Comparative dissolution profiles of two anti-emetic delayed release dosage forms of doxylamine and pyridoxine: Xonvea® tablets vs. Cariban® capsules

OBJECTIVE

Nausea and vomiting of pregnancy is a common disease that affects many women suffering from mild to severe symptoms. Amongst the different treatments, a fixed dose combination of doxylamine and pyridoxine has been proven safe and effective although the mechanism of action is not well established. There are different pharmaceutical dosage forms in the European market. The objective of this study was to compare the characteristics of a capsule formulation, Cariban® and a tablet formulation, Xonvea® to evaluate the potential impact of their release profiles on their onset of action.

MATERIALS AND METHODS

10 mg/10 mg of doxylamine succinate/pyridoxine hydrochloride capsules (Cariban®) and tablets (Xonvea®) were used as reference materials. Appearance, mass, composition, and in vitro dissolution profiles were compared. Bibliographic data from 4 pharmacokinetic studies of Xonvea® and 1 pharmacokinetic study of Cariban® was reviewed.

RESULTS

In vitro dissolution studies showed significant differences in dissolution profiles of tablets and capsules. The later exhibiting some release of both drug substances in acid conditions followed by a non-complete release after a total of 3 hours while the tablets demonstrated gastro-resistant properties and rapid API release in about 20-30 minutes after the acid stage. Comparison of PK data showed greater Cmax for pyridoxine.

CONCLUSIONS

At pH 6.8, complete and faster release of the fixed dose combination for Xonvea® gastro-resistant tablets compared to Cariban® capsules could possibly explain the greater Cmax observed in vivo for the tablet's formulation. This could translate into faster onset of action and relief of nausea for pregnant women taking the tablets vs. the capsules.

The effect of environmental noise isolation on bronchiolitis severity in hospitalised children

AIM

Bronchiolitis is an infectious disease, with no effective treatment. Music and Mozart's works specifically are known to have a positive effect on physiological parameters, while noise is considered harmful. We aim to evaluate the short-term effect of environmental noise detachment and/or music listening on the course of bronchiolitis in hospitalised children.

METHODS

This is a prospective, double-blinded randomised controlled trial. Patients were divided into three intervention groups: 1-Mozart's Sonata, 2-instrumental music, 3-silence. Music was heard via media players and soundproof headphones. Disease severity was evaluated before and after intervention using the Modified Tal score.

RESULTS

Seventy music sessions were included in the analysis (Mozart n = 23, instrumental n = 22, silence n = 25). A one-point drop in the average bronchiolitis severity score was observed in all three groups from 7.1 (CI 95%, 5 to 9.2) to 6.1 (CI 95%, 4.3 to 7.9), p < 0.001. No significant difference was found between the three groups with respect to change in the severity score before and after the intervention.

CONCLUSION

Isolation from disturbing sounds heard in paediatric departments could be considered a simple non-invasive intervention in children hospitalised with bronchiolitis. Further studies are warranted to evaluate long-term effects of this intervention and the specific effect of music.

Polarizing receptor activation dissociates fibroblast growth factor 2 mediated inhibition of myelination from its neuroprotective potential

Fibroblast growth factor (FGF) signaling contributes to failure of remyelination in multiple sclerosis, but targeting this therapeutically is complicated by its functional pleiotropy. We now identify FGF2 as a factor up-regulated by astrocytes in active inflammatory lesions that disrupts myelination via FGF receptor 2 (FGFR2) mediated activation of Wingless (Wnt) signaling; pharmacological inhibition of Wnt being sufficient to abrogate inhibition of myelination by FGF2 in tissue culture. Using a novel FGFR1-selective agonist (F2 V2) generated by deleting the N-terminal 26 amino acids of FGF2 we demonstrate polarizing signal transduction to favor FGFR1 abrogates FGF mediated inhibition of myelination but retains its ability to induce expression of pro-myelinating and immunomodulatory factors that include Cd93, Lif, Il11, Hbegf, Cxcl1 and Timp1. Our data provide new insights into the mechanistic basis of remyelination failure in MS and identify selective activation of FGFR1 as a novel strategy to induce a neuroprotective signaling environment in multiple sclerosis and other neurological diseases.

