Genetics of the quantitative Lp(a) lipoprotein trait

The Lp(a) lipoprotein is a complex particle composed of a low density lipoprotein (LDL)-like lipoprotein and the disulfide bonded Lp(a) glycoprotein. The complex represents a quantitative genetic trait. SDS gel electrophoresis under reducing conditions of sera followed by immunoblotting with affinity-purified polyclonal anti-Lp(a) demonstrated inter- and intra-individual size heterogeneity of the glycoprotein with apparent Mr in the range 400-700kDa. According to their relative mobilities compared to apo B-100 the Lp(a) patterns were categorized into phenotypes F, B, S1, S2, S3 und S4 and into the respective double-band phenotypes. This size heterogeneity seems to be controlled by multiple alleles designated LpF, LpB, LpS1, LpS2, LpS3, LpS4 and a null allele (LpO) at a single locus. Phenotype frequencies observed in 441 unrelated subjects were in good agreement with those expected from the genetic hypothesis. Comparison of Lp(a) lipoprotein concentrations in the different phenotypes revealed a highly significant association of phenotypes B, S1 and S2 with high, and phenotypes S3 und S4 with intermediate Lp(a) concentrations. A third mode is represented by the null phenotype were no Lp(a) band is detected upon immunoblotting and Lp(a) lipoprotein is low or absent. We conclude that the same gene locus is involved in determining Lp(a) glycoprotein phenotype and Lp(a) lipoprotein concentrations in plasma. This major gene seems to be the Lp(a) glycoprotein structural gene locus.     

Characterisation of the newly identified human Ump1 homologue POMP and analysis of LMP7(beta 5i) incorporation into 20 S proteasomes

Biogenesis of mammalian 20 S proteasomes occurs via precursor complexes containing alpha and unprocessed beta subunits. A human homologue of the yeast proteasome maturation factor Ump1 was identified in 2D gels of 16 S precursor preparations and designated as POMP (proteasome maturation protein). We show that POMP is detected only in precursor fractions and not in fractions containing mature 20 S proteasome. Northern blot experiments revealed that expression of POMP is induced after treatment with interferon gamma. To analyse the role of the beta 5 propeptide for proper maturation and incorporation of the beta 5 subunit into the complex, human T2 cells, which highly express derivatives of the beta 5i subunit (LMP7), were studied. In contrast to yeast, the presence of the beta 5 propeptide is not essential for incorporation of LMP7 into the proteasome complex. Mutated LMP7 subunits either carrying the prosequence of beta 2i (LMP2) or containing a mutation in the active threonine site are incorporated like wild-type LMP7, while a LMP7 derivative lacking the prosequence completely is incorporated to a lesser extent. Although the absence of the prosequence does not affect incorporation of LMP7, its deletion leads to delayed proteasome maturation and thereby to an accumulation of precursor complexes. As a result of the precursor accumulation, an increased amount of the POMP protein can be detected in these cells.     

Sipaucins A-C,sesquiterpenoids from Siparuna pauciflora

The phytochemical investigation of the leaves of Siparuna pauciflora yielded three novel sesquiterpenoids: the germacrane sipaucin A, the elemane sipaucin B and sipaucin C, comprising a new type of carbon skeleton. In addition, four known aporphine alkaloids-nor-boldine, boldine, laurotetanine, and N-methyl-laurotetanine-were obtained. The evaluation of the antiplasmodial activity of the isolated compounds against two strains of Plasmodium falciparum (PoW, Dd2) showed a moderate activity of nor-boldine.     

Surfactant protein A is defective in abrogating inflammation in asthma

Surfactant protein A (SP-A) regulates a variety of immune cell functions. We determined the ability of SP-A derived from normal and asthmatic subjects to modulate the inflammatory response elicited by Mycoplasma pneumoniae, a pathogen known to exacerbate asthma. Fourteen asthmatic and 10 normal control subjects underwent bronchoscopy with airway brushing and bronchoalveolar lavage (BAL). Total SP-A was extracted from BAL. The ratio of SP-A1 to total SP-A (SP-A1/SP-A) and the binding of total SP-A to M. pneumoniae membranes were determined. Airway epithelial cells from subjects were exposed to either normal or asthmatic SP-A before exposure to M. pneumoniae. IL-8 protein and MUC5AC mRNA were measured. Total BAL SP-A concentration did not differ between groups, but the percentage SP-A1 was significantly increased in BAL of asthmatic compared with normal subjects. SP-A1/SP-A significantly correlated with maximum binding of total SP-A to M. pneumoniae, but only in asthma. SP-A derived from asthmatic subjects did not significantly attenuate IL-8 and MUC5AC in the setting of M. pneumoniae infection compared with SP-A derived from normal subjects. We conclude that SP-A derived from asthmatic subjects does not abrogate inflammation effectively, and this dysfunction may be modulated by SP-A1/SP-A.     

Binding structure of the leucine aminopeptidase inhibitor microginin FR1

Natural bioactive compounds are of general interest for pharmaceutical research because they may serve as leads in drug development campaigns. Among them, microginins are linear peptides known to inhibit various exopeptidases. The crystal structure of microginin FR1 from Microcystis sp. bound to bovine lens leucine aminopeptidase was established at 1.73 Å resolution. The observed binding structure could be beneficial for the design of potent aminopeptidase inhibitors.     

Artifact due to differential error when cases and controls are imputed from different platforms

Including previously genotyped controls in a genome-wide association study can provide cost-savings, but can also create design biases. When cases and controls are genotyped on different platforms, the imputation needed to provide genome-wide coverage will introduce differential measurement error and may lead to false positives. We compared genotype frequencies of two healthy control groups from the Nurses’ Health Study genotyped on different platforms [Affymetrix 6.0 (n = 1,672) and Illumina HumanHap550 (n = 1,038)]. Using standard imputation quality filters, we observed 9,841 single-nucleotide polymorphisms (SNPs) out of 2,347,809 (0.4%) significant at the 5 × 10⁻⁸ level. We explored three methods for controlling for this Type I error inflation. One method was to remove platform effects using principal components; another was to restrict to SNPs of highest quality imputation; and a third was to genotype some controls alongside cases to exclude SNPs that are statistical artifact. The first method could not reduce the Type I error rate; the other two could dramatically reduce the error rate, although both required that a portion of SNPs be excluded from analysis. Ideally, the biases we describe would be eliminated at the design stage, by genotyping sufficient numbers of cases and controls on each platform. Researchers using imputation to combine samples genotyped on different platforms with severely unbalanced case–control ratios should be aware of the potential for inflated Type I error rates and apply appropriate quality filters. Every SNP found with genome-wide significance should be validated on another platform to verify that its significance is not an artifact of study design.     

Pilot scale photobioreactor system for land-based macroalgae cultivation

Journal of Applied Phycology - Marine macroalgae such as Ulva intestinalis have promising properties as feedstock for cosmetics and pharmaceuticals. However, since the quantity and quality of...