Identification of cutC and cutF (nlpE) genes involved in copper tolerance in Escherichia coli

It has been suggested previously that copper transport in Escherichia coli is mediated by the products of at least six genes, cutA, cutB, cutC, cutD, cutE, and cutF. A mutation in one or more of these genes results in an increased copper sensitivity (D. Rouch, J. Camakaris, and B. T. O. Lee, p. 469-477, in D. H. Hamer and D. R. Winge, ed., Metal Ion Homeostasis: Molecular Biology and Chemistry, 1989). Copper-sensitive cutC and cutF mutants were transformed with a genomic library of E. coli, and copper-tolerant transformants were selected. Two distinct clones were identified, each of which partially restores copper tolerance in both the cutC and cutF mutants of E. coli. Subcloning, physical mapping, and sequence analysis have revealed that the cutC gene is located at 42.15 min on the E. coli genome and encodes a cytoplasmic protein of 146 amino acids and that the cutF gene is located at 4.77 min on the E. coli genome and is allelic to the nlpE gene independently identified by Silhavy and coworkers (W. B. Snyder, L. J. B. Davis, P. N. Danese, C. L. Cosma, and T. J. Silhavy, J. Bacteriol. 177:4216-4223, 1995). Results from the genetic mapping of the copper-sensitive mutations in the cutF mutant and sequencing of the cutC and cutF (nlpE) alleles from both cutC and cutF mutants indicate that both the cutC and cutF mutants are in fact double mutants altered in these two genes, and mutations in both the genes appear to be required for the copper-sensitive phenotype in each mutant.

Ability of the Atherosclerosis Risk in Communities (ARIC)/Baecke Questionnaire to assess leisure-time physical activity

BACKGROUND

The Atherosclerosis Risk in Communities (ARIC)/Baecke Questionnaire is a general survey of both occupational and leisure (sport and exercise related and non-sport and exercise related) physical activity.

METHODS

Its ability to assess leisure physical activity was studied in 78 men and women, age 20-59 years, by comparison to: six 48-hour physical activity records; 14 48-hour Caltrac accelerometer readings (Caltrac); three peak oxygen consumption (VO2 peak) determinations; and per cent body fat. These criteria measures were obtained over a year's duration.

RESULTS

The following associations were evident in men and women respectively, between sport and exercise physical activity and: physical activity record heavy intensity activity (r = 0.73 and r = 0.63); VO2 peak (r = 0.67 and r = 0.45); and per cent body fat (r = -0.37, P = 0.08 and r = -0.44). Less concordance was evident (r = 0.39 for men and r = 0.23, NS, for women) between non-sport and exercise physical activity and physical activity record light intensity activity. Questionnaire and physical activity record indices of total leisure activity tended to be more closely related in men (r = 0.59) than women (r = 0.33). For both men and women, survey results were not closely associated with Caltrac readings.

CONCLUSIONS

Although there are weaknesses, questionnaire strengths consistent for both men and women include: ease of administration, high reliability, and accurate assessment of heavy intensity activity as well as light intensity activities such as walking and bicycling.

Hepatopulmonary syndrome in liver cirrhosis: report of a case

A 52-year-old woman suffered from exertional dyspnea, 5 years after she was diagnosed with cirrhosis of the liver. Hypoxemia was suspected because of persistent exertional dyspnea and was confirmed by contiguous arterial blood gas tests. After excluding other cardiopulmonary factors, a series of studies including lung perfusion scan, echocardiography and cardiopulmonary cineangiography revealed the cause of hypoxemia to be the patient's liver disease. Hepatopulmonary syndrome was diagnosed. Despite supplemental oxygen therapy and oral garlic powder for 6 months, the patient still had exertional dyspnea and platypnea, and arterial blood gas results did not improve. We report this case to call attention to arterial oxygen desaturation in cases of cirrhosis of the liver, and to emphasize that deteriorating oxygenation in patients with chronic liver disease may be an indication for liver transplantation, as such functional microvascular abnormalities could be reversed by liver transplantation.

The umpA gene of Escherichia coli encodes phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (lgt) and regulates thymidylate synthase levels through translational coupling

Using a combination of biochemical, physical, and genetic techniques, we have shown that the umpA gene of Escherichia coli is allelic with the lgt (phosphatidylglycerol:prolipoprotein diacylglyceryl transferase) of Salmonella typhimurium. These genes are essential for the viability of the respective organism and exhibit 92.8% sequence identity at the amino acid level. In E. coli, lgt and thyA (thymidylate synthase) form an operon. Thymidylate synthase levels are regulated by transcription from the lgt promoter and by translational coupling.

