Interaction with AEG-1 and MDM2 is associated with glioma development and progression and correlates with poor prognosis

Glioma is the most common central nervous system tumor with poor prognosis. The AEG-1 (Astrocyte Elevated Gene 1) gene displays oncogenic characteristics, including proliferation, metastasis, chemoresistance, invasion, and evasion of apoptosis, and is strongly linked to the occurrence of glioma. Here, we elucidated the potential contribution of AEG-1 in human glioma pathogenesis. In glioma cells, AEG-1 could directly interact with Murine Double Minute-2 (MDM2) protein resulting in MDM2-p53-mediated cell proliferation and apoptosis. MDM2 is being revealed as an oncoprotein, which is involved in many human cancers progression. By immunohistochemical and a multivariate analysis, expressions of AEG-1 and MDM2 were elevated in glioma and high AEG-1 and MDM2 expressions were showed to be correlated with poor prognosis. AEG-1-MDM2 interaction prolonged stabilization of MDM2 where AEG-1 inhibited ubiquitination and subsequent proteasome-mediated degradation of MDM2 protein. Moreover, slicing AEG-1 blocked MDM2 expression and then impacted MDM2-p53 pathway that influenced cell proliferation and apoptosis. These findings uncover a novel AEG-1-MDM2 interplay by which AEG-1 augments glioma progression and reveal a viable potential therapy for the treatment of glioma patients.     

价格随供求变化的捕获问题

本文对开放式渔场建立了价格随供求而变化的捕获模型,对模型进行了详细的分析,并从生态学和经济学的角度对结果作了解释。为生物资源的实际管理提供了理论依据。     

Tau interacts with Golgi membranes and mediates their association with microtubules

Tau, a microtubule-associated protein enriched in the axon, is known to stabilize and promote the formation of microtubules during axonal outgrowth. Several studies have reported that tau was associated with membranes. In the present study, we further characterized the interaction of tau with membranous elements by examining its distribution in subfractions enriched in either Golgi or endoplasmic reticulum membranes isolated from rat brain. A subfraction enriched with markers of the medial Golgi compartment, MG160 and mannosidase II, presented a high tau content indicating that tau was associated with these membranes. Electron microscope morphometry confirmed the enrichment of this subfraction with Golgi membranes. Double-immunogold labeling experiments conducted on this subfraction showed the direct association of tau with vesicles labeled with either an antibody directed against MG160 or TGN38. The association of tau with the Golgi membranes was further confirmed by immunoisolating Golgi membranes with an anti-tau antibody. Immunogold labeling confirmed the presence of tau on the Golgi membranes in neurons in vivo. Overexpression of human tau in primary hippocampal neurons induced the formation of large Golgi vesicles that were found in close vicinity to tau-containing microtubules. This suggested that tau could serve as a link between Golgi membranes and microtubules. Such role for tau was demonstrated in an in vitro reconstitution assay. Finally, our results showed that some tau isoforms present in the Golgi subfraction were phosphorylated at the sites recognized by the phosphorylation-dependent antibodies PHF-1 and AT-8.     

Adducts with haemoglobin and with DNA in epichlorohydrin-exposed rats

Epichlorohydrin (1-chloro-2,3-epoxypropane; ECH) is an important industrial chemical and a carcinogen in experimental animals. The main aims of the present study were to characterize the adduct formation in female Wistar rats and to identify adducts that could potentially be used in human biomonitoring studies. The total binding of radioactivity to haemoglobin in rats administered 0, 0. 11, 0.22, 0.43, or 0.97 mmol [3H]ECH/kg body weight by i.p. injection, and sacrificed 24 h after treatment, was linearly related to a dose up to 0.43 mmol/kg body weight. The binding at the highest dose was higher than predicted by extrapolation from lower doses, indicating saturation of a metabolic process for elimination of ECH. Ion-exchange chromatography of a globin hydrolysate showed one major radioactivity peak corresponding to S-(3-chloro-2-hydroxypropyl)cysteine. The half-life of this adduct was estimated as about 4 days by analysis of globin from rats administered 0.43 mmol/kg body weight and sacrificed after 1, 2 and 9 days. Crosslinking of the adduct, presumably with glutathione, appeared to be the predominant secondary reaction. Hydrolysis of N-(3-chloro-2-hydroxypropyl)valine, the primary reaction product of ECH with N-terminal valine, would give N-(2,3-dihydroxypropyl)valine. A sensitive gas chromatography/mass spectrometry method for the dihydroxypropyl adduct was used to follow its formation and removal after administration of nonlabelled ECH (0.11 mmol/kg body weight). The level of this adduct reached a maximum of about 20 pmol/g globin after a few weeks, corresponding to about 0.1% of the initial binding of ECH to globin. N-7-(3-Chloro-2-hydroxypropyl)guanine was detected in rats administered 0.97 mmol [3H]ECH/kg body weight and sacrificed 6 h after treatment. The adduct levels in haemoglobin and DNA were compared with previously reported adduct levels in male Fischer 344 rats exposed to propylene oxide. Despite its higher chemical reactivity, the capacity of ECH to alkylate macromolecules in vivo was found to be somewhat lower than that of propylene oxide.     

