Protein translocation across membranes

Correlation of IL-10 and IL18 with the development of liver cirrhosis associated with hepatitis B virus infection: A systematic review

BACKGROUND

Patients who have been infected with the Hepatitis B virus (HBV) are susceptible to developing liver cirrhosis (LC) and hepatocellular carcinoma (HCC). The objective of this systematic review was to comprehensively scrutinize the existing evidence concerning the association between host genetic polymorphisms and HBV-associated LC.

METHODS

We searched databases of PubMed, Scopus, and Web of Science for relevant articles published from building databases to 25 October 2023.

RESULT

We detected 104 relevant articles, relating to 84 individuals genes. Nine genes had the strong evidence of correlation, including IL-10, IL-18, IL-1B, TGF- β, TLR3, STAT4, IL-1RN, Tim3, and IFN receptors. A positive correlation was found for 33 genes but this data had not yet been replicated, 11 genes had limited or mixed evidence of a correlation, and 34 genes indicated no correlation. IL-10 and IL-18 had the most evidence of correlation. There was a notable amount of diversity in both the design and method of studies and data quality.

CONCLUSION

IL-10 and IL-18 had the most evidence of correlation. There was a notable amount of diversity in both the design and method of studies and data quality. It is of necessary to take into account the fundamental mechanism behind these associations and discern those that are confounded by the coexistence of other LC/HCC risk factors and response to therapy. These results are expected to guide future studies on the genetic susceptibility of HBV-related LC/HCC.

Improved recombinant expression of soluble cathepsin B and L in Escherichia coli

Cysteine cathepsins such as cathepsin B and L play an important role in numerous diseases like acute pancreatitis or SARS-CoV-2 and therefore have high potential for the development of new therapeutics. To be able to screen for potent and selective inhibitors sufficient amounts of protein are required. Here, we present an easy and efficient protocol for the recombinant expression of soluble and active murine cathepsin B and L. For this, we used the strain E. coli SHuffle® T7 Express which is capable of forming disulfide bridges in the cytoplasm. The enzymes were purified by immobilized nickel ion-affinity chromatography. Using different constructs and media, expression levels were significantly improved and expression yields of 80 ± 2 mg L-1 for procathepsin B, which is 16-fold better than previously reported expression yields for procathepsin B, and 37 ± 2 mg L-1 for procathepsin L, were achieved. After activation with dithiothreitol at slightly acidic pH, in vitro kinetic parameters of both cathepsins were determined using the commonly used synthetic substrates Arg-Arg-AMC or Phe-Arg-AMC. Moreover, to investigate the impact of the short C-terminal propeptide of procathepsin B, it was deleted by site-directed mutagenesis, the shortened target protein was expressed and purified, activated in vitro, and its activity was similar to the variant bearing this C-terminal propeptide. KEY POINTS: • Recombinant gene expression of cathepsin B and L in E. coli SHuffle® T7 Express • Soluble cathepsin expression with high expression yields • Investigation of the short C-terminal propeptide of cathepsin B.

Polymer translocation: effects of periodically driven confinement

We study the influence of confinement on the dynamics of translocation of a linear polymer chain in a good solvent through a cone-shaped pore. Using the Langevin dynamics simulations, we calculate both the first attempt time and translocation time as a function of the position of the back wall and apex angle α. As the in vivo confining environment is inherently dynamic, we extended the present study to explore the consequences of a periodically driven back wall and apex angles on the translocation dynamics. Our findings reveal that the translocation time initially decreases as the driving frequency increases, but increases after a certain frequency. The frequency at which the translocation time is found to be minimum is referred to as the resonance activation. Analyzing the distribution of translocation times around this frequency renders interesting information about the translocation process. We further explore the translocation dynamics by calculating the residence time of individual monomers, shedding light on the microscopic aspects of the process.

Manipulation of Interleukin-6 (IL-6) and Transforming Growth Factor Beta-1(TGFβ-1) towards viral induced liver cancer pathogenesis

Hepatocellular carcinoma (HCC) is the most common liver malignancy. Early diagnosis of HCC has always been challenging. This study aims to assess the pathogenicity and the prevalence of IL-6 -174G/C (rs1800795) and TGFβ-1 +29C/T (rs1800470) polymorphisms in HCV-infected HCC patients. Experimental strategies are integrated with computational approaches to analyse the pathogenicity of the TGFβ-1 +29C/T and IL-6-174 G/C polymorphisms in HCV-induced HCC. AliBaba2 was used to predict the effect of IL-6-174 G/C on transcription factor binding site in IL-6 gene. Structural changes in the mutant TGFβ-1 structure were determined through project HOPE. To assess the polymorphic prevalence of IL-6 -174G/C and TGFβ-1 +29C/T genotypes in HCC and control subjects, amplification refractory mutation system PCR (ARMS-PCR) was performed on 213 HCC and 216 control samples. GraphPad Prism version 8.0 was used for the statistical analysis of the results. In-silico analysis revealed the regulatory nature of both IL-6 -174G/C and TGFβ-1 +29C/T polymorphisms. ARMS-PCR results revealed that the individuals carrying TT genotype for TGFβ-1 gene have an increased risk of developing HCC (p<0.0001, OR = 5.403, RR = 2.062) as compared to individuals with CT and CC genotype. Similarly, GC genotype carriers for IL-6 gene exhibit an increased risk of HCC susceptibility (p<0.0001, OR = 2.276, RR = 1.512) as compared to the people carrying the GG genotype. Genotype TT of TGFβ-1 gene and genotype GC of IL-6 gene are found to be associated with HCV-induced HCC. IL-6 polymorphism may alter its transcription that leads to its pathogenicity. TGFβ-1 polymorphism may alter protein structure stability.

For the road: calibrated maternal investment in light of extracellular symbiont transmission

Faithful transmission of beneficial symbionts is critical for the persistence of mutualisms. Many insect groups rely on extracellular routes that require microbial symbionts to survive outside the host during transfer. However, given a prolonged aposymbiotic phase in offspring, how do mothers mitigate the risk of symbiont loss due to unsuccessful transmission? Here, we investigated symbiont regulation and reacquisition during extracellular transfer in the tortoise beetle, Chelymorpha alternans (Coleoptera: Cassidinae). Like many cassidines, C. alternans relies on egg caplets to vertically propagate its obligate symbiont Candidatus Stammera capleta. On average, each caplet is supplied with 12 symbiont-bearing spheres where Stammera is embedded. We observe limited deviation (±2.3) in the number of spheres allocated to each caplet, indicating strict maternal control over symbiont supply. Larvae acquire Stammera 1 day prior to eclosion but are unable to do so after hatching, suggesting that a specific developmental window governs symbiont uptake. Experimentally manipulating the number of spheres available to each egg revealed that a single sphere is sufficient to ensure successful colonization by Stammera relative to the 12 typically packaged within a caplet. Collectively, our findings shed light on a tightly regulated symbiont transmission cycle optimized to ensure extracellular transfer.