Ceramide reverses brefeldin A (BFA) resistance in BFA-resistant cell lines

We have found that C6 ceramide, a cell-permeable ceramide analog, partially restored the brefeldin A (BFA) sensitivity in a BFA-resistant mutant of Vero cells (BER-40) and in the naturally BFA-resistant Madin-Darby canine kidney (MDCK) cells. Incubation of BER-40 and MDCK cells with low concentrations of C6 ceramide resulted in (i) a pronounced increase in BFA cytotoxicity as measured by the inhibition of [3H]thymidine incorporation and the inhibition of colony formation by BFA, (ii) a significant protection by BFA against ricin cytotoxicity, and (iii) an inhibition of bulk protein secretion by BFA in BER-40 and MDCK cells. Related sphingolipids including sphingosine, sphingomyelin, and lactosylceramide and other unrelated lipid second messengers such as arachidonic acid and 1,2-diacylglycerol did not elicit the protection of BER-40 and MDCK cells against ricin cytotoxicity by BFA. C6 ceramide was the most effective among the ceramides with different acyl chain lengths. Interestingly, dihydro-C6 ceramide, which lacks the trans double bond in the sphingoid base, had no effect. On the other hand, C6 ceramide did not enhance BFA sensitivity in BFA-sensitive Vero cells. The LD50 of C6 ceramide were similar in Vero and BER-40 cells. Fluorescence microscopic studies revealed that C6 ceramide induced the redistribution of beta-COP from the Golgi membranes to a more dispersed localization in both BFA-sensitive and BFA-resistant cell lines, mimicking the effect of BFA. Suboptimal concentration of C6 ceramide also restored the effect of BFA on the beta-COP distribution in BER-40 and MDCK cells. These results indicate that C6 ceramide restores the BFA sensitivity in BFA-resistant BER-40 and MDCK cells.

Bowel perforation--a fatal complication following renal transplantation: a report of two cases

From May 1983 to January 1993, 162 patients received renal transplantation at Taichung Veterans General Hospital. Two patients developed bowel perforation after this surgery. One was proved at 21 days and another, at 13 days after renal transplantation. Both patients died as a direct result of the perforation. From a review of literature, the average incidence is 2.7%, and the average mortality rate is 56.5%. Because of this high mortality rate, a high clinical suspicion, prompt and adequate surgical intervention, reduction of immunosuppressive agents and effective antibiotic coverage should contribute to a decline in mortality.

Relationship of protein structure of isoleucyl-tRNA synthetase with pseudomonic acid resistance of Escherichia coli. A proposed mode of action of pseudomonic acid as an inhibitor of isoleucyl-tRNA synthetase

To elucidate the mode of action of pseudomonic acid, we have compared the deduced amino acid sequences of isoleucyl-tRNA synthetases (ILeRS) from wild-type Escherichia coli strain MC4100, a pseudomonic acid-resistant mutant (strain PS102) of MC4100, and a pseudomonic acid-producing strain, Pseudomonas fluorescens. Compared with the wild-type enzyme, the deduced amino acid sequence of E. coli mutant ileS gene in strain PS102 shows a single amino acid substitution of leucine for phenylalanine at residue 594 of the IleRS. This mutational alteration in IleRS of an E. coli pseudomonic acid-resistant mutant resides in a region of the enzyme in close proximity to one of the consensus sequences of class I aminoacyl-tRNA synthetases, the KMSKS sequence between residues 602 and 606 of the E. coli IleRS. DNA sequence of the cloned ileS gene predicts that the P. fluorescens IleRS consists of 943 amino acids with 54% identity with the E. coli IleRS. The P. fluorescens ileS gene and the wild type and PS102 alleles of E. coli ileS were cloned into an expression vector, pEXPCR, and the sensitivities of E. coli DH5 alpha cells harboring each of these plasmids were compared. The cells harboring the P. fluorescens ileS were found to be most resistant to pseudomonic acid, while the transformants expressing the PS102 IleRS were more resistant than those containing the wild-type E. coli IleRS. IleRS purified from the wild-type E. coli was specifically cleaved by trypsin between Lys605 and Ser606 in the region of K602MSKS606. The protection of the IleRS from the trypsin digestion was found with pseudomonic acid or ATP, but not with isoleucine or tRNA(1Ile). Based on these results, we propose that pseudomonic acid binds to IleRS in the vicinity of the KMSKS sequence that is an ATP-binding subsite, and that pseudomonic acid is a bifunctional inhibitor with characteristics of both isoleucine and ATP, for example, an analog of isoleucyladenylate.

