naphthalene dioxygenase (NDO) in complex with nitric oxide are reported. In the presence of the aromatic substrate indole, NO is bound end-on to the active-site mononuclear iron of NDO. The structural observations correlate well with spectroscopic measurements of NO binding to NDO in solution. However, the end-on binding of NO is in contrast to the recently reported structure of oxygen to the active-site iron of NDO that binds side-on. While NO is a good oxygen analogue with many similarities to O(2), the different binding mode of NO to the active-site iron atom leads to different mechanistic implications. Hence, caution needs to be used in extrapolating NO as an analogue to O(2) binding.
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211
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212
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Friemann R, Ivkovic-Jensen MM, Lessner DJ, Yu CL, Gibson DT, Parales RE, Eklund H, Ramaswamy S. Structural insight into the dioxygenation of nitroarene compounds: the crystal structure of nitrobenzene dioxygenase. J Mol Biol 2005; 348:1139-51. [PMID: 15854650 DOI: 10.1016/j.jmb.2005.03.052] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 03/11/2005] [Accepted: 03/17/2005] [Indexed: 12/01/2022]
Abstract
Nitroaromatic compounds are used extensively in many industrial processes and have been released into the environment where they are considered environmental pollutants. Nitroaromatic compounds, in general, are resistant to oxidative attack due to the electron-withdrawing nature of the nitro groups and the stability of the benzene ring. However, the bacterium Comamonas sp. strain JS765 can grow with nitrobenzene as a sole source of carbon, nitrogen and energy. Biodegradation is initiated by the nitrobenzene dioxygenase (NBDO) system. We have determined the structure of NBDO, which has a hetero-hexameric structure similar to that of several other Rieske non-heme iron dioxygenases. The catalytic subunit contains a Rieske iron-sulfur center and an active-site mononuclear iron atom. The structures of complexes with substrates nitrobenzene and 3-nitrotoluene reveal the structural basis for its activity with nitroarenes. The substrate pocket contains an asparagine residue that forms a hydrogen bond to the nitro-group of the substrate, and orients the substrate in relation to the active-site mononuclear iron atom, positioning the molecule for oxidation at the nitro-substituted carbon.
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Abstract
The recent sequencing of the human genome, coupled with advances in biotechnology, is enabling the comprehensive molecular "profiling" of human tissues. In particular, DNA microarrays are powerful tools for obtaining global views of human tumor gene expression. Complex information from tumor "expression profiling" studies can, in turn, be used to create novel molecular cancer diagnostics. We discuss the utility of DNA microarray-based tumor profiling in clinical cancer research, highlight some important recent studies, and identify future avenues of research in this evolving field.
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214
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Du J, Widlund HR, Horstmann MA, Ramaswamy S, Ross K, Huber WE, Nishimura EK, Golub TR, Fisher DE. Critical role of CDK2 for melanoma growth linked to its melanocyte-specific transcriptional regulation by MITF. Cancer Cell 2004; 6:565-76. [PMID: 15607961 DOI: 10.1016/j.ccr.2004.10.014] [Citation(s) in RCA: 301] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2004] [Revised: 09/14/2004] [Accepted: 10/06/2004] [Indexed: 10/26/2022]
Abstract
The genomic organization of the CDK2 gene, which overlaps the melanocyte-specific gene SILV/PMEL17, poses an interesting regulatory challenge. We show that, despite its ubiquitous expression, CDK2 exhibits tissue-specific regulation by the essential melanocyte lineage transcription factor MITF. In addition, functional studies revealed this regulation to be critical for maintaining CDK2 kinase activity and growth of melanoma cells. Expression levels of MITF and CDK2 are tightly correlated in primary melanoma specimens and predict susceptibility to the CDK2 inhibitor roscovitine. CDK2 depletion suppressed growth and cell cycle progression in melanoma, but not other cancers, corroborating previous results. Collectively, these data indicate that CDK2 activity in melanoma is largely maintained at the transcriptional level by MITF, and unlike other malignancies, it may be a suitable drug target in melanoma.