TGFB1 +869 T > C (rs1800470) variant is independently associated with susceptibility, laboratory activity, and TGF-β1 in patients with systemic lupus erythematosus

The aim of this study was to evaluate the association of the +869 T > C (rs1800470) and -509 C > T (rs1800469) TGFB1 variants, individually or in haplotypes structure, with susceptibility, autoantibodies, disease activity, and TGF-β1 plasma levels in patients with systemic lupus erythematosus (SLE). The study included 203 patients with SLE and 165 healthy controls. TGFB1 variants were determined by real-time polymerase chain reaction (qPCR). Plasma levels of TGF-β1 were determined using immunofluorimetric assay. The TGFB1 + 869 CC genotype was associated with SLE susceptibility (OR: 1.710, 95%CI: 1.020-2.866, p = 0.042) and with reduction of C4 (p = 0.040) and TGF-β1 levels (p = 0.044). In addition, patients with TGFB1 + 869 TC and CC genotypes and positive anti-dsDNA had lower TGF-β1 levels than those with TT (p = 0.004). TGFB1 -509 TT genotype was associated with reduced levels of C4 (p = 0.032). There was no association between haplotypes and clinical and laboratory parameters. Our data demonstrated that the TGFB1 + 869 T > C variant could be used as a genetic marker for SLE susceptibility and both variants as predictors of laboratory activity. This is the first study to demonstrate that TGF-β1 levels could be modulated by the interaction between TGFB1 + 869 C allele, in homozygosity, or heterozygosity, and the presence of anti-dsDNA.

Physical insights into the blood-brain barrier translocation mechanisms

The number of individuals suffering from diseases of the central nervous system (CNS) is growing with an aging population. While candidate drugs for many of these diseases are available, most of these pharmaceutical agents cannot reach the brain rendering most of the drug therapies that target the CNS inefficient. The reason is the blood-brain barrier (BBB), a complex and dynamic interface that controls the influx and efflux of substances through a number of different translocation mechanisms. Here, we present these mechanisms providing, also, the necessary background related to the morphology and various characteristics of the BBB. Moreover, we discuss various numerical and simulation approaches used to study the BBB, and possible future directions based on multi-scale methods. We anticipate that this review will motivate multi-disciplinary research on the BBB aiming at the design of effective drug therapies.

Zooming in on the phycosphere: the ecological interface for phytoplankton-bacteria relationships

By controlling nutrient cycling and biomass production at the base of the food web, interactions between phytoplankton and bacteria represent a fundamental ecological relationship in aquatic environments. Although typically studied over large spatiotemporal scales, emerging evidence indicates that this relationship is often governed by microscale interactions played out within the region immediately surrounding individual phytoplankton cells. This microenvironment, known as the phycosphere, is the planktonic analogue of the rhizosphere in plants. The exchange of metabolites and infochemicals at this interface governs phytoplankton-bacteria relationships, which span mutualism, commensalism, antagonism, parasitism and competition. The importance of the phycosphere has been postulated for four decades, yet only recently have new technological and conceptual frameworks made it possible to start teasing apart the complex nature of this unique microbial habitat. It has subsequently become apparent that the chemical exchanges and ecological interactions between phytoplankton and bacteria are far more sophisticated than previously thought and often require close proximity of the two partners, which is facilitated by bacterial colonization of the phycosphere. It is also becoming increasingly clear that while interactions taking place within the phycosphere occur at the scale of individual microorganisms, they exert an ecosystem-scale influence on fundamental processes including nutrient provision and regeneration, primary production, toxin biosynthesis and biogeochemical cycling. Here we review the fundamental physical, chemical and ecological features of the phycosphere, with the goal of delivering a fresh perspective on the nature and importance of phytoplankton-bacteria interactions in aquatic ecosystems.

A novel lily anther-specific gene encodes adhesin-like proteins associated with exine formation during anther development

The anther-specific gene LLA1271 isolated from lily (Lilium longiflorum Thunb.) anthers is novel and exists in two forms. The protein encoded by LLA1271 may represent an adhesin-like protein first found in higher plants. The protein contains a typical N-terminal signal peptide followed by a highly conserved repeat domain. The LLA1271 gene is temporally expressed at the phase of microspore development. RNA blot and RNA in situ hybridization analyses demonstrated that the gene was expressed both in the tapetum and in the microspore. The gene is endo- and exogenously induced by gibberellin. Studies with the gibberellin biosynthesis inhibitor uniconazole and an inhibitor of ethylene activity, 2,5-norbornadien (NBD), revealed that LLA1271 is negatively regulated by ethylene, and a cross-talk of regulation between gibberellin and ethylene occurs in young anthers. The treatment with NBD caused the tapetum to become densely cytoplasmic and highly polarized, whereas uniconazole arrested tapetal development in a state close to that of a tapetum without treatment. The LLA1271 protein is heat stable and heterogeneous. An immunoblot of separated protein fractions of the anther revealed that the LLA1271 protein was detected in protein fraction of the microspore released from the cell wall by treatment with either 0.5% or 2% Triton X-100. Ectopic expression of LLA1271 resulted in impaired stamen and low pollen germination. Scanning electron microscopy of TAP::LLA1271 pollen showed distorted exine formation and patterning. The LLA1271 protein once synthesized in both the tapetum and microspore is secreted and deposited on the surface of microspores, moderately affecting exine formation and patterning.

Interaction between smoking and functional polymorphism in the TGFB1 gene is associated with ischaemic heart disease and myocardial infarction in patients with rheumatoid arthritis: a cross-sectional study

INTRODUCTION

Transforming growth factor-beta1 (TGF-beta1) is a pleiotropic cytokine that plays important roles in immunity and inflammation. Some studies have suggested that polymorphism in the TGFB1 gene is associated with heart disease in the general population. The purpose of the present study was to determine whether common single-nucleotide polymorphisms (SNP) in the TGFB1 gene are associated with ischaemic heart disease (IHD) and/or myocardial infarction (MI) in patients with rheumatoid arthritis (RA), and to investigate the influence of smoking on any association.

METHODS

PCR-based assays were used to determine the genotypes of TGFB1 SNPs including TGFB1-509 C/T (rs1800469, in the promoter region), +868 T/C (rs1800470, in exon 1) and +913 G/C (rs1800471, in exon 1) in 414 subjects with established RA. Genotyping for the +868 SNP was also carried out on a second study population of RA patients (n = 259) with early disease. Serum levels of TGF-beta1 were measured using a commercial ELISA kit. Smoking history and IHD/MI status were obtained on each patient. Associations with IHD/MI were assessed using contingency tables and logistic regression analyses.

RESULTS

The heterozygous genotype of TGFB+868 was associated with an increased risk of IHD (OR 2.14, 95% CI 1.30 - 3.55) and MI (OR 2.42, 95% CI 1.30-4.50), compared to the homozygous genotypes combined. Smoking was an independent risk for IHD and MI, and evidence of interaction between smoking and TGFB+868 was found. Multivariate analyses indicated that the strongest associations with IHD and MI were due to the combined effect of the TGFB1+868 TC genotype and smoking (OR 2.75, 95% CI 1.59-4.75; and OR 2.58 95% CI 1.33-4.99, respectively), independent of other cardiovascular risk factors. The association of the +868 TC genotype and evidence of +868 TC-smoking interaction with IHD were replicated in a second population of RA patients with early disease. Serum TGF-beta1 levels were not associated with TGFB1 genetic variations, smoking or IHD/MI status.

CONCLUSIONS

Interaction between smoking and polymorphism in the TGFB1 gene may influence the risk of IHD and MI in patients with RA.

