326
|
Campain JA, Padmanabhan R, Hwang J, Gottesman MM, Pastan I. Characterization of an unusual mutant of human melanoma cells resistant to anticancer drugs that inhibit topoisomerase II. J Cell Physiol 1993; 155:414-25. [PMID: 8097746 DOI: 10.1002/jcp.1041550224] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The topoisomerase II inhibitor, VP-16 (etoposide), is an important component in many chemotherapeutic regimens. To characterize resistance to this drug, the human melanoma cell line, FEM-X, was selected in multiple steps with VP-16. To prevent the development of typical multidrug resistance, an inhibitor of P-glycoprotein, the tiapamil analog, RO-11-2933, was added to the selections. The resultant clone FVP3 is 56-fold resistant to VP-16 and cross-resistant to doxorubicin (Adriamycin) (9-fold) and VM-26 (27-fold). These cells are also two- to four-fold resistant to m-AMSA, daunorubicin, and mitoxantrone. FVP3 is not resistant to the P-glycoprotein substrates vinblastine, does not express the MDR1 gene at detectable levels, and does not show reduced 3H-VP-16 accumulation. Unlike other cell lines that exhibit resistance to inhibitors of topoisomerase II, FVP3 has the same level of topoisomerase II expression and activity as FEM-X. Using live cells treated with VP-16, band depletion assays and KCI/SDS precipitation assays show that topoisomerase II from FVP3 is much less susceptible to drug-induced cleavable complex formation than is that from FEM-X. This difference in sensitivity to VP-16 is also detected using lysates from disrupted cells, but not with isolated nuclei devoid of cytoplasmic and membrane components. In addition, the topoisomerase II present in nuclear extracts from FVP3 is not resistant to the effects of VP-16 as measured by: (1) inhibition of strand passing activity during decatenation of kinetoplast DNA, (2) drug-induced linearization of plasmid DNA, and (3) immunodepletion by VP-16. These results suggest that some component of the cytoplasm or cellular membranes, or a factor depleted from nuclei during their isolation, is responsible for the resistance to VP-16 in FVP3.
Collapse
|
327
|
Dubson MA, Kalke M, Hwang J. Linear decay of islands on metal surfaces. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:10044-10047. [PMID: 10005106 DOI: 10.1103/physrevb.47.10044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
328
|
Chen S, Hwang J, Deng PS. Inhibition of NAD(P)H:quinone acceptor oxidoreductase by flavones: a structure-activity study. Arch Biochem Biophys 1993; 302:72-7. [PMID: 8470908 DOI: 10.1006/abbi.1993.1182] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A structure-activity study was carried out to determine the important regions of baicalein and oroxylin A, two flavones isolated from the Chinese herb Scutellariae radix, in inhibiting NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2; DT-diaphorase). This quinone reductase is a vitamin K reductase. It is a target for and has been used as a model enzyme to investigate the mode of action of oral anticoagulants. The two flavones were found to inhibit this quinone reductase in nanomolar ranges. The 5-hydroxyl, 7-hydroxyl, 8-hydroxyl, and 2-phenyl groups of these flavones were found to be important for their inhibition of the enzyme. The inhibition profiles of the flavones on the NADH-menadione reductase activity, the NADH-potassium ferricyanide reductase activity, and the NADH-methyl red reductase activity of this enzyme were different. Therefore, even though the flavones were found to be competitive inhibitors with respect to NADH, they probably did not inhibit the enzyme by binding to the nicotinamide nucleotide binding site. Inhibition kinetic studies which indicated that these compounds bound to different sites than those for dicoumarol and phenindone were performed. These results indicate that these flavones are a new type of inhibitor of NAD(P)H:quinone acceptor oxidoreductase and potentially useful as anticoagulant drugs.
