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1.
Ann Oncol ; 29(1): 215-222, 2018 01 01.
Article in English | MEDLINE | ID: mdl-29045551

ABSTRACT

Background: Radiotherapy is an effective treatment of intermediate/high-risk locally advanced prostate cancer, however, >30% of patients relapse within 5 years. Clinicopathological parameters currently fail to identify patients prone to systemic relapse and those whom treatment intensification may be beneficial. The purpose of this study was to independently validate the performance of a 70-gene Metastatic Assay in a cohort of diagnostic biopsies from patients treated with radical radiotherapy and androgen deprivation therapy. Patients and methods: A bridging cohort of prostate cancer diagnostic biopsy specimens was profiled to enable optimization of the Metastatic Assay threshold before further independent clinical validation in a cohort of diagnostic biopsies from patients treated with radical radiotherapy and androgen deprivation therapy. Multivariable Cox proportional hazard regression analysis was used to assess assay performance in predicting biochemical failure-free survival (BFFS) and metastasis-free survival (MFS). Results: Gene expression analysis was carried out in 248 patients from the independent validation cohort and the Metastatic Assay applied. Ten-year MFS was 72% for Metastatic Assay positive patients and 94% for Metastatic Assay negative patients [HR = 3.21 (1.35-7.67); P = 0.003]. On multivariable analysis the Metastatic Assay remained predictive for development of distant metastases [HR = 2.71 (1.11-6.63); P = 0.030]. The assay retained independent prognostic performance for MFS when assessed with the Cancer of the Prostate Assessment Score (CAPRA) [HR = 3.23 (1.22-8.59); P = 0.019] whilst CAPRA itself was not significant [HR = 1.88, (0.52-6.77); P = 0.332]. A high concordance [100% (61.5-100)] for the assay result was noted between two separate foci taken from 11 tumours, whilst Gleason score had low concordance. Conclusions: The Metastatic Assay demonstrated significant prognostic performance in patients treated with radical radiotherapy both alone and independent of standard clinical and pathological variables. The Metastatic Assay could have clinical utility when deciding upon treatment intensification in high-risk patients. Genomic and clinical data are available as a public resource.


Subject(s)
Biopsy/methods , Prostatic Neoplasms/pathology , Prostatic Neoplasms/radiotherapy , Aged , Cohort Studies , Disease-Free Survival , Gene Expression Profiling , Humans , Kaplan-Meier Estimate , Male , Middle Aged , Neoplasm Metastasis , Neoplasm Staging , Proportional Hazards Models , Prostatic Neoplasms/genetics , Reproducibility of Results , Retrospective Studies , Risk Assessment/methods , Risk Factors
2.
Sci Rep ; 7(1): 15417, 2017 11 13.
Article in English | MEDLINE | ID: mdl-29133863

ABSTRACT

We propose a simple real-time index of global human-induced warming and assess its robustness to uncertainties in climate forcing and short-term climate fluctuations. This index provides improved scientific context for temperature stabilisation targets and has the potential to decrease the volatility of climate policy. We quantify uncertainties arising from temperature observations, climate radiative forcings, internal variability and the model response. Our index and the associated rate of human-induced warming is compatible with a range of other more sophisticated methods to estimate the human contribution to observed global temperature change.

3.
Q J R Meteorol Soc ; 141(687): 550-562, 2015 Jan.
Article in English | MEDLINE | ID: mdl-26300564

ABSTRACT

Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.

4.
J Geophys Res Atmos ; 120(18): 9043-9058, 2015 09 27.
Article in English | MEDLINE | ID: mdl-26937327

ABSTRACT

A future decline in solar activity would not offset projected global warmingA future decline in solar activity could have larger regional effects in winterTop-down mechanism contributes to Northern Hemisphere regional response.