Short-Term High-Flow Nasal Cannula for Moderate to Severe Bronchiolitis Is Effective in a General Pediatric Ward

We examined the clinical and physiological benefits of heated humidified high-flow nasal cannula (HHHFNC) in treating pediatric bronchiolitis in a general pediatric ward. Children aged 0 to 2 years, hospitalized with moderate to severe bronchiolitis, were connected to HHHFNC. Each child was evaluated at 4- to 10-hour intervals, both on and off the device, using the Wang et al Bronchiolitis Severity score and transcutaneous CO₂ monitor. Sixteen children were included in the final analysis. The Bronchiolitis Severity score improved by 3 points during the first and second intervals (P = .001). Transcutaneous CO₂ values were reduced by an average 8.7 mm Hg (P = .001). No adverse effects were noted in children connected to the device. The HHHFNC device used in a general pediatric ward setting served as a safe and efficacious tool in treating moderate to severe bronchiolitis. Immediate clinical and physiological improvement was observed and maintained 1 to 4 hours after disconnection from the device.

Neutralizing antibody to FGFR2 can act as a selective biomarker and potential therapeutic agent for gastric cancer with FGFR2 amplification

Fibroblast growth factor receptor 2 (FGFR2) amplification has been reported in 5-10% of gastric cancer (GC) and is associated with poor prognosis. In this study, we characterized the anti-tumor effect of PRO-007, a newly developed recombinant monoclonal antibody that targets FGFR2, in GC cell lines KATO III (with FGFR2 amplification) and NCI-N87 (without FGFR2 amplification). Validation was performed in parallel using two patient-derived tumor cells (PDCs) from patients with GC. Cell viability assays were performed using FGFR2-transfected NCI-N87 cells and FGFR2-knockdown KATO III cells that were generated using short hairpin RNA (shRNA). PRO-007 reduced KATO III cell viability (P = 0.0034) but not that of NCI-N87 cells (P = 0.3710). PRO-007 also significantly reduced KATO III cell invasiveness (P < 0.0001) but not NCI-N87 cell invasiveness (P = 0.8136). Immunoblot analysis showed that PRO-007 treatment decreased the levels of phosphorylated AKT and ERK. The FGFR2-inhibitory activity of PRO-007 was confirmed in genetically modified GC cell lines. Cell viability of FGFR2-overexpressing NCI-N87 cells was significantly decreased by PRO-007, while KATO III cells were significantly resistant to the treatment when FGFR2 was knocked down by FGFR2 shRNA transfection. Furthermore, PRO-007 had a synergistic effect with ramucirumab on the invasiveness of cancer cells with FGFR2 amplification. Consistent results were obtained using PDCs from patients with GC. Overall, these preclinical data support the further clinical development of PRO-007 as a potential therapeutic agent for patients with FGFR2-amplified GC.

Primary infection with human herpes virus type 6, post-pediatric liver transplantation-A pathogen to remember

BACKGROUND

In recent years, liver transplantation (LT) has become a well-accepted therapeutic modality for children with end-stage liver disease, with transplantation surgery being performed at a younger age. Human herpes virus 6 (HHV-6) infection occurs in most children within the first 2 years of life, therefore, data on primary HHV-6 infection in pediatric liver transplant recipients is scarce.

OBJECTIVE

To describe the course of primary HHV-6 infection after pediatric LT.

METHODS

Medical files, between the years 2015-2016, of post-LT pediatric patients with suspected primary HHV-6 infection were reviewed. Clinical and laboratory data for enrolled cases were evaluated. Primary infection was defined as DNAemia in children who were seronegative prior to transplantation or seroconversion from negative to positive IgG posttransplantation.

RESULTS

Four cases of primary HHV-6 (type B) infection were identified among the 26 children who had undergone LT at our center during the study period. All patients were <1 year old and presented with fever, hepatitis, and elevated inflammatory markers, most (75%) within a short-period posttransplantation. All were initially treated with empiric antibiotics for a suspected bacterial infection and three underwent liver biopsy, one showing signs of rejection. Three were treated with antiviral therapy with a gradual resolution of symptoms.

DISCUSSION

Primary HHV-6 should be taken into account in young children shortly after LT, especially when presenting with fever and elevated liver enzymes. Treatment with antiviral therapy should be considered.

CONCLUSIONS

In young infants post-LT, a high index of suspicion may promote early detection of HHV-6 primary infection and prevent serious complications.