Collapse
|
329
|
Hwang J, Pyun Y, Kokini J. Sidechains of pectins: some thoughts on their role in plant cell walls and foods. Food Hydrocoll 1993. [DOI: 10.1016/s0268-005x(09)80023-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
330
|
Kingsmore SF, Tang CM, Lo CK, Hui CF, Hwang J, Seldin MF. Genetic mapping of the mouse topoisomerase II alpha gene to chromosome 11. Mamm Genome 1993; 4:288-9. [PMID: 8389625 DOI: 10.1007/bf00417440] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
|
331
|
Hwang J. [[The effect of demographic changes on the unemployment rate in Taiwan: 1978-1990]]. IN'GU MUNJE NONJIP = JOURNAL OF POPULATION STUDIES 1992:61-71. [PMID: 12222448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
"The purpose of this paper is to compute the effects of changes in the composition of age, sex, and labor force participation rate, and education of population and labor force on the overall unemployment rate in Taiwan. The results show that the changes in the composition of age-sex and labor force participation rate have had an increasingly significant downward pressure on the overall unemployment rate. However, the compositional changes in...education [and sex] have exerted considerable upward pressure on the overall unemployment rate...." Recommendations for future policy directions are made. (SUMMARY IN ENG)
Collapse
|
332
|
Shiah HS, Chen TY, Chang CM, Chow JT, Kung HJ, Hwang J. Pseudomonas exotoxin A-epidermal growth factor (EGF) mutant chimeric protein as an indicator for identifying amino acid residues important in EGF-receptor interaction. J Biol Chem 1992; 267:24034-40. [PMID: 1429738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Epidermal growth factor (EGF) was fused to the carboxyl end of a modified pseudomonas exotoxin A that has its toxin binding domain deleted. This chimeric toxin designated as PE(delta Ia)-EGF kills A431 cells through the EGF receptor-mediated pathway. In this study, we used a random mutagenesis approach to make point mutations on EGF, followed by replacing the wild type EGF in PE(delta Ia)-EGF with these EGF mutants. We have constructed 14 different PE(delta Ia)-EGFmutants, and examined their EGF receptor binding activity as well as their cytotoxicity to A431 cells. Our results showed that individual mutations of Val19 to Glu and Val34 to Asp in the EGF domain of PE(delta Ia)-EGFmutants resulted in an increase in the binding affinity to EGF receptor and cytotoxicity to A431 cells. On the other hand, individual mutations of His16 to Asp and Gly18 to Ala in the EGF domain of PE(delta Ia)-EGFmutants lead to a decrease in the binding affinity to EGF receptor and cytotoxicity to A431 cells. In addition, mutations of any of the cysteine residues of EGF in PE(delta Ia)-EGFmutants resulted in the loss of their binding activity to EGF receptor and a corresponding loss of their cytotoxicity. This study indicates that the cytotoxicity of PE(delta Ia)-EGFmutant to EGF receptor-bearing cells may be used as an indicator to screen mutations of EGF important in EGF-receptor interactions.
Collapse
|
333
|
Shiah H, Chen T, Chang C, Chow J, Kung H, Hwang J. Pseudomonas exotoxin A-epidermal growth factor (EGF) mutant chimeric protein as an indicator for identifying amino acid residues important in EGF-receptor interaction. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)35941-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
334
|
Wolff J, Hwang J, Sackett DL, Knipling L. Colchicine photosensitizes covalent tubulin dimerization. Biochemistry 1992; 31:3935-40. [PMID: 1567846 DOI: 10.1021/bi00131a007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pure rat brain tubulin can be cross-linked by ultraviolet irradiation of tubulin-colchicine complexes at the high-wavelength maximum of colchicine to form covalent dimers greater than trimers greater than tetramers. With colchicine concentrations approximately 3 x 10(-4) M (mole ratio to tubulin 3-12) and irradiation for 5-10 min at 95-109 mW/cm2, the yield of dimers is 11-17% and of trimers is 4-6% of the total tubulin. The oligomers show polydispersity and anomalously high apparent molecular masses that converge toward expected values in low-density gels. Maximal dimer yields are obtained with MTC and the decreasing photosensitizing potency is MTC greater than colchicine greater than colchicide greater than isocolchicine greater than thiocolchicine. Single-ring troponoids also promote dimerization. Evidence is presented suggesting that the initial, low-affinity, binding step of colchicine and its analogues is sufficient to photosensitize tubulin dimerization.
Collapse
|
335
|
Bishop GA, Hwang J. Use of a cellular ELISA for the detection of cell surface antigens. Biotechniques 1992; 12:326-30. [PMID: 1571137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A sensitive, convenient and inexpensive enzyme-linked immunosorbent assay (ELISA) is described for the detection and relative quantitation of cell surface antigens. The cells to be tested are rapidly glutaraldehyde-fixed to the wells of microtiter plates, which can be stored for later assay, if desired. Alternatively, adherent cells may be left unfixed. Following incubation with antibodies specific for the antigens of interest, an enzyme-linked second antibody conjugate is added, followed by the substrate for the enzyme, as in a conventional ELISA for soluble proteins. The method is a sensitive and accurate alternative to immunofluorescence flow cytometry for rapid and inexpensive screening of large numbers of cell samples.