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215
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Thulasimani M, Ramaswamy S. Some additional points on the obstetric perspective of epilepsy. Am J Obstet Gynecol 2004; 191:2174; author reply 2175. [PMID: 15592309 DOI: 10.1016/j.ajog.2004.06.116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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216
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Ramaswamy S, Hovis J. Discriminant analysis of clinical color vision tests and color related tasks. J Vis 2004. [DOI: 10.1167/4.11.77] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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217
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Ramaswamy S, Pohl CR, Marshall GR, Plant TM. A switch from continuous to episodic testicular testosterone release in response to pulsatile LH stimulation in juvenile rhesus monkeys (Macaca mulatta). J Endocrinol 2004; 183:61-8. [PMID: 15525574 DOI: 10.1677/joe.1.05809] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This study examined the ontogeny of the testicular testosterone response to precocious pulsatile LH stimulation in the juvenile rhesus monkey. LH stimulation was achieved with an i.v. infusion (one pulse every 3 h) of either single-chain human (sch)LH, administered alone or in combination with recombinant human (rh)FSH, or recombinant monkey (rm)LH in combination with rmFSH. Homologous gonadotropin treatment resulted in an adult profile of circulating mLH concentrations. The schLH infusions produced a similar pulsatile pattern in circulating LH with peak concentrations of approximately 5 IU/l. Although a robust testicular testosterone response was observed after 24 h of intermittent LH stimulation, surprisingly testosterone release at this time was continuous. The apulsatile mode of testosterone secretion, however, did not persist, and a switch to an unequivocal episodic mode of secretion, comparable to that observed in adult monkeys, occurred by day 4 of LH stimulation. FSH did not influence the pattern of the testosterone response. We conclude from these findings that progenitor Leydig cells in the primate testis are able to respond rapidly to a physiological LH stimulus. While the cell biology underlying the switch from a continuous to a pulsatile mode of testosterone secretion remains unclear, we suggest that this phenomenon may be related to the hypothesis that episodic testosterone secretion is required for the operation of the neuroendocrine axis governing testicular function.
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218
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Yang J, Mani SA, Donaher JL, Ramaswamy S, Itzykson RA, Come C, Savagner P, Gitelman I, Richardson A, Weinberg RA. Twist, a master regulator of morphogenesis, plays an essential role in tumor metastasis. Cell 2004; 117:927-39. [PMID: 15210113 DOI: 10.1016/j.cell.2004.06.006] [Citation(s) in RCA: 2891] [Impact Index Per Article: 144.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Revised: 03/01/2004] [Accepted: 05/03/2004] [Indexed: 12/12/2022]
Abstract
Metastasis is a multistep process during which cancer cells disseminate from the site of primary tumors and establish secondary tumors in distant organs. In a search for key regulators of metastasis in a murine breast tumor model, we have found that the transcription factor Twist, a master regulator of embryonic morphogenesis, plays an essential role in metastasis. Suppression of Twist expression in highly metastatic mammary carcinoma cells specifically inhibits their ability to metastasize from the mammary gland to the lung. Ectopic expression of Twist results in loss of E-cadherin-mediated cell-cell adhesion, activation of mesenchymal markers, and induction of cell motility, suggesting that Twist contributes to metastasis by promoting an epithelial-mesenchymal transition (EMT). In human breast cancers, high level of Twist expression is correlated with invasive lobular carcinoma, a highly infiltrating tumor type associated with loss of E-cadherin expression. These results establish a mechanistic link between Twist, EMT, and tumor metastasis.