Risk factors for early invasive fungal infections in paediatric liver transplant recipients

Invasive fungal infections (IFIs) postliver transplantation are a frequent cause of morbidity and mortality; however, studies reporting on these infections in the paediatric population are scarce. To investigate the incidence and risk factors of IFIs in paediatric liver transplant recipients during the early posttransplantation period (≤3 months). Data were collected for all paediatric liver transplant recipients registered in a national transplantation center from 2004 to 2014. Using a stepwise logistic regression to identify independent risk factors for IFIs, a predictive model was formulated. Ten IFIs were identified in 81 liver transplant recipients (12.3%) all occurring during the first month posttransplantation. Candida species were responsible for nine cases (90%), of which four were non-albicans Candida (44%). Significant risk factors were identified; recipient of multiple blood product transfusions during transplantation, prolonged use of indwelling intravenous catheter, prolonged IV antibiotic treatment, surgical complications, pulse steroid treatment and living donor liver transplantation. The predictive model used two clinical parameters to define high-risk patients: a living donor transplantation and duration of IV antibiotic treatment (area under the ROC curve 0.918). IFIs are a significant complication occurring in the first month posttransplantation. Future studies are required to assess efficacy of targeted antifungal prophylaxis in high risk patients.

[INSPIRATORY STRIDOR OF A NON-TRADITIONAL CAUSE]

INTRODUCTION

Stridor is a respiratory sound caused by turbulent air flow through narrow airways. The most common cause for acute inspiratory stridor is a viral infection of the upper airways, causing laryngotracheitis (Croup). Other common causes include an allergic reaction, foreign body aspiration and trauma.

BACKGROUND

A nine week old infant with a history of meningomyelocele repair perinatally presented to the emergency room with alternating inspiratory stridor. The infant did not have a history of a recent febrile illness, and he did not suffer from cough or any other symptoms suggesting a foreign body aspiration. After the common causes of stridor were ruled out, an MRI was performed - demonstrating Chiari malformation Type 2, with herniation of the cerebellar tonsils and medullary compression. Bronchoscopy demonstrated the rare cause of the intermittent stridor - intermittent vocal cord paralysis, caused by the raised intracranial pressure and medullary compression. Due to rapid clinical deterioration, emergent surgical decompression was performed with complete recovery.

CONCLUSIONS

This case report raises a rare and important cause of inspiratory stridor. Physicians should be alert to the symptoms suggesting a Chiari malformation in every child with a relevant medical history presenting with stridor.

DISCUSSION

Intermittent stridor is mostly caused by an upper respiratory infection in a child with narrowed airways, allergic laryngotracheitis, or laryngomalacia. A less common cause of stidor of this kind is vocal cord paralysis, which may be caused by a symptomatic Chiari malformation.

Protracted febrile myalgia syndrome treated with pulse of corticosteroids

OBJECTIVE

This study describes our 5-year experience treating protracted febrile myalgia syndrome (PFMS) with pulsed doses of corticosteroids.

METHODS

Eight patients with PFMS who received pulse corticosteroid therapy were identified from the electronic database of a tertiary pediatric medical center (2011-2016). Their clinical and laboratory data were collected. Differences in continuous variables between hospital admission and discharge were analyzed using Wilcoxon's matched pairs test.

RESULTS

There were 6 female and 2 male patients of median age 10.45 years (range 6.2-17.1) Six patients were found to be homozygous for the M694V mutation. In 4 patients, PFMS was the first-ever manifestation of familial Mediterranean fever. Pulse corticosteroid therapy was administered at a dose of 10mg/kg for 3 days. Pain was alleviated (visual analog scale score, 0) within hours of initiation of therapy, although pain flare-ups lasting for minutes to hours were still observed during hospitalization. At discharge, all patients were prescribed continuous oral corticosteroids (1-2mg/kg) with gradual tapering down over 6 weeks.

CONCLUSION

Pulse corticosteroid therapy is effective in alleviating PFMS pain; however, it does not completely abort a PFMS episode.

Real-life comparison of three general paediatric wards showed similar outcomes for children with bronchiolitis despite different treatment regimens

AIM

This study evaluated the effectiveness of three different treatments for bronchiolitis in a tertiary paediatric facility.

METHODS

Patients with bronchiolitis who were younger than two years of age and were randomly allocated to three general wards at Schneider Children's Medical Center, Israel, after admission were included. Different treatment protocols in the wards were retrospectively compared.

RESULTS

The study comprised 286 children. The clinical and laboratory parameters on admission were similar between the wards. In Ward C where nebulised hypertonic saline was infrequently administered (6.7%), the mean number of days with oxygen saturation under 92% and the meanlength of hospital stay (1.8 and 3.8 days) were significantly lower than Ward A (2.8 and 5.3 days) and Ward B, (2.9 and 4.7 days) where nebulised hypertonic saline was given more frequently (38.7%-74.7%). Multivariate analysis indicated that low saturation on admission, leukocytosis and use of nebulised hypertonic saline or adrenalin were independent predictors of a longer period of desaturation and hospital stay.

