CCPG1 recognizes endoplasmic reticulum luminal proteins for selective ER-phagy

The endoplasmic reticulum (ER) is a major cell compartment where protein synthesis, folding, and posttranslational modifications occur with assistance from a wide variety of chaperones and enzymes. Quality control systems selectively eliminate abnormal proteins that accumulate inside the ER due to cellular stresses. ER-phagy, that is, selective autophagy of the ER, is a mechanism that maintains or reestablishes cellular and ER-specific homeostasis through removal of abnormal proteins. However, how ER luminal proteins are recognized by the ER-phagy machinery remains unclear. Here, we applied the aggregation-prone protein, six-repeated islet amyloid polypeptide (6xIAPP), as a model ER-phagy substrate and found that cell cycle progression 1 (CCPG1), which is an ER-phagy receptor, efficiently mediates its degradation via ER-phagy. We also identified prolyl 3-hydroxylase family member 4 (P3H4) as an endogenous cargo of CCPG1-dependent ER-phagy. The ER luminal region of CCPG1 contains several highly conserved regions that we refer to as cargo-interacting regions (CIRs); these interact directly with specific luminal cargos for ER-phagy. Notably, 6xIAPP and P3H4 interact directly with different CIRs. These findings indicate that CCPG1 is a bispecific ER-phagy receptor for ER luminal proteins and the autophagosomal membrane that contributes to the efficient removal of aberrant ER-resident proteins through ER-phagy.

ER-Phagy: Quality and Quantity Control of the Endoplasmic Reticulum by Autophagy

The endoplasmic reticulum (ER) is the largest organelle and has multiple roles in various cellular processes such as protein secretion, lipid synthesis, calcium storage, and organelle biogenesis. The quantity and quality of this organelle are controlled by the ubiquitin-proteasome system and autophagy (termed "ER-phagy"). ER-phagy is defined as the degradation of part of the ER by the vacuole or lysosomes, and there are at least two types of ER-phagy: macro-ER-phagy and micro-ER-phagy. In macro-ER-phagy, ER fragments are enclosed by autophagosomes, which is mediated by ER-phagy receptors. In micro-ER-phagy, a portion of the ER is engulfed directly by the vacuole or lysosomes. In these two pathways, some proteins in the ER lumen can be recognized selectively and subjected to ER-phagy. This review summarizes our current knowledge of ER-phagy, focusing on its membrane dynamics, molecular mechanisms, substrate specificity, and physiological significance.

Phosphorylation by casein kinase 2 enhances the interaction between ER-phagy receptor TEX264 and ATG8 proteins

Selective autophagy cargos are recruited to autophagosomes primarily by interacting with autophagosomal ATG8 family proteins via the LC3-interacting region (LIR). The upstream sequence of most LIRs contains negatively charged residues such as Asp, Glu, and phosphorylated Ser and Thr. However, the significance of LIR phosphorylation (compared with having acidic amino acids) and the structural basis of phosphorylated LIR-ATG8 binding are not entirely understood. Here, we show that the serine residues upstream of the core LIR of the endoplasmic reticulum (ER)-phagy receptor TEX264 are phosphorylated by casein kinase 2, which is critical for its interaction with ATG8s, autophagosomal localization, and ER-phagy. Structural analysis shows that phosphorylation of these serine residues increases binding affinity by producing multiple hydrogen bonds with ATG8s that cannot be mimicked by acidic residues. This binding mode is different from those of other ER-phagy receptors that utilize a downstream helix, which is absent from TEX264, to increase affinity. These results suggest that phosphorylation of the LIR is critically important for strong LIR-ATG8 interactions, even in the absence of auxiliary interactions.

Should I bend or should I grow: the mechanisms of droplet-mediated autophagosome formation

Phase-separated droplets with liquid-like properties can be degraded by macroautophagy/autophagy, but the mechanism underlying this degradation is poorly understood. We have recently derived a physical model to investigate the interaction between autophagic membranes and such droplets, uncovering that intrinsic wetting interactions underlie droplet-membrane contacts. We found that the competition between droplet surface tension and the increasing tendency of growing membrane sheets to bend determines whether a droplet is completely engulfed or isolated in a piecemeal fashion, a process we term fluidophagy. Intriguingly, we found that another critical parameter of droplet-membrane interactions, the spontaneous curvature of the membrane, determines whether the droplet is degraded by autophagy or - counterintuitively - serves as a platform from which autophagic membranes expand into the cytosol. We also discovered that the interaction of membrane-associated LC3 with the LC3-interacting region (LIR) found in the autophagic cargo receptor protein SQSTM1/p62 and many other autophagy-related proteins influences the preferred bending directionality of forming autophagosomes in living cells. Our study provides a physical account of how droplet-membrane wetting underpins the structure and fate of forming autophagosomes.