5.
Br J Radiol ; 84(1005): 813-8, 2011 Sep.
Article in English | MEDLINE | ID: mdl-21159811

ABSTRACT

OBJECTIVE: Consistency in target organ and organ at risk position from planning to treatment is an important basic principle of radiotherapy. This study evaluates the effectiveness of bladder-filling instructions in achieving a consistent and reproducible bladder volume at the time of planning CT and daily during the course of radical radiotherapy for prostate cancer. It also assessed the rate of bladder filling before and at the end of radiotherapy. METHODS: 30 men attending for radiation therapy planning for prostate cancer received written and verbal bladder-filling instructions. They had their bladder volume assessed using a bladder ultrasound scanner post-void, immediately prior to planning CT scan and then daily immediately prior to treatment while in the therapy position. The inflow was calculated using the void and full bladder volumes and the time for the bladder to fill. RESULTS: The mean bladder volume at the time of planning was 282 ml (range 89-608 ml, standard deviation (SD) = 144.5 ml). This fell during treatment, with a mean value for all treatments of 189 ml (range 11-781 ml, SD = 134 ml). During radiotherapy, 76% (828/1090), 53% (579/1090) and 36% (393/1090) of bladder volumes had >50 ml, >100 ml and >150 ml difference, respectively when compared with their volume at the time of planning. Inflow reduced from 4.6 ml min(-1), SD = 2.9 min(-1) at planning to 2.5 min(-1), SD = 1.8 min(-1) after radiotherapy. CONCLUSION: The Bladderscan device (BVI 6400 Bladderscan, Verathon Medical UK, Sandford, UK) provides an effective means of assessing bladder volume prior to radiotherapy for prostate cancer. The evaluated bladder-filling protocol does not produce consistent, reproducible bladder volumes for radiotherapy.


Subject(s)
Prostatic Neoplasms/physiopathology , Prostatic Neoplasms/radiotherapy , Radiotherapy, Conformal , Urinary Bladder/diagnostic imaging , Aged , Humans , Male , Middle Aged , Observer Variation , Organ Size , Pilot Projects , Prostatic Neoplasms/pathology , Tomography, X-Ray Computed , Ultrasonography , Urinary Bladder/pathology
6.
J Phys Chem A ; 112(49): 12597-601, 2008 Dec 11.
Article in English | MEDLINE | ID: mdl-19053547

ABSTRACT

Stark effect measurements of the permanent electric dipole moments of p-aminobenzoic acid (PABA) in the gas phase are reported based on studies of its fully resolved S1<--S0 electronic spectrum in the presence of an electric field. Ground-state (S0) PABA has mu = 3.3 D, whereas excited-state (S1) PABA has mu = 4.4 D. Despite PABA's reputation as a "push-pull" molecule, the photon-induced change in both the magnitude and orientation of mu is relatively small. Possible reasons for this behavior are discussed.

7.
Clin Oncol (R Coll Radiol) ; 20(10): 738-44, 2008 Dec.
Article in English | MEDLINE | ID: mdl-18951769

ABSTRACT

AIMS: To report the results of I(125) prostate brachytherapy from a central, prospectively collected database of three UK institutions. MATERIALS AND METHODS: All patients treated with I(125) permanent prostate brachytherapy at the Christie Hospital, Manchester (CHM), Cookridge Hospital, Leeds (CKL) and Mount Vernon Hospital, Northwood, London (MVL) since 2003 have been prospectively registered on a detailed central database. Patient, tumour, pre- and post-implant dosimetry data have been recorded. Urinary toxicity as assessed by the International Prostate Symptom Score, catheterisation and urinary stricture rates after implant have been documented and biochemical failure determined, using both the American Society for Therapeutic Radiology and Oncology (ASTRO) consensus and the Phoenix (nadir + 2 ng/ml) definition. RESULTS: In total, 1535 patients were registered on the database between January 2003 and October 2006, including 432 from CHM, 926 from CKL and 177 from MVL, with a median follow-up of 21 months (range 1-56). Patient and tumour characteristics were similar at all centres. Pre-implant dose indices were comparable between centres, except for the V150, with median values of 51.9, 64.3 and 69.8% at CHM, CKL and MVL, respectively. Median post-implant dose parameters were lower than pre-planned constraints by up to 33.0% at each centre for all values, except at CKL where the V200 was 23.9% higher. The International Prostate Symptom Score increased from a median of 5 at baseline to 18, 6 weeks after implant, but was not significantly different to baseline values by 12 months. Nine per cent of men required catheterisation after implant for a median duration of 53 days, but urinary stricture rates remained low at 1%. Neoadjuvant hormonal manipulation was used in 228 men (15%) for downsizing and 159 (10%) for intermediate/high-risk disease. Collated biochemical failure rates were low at this point of follow-up, with actuarial 2-year ASTRO and Phoenix biochemical failure-free survival rates of 94.4 and 94.5%, respectively, consistent with other large single centre reports. When post-implant dosimetric factors were assessed for a relationship to biochemical failure, no indices consistently predicted for improved ASTRO and Phoenix biochemical failure-free survival rates. CONCLUSIONS: This ongoing collaboration shows that with limited infrastructure (a single industry-sponsored data manager), a large multi-institutional database estimated to represent one-third of implants carried out in the UK during this time can be developed. Patient selection was similar across all centres and adhered to published guidelines. Early biochemical and toxicity outcomes confirm the efficacy and tolerability of I(125) prostate brachytherapy in a large cohort of patients. A further analysis is planned.