CONCLUSION

Different treatment protocols for bronchiolitis were used in three paediatric wards in this real-life study. No treatment regimen proved superior. Inhalations of hypertonic saline or adrenaline were associated with a longer hospital stay.

Children after renal transplantation hospitalized for fever: Is empirical antibiotic treatment always justified?

Infections are a major cause of morbidity and mortality after renal transplantation. However, data focusing on children are scarce. The objective of this study was to investigate the frequency and predictors of bacterial infection in pediatric renal transplant recipients in a specific setting of hospitalization due to fever. Clinical and laboratory data were retrospectively collected for all pediatric renal transplant recipients hospitalized for fever in a national renal transplantation center from 2004 to 2012. One hundred and sixty-eight hospital admissions for fever of 52 children were analyzed. A bacterial etiology was diagnosed in 85 admissions (50.6%); 49 cases (57.6%) were documented microbiologically and 36 (42.4%) clinically. Risk factors and markers of bacterial infection included older age, presence of a central venous catheter, sonographic findings, and elevated inflammatory indices. C-reactive protein level was a more sensitive marker than white blood cell count and absolute neutrophil count. In patients without identified risk factors, no bacterial infections were diagnosed. Pediatric renal transplant recipients hospitalized for fever are at high risk of bacterial infections and usually require empirical antibiotic treatment at admission. However, there is a minority of low-risk patients in whom clinicians may consider withholding antibiotic treatment with close follow-up.

Sequential exposure to fibroblast growth factors (FGF) 2, 9 and 18 enhances hMSC chondrogenic differentiation

OBJECTIVE

To test the effects of sequential exposure to FGF2, 9 and 18 on human Mesenchymal Stem Cells (hMSC) differentiation during in vitro chondrogenesis.

DESIGN

Control and FGF2-expanded hMSC were cultured in aggregates in the presence of rhFGF9, rhFGF18 or rhFGFR3-specific signaling FGF variants, starting at different times during the chondroinductive program. Quantitative real time polymerase chain reaction (qRT-PCR) and immunocytochemistry were performed at different stages. The aggregate cultures were switched to a hypertrophy-inducing medium along with rhFGFs and neutralizing antibodies against FGFR1 and FGFR3. Histological/immunohistochemical/biochemical analyses were performed.

RESULTS

FGF2-exposed hMSC during expansion up-regulated Sox9 suggesting an early activation of the chondrogenic machinery. FGF2, FGF9 and 18 modulated the expression profile of FGFR1 and FGFR3 in hMSC during expansion and chondrogenesis. In combination with transforming growth factor-beta (TGF-β), FGF9 and FGF18 inhibited chondrogenesis when added at the beginning of the program (≤ d7), while exhibiting an anabolic effect when added later (≥d14), an effect mediated by FGFR3. Finally, FGFR3 signaling induced by either FGF9 or FGF18 delayed the appearance of spontaneous and induced hypertrophy-related changes.

CONCLUSIONS

The stage of hMSC-dependent chondrogenesis at which the growth factors are added impacts the progression of the differentiation program: increased cell proliferation and priming (FGF2); stimulated early chondrogenic differentiation (TGF-β, FGF9/FGF18) by shifting the chondrogenic program earlier; augmented extracellular matrix (ECM) production (FGF9/FGF18); and delayed terminal hypertrophy (FGF9/FGF18). Collectively, these factors could be used to optimize pre-implantation conditions of hMSC when used to engineer cartilage grafts.

Inhibition of tumor angiogenesis and growth by a small-molecule multi-FGF receptor blocker with allosteric properties

Receptor tyrosine kinases (RTK) are targets for anticancer drug development. To date, only RTK inhibitors that block orthosteric binding of ligands and substrates have been developed. Here, we report the pharmacologic characterization of the chemical SSR128129E (SSR), which inhibits fibroblast growth factor receptor (FGFR) signaling by binding to the extracellular FGFR domain without affecting orthosteric FGF binding. SSR exhibits allosteric properties, including probe dependence, signaling bias, and ceiling effects. Inhibition by SSR is highly conserved throughout the animal kingdom. Oral delivery of SSR inhibits arthritis and tumors that are relatively refractory to anti-vascular endothelial growth factor receptor-2 antibodies. Thus, orally-active extracellularly acting small-molecule modulators of RTKs with allosteric properties can be developed and may offer opportunities to improve anticancer treatment.