Interaction of calmodulin with the red cell and its membrane skeleton and with spectrin

The binding of calmodulin to red cell membrane cytoskeletons and to purified spectrin from red cells and bovine brain spectrin (fodrin) has been examined. Under physiological solvent conditions binding can be measured by ultracentrifugal pelleting assays. The membrane cytoskeletons contained a single class of binding sites, with a concentration similar to that of spectrin dimers and an association constant of 1.5 X 10(5) M-1. Binding is calcium dependent and is suppressed by the calmodulin inhibitor trifluoperazine. The binding showed a marked dependence on ionic strength, with a maximum at 0.05 M, and a steep dependence on pH, with a maximum at pH 6.5. It was unaffected by 5 mM magnesium. An azidocalmodulin derivative, under the conditions of our experiments, did not label the spectrin-containing complex, although it could be used to demonstrate binding to fodrin. Binding of calmodulin to spectrin tetramers and fodrin in solution could be demonstrated by a pelleting assay after addition of F-actin. Calculations (which are necessarily rough) suggest that at the free calcium concentration prevailing in a normal red cell about 1 in 20 of the calmodulin binding sites in spectrin will be occupied; this proportion will rise rapidly with increasing intracellular calcium. To determine whether inhibition of calmodulin binding to red cell proteins disturbs the control of cell shape, as has been suggested, calcium ions were removed from the cell by addition of an ionophore and of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to the external medium. This did not affect the discoid shape. Trifluoperazine still induced stomatocytosis, exactly as in untreated cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ataxin-3 interactions with rad23 and valosin-containing protein and its associations with ubiquitin chains and the proteasome are consistent with a role in ubiquitin-mediated proteolysis

Machado-Joseph disease is caused by an expansion of a trinucleotide CAG repeat in the gene encoding the protein ataxin-3. We investigated if ataxin-3 was a proteasome-associated factor that recognized ubiquitinated substrates based on the rationale that (i) it is present with proteasome subunits and ubiquitin in cellular inclusions, (ii) it interacts with human Rad23, a protein that may translocate proteolytic substrates to the proteasome, and (iii) it shares regions of sequence similarity with the proteasome subunit S5a, which can recognize multiubiquitinated proteins. We report that ataxin-3 interacts with ubiquitinated proteins, can bind the proteasome, and, when the gene harbors an expanded repeat length, can interfere with the degradation of a well-characterized test substrate. Additionally, ataxin-3 associates with the ubiquitin- and proteasome-binding factors Rad23 and valosin-containing protein (VCP/p97), findings that support the hypothesis that ataxin-3 is a proteasome-associated factor that mediates the degradation of ubiquitinated proteins.     

The interaction of cadmium with calcium and cisplatin with chloride

Changes in the locomotor rate of the ciliateTetrahymena pyriformis were used to quantitatively evaluate chemical interactions produced by: cadmium in combination with varying amounts of calcium, andcis-dichlorodiammineplatinum (II) (cisplatin) with varying amounts of sodium chloride. Cadmium (as CdCl₂) produces a measurable decline in the locomotor rate of the cells. Cadmium's detrimental effect can be reduced by the addition of calcium (as CaCl₂) in combination with cadmium. At a ratio of 30∶1 (calcium: cadmium), cadmium's negative effect upon motility is essentially nullified. It is suggested that the “protective” action afforded by calcium stems from the chemical similarity of the two cations and their involvement/competition for molecular sites responsible for the energy release and/or delivery of ciliary activity. Cisplatin will also effect a reduction in ciliary activity. However, the interaction between cisplatin, sodium chloride, and the cell appears more complex than that found with cadmium-calcium. At the lower range of chloride (as NaCl) used in this study, increased chloride concentration produces an increase in cisplatin's action against ciliary activity. At the higher levels, the chloride reduced cisplatin's negative effects. It is suggested that the increases in cisplatin's effects are caused by mass chemical action of increased chloride, which increases the concentration of the nonpolar cisplatin. The reduced effects found with the higher concentrations of sodium chloride may be because of the presence and action of elevated NaCl in/on the cell. This study clearly demonstrates differences in biologically relevant chemical interactions occurring with the two sets: cadmium-calcium and cisplatin-chloride.     

