Impact of trehalose and mycolate biosynthesis on the cell envelope of a Corynebacterium glutamicum L-lysine production strain

In contrast to other Gram-positive bacteria all members of the suborder of Corynebacterineae, including Corynebacterium glutamicum, contain a cell envelope that comprises an outer lipid bilayer, the mycolate layer, which is considered as permeability barrier. Trehalose is an important component of the mycolate layer and involved in the biosynthesis of mycolate. The first step of mycolate biosynthesis, the condensation of trehalose monomycolate was proven to be located in the cell envelope. The composition of the mycolate layer was specifically manipulated by growing a trehalose deficient strain on different carbon sources in the absence and presence of trehalose to investigate the importance of trehalose for the corynebacterial mycolate layer. A strain deficient in trehalose biosynthesis deriving from a C. glutamicum L-lysine production strain was chosen to examine whether the alteration of the cell envelope could improve lysine production and to test whether lysine excretion was correlated with the permeability of the cell envelope. Trehalose was shown to be essential for mycolate synthesis, when sucrose or fructose were the carbon source, whereas glucose could replace trehalose as acceptor and translocator of mycolic acids. External trehalose substituted cytoplasmic trehalose only partially for mycolate synthesis so that supplementation of the medium with trehalose could not completely restore the properties of the mycolate layer of the trehalose deficient strain to those of the parental strain. An imperfect mycolate layer increased the permeability of the cell envelope, and at the same time enhanced the excretion of lysine and triggered the excretion of glutamate. Since synthesis alone of the native components of the mycolate layer was not sufficient to restore its native properties, the packing of the mycolate layer seemed to be crucial for its low permeability. The physiological function of one of the three different trehalose metabolic pathways of C. glutamicum, of the OtsAB-pathway, was unknown. Analysis of trehalose synthesis of strains defective in individual trehalose synthesis pathways showed that the OtsAB-pathway was the predominant trehalose synthesis pathway under carbon limiting conditions. Since trehalose is the predominant compatible solute under nitrogen limitation, the OtsAB-pathway might be necessary to synthesise trehalose as protectant against osmotic stress, when C. glutamicum is exposed to the coincidental limitation of carbon and nitrogen, which occurs frequently in its natural soil habitat

Inverse signaling - a new concept for effects of the transmembrane chemokines

Ein neuer Mechanismus der Signaltransduktion von transmembranen Chemokinen durch Bindung des löslichen Chemokins an die transmembrane Form.A new signal transduction mechanism of the transmembrane chemokines which accrues after binding of the soluble chemokine to its transmembrane counterpart

Periodic 1.5 ka climate variations during MIS 2 in the belt of Southern Hemispheric westerlies

Lacustrine sediments retrieved from Laguna Potrok Aike in the framework of the Potrok Aike Maar Lake Sediment Archive Drilling Project (PASADO) offer the possibility to investigate climate variations of the past ~51 cal ka BP in Southern Hemispheric midlatitudes, Argentinean Patagonia. This study focuses on short-term cyclicities in the Ca and magnetic susceptibility data sets between 51 and 15 cal ka BP. The record yields a climate pattern with a periodicity of 1.5 ka during Marine Oxygen Isotope Stage 2 (MIS 2) detected in the Southern Hemisphere from 31 to 17 cal ka BP for the first time. MIS 2 is known for constantly cold temperatures, whereas prominent climate variations paced by a 1.5 ka periodicity occurred during MIS 3. Our study documents that minor latitudinal oscillations of the Southern Hemispheric westerlies and the polar easterlies with a 1.5 ka periodicity also took place during MIS 2. However, we assume that because of a major northward displacement of the Southern Hemispheric westerlies, these oscillations did not sufficiently affect the zone of Circumpolar Deep Waters and an increased greenhouse effect by upwelling of CO2-rich deep waters did not occur. This mechanism illustrates why prominent climate events fail to appear during MIS 2

Genetically programmed changes in transcription of the novel progranulin regulator