Fibroblast growth factor 4 and its novel splice isoform have opposing effects on the maintenance of human embryonic stem cell self-renewal

Human embryonic stem cells (HESCs) are unique in their capacity to self-renew while remaining pluripotent. This undifferentiated state must be actively maintained by secreted factors. To identify autocrine factors that may support HESC growth, we have taken a global genetic approach. Microarray analysis identified fibroblast growth factor 4 (FGF4) as a prime candidate for autocrine signaling. Furthermore, the addition of recombinant FGF4 to HESCs supports their proliferation. We show that FGF4 is produced by multiple undifferentiated HESC lines, along with a novel fibroblast growth factor 4 splice isoform (FGF4si) that codes for the amino-terminal half of FGF4. Strikingly, although FGF4 supports the undifferentiated growth of HESCs, FGF4si effectively counters its effect. Furthermore, we show that FGF4si is an antagonist of FGF4, shutting down FGF4-induced Erk1/2 phosphorylation. Expression analysis shows that both isoforms are expressed in HESCs and early differentiated cells. However, whereas FGF4 ceases to be expressed in mature differentiated cells, FGF4si continues to be expressed after cell differentiation. Targeted knockdown of FGF4 using small interfering RNA increased differentiation of HESCs, demonstrating the importance of endogenous FGF4 signaling in maintaining their pluripotency. Taken together, these results suggest a growth-promoting role for FGF4 in HESCs and a putative feedback inhibition mechanism by a novel FGF4 splice isoform that may serve to promote differentiation at later stages of development.

Distinct fibroblast growth factor (FGF)/FGF receptor signaling pairs initiate diverse cellular responses in the oligodendrocyte lineage

Fibroblast growth factors (FGFs) have been implicated in numerous cellular processes, including proliferation, migration, differentiation, and survival. Whereas FGF-2, the prototypic ligand in a family of 22 members, activates all four tyrosine kinase FGF receptors (FGFR1-FGFR4), other members demonstrate a higher degree of selectivity. Oligodendrocytes (OLs), the myelin-producing cells of the CNS, are highly influenced by FGF-2 at all stages of their development. However, how other FGFs and their cognate receptors orchestrate the development of OLs is essentially undefined. Using a combination of specific FGF ligands and receptor blocking antibodies, we now show that FGF-8 and FGF-17 target OL progenitors, inhibiting their terminal differentiation via the activation of FGFR3, whereas FGF-9 specifically targets differentiated OLs, triggering increases in process growth via FGFR2 signaling; FGF-18 targets both OL progenitors and OLs via activation of both FGFR2 and FGFR3. These events are highly correlated with changes in FGF receptor expression from FGFR3 to FGFR2 as OL progenitors differentiate into mature OLs. In addition, we demonstrate that, although activation of FGFR1 by FGF-2 leads to proliferation of OL progenitors, it produces deleterious effects on differentiated OLs (i.e., aberrant reentry into cell cycle and down-regulation of myelin proteins with a loss of myelin membrane). These data suggest that ligand availability, coupled with changes in FGF receptor expression, yield a changing repertoire of ligand-receptor signaling complexes that contribute critically to the regulation of both normal OL development and potential OL/myelin pathogenesis.

The inhibitory anti-FGFR3 antibody, PRO-001, is cytotoxic to t(4;14) multiple myeloma cells

The association of fibroblast growth factor receptor 3 (FGFR3) expression with t(4;14) multiple myeloma (MM) and the demonstration of the transforming potential of this receptor tyrosine kinase (RTK) make it a particularly attractive target for drug development. We report here a novel and highly specific anti-FGFR3-neutralizing antibody (PRO-001). PRO-001 binds to FGFR3 expressed on transformed cells and inhibits FGFR3 autophosphorylation and downstream signaling. The antibody inhibited the growth of FGFR3-expressing FDCP cells (IC(50) of 0.5 microg/mL) but not that of cells expressing FGFR1 or FGFR2, and potently inhibited FGFR3-dependent solid tumor growth in a mouse xenograft model. Furthermore, PRO-001 inhibited the growth of the FGFR3-expressing, human myeloma cell line, UTMC2. Inhibition of viability was still observed when cells were cocultured with stroma or in the presence of IL-6 or IGF-1. PRO-001 did not inhibit constitutive activation of K650E, G384D, and Y373C FGFR3 in myeloma cell lines and failed to inhibit the growth of these cells. Most importantly, however, PRO-001 induced cytotoxic responses in primary t(4;14)(+) MM samples with an increase in apoptotic index of 20% to 80% as determined by annexin V staining. The data demonstrate that PRO-001 is a potent and specific inhibitor of FGFR3 and deserves further study for the treatment of FGFR3-expressing myeloma.