Interstitial Lung Disease with Anti-melanoma Differentiation-associated Protein 5 Antibody: Rapidly Progressive Perilobular Opacity

Objective Rapidly progressive interstitial lung disease (RP-ILD) with anti-melanoma differentiation-associated protein 5 (MDA5) antibody potentially presents with a fatal clinical course and requires early intensive treatment. Recently, perilobular opacity was reported to pathologically correspond to the acute phase of diffuse alveolar damage in RP-ILD with anti-MDA5 antibody. We aimed to investigate whether or not perilobular opacity was a common radiological finding in RP-ILD patients with anti-MDA5 antibody. Methods We conducted a retrospective review of the medical records of eight consecutive patients with RP-ILD with anti-MDA5 antibody. The clinical features and radiological findings of follow-up computed tomography (CT) during the course of their disease were evaluated. Results Among eight RP-ILD patients with anti-MDA-5 antibody, six showed perilobular opacity in the lower lobes, and the remaining two had only consolidation on high-resolution CT. Of note, the perilobular opacity in all six patients thickened and progressed to consolidation with a loss of lung volume in a short period. Despite intensive treatment, 6 patients (75%) died within 100 days after the first visit. Notably, the two patients with consolidation presented with a very rapid clinical course and died in 13 days each. In the two survivors, the perilobular opacity and consolidation recovered with improvement in the loss of lung volume. Conclusion Rapidly progressive perilobular opacity that thickens and progresses to consolidation is characteristic of RP-ILD with anti-MDA5 antibody. Chest physicians should immediately check the status of anti-MDA-5 antibody in order to initiate early aggressive therapy in RP-ILD patients with rapidly progressive perilobular opacity.

Intrinsically Disordered Protein TEX264 Mediates ER-phagy

Certain proteins and organelles can be selectively degraded by autophagy. Typical substrates and receptors of selective autophagy have LC3-interacting regions (LIRs) that bind to autophagosomal LC3 and GABARAP family proteins. Here, we performed a differential interactome screen using wild-type LC3B and a LIR recognition-deficient mutant and identified TEX264 as a receptor for autophagic degradation of the endoplasmic reticulum (ER-phagy). TEX264 is an ER protein with a single transmembrane domain and a LIR motif. TEX264 interacts with LC3 and GABARAP family proteins more efficiently and is expressed more ubiquitously than previously known ER-phagy receptors. ER-phagy is profoundly blocked by deletion of TEX264 alone and almost completely by additional deletion of FAM134B and CCPG1. A long intrinsically disordered region of TEX264 is required for its ER-phagy receptor function to bridge the gap between the ER and autophagosomal membranes independently of its amino acid sequence. These results suggest that TEX264 is a major ER-phagy receptor.

Old age and underlying interstitial abnormalities are risk factors for development of ARDS after pleurodesis using limited amount of large particle size talc

BACKGROUND AND OBJECTIVE

Talc pleurodesis is commonly performed to manage refractory pleural effusion or pneumothorax. It is considered as a safe procedure as long as a limited amount of large particle size talc is used. However, acute respiratory distress syndrome (ARDS) is a rare but serious complication after talc pleurodesis. We sought to determine the risk factors for the development of ARDS after pleurodesis using a limited amount of large particle size talc.

METHODS

We retrospectively reviewed patients who underwent pleurodesis with talc or OK-432 at the University of Tokyo Hospital.

RESULTS

Twenty-seven and 35 patients underwent chemical pleurodesis using large particle size talc (4 g or less) or OK-432, respectively. Four of 27 (15%) patients developed ARDS after talc pleurodesis. Patients who developed ARDS were significantly older than those who did not (median 80 vs 66 years, P = 0.02) and had a higher prevalence of underlying interstitial abnormalities on chest computed tomography (CT; 2/4 vs 1/23, P < 0.05). No patient developed ARDS after pleurodesis with OK-432. This is the first case series of ARDS after pleurodesis using a limited amount of large particle size talc.

CONCLUSION

Older age and underlying interstitial abnormalities on chest CT seem to be risk factors for developing ARDS after talc pleurodesis.

Myeloperoxidase Anti-Neutrophil Cytoplasmic Antibody-Positive Interstitial Pneumonia Associated with Granulomatosis with Polyangiitis Diagnosed by Surgical Lung Biopsy

Granulomatosis with polyangiitis (GPA) is a rare systemic vasculitis that often involves the lung. However, interstitial pneumonia (IP) is rarely seen in GPA patients. We herein report 3 cases of IP associated with GPA diagnosed by surgical lung biopsy. High-resolution CT showed uniform subpleural reticular opacity with traction bronchiectasis. Biopsies from all 3 patients revealed neutrophilic capillaritis, microabscesses with giant cells, and coexisting histological findings of usual IP pattern or fibrosing nonspecific IP pattern. All 3 patients had elevated levels of serum myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA), but not proteinase 3-ANCA. We diagnosed GPA and treated with corticosteroid and cyclophosphamide. Follow-up CT showed improvement of the lesions in all patients. Surgical lung biopsy specimens which revealed GPA enabled us to conduct the most suitable therapy. This report indicates the importance of surgical lung biopsy for differentiating idiopathic IPs from GPA-associated IP and suggests a relationship between MPO-ANCA and IP in GPA.