Lipid modification of bacterial prolipoprotein. Transfer of diacylglyceryl moiety from phosphatidylglycerol

The peptide, MKATKLVLGAVILGSTLLAGCSSN, corresponding to the N-terminal 24 amino acids of Braun's prolipoprotein, was used to study the lipid modification of prolipoprotein in Escherichia coli by measuring the rate of incorporation of either [2-3H]glycerol or [9,10-3H]palmitate from the corresponding labeled phosphatidylglycerol into the peptide. Using E. coli strains containing varying levels of prolipoprotein diacylglyceryl modification activities due to mutations in or overexpression of the gene involved in diacylglyceryl modification (lgt), we have shown that the activities based on the peptide assay correlated well with the prolipoprotein-based assay. Further, we have followed the fate of the lipid substrate, phosphatidylglycerol, during the modification reaction and found that lipid modification of prolipoprotein involves the transfer of diacylglyceryl moiety from phosphatidylglycerol to the sulfhydryl group of the cysteine residue with the concomitant formation of sn-glycerol 1-phosphate. This mechanism is contrary to the previously proposed two-step mechanism of an initial glyceryl transferase followed by O-acyl transfer (Chattopadhyay, P.K., and Wu, H.C. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 5318-5322). Accordingly, the enzyme that catalyzes this activity has been named phosphatidylglycerol-prolipoprotein diacylglyceryl transferase. The revised pathway for the lipoprotein biogenesis in bacteria consists of three successive reactions catalyzed by prolipoprotein diacylglyceryl transferase, signal peptidase II, and apolipoprotein N-acyltransferase.

Association of heterotrimeric GTP binding regulatory protein (Go) with mitosis

BACKGROUND

The heterotrimeric GTP-binding regulatory proteins (or G proteins) play an important role in regulation of membrane signal transduction. Previously, we have identified the beta-subunit of G proteins (G beta) to be closely associated with mitotic spindles. In the present study, we have conducted experiments to examine whether the G alpha subunit is also associated with mitotic spindles.

EXPERIMENTAL DESIGN

We prepared polyclonal antibodies against synthetic oligopeptides from different G alpha subunits and used them to localize G alpha in a nasopharyngeal carcinoma cell line by both immunohistochemistry and immunoelectron microscopy, and to see whether any specific G alpha subunit was present in the mitotic spindle region. Subsequently, we used a colocalization method to identify the overlapping distributions of specific G alpha subunits and beta-tubulin. To be sure that the findings represented a general phenomenon, several other cell types were also examined. To identify whether the G alpha subunit in the mitotic spindle was present in a heterotrimeric form, we performed ADP ribosylation experiments.

RESULTS

(a) Only Go alpha subunit but not Gi alpha or Gs alpha was localized in the mitotic spindle. (b) Go alpha was colocalized with beta-tubulin in the mitotic spindle. (c) The precise site of localization of Go alpha on spindle microtubules was confirmed by immunoultrastructural study. (d) The association of Go alpha with the mitotic spindle could be found in both human and animal cell types. (e) The mitotic spindle preparation could be ADP ribosylated in the presence of pertussis toxin.

CONCLUSIONS

The heterotrimeric Go protein is shown to be closely associated with the mitotic spindle. This finding suggests that Go protein may play some role in the regulation of mitotic spindles in addition to its regulation of signal transduction in neuronal cell membranes.

Effect of lovastatin on the cytotoxicity of ricin, modeccin, Pseudomonas toxin, and diphtheria toxin in brefeldin A-sensitive and -resistant cell lines