Transforming growth factor β 869C/T and interleukin 6 -174G/C polymorphisms relate to the severity and progression of bone-erosive damage detected by ultrasound in rheumatoid arthritis

Introduction

Single nucleotide polymorphisms (SNPs) of transforming growth factor β (TGF-β) and IL-6 genes (respectively, 869C/T and -174G/C) have been associated with radiographic severity of bone-erosive damage in patients with rheumatoid arthritis (RA). Musculoskeletal ultrasound (US) is more sensitive than radiography in detecting bone erosion. We analyzed the association between TGF-β 869C/T and IL-6 -174G/C SNPs and bone-erosive damage, evaluated by US, in a cohort of patients with severely active RA.

Methods

Seventy-seven patients were enrolled before beginning anti-TNF treatment. Disease activity was measured using the disease activity score in 28 joints, and the clinical response was evaluated according to the European League Against Rheumatism response criteria. Rheumatoid factor (RF) and anticitrullinated protein/peptide antibodies (ACPAs) were detected. The 869C/T TGF-β and -174G/C IL-6 SNPs were analyzed by PCR amplification. US was performed to assess the bone surfaces of metacarpophalengeal (MCP), proximal interphalangeal (PIP) and metatarsophalangeal (MTP) joints by obtaining multiplanar scans. According to the number of erosions per joint, a semiquantitative score ranging from 0 to 3 was calculated in each anatomical site to obtain a MCP total erosion score (TES), a PIP TES and a MTP TES, all ranging from 0 to 30, and a global patient TES calculated as the sum of these scores (range, 0 to 90).

Results

Patients carrying the TGF-β 869TT genotype showed a statistically significant lower MTP TES than those with the CC or CT genotype (mean MTP TES ± standard deviation for 869TT 6.3 ± 5.7 vs. 869CC/CT 11.7 ± 7.8; P = 0.011). Interestingly, patients with the TT genotype showed dichotomous behavior that was dependent on autoantibody status. In the presence of ACPAs and/or RF, the TT genotype was associated with lower erosion scores at all anatomical sites compared with the CC and CT genotypes. Conversely, the same 869TT patients showed higher erosion scores in the absence of ACPAs or RF.

Conclusions

In RA patients, TGF-β 869C/T SNPs could influence the bone-erosive damage as evaluated by US. The serological autoantibody status (ACPAs and RF) can modulate this interaction.

Prediction of the exposure status of transmembrane beta barrel residues from protein sequence

We present BTMX (Beta barrel TransMembrane eXposure), a computational method to predict the exposure status (i.e. exposed to the bilayer or hidden in the protein structure) of transmembrane residues in transmembrane beta barrel proteins (TMBs). BTMX predicts the exposure status of known TM residues with an accuracy of 84.2% over 2,225 residues and provides a confidence score for all predictions. Predictions made are in concert with the fact that hydrophobic residues tend to be more exposed to the bilayer. The biological relevance of the input parameters is also discussed. The highest prediction accuracy is obtained when a sliding window comprising three residues with similar C(α)-C(β) vector orientations is employed. The prediction accuracy of the BTMX method on a separate unseen non-redundant test dataset is 78.1%. By employing out-pointing residues that are exposed to the bilayer, we have identified various physico-chemical properties that show statistically significant differences between the beta strands located at the oligomeric interfaces compared to the non-oligomeric strands. The BTMX web server generates colored, annotated snake-plots as part of the prediction results and is available under the BTMX tab at http://service.bioinformatik.uni-saarland.de/tmx-site/. Exposure status prediction of TMB residues may be useful in 3D structure prediction of TMBs.

Translocation of α-helix chains through a nanopore

The translocation of α-helix chains through a nanopore is studied through Langevin dynamics simulations. The α-helix chains exhibit several different characteristics about their average translocation times and the α-helix structures when they transport through the nanopores under the driving forces. First, the relationship between average translocation times τ and the chain length N satisfies the scaling law, τ∼N(α), and the scaling exponent α depends on the driving force f for the small forces while it is close to the Flory exponent (ν) in the other force regions. For the chains with given chain lengths, it is observed that the dependence of the average translocation times can be expressed as τ∼f(-1/2) for the small forces while can be described as τ∼f in the large force regions. Second, for the large driving force, the average number of α-helix structures N(h) decreases first and then increases in the translocation process. The average waiting time of each bead, especially of the first bead, is also dependent on the driving forces. Furthermore, an elasticity spring model is presented to reasonably explain the change of the α-helix number during the translocation and its elasticity can be locally damaged by the large driving forces. Our results demonstrate the unique behaviors of α-helix chains transporting through the pores, which can enrich our insights into and knowledge on biopolymers transporting through membranes.

Identification and properties of insect resistance-associated maize anionic peroxidases

Previous studies with transgenic plants have indicated a tobacco anionic peroxidase can confer enhanced resistance to a variety of insects when expressed in different plant species. Tissue that expresses high levels of this enzyme often browns rapidly when damaged. Maize roots damaged under sterile conditions browned and had an anionic peroxidase induced. When introduced biolistically, maize callus transformants expressing a maize peroxidase gene with a predicted isoelectric point of ca. 5.1 produced browner callus compared to a corresponding beta-glucuronidase (GUS) transformant as callus aged. Higher production of only one isozyme of ca. pI 4.5 was noted. When the callus was fed to two maize pest caterpillar species, growth rates were slower (as reflected by weights) relative to the GUS callus. Based on examination of published information and electrophoretic properties, this gene appears to code for Px11, a peroxidase isozyme that is primarily produced in root tissue and callus. When sequence of the gene in several inbreds was examined, coding variations were noted, and abilities to utilize ferulic and p-coumaric acids differed. These coding differences may influence the ability of corresponding forms of the peroxidase to promote resistance. In addition to potential use in marker assisted breeding, enhanced expression of this anionic peroxidase through breeding or genetic engineering may lead to enhanced insect or disease resistance.

Characterization of vacuolar and extracellular beta(1,3)-glucanases of tobacco: Evidence for a strictly compartmentalized plant defense system

beta(1,3)-Glucanases are a class of hormonally and developmentally regulated plant hydrolytic enzymes, which are also induced upon pathogen infection, suggesting a role of these hydrolases in the defense response to pathogens. We have purified several beta(1,3)-glucanases present in tobacco leaves from control plants and from plants treated with salicylic acid or infected with Pseudomonas syringae and studied in detail the subcellular localization of the different isoforms. Partial protein sequence analysis demonstrated that each of the different isoforms had a unique amino acid sequence and was therefore encoded by a different gene. We have also demonstrated that two of these isoforms, similar to the cytokinin/auxin-regulated isoforms previously isolated from tobacco cell suspensions, are located in the central vacuole. Upon salicylic acid treatment or P. syringae infection, three secreted isoforms are induced, belonging to the so-called pathogenesis-related proteins. These pathogenesis-related beta(1,3)-glucanases are all distinct from each other and also different from the vacuolar isoforms. We demonstrate that the vacuolar isoforms are not secreted to the extracellular spaces of the plant following pathogen infection, suggesting that any function they play in the plant defense response is restricted to an intracellularly coordinated defense process.