Cardiogenic syncope possibly related to bevacizumab-containing combination chemotherapy for advanced non-small cell lung cancer

We report the case of a 55-year-old man with stage IV lung adenocarcinoma who received carboplatin-paclitaxel-bevacizumab chemotherapy as second-line therapy. After four cycles of chemotherapy, he experienced syncope with a decrease in blood pressure. Electrocardiography (ECG) revealed atrial fibrillation. Cardiac ultrasonography showed a markedly reduced ejection fraction (45%), with moderate decrease in comparison to that before chemotherapy (66%). Bisoprolol fumarate was initiated, and the conversion to sinus rhythm was detected by ECG 4 days after the syncope. At that time, no improvement in the ejection fraction was detected. Bevacizumab-associated cardiotoxicity was suspected, and bevacizumab maintenance therapy was discontinued, although the chemotherapy achieved a stable disease status based on the Response Evaluation Criteria in Solid Tumors. Two months after bevacizumab cessation, the ejection fraction improved to pretreatment level (62%). To the best of our knowledge, this is the first report on cardiogenic syncope due to left ventricular dysfunction that is most consistent with bevacizumab-associated cardiotoxicity in non-small cell lung cancer (NSCLC). Our results indicate that bevacizumab could lead to cardiotoxicity in patients with NSCLC and suggest the importance of the follow-up cardiac ultrasonography.

[[COMPLIANCE RATE OF STANDARD TREATMENT REGIMEN AND OPTIMAL DOSE OF ANTI-TUBERCULOSIS DRUGS IN LATE ELDERLY PATIENTS WITH PULMONARY TUBERCULOSIS].]

The proportion of the elderly in patients with pulmonary tuberculosis is increasing, and failure to complete the standard treatment regimen is not uncommon in these patients. We examined the compliance rate and prob- lems of the standard regimen in the late elderly pulmonary tuberculosis patients. [Methods] We reviewed the medical records of late elderly patients with pulmonary tuberculosis aged 75 or above who were smear-positive and treated in Kanagawa Cardiovascular and Respiratory Center between January 2011 and December 2014. Our retrospective study examined patient characteris- tics, imaging findings, laboratory results, and outcomes. The compliance rate of standard regimen during the hospitaliza- tion period was calculated. We compared the discontinua- tion rate and the incidence of adverse drug reactions by body weight equivalent doses of anti-tuberculosis drugs. [Results] A total of 298 patients were included in this study, and 76% of those patients were aged 80 or above. Anti-tuberculosis therapy was not able to be initiated for 3 patients (1%), and treatment other than standard regimen was inevitably introduced at initiation in 21 patients. The remaining 274 patients (92%) were administered the stan- dard regimen. Among them, at least one medication was subsequently discontinued for 85 patients (29%), and the medication was changed due to drug resistance in 6 patients . (2%). The remaining 183 patients (61%) complied with the standard regimen during hospitalization. In the comparison by body weight equivalent dose, significantly more patients discontinued their medication in the group using ethambutol with a higher standard dose per weight (37% vs. 21%, p=0.02). [Conclusion] Nearly 40% of the late elderly patients could not comply with the standard regimen. We may need to be more careful when calculating ethambutol equivalent dose.

Radiological and Pathological Correlation in Anti-MDA5 Antibody-positive Interstitial Lung Disease: Rapidly Progressive Perilobular Opacities and Diffuse Alveolar Damage

We herein present the first case of rapidly progressive interstitial lung disease (RP-ILD) with anti-melanoma differentiation-associated protein 5 (MDA5) antibody evaluated by surgical lung biopsy (SLB). High-resolution CT scan revealed perilobular opacities, which rapidly became thicker and formed consolidation, resulting in remarkable loss of lung volume. Specimens taken from SLB revealed membranous organization with alveolar occlusion, dilation of alveolar ducts, and sacs with collapsed alveoli, which are typical features of diffuse alveolar damage (DAD). Rapidly progressive perilobular opacities may be characteristic of RP-ILD with anti-MDA5 antibody and DAD.

Successful treatment with alectinib after crizotinib-induced interstitial lung disease

We herein report a case of a 46-year-old woman with anaplastic lymphoma kinase (ALK)-rearranged stage IV lung adenocarcinoma who received the ALK inhibitor crizotinib as second-line therapy. On the 47th day following crizotinib initiation, a chest computed tomography scan revealed ground-glass opacities with a clinical manifestation of desaturation, although a partial response to treatment was detected. The diagnosis of crizotinib-induced interstitial lung disease (ILD) was confirmed, and crizotinib was discontinued, followed by the initiation of corticosteroid therapy. After improvement of ILD with corticosteroid therapy, alectinib was administered as salvage therapy, resulting in tumor shrinkage without any recurrence of ILD. To the best of our knowledge, this is the first report of successful alectinib treatment following crizotinib-induced ILD. Our results indicate that alectinib could be a promising alternative treatment option in patients with crizotinib-induced ILD.