Subject(s)
Brachytherapy , Prostatic Neoplasms/radiotherapy , Adult , Aged , Aged, 80 and over , Brachytherapy/adverse effects , Databases, Factual , Humans , Iodine Radioisotopes , Male , Middle Aged , Prostate-Specific Antigen/analysis , Prostatic Neoplasms/metabolism , Prostatic Neoplasms/physiopathology , Radiotherapy Dosage , Treatment Outcome , United Kingdom
8.
J Med Imaging Radiat Oncol ; 52(2): 194-6, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18373814

ABSTRACT

Cranial nerve palsies have previously been reported in metastatic prostate carcinoma, usually occurring late in the course of the disease. We describe the case of a 55-year-old man whose diagnosis of prostate cancer was made following investigation of multiple cranial nerve palsies.


Subject(s)
Carcinoma/diagnosis , Cranial Nerve Diseases/etiology , Prostatic Neoplasms/diagnosis , Skull Base Neoplasms/diagnosis , Skull Base/pathology , Carcinoma/secondary , Carcinoma/therapy , Diagnosis, Differential , Facial Nerve Diseases/etiology , Headache/etiology , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Prostatic Neoplasms/pathology , Prostatic Neoplasms/therapy , Radionuclide Imaging , Skull Base/diagnostic imaging , Skull Base Neoplasms/secondary , Skull Base Neoplasms/therapy , Tomography, X-Ray Computed
10.
Colorectal Dis ; 9(4): 328-31, 2007 May.
Article in English | MEDLINE | ID: mdl-17432984

ABSTRACT

OBJECTIVE: The use of prostate brachytherapy (BT) in the management of prostate cancer is increasing. BT is often chosen because of its perceived lower toxicity when compared with other radical therapy options. Rarely however serious complications can occur. One such complication is recto-urethral fistula (RUF). We report the incidence of RUF following BT at our centre and review the potential factors in fistula development. METHOD: A prospectively collected database was used to identify cases of RUF among 1455 patients treated with prostate BT at a single UK centre with at least 2 years of follow up. This included patients treated with BT monotherapy, as well as those treated with BT combined with external beam radiotherapy and BT used as salvage as all these groups have a higher incidence of RUF. Implant dose and volume characteristics for those patients, their co-morbidities and history of endoscopic procedures were recorded. RESULTS: Recto-urethral fistula was identified in three (0.2%) patients, occurring at 19-27 months following BT. All these patients had BT monotherapy. All three patients had rectal symptoms after their BT and had been investigated with endoscopy and low rectal biopsy. Subsequent surgical management with faecal and/or urinary diversion was required. On review of patients' BT details, radiation dose and volume parameters were higher on the postprocedure CT calculations than had been suggested by the preimplant plan. No other predisposing risk factors for RUF were identified. CONCLUSION: The incidence of RUF in our population is low. RUF following BT has been associated with rectal biopsy in previous series and this is confirmed in our report. Gastrointestinal specialists should not perform biopsy of the anterior rectum in patients who have had BT unless there is a very high clinical suspicion of malignancy.