Human combinatorial Fab library yielding specific and functional antibodies against the human fibroblast growth factor receptor 3

The human combinatorial antibody library Fab 1 (HuCAL-Fab 1) was generated by transferring the heavy and light chain variable regions from the previously constructed single-chain Fv library (Knappik, A., Ge, L., Honegger, A., Pack, P., Fischer, M., Wellnhofer, G., Hoess, A., Wölle, J., Plückthun, A., and Virnekäs, B. (2000) J. Mol. Biol. 296, 57-86), diversified in both complementarity-determining regions 3 into a novel Fab display vector, yielding 2.1 x 10(10) different antibody fragments. The modularity has been retained in the Fab display and screening plasmids, ensuring rapid conversion into various antibody formats as well as antibody optimization using prebuilt maturation cassettes. HuCAL-Fab 1 was challenged against the human fibroblast growth factor receptor 3, a potential therapeutic antibody target, against which, to the best of our knowledge, no functional antibodies could be generated so far. A unique screening mode was designed utilizing recombinant functional proteins and cell lines differentially expressing fibroblast growth factor receptor isoforms diversified in expression and receptor dependence. Specific Fab fragments with subnanomolar affinities were isolated by selection without any maturation steps as determined by fluorescence flow cytometry. Some of the selected Fab fragments completely inhibit target-mediated cell proliferation, rendering them the first monoclonal antibodies against fibroblast growth factor receptors having significant function blocking activity. This study validates HuCAL-Fab 1 as a valuable source for the generation of target-specific antibodies for therapeutic applications.

FGF receptors ubiquitylation: dependence on tyrosine kinase activity and role in downregulation

A crucial aspect of ligand-mediated receptor activation and shut-down is receptor internalization and degradation. Here we compared the ubiquitylation of either wild type or a K508A 'kinase-dead' mutant of fibroblast growth factor receptor 3 (FGFR3) with that of its naturally occurring overactive mutants, G380R as in achondroplasia, or K650E involved in thanatophoric dysplasia. Fibroblast growth factor receptors ubiquitylation was found to be directly proportional to their intrinsic tyrosine kinase activity, both of which could be blocked using kinase inhibitors. Despite excessive ubiquitylation, both overactive mutants failed to be efficiently degraded, even when challenged with ligand or overexpression of c-Cbl, a putative E3 ligase. We conclude that phosphorylation is essential for FGFR3 ubiquitylation, but is not sufficient to induce downregulation of its internalization resistant mutants.

Insight into Schmid metaphyseal chondrodysplasia from the crystal structure of the collagen X NC1 domain trimer

Collagen X is expressed specifically in the growth plate of long bones. Its C1q-like C-terminal NC1 domain forms a stable homotrimer and is crucial for collagen X assembly. Mutations in the NC1 domain cause Schmid metaphyseal chondrodysplasia (SMCD). The crystal structure at 2.0 A resolution of the human collagen X NC1 domain reveals an intimate trimeric assembly strengthened by a buried cluster of calcium ions. Three strips of exposed aromatic residues on the surface of NC1 trimer are likely to be involved in the supramolecular assembly of collagen X. Most internal SMCD mutations probably prevent protein folding, whereas mutations of surface residues may affect the collagen X suprastructure in a dominant-negative manner.

Cloning and characterization of 4EHP, a novel mammalian eIF4E-related cap-binding protein

All eukaryotic mRNAs (except organellar) are capped at their 5' end. The cap structure (m7GpppN, where N is any nucleotide) is extremely important for the processing and translation of mRNA. Several cap-binding proteins that facilitate these processes have been characterized. Here we describe a novel human cytoplasmic protein that is 30% identical and 60% similar to the human translation initiation factor 4E (eIF4E). We demonstrate that this protein, named 4E Homologous Protein (4EHP), binds specifically to capped RNA in an ATP- and divalent ion-independent manner. The three-dimensional structure of 4EHP, as predicted by homology modeling, closely resembles that of eIF4E and site-directed mutagenesis analysis of 4EHP strongly suggests that it shares with eIF4E a common mechanism for cap binding. A putative function for 4EHP is discussed.