Interactions of retinol with binding proteins: studies with retinol-binding protein and with transthyretin.

The interactions within the molecular complex in which retinol circulates in blood were studied. To monitor binding between retinol-binding protein (RBP) and transthyretin (TTR), TTR was labeled with a long-lived fluorescence probe (pyrene). Changes in the rotational volume of TTR following its association with RBP were monitored by fluorescence anisotropy of the probe. Titration of TTR with holo-RBP revealed the presence of 1.5 binding sites characterized by a dissociation constant Kd = 0.07 microM. At 0.15 M NaCl, binding of RBP to TTR showed an absolute requirement for the native ligand, retinol. At higher ionic strength (0.5 M NaCl), RBP complexed with retinal also bound to TTR with high affinity (Kd = 0.134 microM). RBP containing retinoic acid did not bind to TTR even at the high salt concentration. The data suggest that the TTR binding site on RBP is in close proximity to the retinoid binding site and that the head group of retinoic acid, when bound to RBP, presents steric hindrance for the interactions with TTR. The implications of the data for selectivity in retinoid transport in the circulation are discussed. The kinetics of the steps leading to complete dissociation of the retinol-RBP-TTR complex was also studied. The first step of this process was dissociation of retinol, which had a rate constant of 0.06/min. Following loss of retinol, the two proteins dissociate. The rate of dissociation is slow (k = 0.055/h), however, indicating that the complex apo-RBP-TTR will be an important factor in regulating serum levels of retinol.     

Symptoms Associated with Victimization in Patients with Schizophrenia and Related Disorders

Background

Patients with psychoses have an increased risk of becoming victims of violence. Previous studies have suggested that higher symptom levels are associated with a raised risk of becoming a victim of physical violence. There has been, however, no evidence on the type of symptoms that are linked with an increased risk of recent victimization.

Methods

Data was taken from two studies on involuntarily admitted patients, one national study in England and an international one in six other European countries. In the week following admission, trained interviewers asked patients whether they had been victims of physical violence in the year prior to admission, and assessed symptoms on the Brief Psychiatric Rating Scale (BPRS). Only patients with a diagnosis of schizophrenia or related disorders (ICD-10 F20–29) were included in the analysis which was conducted separately for the two samples. Symptom levels assessed on the BPRS subscales were tested as predictors of victimization. Univariable and multivariable logistic regression models were fitted to estimate adjusted odds ratios.

Results

Data from 383 patients in the English sample and 543 patients in the European sample was analysed. Rates of victimization were 37.8% and 28.0% respectively. In multivariable models, the BPRS manic subscale was significantly associated with victimization in both samples.

Conclusions

Higher levels of manic symptoms indicate a raised risk of being a victim of violence in involuntary patients with schizophrenia and related disorders. This might be explained by higher activity levels, impaired judgement or poorer self-control in patients with manic symptoms. Such symptoms should be specifically considered in risk assessments.     

Mutation-positive and mutation-negative patients with Cowden and Bannayan-Riley-Ruvalcaba syndromes associated with distinct 10q haplotypes

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) encodes a tumor-suppressor phosphatase frequently mutated in both sporadic and heritable forms of human cancer. Germline mutations are associated with a number of heritable cancer syndromes that are jointly referred to as the "PTEN hamartoma tumor syndrome" (PHTS) and include Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like syndrome. Germline PTEN mutations have been identified in a significant proportion of patients with PHTS; however, there are still many individuals with classic diagnostic features for whom mutations have yet to be identified. To address this, we took a haplotype-based approach and investigated the association of specific genomic regions of the PTEN locus with PHTS. We found this locus to be characterized by three distinct haplotype blocks 33 kb, 65 kb, and 43 kb in length. Comparisons of the haplotype distributions for all three blocks differed significantly among patients with PHTS and controls (P=.0098, P<.0001, and P<.0001 for blocks 1, 2, and 3, respectively). "Rare" haplotype blocks and extended haplotypes account for two-to-threefold more PHTS chromosomes than control chromosomes. PTEN mutation-negative patients are strongly associated with a haplotype block spanning a region upstream of PTEN and the gene's first intron (P=.0027). Furthermore, allelic combinations contribute to the phenotypic complexity of this syndrome. Taken together, these data suggest that specific haplotypes and rare alleles underlie the disease etiology in these sample populations; constitute low-penetrance, modifying loci; and, specifically in the case of patients with PHTS for whom traditional mutations have yet to be identified, may harbor pathogenic variant(s) that have escaped detection by standard PTEN mutation-scanning methodologies.     