The importance of bacterial and viral infections associated with adult asthma exacerbations in clinical practice

BACKGROUND

Viral infection is one of the risk factors for asthma exacerbation. However, which pathogens are related to asthma exacerbation in adults remains unclear.

OBJECTIVE

The relation between various infections and adult asthma exacerbations was investigated in clinical practice.

METHODS

The study subjects included 50 adult inpatients due to asthma exacerbations and 20 stable outpatients for comparison. The pathogens from a nasopharyngeal swab were measured by multiplex PCR analysis.

RESULTS

Asthma exacerbations occurred after a common cold in 48 inpatients. The numbers of patients with viral, bacterial, or both infections were 16, 9, and 9, respectively. The dominant viruses were rhinoviruses, respiratory syncytial virus, influenza virus, and metapneumovirus. The major bacteria were S. pneumoniae and H. influenzae. Compared to pathogen-free patients, the patients with pathogens were older and non-atopic and had later onset of disease, lower FeNO levels, lower IgE titers, and a higher incidence of comorbid sinusitis, COPD, or pneumonia. Compared to stable outpatients, asthma exacerbation inpatients had a higher incidence of smoking and comorbid sinusitis, COPD, or pneumonia. Viruses were detected in 50% of stable outpatients, but a higher incidence of rhinovirus, respiratory syncytial virus, and metapneumovirus infections was observed in asthma exacerbation inpatients. H. influenzae was observed in stable asthmatic patients. Other bacteria, especially S. pneumoniae, were important in asthma exacerbation inpatients.

CONCLUSION

Viral or bacterial infections were observed in 70% of inpatients with an asthma exacerbation in clinical practice. Infection with S. pneumoniae was related to adult asthma exacerbation.

Pulmonary Aluminosis Diagnosed with In-air Microparticle Induced X-ray Emission Analysis of Particles

We herein present a case of pulmonary aluminosis diagnosed with in-air microparticle induced X-ray emission (in-air micro-PIXE) analysis. The diagnosis of pulmonary aluminosis was supported by the occupational exposure to aluminum, ground glass opacity and ill-defined centrilobular nodular opacities seen in high resolution CT, and respiratory bronchioles accompanied by pigmented dust by histological examination by in-air micro-PIXE analysis of the lung tissues. The possibility of developing this rare condition should not be underestimated in workers at high-risk jobs. This is an important report showing the usefulness of an in-air micro-PIXE analysis for the early diagnosis of aluminosis.

Molecular cloning and characterization of a copper chaperone for copper/zinc superoxide dismutase from the rat

Copper chaperone is an essential cytosolic factor that maintains copper homeostasis in living cells. Cytosolic metallochaperones have been recently identified in plant, yeast, rodents, and human cells. During our investigation, we found a new member of the copper chaperone family for copper/zinc superoxide dismutase, which was cloned from rats. The new copper chaperone was named rCCS (rat Copper Chaperone for Superoxide dismutase). The cDNA of rCCS was found to have a length of 1094 bp, and the protein analyzed from the cDNA was deduced to contain 274 amino acids. The amino acid sequence of rCCS consists of three domains: A metal binding domain, which has a MXCXXC motif in domain I, a homolog of the Cu/Zn SOD in domain II, and a CXC motif in domain III. The binding of rCCS to Cu/Zn SOD was analyzed by GST column binding assay, and the domain II of rCCS was found to be essential for binding to Cu/Zn SOD, which in turn activates Cu/Zn SOD.

Laboratory-scale bioremediation of oil-contaminated soil of Kuwait with soil amendment materials

A huge amount of oil-contaminated soil remains unremediated in the Kuwait desert. The contaminated oil has the potentiality to cause pollution of underground water and to effect the health of people in the neighborhood. In this study, laboratory scale bioremediation experiments were carried out. Hyponex (Hyponex, Inc.) and bark manure were added as basic nutrients for microorganisms, and twelve kinds of materials (baked diatomite, microporous glass, coconut charcoal, an oil-decomposing bacterial mixture (Formula X from Oppenheimer, Inc.), and eight kinds of surfactants) were applied to accelerate the biodegradation of oil hydrocarbons. 15% to 33% of the contaminated oil was decomposed during 43 weeks' incubation. Among the materials tested, coconut charcoal enhanced the biodegradation. On the contrary, the addition of an oil-decomposing bacterial mixture impeded the biodegradation. The effects of the other materials were very slight. The toxicity of the biodegraded compounds was estimated by the Ames test and the tea pollen tube growth test. Both of the hydrophobic (dichloromethane extracts) and hydrophilic (methanol extracts) fractions showed a very slight toxicity in the Ames test. In the tea pollen tube growth test, the hydrophobic fraction was not toxic and enhanced the growth of pollen tubes.