A novel functional human eukaryotic translation initiation factor 4G

Mammalian eukaryotic translation initiation factor 4F (eIF4F) is a cap-binding protein complex consisting of three subunits: eIF4E, eIF4A, and eIF4G. In yeast and plants, two related eIF4G species are encoded by two different genes. To date, however, only one functional eIF4G polypeptide, referred to here as eIF4GI, has been identified in mammals. Here we describe the discovery and functional characterization of a closely related homolog, referred to as eIF4GII. eIF4GI and eIF4GII share 46% identity at the amino acid level and possess an overall similarity of 56%. The homology is particularly high in certain regions of the central and carboxy portions, while the amino-terminal regions are more divergent. Far-Western analysis and coimmunoprecipitation experiments were used to demonstrate that eIF4GII directly interacts with eIF4E, eIF4A, and eIF3. eIF4GII, like eIF4GI, is also cleaved upon picornavirus infection. eIF4GII restores cap-dependent translation in a reticulocyte lysate which had been pretreated with rhinovirus 2A to cleave endogenous eIF4G. Finally, eIF4GII exists as a complex with eIF4E in HeLa cells, because eIF4GII and eIF4E can be purified together by cap affinity chromatography. Taken together, our findings indicate that eIF4GII is a functional homolog of eIF4GI. These results may have important implications for the understanding of the mechanism of shutoff of host protein synthesis following picornavirus infection.

The human homologue of the yeast Prt1 protein is an integral part of the eukaryotic initiation factor 3 complex and interacts with p170

Eukaryotic initiation factor 3 (eIF3) is a large multisubunit complex that stabilizes the ternary complex, eIF2 x GTP x tRNA(Met)i and promotes mRNA binding to the 40 S ribosomal subunit. eIF3 also functions as a ribosome subunit anti-association factor. The molecular mechanisms by which eIF3 exerts these functions are poorly understood. We describe here the cloning of the cDNA encoding the human homologue of the yeast eIF3 subunit Prt1. The human PRT1 cDNA encodes a protein of predicted molecular mass of 98.9 kDa that migrates at 116 kDa on SDS-polyacrylamide gels. Human and yeast Prt1 share 31% identity and 50% similarity at the amino acid level. The homology is distributed throughout the entire protein, except for the amino terminus, and is particularly high in the central portion of the protein, which contains a putative RNA recognition motif. hPrt1 is recognized by an antibody raised against eIF3, and an affinity-purified antibody to recombinant hPrt1 recognizes a protein migrating at 116 kDa in a purified eIF3 preparation. Far Western analysis shows that hPrt1 interacts directly with the p170 subunit of eIF3. Mapping studies identify the RNA recognition motif as the region required for association with p170. Taken together, these experiments demonstrate that hPrt1 is a component of eIF3. Our data, combined with those of Hershey and co-workers, suggest that mammalian eIF3 is composed of at least 10 subunits: p170, p116 (hPrt1), p110, p66, p48, p47, p44, p40, p36, and p35.

A unified pathway for the degradation of ornithine decarboxylase in reticulocyte lysate requires interaction with the polyamine-induced protein, ornithine decarboxylase antizyme

Recent studies have provided convincing evidence to add to a number of earlier observations suggesting that the rapid intracellular degradation of mammalian ornithine decarboxylase (ODC) is further accelerated by the action of ornithine decarboxylase antizyme (ODC-Az), a polyamine-induced protein. However, the mechanism whereby ODC-Az exerts its effect in this proteolytic process is mostly unknown. Here, by using reticulocyte-lysate-based synthesis and degradation systems, we demonstrate that interaction of ODC-Az with ODC results in two related outcomes: (a) ODC is inactivated as a result of its monomerization, and (b) ODC degradation is dramatically accelerated. While ODC inactivation requires the integrity of the ODC-Az binding site of ODC and the ODC binding site of ODC-Az, acceleration in ODC degradation also requires the previously characterized carboxyl-terminal destabilizing segment of ODC and a specific segment of ODC-Az that may be functionally distinct from that required for ODC binding. Interestingly, an active ODC variant with a mutant ODC-Az binding site is stable under basal degradation conditions. This, together with the ability of anti-(ODC-Az) antibody to specifically inhibit the basal degradation of ODC in the lysate, suggests that ODC-Az is an essential general mediator of ODC degradation. Based on these observations, we propose a model for the degradation of ODC which always require interaction with antizyme.