Xp-duplications with and without sex reversal

Duplications in Xp including the DSS (dosage sensitive sex reversal) region cause male to female sex reversal. We investigated two patients from families with Xp duplications. The first case was one of two sisters with karyotype 46,XY, der(22), t(X;22)(p11.3;p11)mat and unambiguous female genitalia. The living sister was developmentally retarded, and showed multiple dysmorphic features and an acrocallosal syndrome. The second case was a boy with a maternally inherited direct duplication of Xp21.3-pter with the breakpoint close to the DSS locus. He had multiple abnormalities and micropenis, but otherwise unambiguous male genitalia. We performed quantitative Southern blot analysis with probes from Xp22.13 to p21.2 to define the duplicated region. Clinical, cytogenetic, and molecular data from both patients were compared with those of previously reported related cases. A comparison of the extragenital symptoms revealed no differences between patients with or without sex reversal. In both cases, the symptoms were non-specific. Among 22 patients with a duplication in Xp, nine had unambiguous female genitalia and a well-documented duplication of the DSS region. Two patients with duplication of DSS showed ambiguous external genitalia. From these data, we conclude that induction of testicular tissue may start in these patients, but that the type of genitalia depends on the degree of subsequent degeneration by a gene in DSS.     

Histamine chloramine reactivity with thiol compounds, ascorbate, and methionine and with intracellular glutathione

Histamine is stored in granules of mast cells and basophils and released by inflammatory mediators. It has the potential to intercept some of the HOCl generated by the neutrophil enzyme, myeloperoxidase, to produce histamine chloramine. We have measured rate constants for reactions of histamine chloramine with methionine, ascorbate, and GSH at pH 7.4, of 91 M(-1)s(-1), 195 M(-1)s(-1), and 721 M(-1)s(-1), respectively. With low molecular weight thiols, the reaction was with the thiolate and rates increased exponentially with decreasing thiol group pK(a). Comparing rate constants for different chloramines reacting with ascorbate or a particular thiol anion, these were higher when there was less negative charge in the vicinity of the chloramine group. Histamine chloramine was the most reactive among biologically relevant chloramines. Consumption of histamine chloramine and oxidation of intracellular GSH were examined for human fibroblasts. At nontoxic doses, GSH loss over 10 min was slightly greater than that with HOCl, but the cellular uptake of histamine chloramine was 5-10-fold less. With histamine chloramine, GSSG was a minor product and most of the GSH was converted to mixed disulfides with proteins. HOCl gave a different profile of GSH oxidation products, with significantly less GSSG and mixed disulfide formation. There was irreversible oxidation and losses to the medium, as observed with HOCl and other cell types. Thus, histamine chloramine shows high preference for thiols both in isolation and in cells, and in this respect is more selective than HOCl.     

PTH and interactions with bisphosphonates

We report that a therapeutic dose of the antiresorptive bisphosphonate alendronate administered to skeletally mature rats for the duration of 16 weeks significantly blunted the anabolic response to a high dose SDZ PTS 893 in the tibia and femur but not in lumbar vertebra. Effects were seen at the level of bone mass (DEXA, pQCT) as well as in biomechanical tests. In one arm of this study, rats were switched to vehicle injections after 8 weeks on alendronate for another 8 weeks before being challenged with the anabolic stimulus (washout). This recovery period was insufficient for full recovery and the response to SDZ PTS 893 was still greatly reduced after this procedure. Serial pQCT-measurements suggest that part of the interaction happened during the first two weeks of PTH treatment when bone-lining cells are activated by the anabolic drug. In addition bisphosphonate pretreated rats failed to catch up with the vehicle control at all time points suggesting a second level of drug interaction. The failure of the 'washout' period to restore the normal response to PTH is suggestive of a physico-chemical interaction on the level of the matrix embedded bisphosphonate with the overlaying bone lining cells, rather than of direct effects of the drug on osteoblasts or their precursor cells. Overall the data raises the possibility, that bisphosphonate treated patients respond to PTH and SDZ PTS 893 with a delay which could affect the shorter bone mass measurements carried out at 6 months to 1 year. Additionally, bisphosphonate pre-treated rats did not develop the full anabolic response over time. Clinical investigators studying anabolic drugs such as PTH should be aware of potential long-term interactions of bisphosphonates when assessing the outcome of their experiments. However, the beneficial effect of bisphosphonates like alendronate on PTH-induced bone remodeling, as well as its potent action in the protection of bone loss after cessation of anabolic therapy might outweigh the worries about a small delay in the bone response to parathyroid hormone.     