Influence of transforming growth factor-beta1 gene polymorphism at codon 10 on the development of cirrhosis in chronic hepatitis B virus carriers

Transforming growth factor (TGF)-beta1 is a key cytokine producing extracellular matrix. We evaluated the effect of TGF-beta1 gene polymorphism at codon 10 on the development of cirrhosis in patients with chronic hepatitis B. One hundred seventy eight patients with chronic hepatitis (CH, n=57) or liver cirrhosis (LC, n=121), who had HBsAg and were over 50 yr old, were enrolled. The genotypes were determined by single strand conformation polymorphism. There were no significant differences in age and sex ratio between CH and LC groups. HBeAg positivity and detection rate of HBV DNA were higher in LC than in CH groups (P=0.055 and P=0.003, respectively). There were three types of TGF-beta1 gene polymorphism at codon 10: proline homozygous (P/P), proline/leucine heterozygous (P/L), and leucine homozygous (L/L) genotype. In CH group, the proportions of P/P, P/L, and L/L genotype were 32%, 51%, and 17%, respectively. In LC group, the proportions of those genotypes were 20%, 47%, and 33%, respectively. The L/L genotype was presented more frequently in LC than in CH groups (P=0.017). Multivariate logistic regression analysis confirms that detectable HBV DNA (odds ratio [OR]: 3.037, 95% confidence interval [CI]: 1.504-6.133, P=0.002) and L/L genotype (OR: 3.408, 95% CI: 1.279-9.085, P=0.014) are risk factors for cirrhosis.

Analysis of monoclonal antibody product heterogeneity resulting from alternate cleavage sites of signal peptide

Signal peptides used in biosynthesis of proteins are cleaved at a very specific site by signal peptidase during posttranslational translocation of cytoplasmic proteins across the membrane. In some cases, however, there can be cleavage at nonspecific sites, giving rise to heterogeneity in the mature protein, which manifests itself as either elongation or truncation of the N terminus of the mature protein. When used as biopharmaceutical therapeutics, such heterogeneities may be a cause for concern, depending on the nature of the heterogeneity. This article describes the determination of such heterogeneity by peptide mapping in both the heavy chain and the light chain (LC) of a Chinese hamster ovary (CHO) cell-expressed monoclonal antibody (mAb). The peptide map method described here was capable of detecting the extended N-terminal peptides at levels as low as 1% relative to the peak area of the intact N-terminal peptide. The LC of a mAb product was truncated at its N termini by two amino acid residues at approximately 3-4% levels, resulting from alternate signal peptide cleavage. This article describes the quantitation of this truncation by liquid chromatography-mass spectrometry (LC-MS) peptide mapping. Also described is analysis and characterization of LC truncation by reduced and denatured capillary electrophoresis in sodium dodecyl sulfate (CE-SDS). The truncated mAb, which was devoid of the two N-terminal amino acids, was engineered and shown to migrate as the "pre-LC" peak in reduced CE-SDS assay. The amount of the pre-LC peak recovered from the CE-SDS assay was shown to correlate with the amount of truncated peptide observed from the reduced and alkylated peptide map of the engineered mAb.

Functional analysis and subcellular localization of two geranylgeranyl diphosphate synthases from Penicillium paxilli

The filamentous fungus Penicillium paxilli contains two distinct geranylgeranyl diphosphate (GGPP) synthases, GgsA and GgsB (PaxG). PaxG and its homologues in Neotyphodium lolii and Fusarium fujikuroi are associated with diterpene secondary metabolite gene clusters. The genomes of other filamentous fungi including Aspergillus fumigatus, Aspergillus nidulans, Aspergillus niger, Aspergillus oryzae and Fusarium graminearum also contain two or more copies of GGPP synthase genes, although the diterpene metabolite capability of these fungi is not known. The objective of this study was to understand the biological significance of the presence of two copies of GGPP synthases in P. paxilli by investigating their subcellular localization. Using a carotenoid complementation assay and gene deletion analysis, we show that P. paxilli GgsA and PaxG have GGPP synthase activities and that paxG is required for paxilline biosynthesis, respectively. In the DeltapaxG mutant background ggsA was unable to complement paxilline biosynthesis. A GgsA-EGFP fusion protein was localized to punctuate organelles and the EGFP-GRV fusion protein, containing the C-terminus tripeptide GRV of PaxG, was localized to peroxisomes. A truncated PaxG mutant lacking the C-terminus tripeptide GRV was unable to complement a DeltapaxG mutant demonstrating that the tripeptide is functionally important for paxilline biosynthesis.

Ultrastructure of inclusion bodies in annulus cells in the degenerating human intervertebral disc

The rough endoplasmic reticulum (rER) of the cell has an architectural editing function that checks whether protein structure and three-dimensional assembly have occurred properly prior to export of newly synthesized material out of the cell. If these have been faulty, the material is retained within the rER as an inclusion body. Inclusion bodies have been identified previously in chondrocytes and osteoblasts in chondrodysplasias and osteogenesis imperfecta. Inclusion bodies in intervertebral disc cells, however, have only recently been recognized. Our objectives were to use transmission electron microscopy to analyze more fully inclusion bodies in the annulus pulposus and to study the extracellular matrix (ECM) surrounding cells containing inclusion bodies. ECM frequently encapsulated cells with inclusion bodies, and commonly contained prominent banded aggregates of Type VI collagen. Inclusion body material had several morphologies, including relatively smooth, homogeneous material, or a rougher, less homogeneous feature. Such findings expand our knowledge of the fine structure of the human disc cell and ECM during disc degeneration, and indicate the potential utility of ultrastructural identification of discs with intracellular inclusion bodies as a screening method for molecular studies directed toward identification of defective gene products in degenerating discs.

Biased codon usage in signal peptides: a role in protein export

The signal peptide of proteins exported via the general secretory pathway encodes structural features that enable the targeting and export of the protein to the periplasm. Recent studies have shown biased codon usage at the second amino acid position and a high usage of non-optimal codons within the signal peptide. Altering these biases in codon usage can have deleterious effects on protein folding and export. We propose that these codon-usage biases act in concert to optimize the export process through modulating ribosome spacing on the transcript. This highlights a new aspect of protein export and implies that codon usage in the signal peptide encodes signals that are important for protein targeting and export to the periplasm.

Delivery of peptide and protein drugs over the blood-brain barrier

Peptide and protein (P/P) drugs have been identified as showing great promises for the treatment of various neurodegenerative diseases. A major challenge in this regard, however, is the delivery of P/P drugs over the blood-brain barrier (BBB). Intense research over the last 25 years has enabled a better understanding of the cellular and molecular transport mechanisms at the BBB, and several strategies for enhanced P/P drug delivery over the BBB have been developed and tested in preclinical and clinical-experimental research. Among them, technology-based approaches (comprising functionalized nanocarriers and liposomes) and pharmacological strategies (such as the use of carrier systems and chimeric peptide technology) appear to be the most promising ones. This review combines a comprehensive overview on the current understanding of the transport mechanisms at the BBB with promising selected strategies published so far that can be applied to facilitate enhanced P/P drug delivery over the BBB.