Polyamines regulate the expression of ornithine decarboxylase antizyme in vitro by inducing ribosomal frame-shifting

We provide here an example of a mammalian cellular gene expressed by frame-shifting. Conventional reading of the sequence of ornithine decarboxylase-antizyme mRNA (a protein that modulates the rate of ornithine decarboxylase degradation) results in premature termination at an in-frame termination codon (stop-1), located shortly after the initiation codon. By translating, in vitro in reticulocyte lysate, antizyme mRNA with a full coding capacity and various mutants derived from it, we demonstrate that antizyme expression requires that ribosomes shift from the first open reading frame (termed ORF0) to a second +1 open reading frame (ORF1). Our studies show that this frame-shifting, which occurs at maximal efficiency of approximately 20%, is stimulated by polyamines and requires the functional integrity of the stop codon (stop-1) of ORF0. By introducing in-frame deletions, we have shown that an 87-nt segment surrounding stop-1 enhances frame-shifting efficiency, whereas the 6 nt located just upstream to stop-1 are absolutely essential for this process. Because this segment does not contain sequences that were previously characterized as shifty segments, our results suggest that another mechanism of frame-shifting is involved in mediating antizyme expression.

The 20S proteasome mediates the degradation of mouse and yeast ornithine decarboxylase in yeast cells

Ornithine decarboxylase (ODC), a key enzyme in the biosynthesis of polyamines, is one of the most rapidly degraded proteins in mammalian cells. Recently it has been demonstrated that mammalian ODC is degraded in vitro by the 26S protease that contains the 20S proteasome as its catalytic core, in a reaction that does not require ubiquitin. Here, we show that yeast and mouse ODC are both rapidly degraded in yeast cells and that their degradation severely inhibited in a mutant yeast cell line defective in the chymotryptic activity of proteinase yscE, the yeast 20S proteasome. These results provide compelling genetic support to previous biochemical studies suggesting the involvement of the 20S proteasome in the degradation of ornithine decarboxylase.

Isolation and characterization of the Drosophila ornithine decarboxylase locus: evidence for the presence of two transcribed ODC genes in the Drosophila genome

The polymerase chain reaction (PCR) was used to isolate two Drosophila ornithine decarboxylase (ODC) genes. Two mixtures of degenerate oligonucleotides corresponding to peptides that are fully conserved among ODCs from widely diverged species were used as opposing primers in the PCR with cDNA or genomic DNA as templates. Sequence analysis of the resulting DNA products confirmed their identity as ODC fragments. The genomic PCR product was then used as a probe for screening a Drosophila genomic library, resulting in the isolation of genomic clones representing two distinct ODC genes (dODC1 and dODC2). Sequence analysis of both genes demonstrated that although varying at their coding and noncoding regions, their overall structure is extremely similar containing 6 exons and 5 short introns. Southern blot and sequence analyses revealed that the two ODC genes are arranged in a tandem head-to-tail configuration. Both ODC genes were assigned by in situ hybridization analysis to position 44A on the right arm of the second chromosome. The isolation of cDNA clones corresponding to these two ODC genes demonstrated that both are transcribed in the adult fly. We hope that the isolation of genomic and cDNA clones of Drosophila ODC will permit the investigation of the expression of ODC during Drosophila development and the role of polyamines in this process.

Follicular fluid contents as predictors of success of in-vitro fertilization-embryo transfer

In order to establish criteria for selection of the best ova in in-vitro fertilization-embryo transfer (IVF-ET) programes we have examined the follicular fluid (FF) levels of plasminogen activator (PA), collagenolytic activity, progesterone (P) and alpha 2 macroglobulin (alpha 2M) and related them to the success of pregnancy. PA activity was similar in FF of pregnant and nonpregnant cycles, 13.8 +/- 3.9 mU/ml versus 14.6 +/- 2.9 (mean +/- SEM) respectively. By contrast, FF from pregnant cycles exhibited lower collagenolytic activity (49.6 +/- 3.9% versus 67.9 +/- 3.0; P less than 0.001). Likewise, in a semi-quantitative assay of alpha 2M, only 18.4% of the aspirates from pregnant cycles showed a precipitation line, whereas 76.8% of those from non-pregnant cycles were positive. Levels of P in aspirates from pregnant cycles were in the intermediate range, as compared with those from non-pregnant cycles (0.06-5.5 micrograms/ml versus 0.02-12.0 micrograms/ml). All these assays can be completed before ET and performed in IVF-ET programmes. In conclusion, it seems that a combination of follicular alpha 2M levels and collagenolytic activity, and to a lesser extent addition of P assay, may serve as good criteria for selecting the best embryos for establishment of pregnancy.