Lovastatin, a specific inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, inhibits the biosynthesis of cholesterol and the prenylation of proteins. In this study, we have found that lovastatin inhibited the cytotoxicities of modeccin, ricin, Pseudomonas toxin, and diphtheria toxin in Vero and a brefeldin A (BFA)-resistant mutant of Vero cells (BER-40) to different extents. Among these toxins tested, the cytotoxicity of modeccin was most strongly inhibited by lovastatin in a dose-dependent manner. The protective effect of lovastatin was completely reversed by the addition of mevalonic acid, while the addition of cholesterol had no effect on the cytotoxicity of modeccin in lovastatin-treated cells. These results suggest that prenylated proteins are involved in the intoxication process of modeccin. The addition of cycloheximide to the growth medium also reversed the protective effect of lovastatin, suggesting a requirement of de novo protein synthesis for the protection by lovastatin against toxins. In contrast to Vero and BER-40 cells, no significant effect of lovastatin was observed in naturally BFA-resistant cell lines, PtK1 and MDCK cells, even though similar morphological changes and disassembly of the actin microfilaments were induced by lovastatin in these cell lines as observed in Vero and BER-40 cells. Lovastatin did not affect the binding and internalization of ricin and modeccin in Vero and BER-40 cells. Our results suggest that prenylated cellular proteins are involved in intracellular trafficking or processing of protein toxins, especially modeccin. In PtK1 and MDCK cells, such intracellular vesicle trafficking of protein toxins may be regulated by lovastatin-resistant mechanisms.

Derivation of androgen-independent human LNCaP prostatic cancer cell sublines: role of bone stromal cells

A model of human prostate cancer was established to study cellular interaction between prostate cancer and bone stroma in vivo. In this model, subcutaneous co-injection of 2 non-tumorigenic human cell lines--LNCaP, a prostate cancer cell line, and MS, a bone stromal cell-line--into intact adult male mice resulted in formation of carcinomas that secreted prostate-specific antigen (PSA), a clinically useful human serum prostate cancer marker. In castrated hosts, upon cellular interaction with bone fibroblasts, we observed the progression of these tumors from an androgen-dependent (AD) to an androgen-independent state (AI). We derived 4 LNCaP cell sublines from the chimeric LNCaP/MS tumors: the M subline from intact hosts and the C4, C4-2 and C5 sublines from castrated hosts. The LNCaP sublines had chromosomal markers similar to those of the parental LNCaP cells and distinctly different from those of the MS bone stromal cell line. Although the parental and derived cell lines expressed similar steady-state levels of ornithine decarboxylase transcript, the sublines expressed 5- to 10-fold higher basal steady-state levels of PSA transcript than did the parental LNCaP cell line. The LNCaP sublines formed 13- to 26-fold more soft-agar colonies than the parental LNCaP cell line. The sublines became tumorigenic, yielding an incidence of tumors in intact athymic mice of 7-75%. The LNCaP sublines C4 and C5 (but not the parental and M cell line) formed tumors in castrated hosts when co-injected with bone fibroblasts. A second-generation LNCaP subline, C4-2, was derived from a chimeric tumor induced by co-inoculating castrated mouse with C4 cells and MS cells. We found that C4-2 subline was tumorigenic when inoculated into castrated hosts in the absence of inductive fibroblasts. Moreover, C4-2 was the only subline capable of forming soft-agar colonies when cultured in serum-free medium. In comparison with the parental LNCaP cells, the C4-2 subline expressed lower steady-state levels of androgen receptor (AR) protein and mRNA transcript and lost its androgen responsiveness in vitro. Our results suggest that certain genetic traits of prostate cancer cells may be selected or altered through an "adaptive" mechanism that involves cellular interaction with the bone stromal cells.

Cytotoxic necrotizing factor type 2 produced by virulent Escherichia coli modifies the small GTP-binding proteins Rho involved in assembly of actin stress fibers

Cytotoxic necrotizing factor type 2 (CNF2) produced by Escherichia coli strains isolated from intestinal and extraintestinal infections is a dermonecrotic toxin of 110 kDa. We cloned the CNF2 gene from a large plasmid carried by an Escherichia coli strain isolated from a lamb with septicemia. Hydropathy analysis of the deduced amino acid sequence revealed a largely hydrophilic protein with two potential hydrophobic transmembrane domains. The N-terminal half of CNF2 showed striking homology (27% identity and 80% conserved residues) to the N-terminal portion of Pasteurella multocida toxin. Methylamine protection experiments and immunofluorescence studies suggested that CNF2 enters the cytosol of the target cell through an acidic compartment and induces the reorganization of actin into stress fibers. Since the formation of stress fibers in eukaryotic cells involves Rho proteins, we radiolabeled these small GTP-binding proteins from CNF2-treated and control cells with a Rho-specific ADP-ribosyltransferase. The [32P]ADP-ribosylated Rho proteins from CNF2-treated cells migrated slightly more slowly in SDS/PAGE than did the labeled proteins from the control cells. This shift in mobility of Rho proteins in SDS/PAGE was also observed when CNF2 and the RhoA protein were coexpressed in E. coli. We propose that Rho proteins are the targets of CNF2 in mammalian cells.