Analysis of oil components and hydrocarbon-utilizing microorganisms during laboratory-scale bioremediation of oil-contaminated soil of Kuwait

A huge amount of oil-contaminated soil remains unremediated in the Kuwait desert. The contaminated oil has the potentiality to cause pollution of underground water and to effect the health of people in the neighborhood. We have been studying bioremediation of Kuwait oil-contaminated soil. Chemical analyses of biodegraded compounds and isolation of petroleum hydrocarbon-decomposing microorganisms were carried out. From the chemical analyses, it was revealed that the decomposed compounds were mainly saturated fractions from alumina column chromatography and that the aromatic fractions were not decomposed well. Isolation of bacteria was carried out for eight kinds of hydrocarbons which are components of crude petroleum (n-hexadecane, 2,6,10,14-tetramethylpentadecane, 1,4-diisopropylbenzene, naphthalene, 1-methylnaphthalene, phenanthrene, anthracene, and perylene). Many of the n-hexadecane- and 2,6,10,14-tetramethylpentadecane-decomposing bacteria were isolated, but aromatic compound-decomposing bacteria were not enriched. It was concluded that the slow decomposition of aromatic compounds was due to the low population of aromatic compound-decomposing bacteria in the Kuwait desert soil.

Pulmonary lymphangiomyomatosis diagnosed by effusion cytology. A case report

BACKGROUND

Pulmonary lymphangiomyomatosis (P-LAM) is a rare disease, characterized by an abnormal proliferation of smooth muscle throughout the lung and occurring in females of reproductive age. The typical clinical picture in P-LAM is progressive dyspnea, often punctuated by episodes of chylothorax or pneumothorax, with eventual death from respiratory failure. The definitive diagnosis is usually performed on open lung biopsies.

CASE

The cytologic findings in a chylous pleural effusion from a patient with P-LAM are presented. The effusion contained an abundance of globular cell clusters composed of two distinct cell types, inner core spindle cells and surface flat cells. Immunocytochemical examination revealed that the core cells were derived from immature smooth muscle cells and the surface cells from endothelium. Histologic examination of the excised specimen showed the typical findings of P-LAM, and the dilated peripheral lymphatics contained cell clusters similar to those in the pleural effusion. The cell clusters in the lymphatics in the P-LAM lung tissue appeared to have ruptured into the thoracic cavity.

CONCLUSION

Cell clusters seem to be pathognomonic of P-LAM, and cytologic examination can obviate the need to perform open lung biopsy to confirm the diagnosis.

Lipid transfer particle in the hemolymph of the American cockroach: evidence for its capacity to transfer hydrocarbons between lipophorin particles

A lipid transfer particle (LTP) was isolated and purified from the hemolymph of the adult male American cockroach, Periplaneta americana, essentially according to the method previously developed for the purification of LTP from locust hemolymph. Fast protein liquid chromatography (FPLC) on a Mono Q column was used as the additional step to obtain pure LTP. The electron micrograph of purified cockroach LTP exhibited an unusual and asymmetric shape essentially similar to that reported for Manduca sexta LTP (Ryan et al. 1990. J. Lipid Res. 31:871-879). The cockroach LTP was also found to be basically similar to that of M. sexta and locust in terms of subunit structure and lipid composition, although there were significant differences particularly in the contents of hydrocarbons and diacylglycerol. A simple method for assaying LTP activity was developed, based on the finding that cockroach LTP can catalyze the transfer of labeled hydrocarbons (or diacylglycerol) from labeled high density lipophorin (HDLp) bound with a transfer membrane (Immoblion) to unlabeled HDLp dissolved in saline. This finding reveals that cockroach LTP has the capacity to transfer and/or exchange lipids between lipophorin particles with the same density. It was also demonstrated that cockroach LTP has the capacity to catalyze the transfer and/or exchange of hydrocarbons, in addition to diacylglycerol, between cockroach HDLp and locust low density lipophorin (LDLp).

Further characterization of locust low density lipophorin induced by adipokinetic hormone

This study was designed to resolve basic questions concerning the nature of low density lipophorin (LDLp) which is induced by adipokinetic hormone (AKH). For this purpose, lipophorin was fractionated by density gradient ultracentrifugation and each fraction containing lipophorin was analyzed for diacylglycerol and associated apolipophorin-III (apoLp-III). The diacylglycerol content of LDLp fractions increased significantly as the density of the fraction decreased (116 micrograms/100 micrograms protein at a high density to 209 micrograms/100 micrograms protein at a lower density). On the other hand, the content of diacylglycerol in each fraction of HDLp remained almost constant (33 micrograms/100 micrograms protein). It was also found that the number of apoLp-III molecules associated with LDLp increased as the density decreased (from 6.9 mol/mol LDLp to 13.2 mol/mol LDLp). However, electron microscopic observation showed that LDLp particles in each of the fractions were extremely heterogeneous in size with diameters of 29.4 +/- 6.8 nm, 27.1 +/- 5.5 nm, and 26.3 +/- 5.7 nm for low, medium, and high density fraction, respectively. HDLp particles were very homogeneous in size irrespective of the fraction (15.9 +/- 1.5 nm, 15.6 +/- 1.5 nm, and 15.6 +/- 1.3 nm for the respective fractions). A theoretical analysis based on all the experimental data strongly supports the hypothesis that the heterogeneity in the size of LDLp particles does not reflect different densities, but rather, heterogeneity is the result of intermolecular fusion between LDLp particles of the same density.