Progranulin is a glycoprotein marking chronic inflammation in obesity and type 2 diabetes. Previous studies suggested PSRC1 (proline and serine rich coiled-coil 1) to be a target of genetic variants associated with serum progranulin levels. We aimed to identify potentially functional variants and characterize their role in regulation of PSRC1. Phylogenetic module complexity analysis (PMCA) prioritized four polymorphisms (rs12740374, rs629301, rs660240, rs7528419) altering transcription factor binding sites with an overall score for potential regulatory function of Sall > 7.0. The effects of these variants on transcriptional activity and binding of transcription factors were tested by luciferase reporter and electrophoretic mobility shift assays (EMSA). In parallel, blood DNA promoter methylation of two regions was tested in subjects with a very high (N = 100) or a very low (N = 100) serum progranulin. Luciferase assays revealed lower activities in vectors carrying the rs629301-A compared with the C allele. Moreover, EMSA indicated a different binding pattern for the two rs629301 alleles, with an additional prominent band for the A allele, which was finally confirmed with the supershift for the Yin Yang 1 transcription factor (YY1). Subjects with high progranulin levels manifested a significantly higher mean DNA methylation (P < 1 × 10−7) in one promoter region, which was in line with a significantly lower PSRC1 mRNA expression levels in blood (P = 1 × 10−3). Consistently, rs629301-A allele was associated with lower PSRC1 mRNA expression (P < 1 × 10−7). Our data suggest that the progranulin-associated variant rs629301 modifies the transcription of PSRC1 through alteration of YY1 binding capacity. DNA methylation studies further support the role of PSRC1 in regulation of progranulin serum levels

Atg7-knockdown reduces chemerin secretion in murine adipocytes

Context In obese individuals, adipocyte endocrine function is affected by altered autophagy. Genetic variants in autophagy-related gene 7 (ATG7) correlated with serum chemerin (RARRES2) concentrations. Objectives To investigate a functional interplay between chemerin and ATG7, how it may relate to autophagy-mediated adipocyte dysfunction in obesity, and the relevance of genetic ATG7-variants in chemerin physiology. Design Adipose ATG7-mRNA expression and adiposity measures were available in two human study cohorts. The effect of a high-calorie diet on adipose Rarres2 and Atg7-expression was investigated in mice. In 3T3L1-adipocytes, the effect of Atg7-knockdown on chemerin expression and secretion was studied. The influence of single nucleotide polymorphisms on ATG7-transcription and chemerin physiology were investigated using a luciferase assay. Setting Mouse model, clinical trials, in vitro studies. Participants Native American (n=83) and Caucasian (n=100) cohort. Main outcome measure Adipocyte chemerin expression and secretion. Results In mice fed a high-calorie diet, adipose Atg7-mRNA expression did not parallel an increase in Rarres2-mRNA expression. ATG7-mRNA expression in human subcutaneous adipose tissue correlated with BMI, fat mass (r &gt; 0.27, P &lt; 0.01), and adipocyte cell size (r &gt; 0.42, P &lt; 0.02). Atg7-knockdown in 3T3L1-adipocytes decreased chemerin secretion by 22% (P &lt; 0.04). Rs2606729 in ATG7 was predicted to alter ATG7-transcription and induced higher luciferase activity in vitro (P &lt; 0.0001). Conclusions Human adipose ATG7-mRNA expression relates to measures of adiposity. Atg7-knockdown reduces chemerin secretion from adipocytes in vitro supportive of a functional interplay between ATG7 and chemerin in autophagy-mediated adipocyte dysfunction

Genome-wide meta-analysis identifies novel determinants of circulating serum progranulin

Progranulin is a secreted protein with important functions in processes including immune and inflammatory response, metabolism and embryonic development. The present study aimed at identification of genetic factors determining progranulin concentrations. We conducted a genome-wide association meta-analysis for serum progranulin in three independent cohorts from Europe: Sorbs (N=848) and KORA (N=1628) from Germany and PPP-Botnia (N=335) from Finland (total N=2811). Single nucleotide polymorphisms (SNPs) associated with progranulin levels were replicated in two additional German cohorts: LIFE-Heart Study (Leipzig; N=967) and Metabolic Syndrome Berlin Potsdam (Berlin cohort; N=833). We measured mRNA expression of genes in peripheral blood mononuclear cells (PBMC) by micro-arrays and performed mRNA expression quantitative trait and expression-progranulin association studies to functionally substantiate identified loci. Finally, we conducted siRNA silencing experiments in vitro to validate potential candidate genes within the associated loci. Heritability of circulating progranulin levels was estimated at 31.8% and 26.1% in the Sorbs and LIFE-Heart cohort, respectively. SNPs at three loci reached study-wide significance (rs660240 in CELSR2-PSRC1-MYBPHL-SORT1, rs4747197 in CDH23- PSAP and rs5848 in GRN) explaining 19.4%/15.0% of the variance and 61%/57% of total heritability in the Sorbs/LIFE-Heart Study. The strongest evidence for association was at rs660240 (P=5.75x10-50), which was also associated with mRNA expression of PSRC1 in PBMC (P=1.51x10-21). Psrc1 knockdown in murine preadipocytes led to a consecutive 30% reduction in progranulin secretion. In conclusion, the present meta-GWAS combined with mRNA expression identified three loci associated with progranulin and supports the role of PSRC1 in the regulation of progranulin secretion