Subject(s)
Brachytherapy/adverse effects , Prostatic Neoplasms/radiotherapy , Rectal Fistula/etiology , Urethral Diseases/etiology , Urinary Fistula/etiology , Aged , Humans , Incidence , Magnetic Resonance Imaging , Male , Middle Aged , Prospective Studies , Rectal Fistula/diagnosis , Urethral Diseases/diagnosis , Urinary Fistula/diagnosis
12.
Thorax ; 59(9): 736, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15333846
14.
Eur J Hum Genet ; 9(5): 347-54, 2001 May.
Article in English | MEDLINE | ID: mdl-11378823

ABSTRACT

MUC7 encodes a small salivary mucin, previously called MG2, a glycoprotein with a putative role in facilitating the clearance of oral bacteria. The central domain of this glycoprotein was previously shown to comprise five or six tandemly repeated units of 23 amino-acids which carry most of the O-linked glycans. The polymorphism of these two allelic forms (MUC7*5 or MUC7*6) has been confirmed in this study in which we have analysed a large cohort of subjects (n = 375) of various ethnic origins. We have also identified a novel rare allele with eight tandem repeats (MUC7*8). MUC7*6 was the most common allele (0.78-0.95) in all the populations tested. The tandem repeat arrays of 22 MUC7*5 alleles and 34 MUC7*6 alleles were sequenced. No sequence differences were detected in any of the MUC7*6 alleles. Twenty-one MUC7*5 alleles sequenced lacked the 4th tandem repeat (structure TR12356), while one showed the structure TR12127. The structure of the MUC7*8 allele was TR12343456. Because of the known role of MUC7 in bacterial binding, and thus its potential involvement in susceptibility to chest disease we also tested MUC7 in our previously described series of Northern European atopic individuals with and without associated asthma. The MUC7*5 allele was rarer in the atopic asthmatics than in the atopic non-asthmatics (P = 0.014, OR for no asthma in atopic individuals 3.13, CI 1.01-6.10), and the difference in frequency between all asthmatics and all non-asthmatics was statistically significant (P = 0.009) while there was no difference between atopy and non-atopy (P = 0.199). In this study we also report the electrophoretic analysis of the MUC7 glycoprotein in saliva from individuals of different MUC7 genotype.


Subject(s)
Asthma/genetics , Mucins/genetics , Polymorphism, Genetic , Salivary Proteins and Peptides/genetics , Adult , Amino Acid Sequence , Base Sequence , DNA/analysis , Electrophoresis, Polyacrylamide Gel , Gene Frequency , Genetic Variation , Genotype , Glycoproteins/genetics , Humans , Intercellular Signaling Peptides and Proteins , Molecular Sequence Data , Organometallic Compounds , Peptides , Saliva/chemistry , Sequence Analysis , Tandem Repeat Sequences/genetics
15.
Nat Immunol ; 2(1): 51-7, 2001 Jan.
Article in English | MEDLINE | ID: mdl-11135578

ABSTRACT

Lipopolysaccharide (LPS) induction of the gene encoding interleukin 12 p40 requires remodeling of a promoter-encompassing nucleosome and the Toll-like receptor (TLR)-mediated activation of a c-Rel-containing complex. Analysis of TLR4-mutant mice revealed that remodeling requires TLR signaling. However, Rel proteins and other proteins required for transcription of an integrated p40 promoter were insufficient for remodeling. c-Rel was also unnecessary for remodeling, as remodeling was observed in c-Rel-/- macrophages, which lack p40 transcripts. These results suggest that remodeling requires TLR signaling pathways that diverge from the c-Rel activation pathways. The factors that stimulate remodeling may represent, therefore, newly identified targets of TLR signaling and of agents that regulate inflammatory responses and TH1 development.


Subject(s)
Drosophila Proteins , Interleukin-12/genetics , Membrane Glycoproteins/metabolism , Nucleosomes/metabolism , Promoter Regions, Genetic , Receptors, Cell Surface/metabolism , Animals , CCAAT-Enhancer-Binding Proteins/metabolism , Cell Line , DNA Restriction Enzymes/metabolism , Inflammation/etiology , Inflammation/immunology , Inflammation/metabolism , Lipopolysaccharides/toxicity , Macrophages/immunology , Macrophages/metabolism , Mice , Mice, Inbred C3H , Mice, Inbred C57BL , Mice, Knockout , Mice, Mutant Strains , Nuclear Proteins/metabolism , Proto-Oncogene Proteins c-rel/metabolism , Signal Transduction , Th1 Cells/immunology , Th1 Cells/metabolism , Toll-Like Receptor 4 , Toll-Like Receptors
16.
Am J Respir Cell Mol Biol ; 23(5): 678-86, 2000 Nov.
Article in English | MEDLINE | ID: mdl-11062147