Primary role of adipokinetic hormone in the formation of low density lipophorin in locusts

It was demonstrated that the primary action of adipokinetic hormone (AKH) is to stimulate calcium ion uptake into the fat body cell, subsequently causing the formation of diacylglycerol from triacylglycerol. Furthermore, it was also shown that AKH is not directly responsible for increased diacylglycerol uptake by lipophorin from the fat body. The diacylglycerol level of the fat body was found to increase by an average of 2.4-fold after 90 min of incubation in the presence of AKH. Calcium ion was also found to be essential in the action of AKH on the fat body. Supporting this is the observation that calcium ionophore mimics the AKH action in vivo and in vitro; injection of calcium ionophore into adult locusts as well as incubation of hemolymph with fat body and ionophore caused the transformation of high density lipophorin to low density lipophorin. When the fat body, preincubated with or without AKH, was reincubated with hemolymph, diacylglycerol uptake by lipophorin occurred for both incubations. In some sets of experiments, low density lipophorin particles were formed even in the hemolymph that was incubated with fat body preincubated without AKH, indicating that AKH is not directly responsible for its formation. Calcium ion was found not to be necessary for the diacylglycerol uptake process to occur.

Trehalose, the insect blood sugar, inhibits loading of diacylglycerol by lipophorin from the fat body in locusts

Trehalose, the insect blood sugar, was found to inhibit diacylglycerol uptake by lipophorin from the fat body in vitro. Trehalose inhibited diacylglycerol uptake by about 40%-50% at various physiological concentrations. This suggests that trehalose may play a dual role in the hemolymph, i.e. serving as the insect's fuel and as a regulator in lipid transport.

Lipid transfer particle in locust hemolymph: purification and characterization

A lipid transfer particle (LTP) from the hemolymph of adult male locusts, Locusta migratoria, was isolated and purified. The locust LTP exhibited its capacity to catalyze the exchange of diacylglycerol between low density lipophorin (LDLp) and high density lipophorin (HDLp). Contrary to the LTP reported for the tobacco hornworm, M. sexta, the locust LTP appeared to lack the capacity to promote net transfer of diacylglycerol to form an intermediate density lipophorin, although it seems premature to conclude the complete lack of such a capacity in locust LTP. The original concentration of LTP in hemolymph is assumed to be extremely low compared to that of lipophorin; only a catalytic amount of LTP may be present in the hemolymph (e.g., only 160 micrograms of LTP was obtained from the original hemolymph containing 400 mg protein). The molecular weight of intact LTP was estimated to be about 600,000 and the LTP was comprised of three glycosylated apoproteins, apoLTP-I (mol wt 310K), apoLTP-II (mol wt 89K), and apoLTP-III (mol wt 68K). The locust LTP contained significant amounts of lipids; the total lipid content amounted to 14.4% and the lipids were comprised of 17% hydrocarbons, 44% diacylglycerol, 8% cholesterol, 13% free fatty acid, and 18% phospholipids. The above molecular properties of locust LTP are essentially similar to those reported for M. sexta LTP.

In vitro study of the action of adipokinetic hormone in locusts

The in vitro study was performed in order to demonstrate the structural changes of lipophorin induced in vivo by the injection of adipokinetic hormone (AKH) into adult locusts. After many unsuccessful attempts, we have established the reconstructed incubation system in which purified lipophorin and apolipophorin-III (9 mol/mol lipophorin) are incubated with the fat body in the presence of AKH under a supply of excess oxygen. In this system, high density lipophorin (HDLp) originally present in the incubation medium can be transformed entirely into low density lipophorin (LDLp) due to the loading of an increased amount of diacylglycerol from the fat body. The LDLp formed in this incubation system was exactly the same as the LDLp formed in vivo by the injection of AKH, in terms of density, particle size, diacylglycerol content, and the association with apolipophorin-III (apoLp-III). In the absence of apoLp-III, AKH did not exhibit its function to any extent. It was also demonstrated that the transformation of HDLp to LDLp requires calcium ions. Moreover, it appears that, up to a certain limit, the increase of diacylglycerol content of lipophorin and the amount of apoLp-III associated with lipophorin is nearly proportional to the amount of apoLp-III added to the incubation medium.

Biosynthesis of apolipophorin-III by the fat body in locusts

Biosynthesis of locust apolipophorin-III (apo-III) was studied in vitro. Gel electrophoresis and immunoblotting analyses of the locust hemolymph demonstrated that apo-III first appears in the hemolymph on the day 3 of the adult stage after the final molt and its hemolymph concentration increases thereafter. When incubated in vitro in a medium containing radioactive amino acid, the fat body cells synthesized the radiolabeled apo-III and released it into the medium. The developmental change in the apo-III synthesizing activity in the fat body reflected that of the apo-III concentration in the hemolymph. RNA isolated from the adult fat body directed the synthesis of apo-III as a major translation product in a cell-free system. These results indicate that the fat body is the tissue responsible for the synthesis of the locust apo-III, and biosynthesis of apo-III is developmentally regulated at the level of mRNA in accordance with the flight activity of the locust.

