Synergistic effect of hypoglycemic sulfonylureas and negative phospholipids on calcium transport: ionic and conformational aspects.

peer reviewedIn a two-phase bulk system for the study of ionophoresis, the capacity of hypoglycemic sulfonylureas to translocate Ca2+ was enhanced in a synergistic manner by negatively charged phospholipids. High concentrations of Na+ or K+ had relatively little effect on sulfonylurea-mediated Ca2+ translocation. The acidity constant of hypoglycemic sulfonylureas ranged from 10(-5) to 10(-6). The conformation analysis of Ca2+ -gliquidone complexes with a 1:1 or 1:2 stoichiometry and of a hybrid complex between Ca2+ and both gliquidone and phosphatidylserine revealed configurations suitable for Ca2+ transport across a hydrophobic domain. These findings raise the possibility that the cationic response of the pancreatic B-cell to hypoglycemic sulfonylureas may be due primarily to an alteration of both Ca2+ and H+ transport

Loss of EZH2-like or SU(VAR)3–9-like proteins causes simultaneous perturbations in H3K27 and H3K9 tri-methylation and associated developmental defects in the fungus Podospora anserina

International audienceSelective gene silencing is key to development. It is generally accepted that H3K27me3-enriched heterochromatin maintains transcriptional repression established during early development and regulates cell fate. Conversely, H3K9me3-enriched heterochromatin prevents differentiation but constitutes protection against transposable elements. We exploited the fungus Podospora anserina , a valuable alternative to higher eukaryote models, to question the biological relevance and functional interplay of these two distinct heterochromatin conformations. Results We established genome-wide patterns of H3K27me3 and H3K9me3 modifications, and found these marks mutually exclusive within gene-rich regions but not within repeats. We generated the corresponding histone methyltransferase null mutants and showed an interdependence of H3K9me3 and H3K27me3 marks. Indeed, removal of the PaKmt6 EZH2-like enzyme resulted not only in loss of H3K27me3 but also in significant H3K9me3 reduction. Similarly, removal of PaKmt1 SU(VAR)3–9-like enzyme caused loss of H3K9me3 and substantial decrease of H3K27me3. Removal of the H3K9me binding protein PaHP1 provided further support to the notion that each type of heterochromatin requires the presence of the other. We also established that P. anserina developmental programs require H3K27me3-mediated silencing, since loss of the PaKmt6 EZH2-like enzyme caused severe defects in most aspects of the life cycle including growth, differentiation processes and sexual reproduction, whereas loss of the PaKmt1 SU(VAR)3–9-like enzyme resulted only in marginal defects, similar to loss of PaHP1. Conclusions Our findings support a conserved function of the PRC2 complex in fungal development. However, we uncovered an intriguing evolutionary fluidity in the repressive histone deposition machinery, which challenges canonical definitions of constitutive and facultative heterochromatin

J Proteome Res

The neurodegenerative disorder Alzheimer’s disease (AD) is the most common cause of dementia in the elderly. The presence of neurofibrillary tangles, consisting of hyperphosphorylated tau protein, is one of the major neuropathologic characteristics of the disease, making this protein an attractive biomarker for AD and a possible target for therapy. Here, we describe an optimized immunoprecipitation mass spectrometry method that enables, for the first time, detailed characterization of tau in human cerebrospinal fluid. The identities of putative tau fragments were confirmed using nanoflow liquid chromatography and tandem mass spectrometry. Nineteen tryptic fragments of tau were detected, of which 16 are found in all tau isoforms while 3 represented unique tau isoforms. These results pave the way for clinical CSF studies on the tauopathies

A gene graveyard in the genome of the fungus Podospora comata

WOS:000457456800015International audienceMechanisms involved in fine adaptation of fungi to their environment include differential gene regulation associated with single nucleotide polymorphisms and indels (including transposons), horizontal gene transfer, gene copy amplification, as well as pseudogenization and gene loss. The two Podospora genome sequences examined here emphasize the role of pseudogenization and gene loss, which have rarely been documented in fungi. Podospora comata is a species closely related to Podospora anserina, a fungus used as model in several laboratories. Comparison of the genome of P. comata with that of P. anserina, whose genome is available for over 10 years, should yield interesting data related to the modalities of genome evolution between these two closely related fungal species that thrive in the same types of biotopes, i.e., herbivore dung. Here, we present the genome sequence of the mat+isolate of the P. comata reference strain T. Comparison with the genome of the mat+isolate of P. anserina strain S confirms that P. anserina and P. comata are likely two different species that rarely interbreed in nature. Despite having a 94-99% of nucleotide identity in the syntenic regions of their genomes, the two species differ by nearly 10% of their gene contents. Comparison of the species-specific gene sets uncovered genes that could be responsible for the known physiological differences between the two species. Finally, we identified 428 and 811 pseudogenes (3.8 and 7.2% of the genes) in P. anserina and P. comata, respectively. Presence of high numbers of pseudogenes supports the notion that difference in gene contents is due to gene loss rather than horizontal gene transfers. We propose that the high frequency of pseudogenization leading to gene loss in P. anserina and P. comata accompanies specialization of these two fungi. Gene loss may be more prevalent during the evolution of other fungi than usually thought