ABSTRACT

Most of the genes that encode epithelial mucins are highly polymorphic due to variations in the length of domains of tandemly repeated (TR) coding sequence, the part of the apomucin that is heavily glycosylated. We report here for the first time a difference in the distribution of MUC TR length alleles in chest disease. We examined the distribution of the length alleles of those MUC genes whose expression we have confirmed in the bronchial tree in an age- and sex-matched series of 50 pairs of atopic patients with and without asthma. There was no significant difference in the distribution of alleles of MUC1, MUC4, MUC5AC, and MUC5B. MUC2, however, showed a highly significant difference in distribution. The atopic, nonasthmatic individuals showed an allele distribution that was very different from all our other patient and control groups, this group showing a longer mean allele length. The observations suggest that longer MUC2 alleles may help protect atopic individuals from developing asthma, though the effect may be due to a linked gene. The biological significance of this variation with respect to susceptibility to asthma will merit further investigation, and it will also be important to substantiate this finding on an independent data set.


Subject(s)
Lung Diseases/genetics , Mucins/genetics , Polymorphism, Genetic , Alleles , Humans , Lung Diseases/metabolism , Mucin-2 , Neoplasm Proteins/genetics
17.
Am J Clin Pathol ; 114(2): 258-63, 2000 Aug.
Article in English | MEDLINE | ID: mdl-10941341

ABSTRACT

The distinction between benign follicular hyperplasia (FH) and follicular lymphoma (FL) is sometimes problematic. We wanted to determine whether the expression of bcl-2 of FH was quantitatively different from that of FL, using surface CD20 expression as a discriminator of the various lymphoid compartments. Lymph node cell suspensions from 12 cases of FH and 17 cases of FL were analyzed by flow cytometry using a combined surface CD20 and intracellular bcl-2 staining. CD20- T cells in FH demonstrated the same bcl-2 expression as the CD20+ mantle cells, but the bright CD20+ germinal center cells showed near absence of bcl-2 expression. In contrast, the neoplastic cells of FL showed greater bcl-2 expression than the T cells of the same tumors and all cell populations of FH. This difference was particularly significant between the neoplastic B cells of FL and the germinal center cells of FH. The combined analysis of CD20 and bcl-2 should be useful for the differential diagnosis between FH and FL and particularly applicable to limited samples or when B-cell clonality is in question. Whether the quantitation of bcl-2 expression can be of further discriminatory value in malignant lymphomas remains to be determined.


Subject(s)
Antigens, CD20/analysis , Lymph Nodes/pathology , Lymphoma, Follicular/diagnosis , Proto-Oncogene Proteins c-bcl-2/analysis , Pseudolymphoma/diagnosis , Antibodies, Monoclonal , Cytoplasm/chemistry , DNA, Neoplasm/genetics , Diagnosis, Differential , Flow Cytometry , Gene Rearrangement/genetics , Humans , Lymphoma, Follicular/chemistry , Lymphoma, Follicular/genetics , Polymerase Chain Reaction , Proto-Oncogene Proteins c-bcl-2/genetics , Pseudolymphoma/genetics , Pseudolymphoma/metabolism
18.
J Infect ; 38(3): 162-6, 1999 May.
Article in English | MEDLINE | ID: mdl-10424795

ABSTRACT

OBJECTIVES: Since 1987 there has been an increase in tuberculosis notifications in the U.K., with this increase disproportionately affecting London. A recent national survey suggests that co-infection with HIV occurs in less than 5% of tuberculosis patients. This study asked if local co-infection rates in Inner London differed from the national results. METHODS: 157 consecutive patients starting antituberculous chemotherapy were venesected 2 weeks into treatment. Anonymized blood samples were screened for antibodies for HIV-1 and HIV-2 by enzyme-linked immunosorbent assay (ELISA). Epidemiological data were collected on each patient which was also coded before HIV test results were known. RESULTS: Of 157 patients commencing antituberculous therapy, 39 patients (24.8%) were found to be co-infected with HIV-1. HIV-negative and positive patients were similar in terms of age and sex. When 98 patients giving their country of origin as other than Europe were considered there were 22 co-infected with HIV (22.4%). Of the 39 HIV-positive identified in this study, 37 were also identified by our voluntary HIV testing programme. CONCLUSIONS: This study has shown that there may be very different rates of co-infection at a local level in the U.K. The local variation may be missed by national surveys and diverse local testing procedures. Anonymous testing identified only two patients with tuberculosis and HIV infection who were not identified by our voluntary HIV testing programme and this suggests that offering HIV tests to patients with tuberculosis is largely taken up by those at risk of HIV infection. Surveillance studies of this type are important in identifying marked local variation from the national pattern of HIV and Mycobacterium tuberculosis infection.