Collapse
|
336
|
Ihm G, Noh SK, Lee JI, Hwang J, Kim TW. Modulation of superlattice band structure via delta doping. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 44:6266-6269. [PMID: 9998490 DOI: 10.1103/physrevb.44.6266] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
337
|
Hwang J, Chung W. Erratum: "Scissor mode applied to the yrast band of the rare-earth nuclei nuclei". PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1991; 43:2898. [PMID: 9967363 DOI: 10.1103/physrevc.43.2898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
338
|
Hwang J, Chung W. Scissor mode applied to the yrast band of the rare-earth nuclei. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1990; 42:1380-1385. [PMID: 9966870 DOI: 10.1103/physrevc.42.1380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
339
|
Tsay GJ, Fann RH, Hwang J. Specificity of anti-Scl-70 antibodies in scleroderma: increased sensitivity of detection using purified DNA topoisomerase I from calf thymus. J Rheumatol 1990; 17:1314-9. [PMID: 2174971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A large scale purification of DNA topoisomerase I from calf thymus was obtained using the combinations of 62% ammonium sulfate precipitation, Biorex 70, hydroxylapatite and phenylagarose chromatography. Silver staining of the preparation separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 2 bands of apparent molecular weight of 70 and 60 kDa. Immunoblotting with a serum of anti-Scl-70 specificity also recognized both proteins. Anti-Scl-70 antibodies were detected in 24/32 (75%) patients with diffuse scleroderma by ELISA and 28/32 (87%) had the ability to neutralize the topoisomerase I activity. All of 14 sera with anticentromere antibodies did not react with DNA topoisomerase I by both assays. The presence of anti-Scl-70 antibodies remained disease specific despite the increase in sensitivity of both assays.
Collapse
|
340
|
Ellis GF, Bruni M, Hwang J. Density-gradient-vorticity relation in perfect-fluid Robertson-Walker perturbations. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1990; 42:1035-1046. [PMID: 10012937 DOI: 10.1103/physrevd.42.1035] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
341
|
Heikkila RE, Hwang J, Ofori S, Geller HM, Nicklas WJ. Potentiation by the tetraphenylboron anion of the effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and its pyridinium metabolite. J Neurochem 1990; 54:743-50. [PMID: 2303810 DOI: 10.1111/j.1471-4159.1990.tb02314.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The 1-methyl-4-phenylpyridinium species (MPP+) is the four-electron oxidation product of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and is widely assumed to be the actual neurotoxic species responsible for the MPTP-induced destruction of dopaminergic neurons. MPTP is oxidized by the enzyme monoamine oxidase-B to a dihydropyridinium intermediate which is oxidized further to MPP+, an effective inhibitor of the oxidation of the Complex I substrates glutamate/malate in isolated mitochondrial preparations. In the present study, the tetraphenylboron anion (TPB) greatly potentiated the inhibitory effects of MPP+ and other selected pyridinium species on glutamate/malate respiration in isolated mouse liver mitochondria. At 10 microM TPB, the potentiation ranged from approximately 50-fold to greater than 1,000-fold for the several pyridinium species tested. In other experiments, TPB greatly enhanced the accumulation of [3H]MPP+ by isolated mitochondrial preparations. This facilitation by TPB of MPP+ accumulation into mitochondria explains, at least in part, the potentiation by TPB of the above-mentioned inhibition of mitochondrial respiration. Moreover, TPB addition increased the amount of lactate formed during the incubation of mouse neostriatal tissue slices with MPTP and other tetrahydropyridines. The administration of TPB also potentiated the dopaminergic neurotoxicity of MPTP in male Swiss-Webster mice. All of these observations, taken together, are consistent with the premise that the inhibitory effect of MPP+ on mitochondrial respiration within dopaminergic neurons is the ultimate mechanism to explain MPTP-induced neurotoxicity.
Collapse
|
342
|
Chow JT, Chen MS, Wu HC, Hwang J. Identification of the carboxyl-terminal amino acids important for the ADP-ribosylation activity of Pseudomonas exotoxin A. J Biol Chem 1989; 264:18818-23. [PMID: 2553721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The ADP-ribosylation domain of Pseudomonas exotoxin A (PE) has been identified to reside in structural domain III (residues 405-613) and a portion of domain Ib (residues 385-404) of the molecule (Hwang, J., FitzGerald, D. J., Adhya, S., and Pastan, I. (1987) Cell 48, 129-136). To further determine the carboxyl end region essential for ADP-ribosylation activity, we constructed sequential deletions at the carboxyl-terminal of PE. Our results show that a clone with a deletion of the carboxyl-terminal amino acid residues from Arg-609 to Lys-613 and replaced with Arg-Asn retained wild-type PE ADP-ribosylation activity. Deletion of the terminal amino acid residues from Ala-596 to Lys-613 and replaced with Val-Ile-Asn reduced ADP-ribosylation activity by 75%, while deletions of 36 or more amino acids from the carboxyl terminus completely lose their ADP-ribosylation activity. These modified PEs were also examined for their ability to block PE cytotoxicity. Our results shown that modified PEs which lost their ADP-ribosylation activity correspondingly lost their cytotoxicity. Furthermore, extracts containing PE fragments without ADP-ribosylation activity were able to block the cytotoxic activity of intact PE. Our results thus indicate that carboxyl-terminal amino acids in the Ser-595 region are crucial for ADP-ribosylation activity and, consequently, cytotoxicity of PE. The modified PEs which have lost their ADP-ribosylation activity may also be a route to new PE vaccines.