Structural study of the asparagine-linked oligosaccharides of lipophorin in locusts

The complete structure of oligosaccharides from locust lipophorin was studied. The asparagine-linked oligosaccharides were first liberated from the protein moiety of lipophorin by digestion with almond glycopeptidase (N-oligosaccharide glycopeptidase, EC 3.5.1.52). Two major oligosaccharides (E and F), separated by subsequent thin-layer chromatography, were analyzed by methylation analysis and 1H-NMR. Based on the experimental data, the whole structure of oligosaccharide E was identified as Man alpha 1----2Man alpha 1----6(Man alpha 1----2Man alpha 1----3) Man alpha 1----6(Man alpha 1----2Man alpha 1----2Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4GlcNAc. The data also revealed that oligosaccharide F is identical with oligosaccharide E in the structure, except for one glucose residue that is linked to the nonreducing terminal Man alpha 1----2 residue.

Apolipophorin III in locusts: purification and characterization

Three molecular species of apolipophorin III were purified from adult locust hemolymph by gel filtration and ion-exchange chromatography, and named apo-III-a, apo-III-b, and apo-III-c, respectively. They were indistinguishable by SDS-polyacrylamide gel electrophoresis, immunodiffusion, and in amino acid composition; however, they had different isoelectric points (5.43 for a, 5.11 for b, and 4.98 for c) and, therefore, could be separated by native- or urea-gel electrophoresis. All three apo-IIIs were glycoproteins and contained fucose, mannose, and glucosamine. The total sugar content amounted to about 11% for each of the three apo-IIIs. The molecular weight of apo-III determined by SDS-polyacrylamide gel electrophoresis was approximately 20,000, almost equivalent to the native molecular weight (approximately 19,000) estimated by the sedimentation-equilibrium method. This indicated that the locust apo-III exists in hemolymph as a monomeric form. It was demonstrated that a total 9 moles of apo-III (2 moles apo-III-a, 6 moles apo-III-b, and 1 mole apo-III-c) associate with each mole of lipophorin in response to the action of locust adipokinetic hormone.

Effect of adipokinetic hormone on the structure and properties of lipophorin in locusts

The reversible association of a low molecular weight hemolymph protein (mol wt 20,000 estimated by SDS-polyacrylamide gel electrophoresis) with lipophorin, following treatment with adipokinetic hormone (AKH), was demonstrated by density gradient ultracentrifugation and by specific precipitation of lipophorin from the hemolymph of resting and AKH-injected locusts. The injection of AKH also stimulated the loading of diacylglycerol from fat body by lipophorin and resulted in a lower density lipophorin ("activated lipophorin"). The activated lipophorin particles (diameter 21.7 +/- 3.0 nm, 15.8 to 33.6 nm) were larger and more heterogeneous in size than those of resting lipophorin (14.5 +/- 1.6 nm, 11.9 to 19.2 nm). A theoretical analysis based on the experimental data (e.g., density gradient profile, electron microscopic observation, and diacylglycerol content) suggests that very large lipophorin particles result from intermolecular fusion of the lipophorin molecules that are activated by AKH. Attempts to demonstrate the effect of AKH on the structure of lipophorin, in vitro, were unsuccessful.

Analysis of antifreeze glycoproteins in fish serum

A procedure utilizing high-pressure size-exclusion chromatography that permits rapid screening for both the types of components present in and the quantity of antifreeze glycoprotein in fish serum or solution is described. The applicability of the method is demonstrated by a comparative study of five different fish species, four of which contain the antifreeze glycoprotein and one which does not contain this protein. The antifreeze glycoprotein compositions of two fish of the same species, collected at different locations or under different environmental conditions, are also compared. A linear molecular-weight versus elution-volume function is established for both standard native proteins and the antifreeze glycoproteins, but these two lines do not coincide. The differences in tertiary structure between the antifreeze glycoproteins and normal proteins are presented as an explanation for the nonequivalence of calibration lines.

Insect fat body phosphorylase kinase is Ca2+-independent and acts even at 0 degrees C

Fat body glycogen phosphorylase in some overwintering insects is known to be activated by cold and, therefore, this enzyme acts as a key enzyme that regulates the production of glycerol or trehalose from glycogen during winter. In this paper we report the mechanism of phosphorylase activation by cold: the major phosphorylase kinase (EC 2.7.1.38) of fat body is bound to glycogen and functions at 0 degrees C, whereas phosphorylase phosphatase does not; thus this may cause a slow but continuous accumulation of the active form of phosphorylase in the cold.