Interaction of trichorzianines A and B with model membranes and with the amoeba Dictyostelium

Trichorzianines A (TA) and B (TB) are microheterogeneous mixtures of antibiotic nonadecapeptides of the peptaibol class which interact with lipidic membranes and modify their permeability properties. The TB differ from the TA by replacement of the Gln-18 by a Glu, giving rise to a C-terminal negative charge at neutral pH. The role of this charge on the trichorzianine-lipid interaction was investigated with model membranes by fluorescence spectroscopy and the results were correlated with the biological activity toward the amoeba Dictyostelium discoideum. The interaction of the acidic trichorzianine TB IIIc (Glu-18) with phospholipid bilayers and the subsequent induced permeability were weaker than that exhibited by the uncharged TA IIIc (Gln-18) and MeTB IIIc (TB IIIc monomethyl ester). The unfavourable effect of the negative charge in TB IIIc was strongly enhanced by incorporation of cholesterol in the bilayer. Similarly, TA IIIc as well as MeTB IIIc induced growth inhibition and lysis of the amoeba Dictyostelium at four times lower concentrations than TB IIIc. The results suggested that the interaction of trichorzianines with the phospholipid bilayer and the subsequent modifications of permeability were involved in the inhibitory properties and cell lysis induced by trichorzianines toward Dictyostelium.     

Bioaerosol concentrator performance: comparative tests with viable and with solid and liquid nonviable particles

Aims:  Generally it is more economical to first characterize a concentrator system with nonbiological particles followed by more rigorous bioaerosol testing. This study compares sampling system performance for varions particle types and sizes.
Methods and Results:  Performances of five concentrators were characterized with five nonviable and viable laboratory aerosols, although not every concentrator was tested with all aerosol types. For particle sizes less than c. 6  μ m aerodynamic diameter, similar efficiencies are obtained for all test particles; however, for larger sizes there is a significant difference between liquid and dry particles.
Conclusions:  Aluminium oxide particles provide results over a broad range of sizes with a single test, but the method is less reproducible than other methods. A combination of monodisperse polystyrene spheres and oleic acid droplets provides an accurate representation of the system performance, but ultimately biological particle tests are needed.
Significance and Impact of the Study:  Devices are being developed for concentrating bioaerosol particles in the size range of 1–10  μ m aerodynamic diameter and this study provides insight into data quality for different test methodologies. Also, the results show some current concentrators perform quite poorly.     

Capping of CdSe-ZnS quantum dots with DHLA and subsequent conjugation with proteins

We provide a detailed protocol for designing water-soluble CdSe-ZnS quantum dots (QDs) based on cap exchange of the native hydrophobic shell with dihydrolipoic acid (DHLA) ligands, and the preparation of functional QD bioconjugates for use in immunoassays. Our conjugation strategy is based on non-covalent self-assembly between DHLA-capped QDs and protein appended with either an electrostatic attachment domain (namely, the basic leucine zipper) or a polyhistidine tag. These bioconjugates combine the properties of the QD and attached biomolecule to create structures with desirable luminescent and biologically specific properties. This method also allows the preparation of mixed surface conjugates, which results in the conjugates gaining multiple biological activities. Conjugation of DHLA-capped QDs to maltose binding protein (MBP), the immunoglobulin-G-binding beta2 domain of streptococcal protein G (PG) and avidin will be described. MBP and PG were modified by genetic fusion with either a charged leucine zipper or a polyhistidine interaction domain.     

Differences in brain function and changes with intervention in children with poor spelling and reading abilities

Previous fMRI studies in English-speaking samples suggested that specific interventions may alter brain function in language-relevant networks in children with reading and spelling difficulties, but this research strongly focused on reading impaired individuals. Only few studies so far investigated characteristics of brain activation associated with poor spelling ability and whether a specific spelling intervention may also be associated with distinct changes in brain activity patterns. We here investigated such effects of a morpheme-based spelling intervention on brain function in 20 children with comparatively poor spelling and reading abilities using repeated fMRI. Relative to 10 matched controls, children with comparatively poor spelling and reading abilities showed increased activation in frontal medial and right hemispheric regions and decreased activation in left occipito-temporal regions prior to the intervention, during processing of a lexical decision task. After five weeks of intervention, spelling and reading comprehension significantly improved in the training group, along with increased activation in the left temporal, parahippocampal and hippocampal regions. Conversely, the waiting group showed increases in right posterior regions. Our findings could indicate an increased left temporal activation associated with the recollection of the new learnt morpheme-based strategy related to successful training.     

