Distribution of cortical endoplasmic reticulum determines positioning of endocytic events in yeast plasma membrane

In many eukaryotes, a significant part of the plasma membrane is closely associated with the dynamic meshwork of cortical endoplasmic reticulum (cortical ER). We mapped temporal variations in the local coverage of the yeast plasma membrane with cortical ER pattern and identified micron-sized plasma membrane domains clearly different in cortical ER persistence. We show that clathrin-mediated endocytosis is initiated outside the cortical ER-covered plasma membrane zones. These cortical ER-covered zones are highly dynamic but do not overlap with the immobile and also endocytosis-inactive membrane compartment of Can1 (MCC) and the subjacent eisosomes. The eisosomal component Pil1 is shown to regulate the distribution of cortical ER and thus the accessibility of the plasma membrane for endocytosis.     

Live imaging of mitosomes and hydrogenosomes by HaloTag technology

Hydrogenosomes and mitosomes represent remarkable mitochondrial adaptations in the anaerobic parasitic protists such as Trichomonas vaginalis and Giardia intestinalis, respectively. In order to provide a tool to study these organelles in the live cells, the HaloTag was fused to G. intestinalis IscU and T. vaginalis frataxin and expressed in the mitosomes and hydrogenosomes, respectively. The incubation of the parasites with the fluorescent Halo-ligand resulted in highly specific organellar labeling, allowing live imaging of the organelles. With the array of available ligands the HaloTag technology offers a new tool to study the dynamics of mitochondria-related compartments as well as other cellular components in these intriguing unicellular eukaryotes.     

Barley HvHMA1 Is a Heavy Metal Pump Involved in Mobilizing Organellar Zn and Cu and Plays a Role in Metal Loading into Grains

Heavy metal transporters belonging to the P_1B-ATPase subfamily of P-type ATPases are key players in cellular heavy metal homeostasis. Heavy metal transporters belonging to the P_1B-ATPase subfamily of P-type ATPases are key players in cellular heavy metal homeostasis. In this study we investigated the properties of HvHMA1, which is a barley orthologue of Arabidopsis thaliana AtHMA1 localized to the chloroplast envelope. HvHMA1 was localized to the periphery of chloroplast of leaves and in intracellular compartments of grain aleurone cells. HvHMA1 expression was significantly higher in grains compared to leaves. In leaves, HvHMA1 expression was moderately induced by Zn deficiency, but reduced by toxic levels of Zn, Cu and Cd. Isolated barley chloroplasts exported Zn and Cu when supplied with Mg-ATP and this transport was inhibited by the AtHMA1 inhibitor thapsigargin. Down-regulation of HvHMA1 by RNA interference did not have an effect on foliar Zn and Cu contents but resulted in a significant increase in grain Zn and Cu content. Heterologous expression of HvHMA1 in heavy metal-sensitive yeast strains increased their sensitivity to Zn, but also to Cu, Co, Cd, Ca, Mn, and Fe. Based on these results, we suggest that HvHMA1 is a broad-specificity exporter of metals from chloroplasts and serve as a scavenging mechanism for mobilizing plastid Zn and Cu when cells become deficient in these elements. In grains, HvHMA1 might be involved in mobilizing Zn and Cu from the aleurone cells during grain filling and germination.     

SDCCAG8 obesity alleles and reduced weight loss after a lifestyle intervention in overweight children and adolescents

Genome-wide association analyses (GWAS) contributed to the detection of a number of single-nucleotide polymorphisms (SNPs) associated with obesity. However, little is known about the impact of the obesity-risk alleles on weight loss-related phenotypes after lifestyle interventions. A recent meta-analysis of GWAS reported five genomic loci near or in the genes FTO, MC4R, TMEM18, SDCCAG8, TNKS/MSRA that were associated with obesity in children and adolescents. Here, we analyzed the effect of the 10 SNPs representative of the five loci on measures of weight loss and cardiometabolic risk after a 1-year lifestyle intervention in 401 children and adolescents (mean age 10.74 years; 55.4% female; mean BMI 27.42 kg/m(2), mean BMI-standard deviation score (SDS) 2.37). For confirmation of one locus genotyping of three intronic SNPs in SDCCAG8 was performed in 626 obese adults who completed the 10-week hypoenergetic diet program. Intronic variants of SDCCAG8, which are associated with early onset obesity, are associated with reduced weight loss after a 1-year lifestyle intervention in overweight children and adolescents even after adjusting for age, sex, baseline measurement, or multiple testing (all P < 10(-6)). However, our results could not be confirmed in 626 obese adults undertaking a hypoenergetic diet intervention.     

Synthesis of cholic acid based calixpyrroles and porphyrins

New cholic acid based calix[4]pyrroles and porphyrins were prepared and their properties were studied. It was confirmed by spectral measurements that the superassembly of 5,15-bis(3α,7α,12α-trihydroxy-5β-cholan-24-yl)-10,20-diphenylporphyrin, the best candidate for this study from the conjugates prepared, may be influenced not only by the solvent mixture composition (polar/non-polar component ratio) but by time as well.     

The sub-cellular localization of Sulfolobus DNA replication

Analyses of the DNA replication-associated proteins of hyperthermophilic archaea have yielded considerable insight into the structure and biochemical function of these evolutionarily conserved factors. However, little is known about the regulation and progression of DNA replication in the context of archaeal cells. In the current work, we describe the generation of strains of Sulfolobus solfataricus and Sulfolobus acidocaldarius that allow the incorporation of nucleoside analogues during DNA replication. We employ this technology, in conjunction with immunolocalization analyses of replisomes, to investigate the sub-cellular localization of nascent DNA and replisomes. Our data reveal a peripheral localization of replisomes in the cell. Furthermore, while the two replication forks emerging from any one of the three replication origins in the Sulfolobus chromosome remain in close proximity, the three origin loci are separated.