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MESH Headings
- Animals
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Cadherins/metabolism
- Carcinoma, Lobular/genetics
- Carcinoma, Lobular/metabolism
- Carcinoma, Lobular/pathology
- Cell Line
- Cell Line, Tumor
- Cell Movement
- Epithelial Cells/cytology
- Epithelial Cells/metabolism
- Female
- Gene Expression Regulation, Neoplastic
- Humans
- Luciferases/metabolism
- Lung Neoplasms/secondary
- Mammary Neoplasms, Experimental/genetics
- Mammary Neoplasms, Experimental/metabolism
- Mammary Neoplasms, Experimental/pathology
- Mesoderm
- Mice
- Mice, Inbred BALB C
- Morphogenesis
- Myogenic Regulatory Factors/antagonists & inhibitors
- Neoplasm Invasiveness
- Neoplasm Metastasis
- Neoplasm Transplantation
- Nuclear Proteins/antagonists & inhibitors
- Nuclear Proteins/metabolism
- Organ Size
- RNA, Messenger/metabolism
- RNA, Small Interfering/metabolism
- Repressor Proteins
- Transcription Factors/metabolism
- Twist-Related Protein 1
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LeBrun LA, Park DH, Ramaswamy S, Plapp BV. Participation of histidine-51 in catalysis by horse liver alcohol dehydrogenase. Biochemistry 2004; 43:3014-26. [PMID: 15023053 DOI: 10.1021/bi036103m] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Histidine-51 in horse liver alcohol dehydrogenase (ADH) is part of a hydrogen-bonded system that appears to facilitate deprotonation of the hydroxyl group of water or alcohol ligated to the catalytic zinc. The contribution of His-51 to catalysis was studied by characterizing ADH with His-51 substituted with Gln (H51Q). The steady-state kinetic constants for ethanol oxidation and acetaldehyde reduction at pH 8 are similar for wild-type and H51Q enzymes. In contrast, the H51Q substitution significantly shifts the pH dependencies for steady-state and transient reactions and decreases by 11-fold the rate constant for the transient oxidation of ethanol at pH 8. Modest substrate deuterium isotope effects indicate that hydride transfer only partially limits the transient oxidation and turnover. Transient data show that the H51Q substitution significantly decreases the rate of isomerization of the enzyme-NAD(+) complex and becomes a limiting step for ethanol oxidation. Isomerization of the enzyme-NAD(+) complex is rate limiting for acetaldehyde reduction catalyzed by the wild-type enzyme, but release of alcohol is limiting for the H51Q enzyme. X-ray crystallography of doubly substituted His51Gln:Lys228Arg ADH complexed with NAD(+) and 2,3- or 2,4-difluorobenzyl alcohol shows that Gln-51 isosterically replaces histidine in interactions with the nicotinamide ribose of the coenzyme and that Arg-228 interacts with the adenosine monophosphate of the coenzyme without affecting the protein conformation. The difluorobenzyl alcohols bind in one conformation. His-51 participates in, but is not essential for, proton transfers in the mechanism.
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Ramaswamy S, Gupta M, Goel A, Aaltosalmi U, Kataja M, Koponen A, Ramarao B. The 3D structure of fabric and its relationship to liquid and vapor transport. Colloids Surf A Physicochem Eng Asp 2004. [DOI: 10.1016/j.colsurfa.2004.04.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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222
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Hoy JA, Kundu S, Trent JT, Ramaswamy S, Hargrove MS. The Crystal Structure of Synechocystis Hemoglobin with a Covalent Heme Linkage. J Biol Chem 2004; 279:16535-42. [PMID: 14736872 DOI: 10.1074/jbc.m313707200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The x-ray crystal structure of Synechocystis hemoglobin has been solved to a resolution of 1.8 A. The conformation of this structure is surprisingly different from that of the previously reported solution structure, probably due in part to a covalent linkage between the heme 2-vinyl and His117 that is present in the crystal structure but not in the structure solved by NMR. Synechocystis hemoglobin is a hexacoordinate hemoglobin in which the heme iron is coordinated by both the proximal and distal histidines. It is also a member of the "truncated hemoglobin" family that is much shorter in primary structure than vertebrate and plant hemoglobins. In contrast to other truncated hemoglobins, the crystal structure of Synechocystis hemoglobin displays no "ligand tunnel" and shows that several important amino acid side chains extrude into the solvent instead of residing inside the heme pocket. The stereochemistry of hexacoordination is compared with other hexacoordinate hemoglobins and cytochromes in an effort to illuminate factors contributing to ligand affinity in hexacoordinate hemoglobins.
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Sivasanker M, Reddy PMK, Shashindran CH, Ramaswamy S. Formalin assay parameters differ in confirming the antinociceptive mechanism of domperidone in mice. INDIAN JOURNAL OF EXPERIMENTAL BIOLOGY 2004; 42:429-31. [PMID: 15088695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Domperidone, a prokinetic drug with minimal extrapyramidal side-effects was investigated for its antinociceptive response in mice using formalin assay procedure. Two parameters namely the pain score and the time spent by the animal in licking/biting the formalin injected paw were considered. Domperidone (1, 2.5 or 5 mg/kg; ip) injected 15 min prior to formalin effectively reduced the pain score bringing it to zero at the 15th minute and was also effective till 30 min but to a lesser degree. This effect of domperidone (2.5 mg/kg) was significantly attenuated in naloxone pretreated mice indicating a partial role for opioid pathways. In the other parameter i.e. time spent in licking/biting, domperidone in all the doses employed failed to modify significantly the same by the animal in the early phase. In contrast, a dose related inhibition of the time spent was recorded in the late phase. Besides, a trend towards the enhancement of the inhibitory effect of domperidone (2.5 mg/kg) in the late phase was noticed in naloxone pretreated mice. Possibly, the peripheral analgesic mechanisms may play a role in this response since the late phase was considered akin to inflammation. The results confirm the antinociceptive effect of domperidone and suggest that caution be exercised while selecting the parameters when formalin assay is employed.