Insect hemolymph lipophorin: a mechanism of lipid transport in insects

Lipophorin, formerly called the "diacylglycerol-carrying lipoprotein," exists in the hemolymph of many insects including locust, cockroach, and silkworm. A rapid and efficient method has been developed for the purification of lipophorin, which includes a specific precipitation under low ionic concentration and DEAE-cellulose column chromatography. The final preparation of lipophorin is highly homogeneous, as judged by gel electrophoresis, electronmicroscopy, and immunodiffusion. Molecules of lipophorin from the above three insects are almost globular in shape with a diameter of 13-16 nm. Molecular weights are 600,000-700,000, and the lipid content totals 40-50%. The lipids are comprised of diacylglycerol, cholesterol, and phospholipid. Of particular interest is that the locust and cockroach lipophorin contains large amounts of hydrocarbons in addition to the above lipids. Apoprotein of lipophorin consists of two-non-identical subunits, heavy chain (M.W. 250,000) and light chain (M.W. 85,000); carbohydrate (mainly mannose) is covalently associated only with the heavy chain. Tests of the physiological function of insect lipophorin indicate that it has multiple roles as a true carrier and a reusable shuttle in transporting diacylglycerol, cholesterol, and hydrocarbon from sites of storage, absorption, and synthesis to sites where these lipids are utilized as metabolic fuel, precursors of triacylglycerol and phospholipid synthesis, or structural components of cell membrane and cuticle. In view of this functional multiplicity as a true carrier and reusable shuttle, therefore, the insect lipophorin is unique lipoprotein and essentially different from mammalian plasma lipoproteins.

Diacylglycerol-carrying lipoprotein of hemolymph of the locust and some insects

The diacylglycerol-carrying lipoprotein (DGLP) was purified from hemolymph of the locust, Locusta migratoria, by a rapid method which included a specific precipitation at low ionic concentration and DEAE-cellulose column chromatography. The final preparation was highly homogeneous as judged by gel electrophoresis, electron microscopy, and immunodiffusion. The locust DGLP molecule was almost spherical in shape with a diameter of about 130 A. The molecular weight, determined by a sedimentation equilibrium method, was approximately 580,000. The total lipid content amounted to about 40%. The lipids comprised diacylglycerol (33% of total lipid), hydrocarbon (21%), cholesterol (8%), and phospholipids (36%). The hydrocarbon fraction contained a number of n-alkanes and methylalkanes ranging from C25 to C38 in chain length. Mannose (3%) and glucosamine (0.5%) were associated with the apoprotein of DGLP. Apoprotein of locust DGLP consisted of two subunits, heavy chain (mol wt 250,000) and light chain (mol wt 85,000); carbohydrate (mannose) was associated only with the heavy chain. Tests of physiological function of DGLPs from locust, cockroach, and silkworm suggest that the insect DGLP serves multiple roles as a true carrier molecule in transporting diacylglycerol, cholesterol, and hydrocarbon from sites of storage, absorption, and synthesis to sites where these lipids are utilized as metabolic fuel, precursors for triacylglycerol and phospholipid synthesis, or structural components of cell membrane and cuticle. In addition, the insect DGLPs displayed no species-specificity in terms of the functions, whereas they were immunologically distinguishable.

Diacylglycerol-carrying lipoprotein of hemolymph of the American cockroach: purification, characterization, and function

A diacylglycerol-carrying lipoprotein (DGLP) was isolated from the hemolymph of adult male and female American cockroaches, Periplaneta americana. The purification procedure involved dialysis against distilled water, precipitation at low ionic concentration at pH 6.6, and separation by column chromatography on DEAE-cellulose. The final preparation was homogeneous as judged by polyacrylamide gel electrophoresis and electron microscopy. The lipoprotein comprised over 50% of the total hemolymph protein. The DGLP molecule was almost globular in shape with a diameter of approximately 160 A. The molecular weight, determined by a sedimentation-equilibrium method, was approximately 600,000. Apoprotein of DGLP consisted of two subunits, heavy chain (mol wt 250,000) and light chain (mol wt 85,000). The total lipid content of DGLP amounted to about 50%. The lipids comprised diacylglycerol (15% of total lipid), hydrocarbons (28%), cholesterol (5%), and phospholipids (43%). n-Pentacosane, 3-methylpentacosane, and 6,9-heptacosadiene were identified as major hydrocarbons. Mannose(0.9%) and glucosamine (0.3%) were associated with apoprotein of DGLP. The capacity of the purified DGLP to accept diacylglycerol from both fat body and midgut was demonstrated in vitro; thus it was suggested that the same carrier molecule served to transport this lipid from storage site and absorption site. The possible multiple role of cockroach DGLP in transporting such lipids as diacylglycerol, cholesterol, and hydrocarbon from the site of storage, absorption, or synthesis is discussed.

3,beta-Hydroxy-5agr-cholestan-6-one: A Possible Precursor of agr-Ecdysone Biosynthesis

The conversion of cholesterol into 3beta-hydroxy-5alpha-cholestan-6-one has been demonstrated to occur in prothoracic glands of last instar larvae of the silkworm, Bombyx mori. Incubation of glands containing radiolabeled 3beta-hydroxy-5alpha-cholestan-6-one results in the disappearance of this sterol from the glands and the concomitant appearance of radiolabeled alpha-ecdysone in the medium. The observations suggest that the sterol is an intermediate in the synthesis of alpha-ecdysone.