Comparison of five modalities in localization of primary aldosteronism

BACKGROUND

The best response to surgical treatment of primary aldosteronism occurs in patients with an aldosterone-producing adenoma (APA), so pre-operative localization of the lesion is necessary.

METHODS

A comparison was made of five localizing modalities-computed tomography (CT) of the adrenal gland, magnetic resonance imaging (MRI), dexamethasone suppression-131I-19-cholesterol adrenal scintiscan (DS, NP-59 adrenal scan), adrenal venography (venography) and adrenal venous sampling for aldosterone content (AVS) in 22 patients (12 women, 10 men) with primary aldosteronism; all had undergone operative confirmation within the past 9 years. The age at diagnosis ranged from 27 to 67 years (mean: 39.7).

RESULTS

Unilateral adrenalectomy resulted in normal blood pressure without medication in 63.6% (14/22), and in improvement in 36.4% (8/22). Correct localization of the lesion was obtained in 95% (20/21) by CT, 100% (7/7) by MRI, 80% (12/15) by DS,NP-59 adrenal scan, 100% (6/6) by AVS and 78% (7/9) by venography.

CONCLUSIONS

This experience would advocate CT of the adrenals as the initial means of localizing an APA on an outpatient basis because it is comfortable, safe, inexpensive and gives immediate results. The major role of MRI in the evaluation of adrenal adenoma should be complementary to CT. DS, NP-59 adrenal scan can be an adjuvant method for localization if CT scan results are not definitive. Adrenal venous catheterization with blood sampling for aldosterone content could be reserved for patients whose biochemical finging suggests the presence of an APA, and for whom CT or MRI of the adrenals and DS, NP-59 adrenal scan are inconclusive.

Epidermal growth factor receptor-mediated autocrine and paracrine stimulation of human transitional cell carcinoma

Stromal-epithelial interactions may play a key role in tumor growth and metastasis. We have established a model to study the cellular and molecular basis of this paracrine interaction both in vivo and in vitro using a human transitional cell carcinoma cell line (WH). s.c. coinoculation of 1 x 10(6) WH cells with 1 x 10(6) nontumorigenic fetal rat urogenital sinus mesenchymal (rUGM) cells in athymic mice accelerated carcinoma growth 20 times faster than isolated WH cell inoculations and 4 times faster than coinoculations of the same number of NIH-3T3 or human bladder fibroblasts. Characterization of these chimeric tumors with immunohistochemical and DNA dot-blot analyses documented their predominantly human component. To evaluate the underlying mechanisms involved in this paracrine-mediated in vivo tumor growth acceleration, Northern analyses for growth factors (GFs) and extracellular matrix (ECM) expression in the different cell lines, as well as in vitro mitogenic assays, were performed. Northern analysis revealed basic fibroblast growth factor, transforming growth factor alpha, and epidermal growth factor receptor expression by WH cells but not rUGM cells; ECM components (fibronectin and collagens I and IV) were expressed only in the fibroblast cell lines. Cell type-specific paracrine growth factors are produced by cultured stromal and epithelial cells with a 2-3-fold bidirectional increase in WH and rUGM cell growth when cultured with reciprocal cell-type conditioned medium. An autocrine growth loop was observed for WH but not rUGM cells. WH cell growth is stimulated in vitro by low concentrations of transforming growth factor alpha and epidermal growth factor, while rUGM cell growth is stimulated 3-fold by basic fibroblast growth factor. Antiepidermal growth factor receptor antibodies completely inhibited autocrine and paracrine pathways stimulating WH cell growth, while anti-basic fibroblast growth factor antibodies had no inhibitory effect. These observations suggest that autocrine and paracrine growth factor stimulation of WH bladder carcinoma cell growth is most likely mediated by an epidermal growth factor receptor-related pathway. The predominant expression of ECM by fibroblasts in this model suggests that stromal cell ECM components may modulate tumor cell growth and angiogenesis possibly through mechanisms involving cellular adhesion, chemotaxis, or growth factor action.