Collapse
|
343
|
Chow JT, Chen MS, Wu HC, Hwang J. Identification of the carboxyl-terminal amino acids important for the ADP-ribosylation activity of Pseudomonas exotoxin A. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)51540-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
344
|
Ellis GF, Hwang J, Bruni M. Covariant and gauge-independent perfect-fluid Robertson-Walker perturbations. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1989; 40:1819-1826. [PMID: 10012012 DOI: 10.1103/physrevd.40.1819] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
345
|
Creighton S, Hwang J, Warshel A, Parson W, Norris J. Corrections - Simulating the Dynamics of the Primary Charge Separation Process in Bacterial Photosynthesis. Biochemistry 1989. [DOI: 10.1021/bi00430a602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
346
|
Hwang J, Chen MS. Structure and function relationship of Pseudomonas exotoxin A. An immunochemical study. J Biol Chem 1989; 264:2379-84. [PMID: 2464589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We have raised antisera against Pseudomonas exotoxin A (PE) and domains Ia and III to study the structure-function relationships of PE. Anti-PE antibody (AbPE) was shown to abolish the ADP-ribosylation activity of PE. However, neither antidomain Ia antibody nor antidomain III antibody inhibited the ADP-ribosylation activity of PE. This suggests that the inhibition of ADP-ribosylation by AbPE results from the binding of AbPE to the region between domains Ia and III. Since the binding of AbPE to PE did not inhibit NAD hydrolysis in the absence of elongation factor 2, the inhibitory effect of AbPE on ADP-ribosylation may be due to steric hindrance rather than a direct action on the catalytic function. Thus, the interface between domain Ia and III may be the site of entry of elongation factor 2 during ADP-ribosylation. The antibodies were also used to study both the inhibitory effects of PE on protein synthesis and its cytotoxic activity. Either AbPE or antidomain Ia antibody, but not antidomain III antibody, was able to reverse the inhibition of protein synthesis by PE and to block its cytotoxicity. In addition, rabbits immunized with domain Ia acquired tolerance against 100 micrograms of PE injected subcutaneously. These results suggest that domain Ia is the cell-binding domain of PE and may be used for vaccination against PE-mediated diseases.
Collapse
|
347
|
|
348
|
Hwang J, Pianetta P, Pao Y, Shih CK, Shen Z, Lindberg PA, Chow R. k-resolved alloy bowing in pseudobinary InxGa. PHYSICAL REVIEW LETTERS 1988; 61:877-880. [PMID: 10039453 DOI: 10.1103/physrevlett.61.877] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
349
|
Hwang J, Richert N, Pastan I, Gottesman MM. Mutant KB cells with decreased EGF receptor expression: biochemical characterization. J Cell Physiol 1987; 133:127-34. [PMID: 2444605 DOI: 10.1002/jcp.1041330116] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mutants of the human KB carcinoma cell line resistant to a cytotoxic conjugate of epidermal growth factor and Pseudomonas exotoxin (EGF-PE) express a pleiotropic phenotype, which includes reduced levels of 125I-EGF binding, without altered affinity for EGF (Lyall et al., 1987). Here, the EGF-toxin (ET) resistant mutants were further characterized with respect to the amount and size of the EGF receptor and the level of EGF receptor RNA. These data indicate that decreased binding of 125I-EGF in the mutants is due to reduced amounts of EGF receptor, which is associated with decreased mRNA levels. Changes in other proteins in the ET mutants were also examined. Five of the six ET mutants had a decrease in a 78,000 Mr- membrane glycoprotein. In addition, an increase in a protein with a Mr- of 40,000 and a pl = 8.0 was found in all the mutants, and an increase in a series of proteins with a Mr- of 36,000 and a pl of 6.3-6.5 was found in some of the mutants. These results confirm the pleiotropic nature of the EGF-PE resistant mutants and show that reduced EGF binding is due to altered expression of the EGF receptor gene in the mutants.
Collapse
|
350
|
Yeh J, Bertness KA, Cao R, Hwang J, Lindau I. Bonding characteristics of the sqrt 3. PHYSICAL REVIEW. B, CONDENSED MATTER 1987; 35:3024-3027. [PMID: 9941793 DOI: 10.1103/physrevb.35.3024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
|