Yeast Saccharomyces cerevisiae adiponectin receptor homolog Izh2 is involved in the regulation of zinc, phospholipid and pH homeostasis

[EN] The functional link between zinc homeostasis and membrane-related processes, including lipid metabolism regulation, extends from yeast to humans, and has a likely role in the pathogenesis of diabetes. The yeast Izh2 protein has been previously implicated in zinc ion homeostasis and in the regulation of lipid and phosphate metabolism, but its precise molecular function is not known. We performed a chemogenomics experiment to determine the genes conferring resistance or sensitivity to different environmental zinc concentrations. We then determined at normal, depleted and excess zinc concentrations, the genetic interactions of IZH2 at the genome-wide level and measured changes in the transcriptome caused by deletion of IZH2. We found evidence for an important cellular function of the Rim101 pathway in zinc homeostasis in neutral or acidic environments, and observed that phosphatidylinositol is a source of inositol when zinc availability is limited. Comparison of our experimental profiles with published gene expression and genetic interaction profiles revealed pleiotropic functions for Izh2. We propose that Izh2 acts as an integrator of intra- and extracellular signals in providing adequate cellular responses to maintain homeostasis under different external conditions, including but not limited to alterations in zinc concentrations. Guardar / Salir Siguiente >This work was supported by grant P1-0207 from the Slovenian Research Agency. M.M.U. was supported by the Young Investigator fellowship scheme from the Slovenian Research Agency. Work done in the group of L.Y. was funded by grant BFU2011-30197-C03-03 from the Spanish Ministry of Science and Innovation (Madrid, Spain). C.P. was supported by a pre-doctoral fellowship from the Spanish Research Council.Mattiazzi Usaj, M.; Prelec, M.; Brioznic, M.; Primo Planta, C.; Curk, T.; Scancar, J.; Yenush, L.... (2015). Yeast Saccharomyces cerevisiae adiponectin receptor homolog Izh2 is involved in the regulation of zinc, phospholipid and pH homeostasis. Metallomics. 7(9):1338-1351. https://doi.org/10.1039/c5mt00095e133813517

Inference of the Molecular Mechanism of Action from Genetic Interaction and Gene Expression Data

Inference of new and useful hypotheses from heterogeneous sources of genome-scale experimental data requires new computational methods that can integrate different types of data. Gene expression and genetic interaction data are two most informative data types, each allowing the identification of genes at different levels of cellular regulatory network hierarchy. We present an integrative data analysis approach, which, rather than correlating the findings from the two data sets, uses each type of data independently to identify the components of molecular pathways and combines them into a single directed network. Our computational genomics approach is based on a set of inference rules traditionally used for reasoning on genetic experiments, which we have formalized and implemented in a software tool. The approach uses chemogenetic interaction and expression data to infer the type of relation between the chemical substance (perturber) and a transcription factor by using previous knowledge on the set of genes whose expression the transcription factor in question regulates. We have used the proposed approach to successfully infer the models for the action of the drug rapamycin and of a DNA damaging agent on their molecular targets and pathways in yeast cells. The developed method is available as a web-based tool at http://www.ailab.si/perturbagen

Optical switching of bent-core liquid crystals with azocinnamoyl units

We report on observations of optical switching in bent-core liquid crystals possessing azocinnamoyl groups in both elongated side arms. UV-activated switching was observed in two of the synthesised materials, both of which were studied optically and with dielectric spectroscopy. Polarising microscopy was used to measure the changes in optical transmittance, and while no illumination effect was seen in the nematic phase, visible changes were observed in the smectic phase, most pronounced in the close vicinity of the smectic to nematic-phase transition. Switching dynamics was characterised, and we found that the average switching time varies strongly with temperature. The relaxation process is faster (below (Formula presented.)) and exhibits no significant temperature dependence. Dielectric measurements have shown that the observed smectic C phases were not polar with the molecules possessing a rather small electric dipole moment. Upon illumination, small differences in the dielectric permittivity were observed only in the smectic phase, suggesting that the illumination effect can be attributed to changes in the molecular conformational and orientational order

A neurotoxic phospholipase A2 impairs yeast amphiphysin activity and reduces endocytosis.

BACKGROUND: Presynaptically neurotoxic phospholipases A(2) inhibit synaptic vesicle recycling through endocytosis. PRINCIPAL FINDINGS: Here we provide insight into the action of a presynaptically neurotoxic phospholipase A(2) ammodytoxin A (AtxA) on clathrin-dependent endocytosis in budding yeast. AtxA caused changes in the dynamics of vesicle formation and scission from the plasma membrane in a phospholipase activity dependent manner. Our data, based on synthetic dosage lethality screen and the analysis of the dynamics of sites of endocytosis, indicate that AtxA impairs the activity of amphiphysin. CONCLUSIONS: We identified amphiphysin and endocytosis as the target of AtxA intracellular activity. We propose that AtxA reduces endocytosis following a mechanism of action which includes both a specific protein-protein interaction and enzymatic activity, and which is applicable to yeast and mammalian cells. Knowing how neurotoxic phospholipases A(2) work can open new ways to regulate endocytosis

Systematic genetics and single‐cell imaging reveal widespread morphological pleiotropy and cell‐to‐cell variability

Abstract Our ability to understand the genotype‐to‐phenotype relationship is hindered by the lack of detailed understanding of phenotypes at a single‐cell level. To systematically assess cell‐to‐cell phenotypic variability, we combined automated yeast genetics, high‐content screening and neural network‐based image analysis of single cells, focussing on genes that influence the architecture of four subcellular compartments of the endocytic pathway as a model system. Our unbiased assessment of the morphology of these compartments—endocytic patch, actin patch, late endosome and vacuole—identified 17 distinct mutant phenotypes associated with ~1,600 genes (~30% of all yeast genes). Approximately half of these mutants exhibited multiple phenotypes, highlighting the extent of morphological pleiotropy. Quantitative analysis also revealed that incomplete penetrance was prevalent, with the majority of mutants exhibiting substantial variability in phenotype at the single‐cell level. Our single‐cell analysis enabled exploration of factors that contribute to incomplete penetrance and cellular heterogeneity, including replicative age, organelle inheritance and response to stress

AtxA inhibits endocytosis in an Rvs161-dependent manner.

<p>Relative uptake rates of LY in AtxA-expressing and control strains with wild-type and different <i>rvs</i> deletion backgrounds. The bars represent standard deviations of at least three independent measurements. AtxA-expressing strains were compared to the corresponding control strains, and p-values were calculated using the <i>t-</i>test at a 95% confidence interval. Statistically significant differences are denoted with a star (*).</p

Binding of yeast 14-3-3 proteins to phospholipid vesicles.

<p>Surface plasmon resonance was used to analyze binding of 14-3-3 proteins to phospholipid vesicles. The response after 180 seconds of dissociation phase is shown. Av. – average response in response units (RU), s.d. – standard deviation in RU of at least three independent measurements.</p