Removal of renal cell carcinoma extending into the right atrium using cardiopulmonary bypass, profound hypothermia and circulatory arrest

A 65-year-old man presented with renal cell carcinoma of the right kidney with a tumor thrombus extending up the vena cava to the right atrium. Cardiopulmonary bypass, profound hypothermia and total circulatory arrest were used to create a bloodless field for excision of the renal cell carcinoma and its tumor thrombus. Acute respiratory failure and deep jaundice developed after the operation and the patient was transferred to the intensive care unit for critical care. After respiratory therapy and nutritional support, the liver function was restored. The endotracheal tube was weaned one month later. The patient has had total resolution of all symptoms and there is no evidence of tumor recurrence of distant metastases after 6 months follow-up.

Processing of lipid-modified prolipoprotein requires energy and sec gene products in vivo

The kinetics of processing of glyceride-modified prolipoprotein that accumulated in globomycin-treated Escherichia coli has been found to be affected by sec mutations, i.e., secA, secE, secY, secD, and secF, and by metabolic poisons which affect proton motive force (PMF). The effect of sec mutations on processing of glyceride-modified prolipoprotein in vivo was not due to a secondary effect on PMF. Neither a secF mutation nor metabolic poisons affected the processing of previously accumulated proOmpA protein in vivo, suggesting that the requirements for functional sec gene products and PMF are specific to the processing of lipoprotein precursors by signal peptidase II.

Characterization of a temperature-sensitive mutant of Salmonella typhimurium defective in apolipoprotein N-acyltransferase

On screening 440 temperature-sensitive (ts) mutants of Salmonella typhimurium, a mutant strain SE5312 which accumulated apolipoprotein (ALP) at 42 degrees C was identified. In vitro assay of apolipoprotein N-acyltransferase activity indicated that the mutant cell envelope contained reduced activity as compared to the wild-type strain. Transduction with a Mud-P22 mapping set placed the ts mutation to 14-17 min region of the S. typhimurium chromosome. P22 transduction using transposon insertions in this region revealed a linkage of the ts mutation to cobD (6%), nag (8%), and corC68 (99%). The ts phenotype was complemented by a 2.3-kilobase EcoRI subclone derived from lambda-phage 170 of Kohara's bank of Escherichia coli. Restriction enzyme analysis of the cloned DNA revealed that this 2.3-kilobase EcoRI fragment included the copper transport (cutE) gene in E. coli. The mutant strain SE5312 was copper-sensitive at 30 degrees C, and the complementing clone conferred copper resistance and restored the ALP N-acyltransferase activity in the mutant cell. Wild-type strain of S. typhimurium harboring this clone exhibited elevated levels of ALP N-acyltransferase activity. These results suggest that the cloned gene encodes the ALP N-acyltransferase. Upon shift to the non-permissive temperature, the viability of the mutant cells decreased, and the mutant cells assumed anomalous morphology. Temperature-resistant revertants could be readily isolated, and a subset of tr revertants contained no detectable lipoprotein. A lpp::Tn10 derivative of the mutant SE5312 was also temperature-resistant. These observations suggest that ALP N-acyltransferase is essential for the growth and viability of S. typhimurium, and this requirement is decreased in the absence of major outer membrane lipoprotein.

Isolation and characterization of a temperature-sensitive mutant of Salmonella typhimurium defective in prolipoprotein modification

A temperature-sensitive (ts) mutant of Salmonella typhimurium that accumulated unmodified murein prolipoprotein at 42 degrees C but not at 30 degrees C was identified. In vivo and in vitro studies of the biosynthesis of Braun's lipoprotein revealed that this mutant (SE5221) was defective in the glyceryl modification of prolipoprotein. The ts mutation was mapped to 60.6 min of the S. typhimurium chromosome and was linked to argA and cysH. A clone with a 1.4-kilobase S. typhimurium DNA insert that complemented the ts mutation and restored the prolipoprotein modification activity both in vivo and in vitro was isolated. DNA sequencing of the complementing region revealed an open reading frame encoding a protein with 291 amino acids lacking NH2-terminal signal sequence. This open reading frame is immediately 5' to the thyA gene and is allelic to umpA of Escherichia coli. Wild-type strains harboring the cloned gene exhibited elevated levels of prolipoprotein modification activity. At the non-permissive temperature, the mutation affected both growth and viability, and the mutant cells exhibited anomalous cell morphology. The ts phenotype was suppressed by the introduction of a lpp::Tn10 mutation. These results suggest that the cloned gene encodes prolipoprotein glyceryl transferase (lgt), and in the wild-type background, this prolipoprotein modification enzyme is essential for the growth and viability of S. typhimurium.