MAGI-1 interacts with beta-catenin and is associated with cell-cell adhesion structures

The family of membrane-associated guanylate kinases (MAGUK) comprises peripheral membrane proteins involved in the formation of specialized cell-cell junctions. MAGUK proteins possess a conserved domain composition, containing PDZ, guanylate kinase, and SH3 or WW domains. MAGI-1 is a recently identified member of the MAGUK protein family. Three splice variantsof MAGI-1 have been characterized to date, including MAGI-1a, -1b, and -1c. MAGI-1b is predominantly associated with the crude membrane fraction. Here we show that the fifth PDZ domain of MAGI-1b is essential for membrane localization. We have also identified beta-catenin as a potential ligand for this PDZ domain. MAGI-1b forms complexes with beta-catenin and E-cadherin during the formation of cell-cell junctions in MDCK cells. In agreement with this observation, a significant portion of a GFP fusion of MAGI-1b localizes to the basolateral membrane of polarized MDCK cells.     

Maternal communication with gametes and embryos

Mechanisms for gametes and embryos to interact with their maternal environment are crucial in achieving reproductive success, both in livestock and the human. Long-range (hormones) and short-range signalling molecules play important roles in mediating cell-cell maternal interactions/communications with gametes and embryos. Slight malfunctions or disturbances of the environment that host this interaction can retard embryonic development. This may lead to creation of a memory for the embryo leading to offspring prone to degenerative diseases in adulthood. Despite an overwhelming amount of research and the literature, not all signalling molecules involved and their relationship with each other are known. Progress in the application of high-throughput genomic and proteomic analytical tools, such as microarrays and quantitative proteomic technologies has had a positive impact on our understanding of various aspects of maternal communication with gametes and embryos. Recent advances point to the presence of a local mechanism in the female reproductive tract capable of recognising the arrival of gametes and embryos and modulating the tract's environment accordingly for the next stage. Further investigations are underway to characterise the details of this system. It is important to consider spatial or temporal components of maternal communication with gametes and embryos that may confer consequences for developmental potential. Finally, it seems that the application of a systems biology approach for creation of an interactome map of maternal communication with gametes and embryos is essential and provides an excellent opportunity for an inter-disciplinary collaboration with engineers and mathematical modellers.     

A strategy for solubilizing delipidated apolipoprotein with lysophosphatidylcholine and reconstitution with phosphatidylcholine

The apolipoproteins of insect lipophorin were dissociated in guanidinium chloride and isolated by gel permeation chromatography. Over 98% of the total lipid in lipophorin was associated with apolipophorin I (apoLp-I), thus suggesting this apolipoprotein to be the lipid binding component of the particle. ApoLp-I was delipidated with ethanol/ether and solubilized in buffer that contained radioactive lysophosphatidylcholine ([3H]LPC) above the critical micellar concentration. Sonic irradiation of radioactive phosphatidylcholine ([14C]PC) with [3H]LPC-solubilized apoLp-I at a molar ratio of 318 resulted in reconstituted lipophorin (RLp-I). [3H]LPC was bound to fatty acid free bovine serum albumin and was separated from RLp-I by density gradient ultracentrifugation and gel permeation chromatography. Negatively stained RLp-I particles were quasispherical with an average radium of 55 A, and their overall morphology and secondary structure were similar to those of native hemolymph lipophorin. The RLp-I particle had a rho = 1.137 g/mL, a Mr approximately 5.2 X 10(5), and a [14C]PC:apoLp-I molar ratio of 308. From the compositional analysis, molecular size, trypsinization, and lipolysis with phospholipase A2, we concluded that each RLp-I particle contained one molecule of apoLp-I and a monomolecular layer of [14C]PC. When injected into the hemolymph of adult moths in vivo, RLp-I was loaded with lipid, as judged by a decrease in its density both in the presence and in the absence of adipokinetic hormone. The similarities in morphology and immunology of RLp-I and native lipophorin, together with the ability of RLp-I to load lipid, suggest that reconstituted lipophorins may serve as models to probe lipophorin structure and function.