Transforming growth factor-beta1 869T/C, but not interleukin-6 -174G/C, polymorphism associates with hypertension in rheumatoid arthritis

OBJECTIVES

Part of the deleterious effects of systemic inflammation on the cardiovascular system of patients with RA may be exerted via increased propensity to hypertension. IL-6 and TGF-beta1 are important regulators of the inflammatory response. In some, but not all, studies, IL6 -174G/C (rs1800795) and TGFB1 869T/C (rs1982073) gene polymorphisms have been associated with hypertension in the general population. The present study addressed their potential association with hypertension in RA patients.

METHODS

TGFB1 869T/C and IL6 -174G/C were identified in 400 RA patients and 422 local, non-RA controls using real-time PCR and melting curve analysis. Binary logistic and linear regression models were used to identify the independence of the effects of the polymorphisms on hypertension.

RESULTS

Genotypic and allelic frequencies of the two polymorphisms were similar in RA and controls. Within the RA group, there was no significant association between IL6 -174G/C and hypertension, but TGF 869T-allele carriers had significantly increased prevalence of hypertension compared with CC homozygotes (70.2 vs 55.2%; P = 0.023). This association remained significant after adjustment for other hypertension risk factors and medication (odds ratio = 1.96; 95% CI 1.02, 3.77; P = 0.044), and was more pronounced in patients with increased systemic inflammation.

CONCLUSIONS

This study suggests an association of TGFB1 869T/C, but not of IL6 -174G/C, with hypertension in RA patients. If this finding is confirmed in prospective studies, this polymorphism could be used as a screening tool for RA patients with higher risk of developing hypertension and lead to increased surveillance and earlier treatment.

Elevated serum level and gene polymorphisms of TGF-beta1 in gastric cancer

Transforming growth factor (TGF)-beta1, as a candidate tumor marker, is currently of interest. In this study, serum TGF-beta1 levels in gastric cancer (GC) patients and healthy volunteers were measured using enzyme-linked immunosorbent assay (ELISA). In addition, single nucleotide polymorphisms (SNPs) of the TGF-beta1 gene at codon 10 and codon 25 were identified by means of amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) and sequence analysis. Our results indicated that serum concentrations of TGF-beta1 in GC patients were significantly higher than those in the control, and positively correlated with tumor mass, invasion, metastasis, and clinical stage. The serum TGF-beta1 levels of patients recovering from radical resection were markedly lower than those before surgery. Meanwhile, no deoxyribonucleic acid (DNA) sequence variation at codon 25 of the TGF-beta1 gene was found and a TGF-beta1 gene polymorphism at codon 10 did not show obvious correlations with either TGF-beta1 expression or clinicopathological parameters of GC. Our evidence suggested that serum concentration of TGF-beta1 might be a novel tumor marker for GC and the polymorphisms of TGF-beta1 gene did not play a role as a determinant of serum TGF-beta1 concentration or as a genetic risk factor in the gastric carcinogenesis and progression.

Effect of charge distribution on the translocation of an inhomogeneously charged polymer through a nanopore

We investigate the voltage-driven translocation of an inhomogeneously charged polymer through a nanopore by utilizing discrete and continuous stochastic models. As a simplified illustration of the effect of charge distribution on translocation, we consider the translocation of a polymer with a single charged site in the presence and absence of interactions between the charge and the pore. We find that the position of the charge that minimizes the translocation time in the absence of pore-polymer interactions is determined by the entropic cost of translocation, with the optimum charge position being at the midpoint of the chain for a rodlike polymer and close to the leading chain end for an ideal chain. The presence of attractive and repulsive pore-charge interactions yields a shift in the optimum charge position toward the trailing end and the leading end of the chain, respectively. Moreover, our results show that strong attractive or repulsive interactions between the charge and the pore lengthen the translocation time relative to translocation through an inert pore. We generalize our results to accommodate the presence of multiple charged sites on the polymer. Our results provide insight into the effect of charge inhomogeneity on protein translocation through biological membranes.

Selection for efficient translation initiation biases codon usage at second amino acid position in secretory proteins

The definition of a typical sec-dependent bacterial signal peptide contains a positive charge at the N-terminus, thought to be required for membrane association. In this study the amino acid distribution of all Escherichia coli secretory proteins were analysed. This revealed that there was a statistically significant bias for lysine at the second codon position (P2), consistent with a role for the positive charge in secretion. Removal of the positively charged residue P2 in two different model systems revealed that a positive charge is not required for protein export. A well-characterized feature of large amino acids like lysine at P2 is inhibition of N-terminal methionine removal by methionyl amino-peptidase (MAP). Substitution of lysine at P2 for other large or small amino acids did not affect protein export. Analysis of codon usage revealed that there was a bias for the AAA lysine codon at P2, suggesting that a non-coding function for the AAA codon may be responsible for the strong bias for lysine at P2 of secretory signal sequences. We conclude that the selection for high translation initiation efficiency maybe the selective pressure that has led to codon and consequent amino acid usage at P2 of secretory proteins.

Passage times for unbiased polymer translocation through a narrow pore

We study the translocation process of a polymer in the absence of external fields for various pore diameters b and membrane thickness L. The polymer performs Rouse and reptation dynamics. The mean translocation time (tau(t)) that the polymer needs to escape from a cell and the mean dwell time (tau(d)) that the polymer spends in the pore during the translocation process obey scaling relations in terms of the polymer length N, L, and b/R(g), where R(g) is the radius of gyration for the polymer. We explain these relations using simple arguments based on polymer dynamics and the equilibrium properties of polymers.

Substrate specificity of inner membrane peptidase in yeast mitochondria

The inner membrane protease (IMP) cleaves intra-organelle sorting peptides from precursor proteins in mitochondria of the yeast Saccharomyces cerevisiae. An unusual feature of the IMP is the presence of two catalytic subunits, Imp1p and Imp2p, which recognize distinct substrate sets even though both enzymes belong to the same protease family. This nonoverlapping substrate specificity was hypothesized to result from the recognition of distinct residues at the P'1 position (also termed +1 position) in the protease substrates. Here, we constructed an extensive series of mutations to obtain a profile of the critical cleavage site residues in IMP substrates and conclude that Imp1p, and not Imp2p, recognizes specific P'1 residues. In addition to its specificity for P'1 residues, Imp1p also shows substrate specificity for the P3 (-3) position. In contrast, Imp2p recognizes the P1 (-1) position and the P3 position. Based on this new understanding of IMP substrate specificity, we conducted a survey for candidate IMP substrates in mammalian mitochondria and found consensus Imp2p cleavage sites in mammalian precursors to cytochrome c1 and glycerol-3-phosphate (G-3-P) dehydrogenase. Presence of a putative Imp2p cleavage site in G-3-P dehydrogenase was surprising, as its yeast ortholog contains an Imp1p cleavage site. To address this issue experimentally, we performed the first co-expression of mammalian IMP with proposed mammalian IMP precursors in yeast and show that murine precursors to cytochrome c1 and G-3-P dehydrogenase are cleaved by murine Imp2p. These results suggest, surprisingly, G-3-P dehydrogenase has switched from Imp1p in yeast to Imp2p in mammals.