Subject(s)
AIDS-Related Opportunistic Infections/epidemiology , HIV Infections/epidemiology , HIV Seroprevalence , HIV-1/isolation & purification , HIV-2/isolation & purification , Tuberculosis/epidemiology , AIDS-Related Opportunistic Infections/drug therapy , Adolescent , Adult , Antibodies, Viral/blood , Antitubercular Agents/therapeutic use , Child , Comorbidity , Female , HIV Infections/virology , Hospitalization , Humans , Incidence , London/epidemiology , Male , Middle Aged , Tuberculosis/drug therapy , Urban Population
19.
Biochim Biophys Acta ; 1409(2): 99-105, 1998 Dec 01.
Article in English | MEDLINE | ID: mdl-9838065

ABSTRACT

Fourier transform infrared spectroscopic analysis of CO binding proteins in Rhodobacter sphaeroides reveals the presence of a membrane-bound nitric oxide reductase (Nor). Nor has been clearly distinguished from the cytochrome oxidases by the temperature-dependence of relaxation following photodissociation of the CO complex at cryogenic temperatures. The center frequency and band shape, 1970 cm-1 and 20-30 cm-1 width at half-peak height, are similar to those reported for resonance Raman spectra of purified Paracoccus denitrificans Nor. Additional evidence is presented to indicate this enzyme is part of dissimilatory nitric oxide metabolism and that one of the genes in the nor operon required for production of an active Nor is not required for protein assembly or heme incorporation.


Subject(s)
Rhodobacter sphaeroides/chemistry , Aerobiosis , Cell Membrane/chemistry , Oxidoreductases/chemistry , Rhodobacter sphaeroides/ultrastructure , Spectroscopy, Fourier Transform Infrared
20.
Proc Natl Acad Sci U S A ; 95(25): 14733-8, 1998 Dec 08.
Article in English | MEDLINE | ID: mdl-9843958

ABSTRACT

When lipid synthesis is limited in HepG2 cells, apoprotein B100 (apoB100) is not secreted but rapidly degraded by the ubiquitin-proteasome pathway. To investigate apoB100 biosynthesis and secretion further, the physical and functional states of apoB100 destined for either degradation or lipoprotein assembly were studied under conditions in which lipid synthesis, proteasomal activity, and microsomal triglyceride transfer protein (MTP) lipid-transfer activity were varied. Cells were pretreated with a proteasomal inhibitor (which remained with the cells throughout the experiment) and radiolabeled for 15 min. During the chase period, labeled apoB100 remained associated with the microsomes. Furthermore, by crosslinking sec61beta to apoB100, we showed that apoB100 remained close to the translocon at the same time apoB100-ubiquitin conjugates could be detected. When lipid synthesis and lipoprotein assembly/secretion were stimulated by adding oleic acid (OA) to the chase medium, apoB100 was deubiquitinated, and its interaction with sec61beta was disrupted, signifying completion of translocation concomitant with the formation of lipoprotein particles. MTP participates in apoB100 translocation and lipoprotein assembly. In the presence of OA, when MTP lipid-transfer activity was inhibited at the end of pulse labeling, apoB100 secretion was abolished. In contrast, when the labeled apoB100 was allowed to accumulate in the cell for 60 min before adding OA and the inhibitor, apoB100 lipidation and secretion were no longer impaired. Overall, the data imply that during most of its association with the endoplasmic reticulum, apoB100 is close to or within the translocon and is accessible to both the ubiquitin-proteasome and lipoprotein-assembly pathways. Furthermore, MTP lipid-transfer activity seems to be necessary only for early translocation and lipidation events.


Subject(s)
Apolipoproteins B/biosynthesis , Carrier Proteins/metabolism , Microsomes/metabolism , Protein Processing, Post-Translational , Animals , Apolipoprotein B-100 , Cell Line , Humans
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