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Wang ZC, Lin M, Wei LJ, Li C, Miron A, Lodeiro G, Harris L, Ramaswamy S, Tanenbaum DM, Meyerson M, Iglehart JD, Richardson A. Loss of heterozygosity and its correlation with expression profiles in subclasses of invasive breast cancers. Cancer Res 2004; 64:64-71. [PMID: 14729609 DOI: 10.1158/0008-5472.can-03-2570] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Gene expression array profiles identify subclasses of breast cancers with different clinical outcomes and different molecular features. The present study attempted to correlate genomic alterations (loss of heterozygosity; LOH) with subclasses of breast cancers having distinct gene expression signatures. Hierarchical clustering of expression array data from 89 invasive breast cancers identified four major expression subclasses. Thirty-four of these cases representative of the four subclasses were microdissected and allelotyped using genome-wide single nucleotide polymorphism detection arrays (Affymetrix, Inc.). LOH was determined by comparing tumor and normal single nucleotide polymorphism allelotypes. A newly developed statistical tool was used to determine the chromosomal regions of frequent LOH. We found that breast cancers were highly heterogeneous, with the proportion of LOH ranging widely from 0.3% to >60% of heterozygous markers. The most common sites of LOH were on 17p, 17q, 16q, 11q, and 14q, sites reported in previous LOH studies. Signature LOH events were discovered in certain expression subclasses. Unique regions of LOH on 5q and 4p marked a subclass of breast cancers with "basal-like" expression profiles, distinct from other subclasses. LOH on 1p and 16q occurred preferentially in a subclass of estrogen receptor-positive breast cancers. Finding unique LOH patterns in different groups of breast cancer, in part defined by expression signatures, adds confidence to newer schemes of molecular classification. Furthermore, exclusive association between biological subclasses and restricted LOH events provides rationale to search for targeted genes.
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Gioannini TL, Teghanemt A, Zhang D, Coussens NP, Dockstader W, Ramaswamy S, Weiss JP. Isolation of an endotoxin-MD-2 complex that produces Toll-like receptor 4-dependent cell activation at picomolar concentrations. Proc Natl Acad Sci U S A 2004; 101:4186-91. [PMID: 15010525 PMCID: PMC384716 DOI: 10.1073/pnas.0306906101] [Citation(s) in RCA: 280] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Accepted: 01/20/2004] [Indexed: 12/13/2022] Open
Abstract
Host proinflammatory responses to minute amounts of endotoxins derived from many Gram-negative bacteria require the interaction of lipopolysaccharide-binding protein (LBP), CD14, Toll-like receptor 4 (TLR4) and MD-2. Optimal sensitivity to endotoxin requires an ordered series of endotoxin-protein and protein-protein interactions. At substoichiometric concentrations, LBP facilitates delivery of endotoxin aggregates to soluble CD14 (sCD14) to form monomeric endotoxin-sCD14 complexes. Subsequent interactions of endotoxin-sCD14 with TLR4 and/or MD-2 have not been specifically defined. This study reports the purification of a stable, monomeric, bioactive endotoxin-MD-2 complex generated by treatment of endotoxin-sCD14 with recombinant MD-2. Efficient generation of this complex occurred at picomolar concentrations of endotoxin and nanogram per milliliter doses of MD-2 and required presentation of endotoxin to MD-2 as a monomeric endotoxin-CD14 complex. TLR4-dependent delivery of endotoxin to human embryonic kidney (HEK) cells and cell activation at picomolar concentrations of endotoxin occurred with the purified endotoxin-MD-2 complex, but not with purified endotoxin aggregates with or without LBP and/or sCD14. The presence of excess MD-2 inhibited delivery of endotoxin-MD-2 to HEK/TLR4 cells and cell activation. These findings demonstrate that TLR4-dependent activation of host cells by picomolar concentrations of endotoxin occurs by sequential interaction and transfer of endotoxin to LBP, CD14, and MD-2 and simultaneous engagement of endotoxin and TLR4 by MD-2.
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