Dynamic mitochondrial localization of nuclear transcription factor HMGA1

It has been well established that high mobility group A1 (HMGA1) proteins act within the nucleus of mammalian cells as architectural transcription factors that regulate the expression of numerous genes. Here, however, we report on the unexpected cytoplasmic/mitochondrial localization of the HMGA1 proteins within multiple cell types. Indirect immunofluorescence, electron microscopic immunolocalization, and Western blot studies revealed that, in addition to the nucleus, HMGA1 proteins could also be found in both the cytoplasm and mitochondria of randomly dividing populations of wild-type murine NIH3T3 cells and transgenic human MCF-7 breast cancer epithelial cells expressing a hemagglutinin tagged-HMGA1a fusion protein. While the molecular mechanisms underlying these novel subcellular localization patterns have not yet been determined, initial synchronization studies revealed a dynamic, cell cycle-dependent translocation of HMGA1 proteins from the nucleus into the cytoplasm and mitochondria of NIH3T3 cells. Furthermore, preliminary functionality studies utilizing a modified "chromatin" immunoprecipitation protocol revealed that HMGA1 retains its DNA binding capabilities within the mitochondria and associates with the regulatory D-loop region in vivo. We discuss potential new biological roles for the classically nuclear HMGA1 proteins with regard to the observed nucleocytoplasmic translocation, mitochondrial internalization, and regulatory D-loop DNA binding.

TGF-beta1 polymorphism determines the progression of joint damage in rheumatoid arthritis

OBJECTIVE

To determine whether transforming growth factor-beta1 (TGF-beta1) polymorphisms are associated with susceptibility to rheumatoid arthritis (RA) and to analyse whether they can affect the progression of radiographic severity.

METHODS

A total of 143 RA patients and 148 healthy unrelated controls were tested for the TGF-beta1 polymorphisms using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The TGF-beta1 polymorphisms were not associated with susceptibility to RA, although there was a trend that -509C/T and the 869T/C polymorphisms were associated with RA in the male population. The progression of radiographic severity, which was defined by a modified Sharp score plotted against disease duration, was significantly faster in the carrier of T allele at the -509 (p=0.048).

CONCLUSION

Our data support the hypothesis that TGF-beta1 polymorphism may determine the progression of joint destruction in RA.

Cytoplasmic chaperones in precursor targeting to mitochondria: the role of MSF and hsp 70

Despite extensive study since the early 1980s, the mechanism by which newly synthesized protein precursors are unfolded in the cytoplasm and targeted correctly to the mitochondrial surface prior to translocation through the mitochondrial membranes is understood poorly. Recently, an N-ethylmaleimide (NEM)-sensitive cytoplasmic factor called mitochondrial import stimulation factor (MSF), which catalyses the ATP-dependent unfolding of precursor proteins, was described. Unlike the more general chaperone proteins of the hsp70 families, MSF not only unfolds proteins but also targets the unfolded precursor proteins to the mitochondria. Here, Mihara and Omura summarize what is known about MSF and speculate on how it, and other cytoplasmic factors, may be involved in mitochondrial import.

From pollen tubes to infection threads: recruitment of Medicago floral pectic genes for symbiosis

While the biology of nitrogen-fixing root nodules has been extensively studied, little is known about the evolutionary events that predisposed legume plants to form symbiosis with rhizobia. We have studied the presence and the expression of two pectic gene families in Medicago, polygalacturonases (PGs) and pectin methyl esterases (PMEs) during the early steps of the Sinorhizobium meliloti-Medicago interaction and compared them with related pollen-specific genes. First, we have compared the expression of MsPG3, a PG gene specifically expressed during the symbiotic interaction, with the expression of MsPG11, a highly homologous pollen-specific gene, using promoter-gus fusions in transgenic M. truncatula and tobacco plants. These results demonstrated that the symbiotic promoter functions as a pollen-specific promoter in the non-legume host. Second, we have identified the presence of a gene family of at least eight differentially expressed PMEs in Medicago. One subfamily is represented by one symbiotic gene (MtPER) and two pollen-expressed genes (MtPEF1 and MtPEF2) that are clustered in the M. truncatula genome. The promoter-gus studies presented in this work and the homology between plant PGs, together with the analysis of the PME locus structure and MtPER expression studies, suggest that the symbiotic MsPG3 and MtPER could have as ancestors pollen-expressed genes involved in polar tip growth processes during pollen tube elongation. Moreover, they could have been recruited after gene duplication in the symbiotic interaction to facilitate polar tip growth during infection thread formation.

Cargo sequences are important for Som1p-dependent signal peptide cleavage in yeast mitochondria

The inner membrane protease (IMP) has two catalytic subunits, Imp1p and Imp2p, that exhibit nonoverlapping substrate specificity in mitochondria of the yeast Saccharomyces cerevisiae. The IMP also has at least one noncatalytic subunit, Som1p, which is required to cleave signal peptides from a subset of Imp1p substrates. To understand how Som1p mediates Imp1p substrate specificity, we addressed the possibility that Som1p functions as a molecular chaperone, which binds to specific substrates and directs them to the catalytic site. Our results show that cargo sequences attached to the signal peptide are important for Som1p-dependent presequence cleavage; however, no specific cargo sequence is required. Indeed, we show that a substrate normally destined for Imp2p is cleaved in a Som1p-dependent manner when the substrate is directed to Imp1p. These results argue against the notion that Som1p is a molecular chaperone. Instead, we propose that the cargo of some Imp1p substrates can assume a conformation incompatible with presequence cleavage. Som1p could thus act through Imp1p to improve cleavage efficiency early during substrate maturation.

Signal peptide-dependent targeting of a rice alpha-amylase and cargo proteins to plastids and extracellular compartments of plant cells

alpha-Amylases are important enzymes for starch degradation in plants. However, it has been a long-running debate as to whether alpha-amylases are localized in plastids where starch is stored. To study the subcellular localization of alpha-amylases in plant cells, a rice (Oryza sativa) alpha-amylase, alphaAmy3, with or without its own signal peptide (SP) was expressed in transgenic tobacco (Nicotiana tabacum) and analyzed. Loss-of-function analyses revealed that SP was required for targeting of alphaAmy3 to chloroplasts and/or amyloplasts and cell walls and/or extracellular compartments of leaves and suspension cells. SP was also required for in vitro transcribed and/or translated alphaAmy3 to be cotranslationally imported and processed in canine microsomes. alphaAmy3, present in chloroplasts of transgenic tobacco leaves, was processed to a product with Mr similar to alphaAmy3 minus its SP. Amino acid sequence analysis revealed that the SP of chloroplast localized alphaAmy3 was cleaved at a site only one amino acid preceding the predicted cleavage site. Function of the alphaAmy3 SP was further studied by gain-of-function analyses. beta-Glucuronidase (GUS) and green fluorescence protein fused with or without the alphaAmy3 SP was expressed in transgenic tobacco or rice. The alphaAmy3 SP directed translocation of GUS and green fluorescence protein to chloroplasts and/or amyloplasts and cell walls in tobacco leaves and rice suspension cells. The SP of another rice alpha-amylase, alphaAmy8, similarly directed the dual localizations of GUS in transgenic tobacco leaves. This study is the first evidence of SP-dependent dual translocations of proteins to plastids and extracellular compartments, which provides new insights into the role of SP in protein targeting and the pathways of SP-dependent protein translocation in plants.