Autocrine regulation of prostate-specific antigen gene expression in a human prostatic cancer (LNCaP) subline

Prostate-specific antigen (PSA), a M(r) 34,000 serine protease, is recognized as a useful marker for the detection and prognosis of patients with prostate cancer. Although serum PSA is an excellent prognostic indicator, an increasing number of factors were found to regulate the PSA expression of prostatic cancer cells, which include androgenic steroids, the growth factors (GFs) and the extracellular matrix. The purpose of this study is to define a novel protein factor that may be responsible for regulating PSA expression by androgen-independent (AI) human prostate cancer cells. We have established a LNCaP subline (C4) from a parental LNCaP tumor grown in a castrated host. The C4 subline overexpressed PSA mRNA and protein. Serum-free conditioned medium (CM) isolated from the C4 subline is able to stimulate PSA gene expression in parental LNCaP cells in a concentration-dependent manner. This autocrine PSA-inducing activity was found to be organ specific because CMs from other fibroblast cell lines (such as bone, prostate, kidney, and lung fibroblasts) and the CMs from several prostatic carcinoma cell lines (such as parental LNCaP, PC-3, DU-145) and a bladder transitional carcinoma cell line (WH) fail to exhibit similar activity. The activity of the CM from the C4 subline cannot be substituted by GFs such as TGF-alpha, TGF-beta, bFGF, HGF, KGF, or NGF; neuropeptide (bombesin/GRP); secondary messenger analogue (dibutyryl cAMP); beta 2-adrenergic agonist (isoproterenol); or alpha 1-adrenergic agonist (phenylephrine), indicating that the factor(s) may be a novel prostate-specific autocrine factor (PSAF). Both androgen and PSAF exhibit an additive effect on up-regulating PSA gene expression, suggesting that the signal transduction pathway elicited by PSAF may differ from that mediated by the androgen receptor. Further characterization of PSAF by heat, acid, and trypsin digestion revealed that the PSAF may be a protein factor with a unique amino acid composition. These observations suggest that a novel autocrine pathway mediated by PSAF may be responsible for the overexpression of PSA mRNA and protein in a human prostatic cancer cell line. The potential clinical significance of this factor will be discussed.

Cerulenin inhibits the cytotoxicity of ricin, modeccin, Pseudomonas toxin, and diphtheria toxin in brefeldin A-resistant cell lines

We have found that cerulenin, an antibiotic that inhibits de novo fatty acid and cholesterol biosynthesis and fatty acylation of proteins, strongly inhibited the cytotoxicity of ricin, modeccin, Pseudomonas toxin, and diphtheria toxin in a brefeldin A (BFA)-resistant mutant of Vero cells (BER-40). The protective effect of cerulenin against ricin was also observed in two other BFA-resistant cell lines, Madin-Darby canine kidney, and PtK1 cells. In contrast to BER-40 cells, no significant effect of cerulenin was observed in Vero cells. Cerulenin did not affect the binding of ricin to the cell-surface receptors, but reduced significantly the internalization of ricin in BER-40 cells; no effect of cerulenin on the binding or internalization of ricin was observed in Vero, PtK1, and Madin-Darby canine kidney cells. Endocytic uptake of fluid-phase markers such as horseradish peroxidase and lucifer yellow was inhibited by cerulenin in BER-40 cells, but the endocytosis of transferrin via the coated pit/coated vesicle pathway was slightly increased. Cerulenin inhibited the degradation and excretion of ricin in BER-40 cells, and this effect of cerulenin was not observed in Vero cells. Furthermore, cerulenin inhibited the bulk protein secretion in a dose-dependent manner, with BER-40 cells being more susceptible than Vero cells. These results suggest that in addition to its effect on endocytosis, cerulenin interferes with the intracellular trafficking or processing of toxin molecules, and the vesicle transport system in BER-40 cells appears to be cerulenin-sensitive. Since addition of fatty acids and cholesterol did not reverse the effects of cerulenin, the protective effect of cerulenin against protein toxins is not due to an inhibition of de novo fatty acids and cholesterol biosynthesis.

Characterization of seven newly established nasopharyngeal carcinoma cell lines

BACKGROUND

Nasopharyngeal carcinoma (NPC) has a relatively high incidence in Chinese living in Taiwan, Hong Kong, Singapore, and South China. To better understand this cancer, we have established several new NPC cell lines.

