Mutation of the protein-O-mannosyltransferase enhances secretion of the human urokinase-type plasminogen activator in Hansenula polymorpha

Human urokinase-type plasminogen activator (uPA) is poorly secreted and aggregates in the endoplasmic reticulum of yeast cells due to inefficient folding. A screen for Hansenula polymorpha mutants with improved uPA secretion revealed a gene encoding a homologue of the Saccharomyces cerevisiae protein-O-mannosyltransferase Pmt1p. Expression of the H. polymorpha PMT1 gene (HpPMT1) abolished temperature sensitivity of the S. cerevisiae pmt1 pmt2 double mutant. As in S. cerevisiae, inactivation of the HpPMT1 gene affected electrophoretic mobility of the O-glycosylated protein, extracellular chitinase. In contrast to S. cerevisiae, disruption of HpPMT1 alone caused temperature sensitivity. Inactivation of the HpPMT1 gene decreased intracellular aggregation of uPA, suggesting that enhanced secretion of uPA was due to improvement of its folding in the endoplasmic reticulum. Unlike most of the endoplasmic reticulum membrane proteins, HpPmt1p possesses the C-terminal KDEL retention signal.     

Room temperature transformations induced in SiO2 layers by chemical compounds: I

Transformations in the structure and the composition of SiO₂ films as a result of the action of some organic compounds at room temperature were studied by various methods. Secondary ion mass spectrometry (SIMS) showed that hydrogen-containing species were removed from the SiO₂ layers (which were prepared by the thermal oxidation of silicon wafers) after a prolonged exposure to diethyl ether vapour. Electron microscopy and electron diffraction studies showed that the exposure led to the development of a crystalline phase in the SiO₂ layer. SIMS and transmission electron microscopy measurements both supported the view that the transformation from an amorphous structure to a denser more crystalline phase took place as a result of an interaction between molecules of diethyl ether and the SiO₂ surface. The removal of hydrogen-containing species seems to be a condition for this kind of transformation.In a recent short note¹ we have presented some preliminary results concerning amorphous-to-crystalline phase transformations in SiO₂ films which were prepared by the thermal oxidation of silicon wafers and which were treated at room temperature with various (mainly organic) compounds.Electron microscopy and electron diffraction studies clearly revealed the presence of a crystalline phase. Of the compounds investigated diethyl ether seemed to be the most active in inducing this type of transformation.In the following, more results will be given of investigations performed with the aim of understanding the phenomena and an explanation of the transformation mechanism will be offered.     

N-Terminal Peptide of PGLYRP1/Tag7 Is a Novel Ligand for TREM-1 Receptor

An investigation of innate immunity receptors sheds light on the mechanisms of inflammation and associated immune reactions. One of the key immune regulators is the TREM-1 receptor, which is involved in both inflammation and antitumor immune response. In this article, we have obtained a new ligand for the TREM-1 receptor. The peptide, named N3, is a part of the innate immune protein PGLYRP1/Tag7. It is responsible for activating the TREM-1 signaling pathway. Here, we have demonstrated that the N3 peptide acts like other TREM-1 receptor ligands: its binding results in a mild inflammation response and appearance of cytotoxic lymphocytes. We have shown that cytotoxic populations of lymphocytes in N3 peptide-treated PBMCs are similar to those treated with Tag7 or Hsp70. We also determined the part of the N3 peptide responsible for binding to TREM-1. The resulting peptide (N9) consists of nine amino acids and can be considered as a potential peptide that blocks TREM-1 signaling.