Polymorphisms in the transforming growth factor beta 1 gene and osteoporosis

Transforming growth factor (TGF)-beta1 is the most abundant growth factor in human bone. It is produced by osteoblasts and inhibits osteoclast proliferation and activity and stimulates proliferation and differentiation of preosteoblasts. Several polymorphisms have been described in the TGF-beta1 gene. Previously, we and others have found associations between some of these polymorphisms and bone mass. We therefore wanted to examine if these polymorphisms are also predictors of osteoporotic fractures. The polymorphisms G(-1639)-A, C(-1348)-T, C(-765)insC, T(29)-C, G(74)-C, 713-8delC, C(788)-T, and T(816-20)-C were examined using RFLP and sequencing in 296 osteoporotic patients with vertebral fractures and 330 normal individuals. Bone mineral density (BMD) was examined at the lumbar spine and at the femoral neck by DXA. Genotype distributions were in H-W equilibrium. Linkage disequilibrium was found between the polymorphisms. The T(816-20)-C genotypes were distributed differently among osteoporotic patients and normal controls. The TT genotype was less common in individuals with osteoporotic fractures (chi(2) = 6.02, P < 0.05). BMD was higher in individuals with the TT-genotype (T(816-20)-C) at the lumbar spine, 0.960 +/- 0.173 g/cm(2) compared with individuals with the TC or CC genotypes: 0.849 +/- 0.181 g/cm(2) and 0.876 +/- 0.179 g/cm(2), respectively (P < 0.001, ANOVA). Similar differences between genotypes were found at the different hip regions as well as at the total hip. Individuals with the TT-genotype (C(-1348)-T) had higher bone mass at the femoral neck: 0.743 +/- 0.134 g/cm(2) compared with 0.703 +/- 0.119 g/cm(2) in individuals with TC or CC genotypes (P < 0.05). Individuals with the CC-genotype (T(29)-C) had higher bone mass at the femoral neck, 0.735 +/- 0.128 g/cm(2) compared with 0.703 +/- 0.120 g/cm(2) in individuals with TC or TT genotypes (P < 0.05) and at the total hip: 0.852 +/- 0.166 g/cm(2) vs. 0.818 +/- 0.149 g/cm(2), respectively (P < 0.05). None of the other polymorphisms were distributed differently in patients and controls and did not affect BMD. In conclusion, The TT genotype of the T(816-20)-C polymorphism is less common in patients with osteoporotic fractures and is associated with higher bone mass both at the lumbar spine and at the hip. The C(-1348)-T and T(29)-C polymorphisms were distributed similarly in osteoporotic patients and normal controls, however, the rare genotypes were associated with higher bone mass at the hip.

Factors governing nonoverlapping substrate specificity by mitochondrial inner membrane peptidase

At least three peptidases are involved in cleaving presequences from imported mitochondrial proteins. One of the peptidase, the inner membrane peptidase, has two catalytic subunits, Imp1p and Imp2p, which are structurally related but functionally distinct in the yeast Saccharomyces cerevisiae. Whereas both subunits are members of the type I signal peptidase family, they exhibit nonoverlapping substrate specificities. A clue to the substrate specificity mechanism has come from our discovery of the importance not only of the -1 and -3 residues in the signal peptides cleaved by Imp1p and Imp2p but also the +1 cargo residues attached to the signal peptides. We specifically find that Imp1p prefers substrates having a negatively charged residue (Asp or Glu) at the +1 position, whereas Imp2p prefers substrates having the Met residue at the +1 position. We further suggest that the conformation of the cargo is important for substrate recognition by Imp2p. A role for the cargo in presequence recognition distinguishes Imp1p and Imp2p from other type I signal peptidases.

Expression of MsPG3-GFP fusions in Medicago truncatula'hairy roots' reveals preferential tip localization of the protein in root hairs

Tip growth is a specialized type of polar growth where new cell wall is deposited in a localized region of the cell, the growing tip. These cells show a characteristic zonation, with a high accumulation of secretory vesicles containing cell wall components at the tip, followed by an organelle-enriched zone. MsPG3 is a Medicago sativa polygalacturonase gene isolated in our laboratory, specifically expressed during the interaction of this plant with its symbiotic partner Sinorhizobium meliloti and which might participate in tip growth processes during symbiosis. We have used MsPG3-GFP fusions to study in vivo protein transport processes and localization during root hair growth. Different MsPG3-GFP fusions were expressed in Medicago truncatula'hairy roots' following a protocol developed for this study and also tested by transient expression in onion epidermal cells. Preferential accumulation of an MsPG3-GFP fusion protein in the tip of the growing root hair at different developmental stages was found, confirming the delivery of MsPG3 to the newly synthesized cell wall. This indicates that this protein may participate in tip growth processes during symbiosis and, in addition, that this fusion could be a useful tool to study this process in plants.

Analysis of transforming growth factor beta1 gene polymorphisms in patients with systemic sclerosis

OBJECTIVES

To determine the distribution of transforming growth factor beta1 (TGFbeta1) genotypes at codon 10 (+869 polymorphism) and codon 25 (+915 polymorphism) in patients with scleroderma (SSc). Differences between diffuse and limited SSc (dSSc and lSSc) were also investigated.

METHODS

Patients with lSSc (n=89) and dSSc (n=63) were compared with 147 controls. DNA was isolated from peripheral blood and polymorphisms at codons 10 (C/T) and 25 (G/C) of the TGFbeta1 gene analysed by polymerase chain reaction and sequence specific oligonucleotide probing.

RESULTS

Significantly more patients with SSc than controls carried allele C at codon 10 (controls v SSc, 38% v 48%, chi(2)=8.2, 1df, p=0.004), OR=1.95 (95% CI 1.16 to 3.27). The difference remained when patients with SSc were split into those with limited or diffuse disease, (controls v dSSc, chi(2)=5, 1df, p=0.02 and controls v lSSc, chi(2)=6, 1df, p=0.013). The patients with SSc had significantly more subjects heterozygous at codon 10 (controls v SSc, chi(2)=45, 1df, p<0.0001). Possession of allele C at codon 10 gave an OR=4.8 (95% CI 2.8 to 8.4). No difference in allele frequency was seen between patients with SSc and controls at codon 25. More patients with SSc than controls carried the GG genotype (controls v SSc, 80% v 88%, chi(2)=7, 2df, p=0.027). Possession of allele G gave an OR=1.7 (95% CI 0.5 to 5.9). There was no difference between diffuse and limited disease at either codon.

CONCLUSIONS

These results suggest that patients with SSc are genetically predisposed to high TGFbeta1 production. These polymorphisms do not, however, explain the difference in the clinical phenotypes of limited and diffuse SSc.

Molecular Cloning of Forebrain mRNAs which are Modulated by Sleep Deprivation

Sleep deprivation (SD) experiments have suggested that specific endogenous substances mediate the control of sleep and waking. However, such 'sleep substances' have not yet been unambiguously identified. The isolation of specific molecular markers would make it possible to obtain new insights into the regulatory mechanism underlying sleep and waking. For this purpose, we have used a molecular genetical approach based on subtractive cDNA cloning. Using these techniques, we were able to detect and isolate in rat forebrain four cDNA clones whose corresponding transcripts are expressed at a lower level after 24 h of SD, and six cDNA clones whose corresponding transcripts are expressed at a higher level. For two of the former transcripts, the level showed a significant reduction of approximately 50% after 24 h of SD and a non-significant reduction after 12 h of SD. A significant reduction was also observed after 12 h of cold exposure. A regional analysis of their level under baseline conditions revealed variation during the 24-h cycle. The highest levels tended to occur at the onset of darkness, the beginning of the rat's activity period. Our results are compatible with the hypothesis that the cloned transcripts are associated with the regulation of the sleep-waking cycle. Analysis of their primary structure indicated that these mRNAs have not yet been characterized. The in vivo distribution of these transcripts in the forebrain shows some correspondence to that of receptors of excitatory amino acids, suggesting an association between the functional role of the cloned sequences and this neurotransmission system.