EXPERIMENTAL DESIGN

We collected biopsy specimens from suspected NPC patients and divided each specimen into two parts: the first part was fixed for routine histopathologic examination, and the other part was put into culture medium for primary culture. Once the cell lines were established, they were extensively characterized.

RESULTS

Seven NPC cell lines were established, and all have been passaged more than 100 times. Two lines were derived from keratinizing carcinomas and five from undifferentiated carcinomas. Electron microscopic examination revealed that both dark and light tumor cells contained intermediate filaments with clear desmosome formation. The average doubling time ranged from 10.7 to 16.3 hours. Karyotypic analysis showed multiple chromosome abnormalities with the average chromosome number between 84 and 95. Colony forming efficiency in soft agar was 18-42%. All cell lines could induce solid tumor mass formation when transplanted into nude mice, and the histopathological findings showed two keratinizing and five nonkeratinizing carcinomas. All cell lines contained less acidic keratin polypeptides than basic keratin polypeptides. Strong expression of vimentin in each single cell of all cell lines was also observed. The oncosuppressor retinoblastoma gene in each cell line showed no remarkable abnormality, but retinoblastoma protein was abnormally expressed in some interphase cells. The oncogenes, erbB and c-fgr, were both normally expressed. While the c-myc oncogene in all cell lines was overexpressed when compared with the Burkitt's lymphoma Raji Cell line, the c-myc DNA sequence in each cell line showed neither amplification nor rearrangement.

CONCLUSIONS

The newly established seven NPC cell lines have been well characterized, and all showed overexpression of c-myc oncogene. The oncosuppressor retinoblastoma gene revealed no remarkable rearrangement, but its protein product was abnormal in certain interphase cells of each cell line.

Involvement of the Golgi region in the intracellular trafficking of cholera toxin

The intracellular pathway following receptor-mediated endocytosis of cholera toxin was studied using brefeldin A (BFA), which inhibited protein secretion and induced dramatic morphological changes in the Golgi region. In both mouse Y1 adrenal cells and CHO cells, BFA at 1 micrograms/ml caused a 80-90% inhibition of the cholera toxin (CT)-induced elevation of intracellular cAMP. The inhibition of the cytotoxicity of CT by BFA was also observed in a rounding assay of Y1 adrenal cells. The inhibition of CT cytotoxicity by BFA was dose dependent, with the ID50 value similar to the LD50 of BFA in Y1 adrenal cells. Binding and internalization of [125I]-labeled cholera toxin in Y1 adrenal cells was not affected by BFA. Unlike the BFA-sensitive cell lines such as Y1 adrenal and CHO cells, BFA at 1 micrograms/ml did not inhibit the cytotoxicity of CT in PtK1 cells, of which the Golgi structure was BFA-resistant. These results strongly suggest that a BFA-sensitive Golgi is required for the protection of CT cytotoxicity by BFA. In contrast, elevation of the intracellular cAMP by forskolin, which acts directly on the plasma membrane adenylate cyclase, was not affected by BFA. These observations indicate that the intoxication of target cells by CT requires an intact Golgi region for its intracellular trafficking and/or processing. In this respect, CT shares a common intracellular pathway with ricin, Pseudomonas toxin, and modeccin, even though their structures and modes of action are very different.

The complete amino acid sequence of a Kunitz family trypsin inhibitor from seeds of Acacia confusa

The complete amino acid sequence of a Kunitz-type two-chain trypsin inhibitor was determined for the first time. The sequence of the inhibitor from Acacia confusa (ACTI) was determined by analysis of peptides obtained from the reduced and S-carboxymethylated protein by digestion with endopeptidase Lys-C, endopeptidase Arg-C, and V8 endopeptidase. ACTI is comprised of two chains, namely A and B chains linked by the disulfide bridge between Cys(133) and Cys(141), and the inhibitor consists of 175 amino acid residues, 136 residues in the A-chain and 39 residues in the B-chain. The N-terminal amino acid sequence of ACTI shows extensive homology to the trypsin inhibitors from Acacia elata and Albizzia julibrissin, while the whole amino acid sequence of ACTI has a high degree of homology to the other Kunitz-type trypsin inhibitors from soybeans, winged bean seeds [Psophocarpus tetragonolobus (L) DC.], and seeds of Erythrina species.