Facilitation of pulmonary insulin absorption by H-MAP: pharmacokinetics and pharmacodynamics in rats

PURPOSE

Several low molecular weight amino acids have previously been reported to enable the oral delivery of proteins. In the present studies, the effect of H-MAP (hydroxy methyl amino propionic acid) on the pharmacokinetics (PK) and pharmacodynamics (PD) of porcine insulin delivered to the lungs of rats by spray-instillation (SI) has been determined.

METHODS

Aliquots (100 microl) of increasing doses of porcine insulin alone (0.26, 1.3, 2.6, 13, and 26 U/kg) or combined with increasing doses of H-MAP (5, 10, 16, and 25 mg/kg), at pH 7.2-7.6 were administered intratracheally to fasted anesthetized rats using a micro spray-instillator. Blood samples were collected from the jugular vein at specified intervals and the plasma concentrations of insulin and glucose were determined. The PK and PD of porcine insulin alone following subcutaneous (SC) administration of increasing doses were also determined.

RESULTS

The PK of insulin administered either by SI to the lungs or SC injection were absorption rate dependent, resulting in post-peak half-lives 10 to 25-fold greater than the reported intravenous elimination half-life (3 min). The relative bioavailability (F') of insulin administered alone by SI varied from 23.8 to 80% for the lowest and highest insulin dose, respectively. Co-administration of H-MAP and insulin to the lungs significantly changed the PK and PD of insulin in a dose dependent fashion. Maximum PK and PD responses were obtained at an H-MAP dose of 16 mg/kg and an insulin dose of 1.3 U/kg. At this combination, the relative bioavailability of insulin was increased more than 2.5 fold, maximum concentration (Cmax) increased 2-fold and the minimum plasma glucose concentration (%MPGC) was reduced more than 2-fold with respect to same dose of insulin alone. A greater total reduction in plasma glucose (%TRPG0-->t) was achieved for H-MAP/insulin combination (66+/-5%) compared to insulin alone (47+/-10 %).

CONCLUSION

H-MAP has potential for increasing the pulmonary bioavailability of insulin administered through the lungs.

Immediate and short-term cellular and biochemical responses to pulmonary single-dose studies of insulin and H-MAP

PURPOSE

It was previously reported that co-administration of H-MAP to the airways of the lungs significantly influenced the absorption, disposition. and effect of insulin in a dose-dependent fashion. Doses of H-MAP (16 mg/kg) and insulin (1.3 U/kg) required to achieve maximum pharmacokinetic and pharmacodynamic responses were determined. The purpose of the present study was to evaluate the effects of insulin and H-MAP spray-instilled (SI) to rats on the physiology of the lung. A short-term, single-dose study of insulin alone and combined with H-MAP was performed.

METHODS

Solutions of either insulin (INS), H-MAP, or insulin plus H-MAP (INMA) were SI to the lungs of rats. Lipopolysaccharide solution (LPS) and sodium dodecyl sulfate solution (SDS) were used as positive controls. and normal saline (SAL) was used as negative control. Animals were sacrificed at various time points and bronchoalveolar lavage (BAL) was conducted. BAL fluid was analyzed for local markers of lung injury, such as total cell numbers, differential cell count, total protein content and enzyme activities of lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and N-acetyl glucosaminidase (NAG).

RESULTS

SI of any solution, including normal saline, seems to have a minor but detectable effect on the normal physiology of the lung. SI of positive control solutions resulted in most markers of immunity and lung injury being significantly elevated, notably enzyme activity and white cell infiltrate. In contrast, SI of INS produced a response similar to that of SAL. SI of INMA resulted in a small transient response characterized by a slight increase in the proportion of neutrophils at 24 h, which decreased with time and was comparable to that of SAL at 72

Association of polymorphisms of the transforming growth factor-beta1 gene with genetic susceptibility to osteoporosis

Osteoporosis exhibits a substantial genetic component. Although polymorphisms of a variety of genes have been associated with bone mineral density and genetic susceptibility to osteoporosis, the genes responsible for these traits have not been definitively identified. We have shown that a T869-->C polymorphism of the transforming growth factor-beta1 gene, which results in a Leu-->Pro substitution at amino acid 10, is associated with bone mineral density in Japanese adolescents and postmenopausal women, with genetic susceptibility to both osteoporosis and vertebral fracture, and with the outcome of treatment for osteoporosis with active vitamin D. We have also shown that a C-509-->T polymorphism in the promoter region of this gene is associated with both bone mineral density and the prevalence of osteoporosis in postmenopausal women. In addition, analysis of combined genotypes for both the C-509-->T and T869-->C polymorphisms revealed that bone mineral density decreases and the susceptibility to osteoporosis increases with the number of T alleles. Thus, combined genotyping of the C-509-->T and T869-->C polymorphisms may prove beneficial in the prevention of osteoporosis in postmenopausal Japanese women. I review here the association of transforming growth factor-beta1 gene polymorphisms with genetic susceptibility to osteoporosis, which has provided insight into the function of transforming growth factor-beta1 as well as into the role of genetic factors in the development of osteoporosis.

Crystal structures of mitochondrial processing peptidase reveal the mode for specific cleavage of import signal sequences

BACKGROUND

Mitochondrial processing peptidase (MPP) is a metalloendopeptidase that cleaves the N-terminal signal sequences of nuclear-encoded proteins targeted for transport from the cytosol to the mitochondria. Mitochondrial signal sequences vary in length and sequence, but each is cleaved at a single specific site by MPP. The cleavage sites typically contain an arginine at position -2 (in the N-terminal portion) from the scissile peptide bond in addition to other distal basic residues, and an aromatic residue at position +1. Mitochondrial import machinery recognizes amphiphilic helical conformations in signal sequences. However, it is unclear how MPP specifically recognizes diverse presequence substrates.

RESULTS

The crystal structures of recombinant yeast MPP and a cleavage-deficient mutant of MPP complexed with synthetic signal peptides have been determined. MPP is a heterodimer; its alpha and beta subunits are homologous to the core II and core I proteins, respectively, of the ubiquinol-cytochrome c oxidoreductase complex. Crystal structures of two different synthetic substrate peptides cocrystallized with the mutant MPP each show the peptide bound in an extended conformation at the active site. Recognition sites for the arginine at position -2 and the +1 aromatic residue are observed.

CONCLUSIONS

MPP bound two mitochondrial import presequence peptides in extended conformations in a large polar cavity. The presequence conformations differ from the amphiphilic helical conformation recognized by mitochondrial import components. Our findings suggest that the presequences adopt context-dependent conformations through mitochondrial import and processing, helical for recognition by mitochondrial import machinery and extended for cleavage by the main processing component.