University of Basel

About: University of Basel is a education organization based out in Basel, Basel-Stadt, Switzerland. It is known for research contribution in the topics: Population & Gene. The organization has 25084 authors who have published 52975 publications receiving 2388002 citations. The organization is also known as: Universität Basel & Basel University.

end3 and end4: two mutants defective in receptor-mediated and fluid-phase endocytosis in Saccharomyces cerevisiae.

Abstract: alpha-factor, one of two peptide hormones responsible for synchronized mating between MATa and MAT alpha-cell types in Saccharomyces cerevisiae, binds to its cell surface receptor and is internalized in a time-, temperature-, and energy-dependent manner (Chvatchko, Y., I. Howald, and H. Riezman. 1986. Cell. 46:355-364). After internalization, alpha-factor is delivered to the vacuole via vesicular intermediates and degraded there consistent with an endocytic mechanism (Singer, B., and H. Riezman. 1990. J. Cell Biol. 110:1911-1922; Chvatchko, Y., I. Howald, and H. Riezman. 1986. Cell. 46:355-364). We have isolated two mutants that are defective in the internalization process. Both mutations confer a recessive, temperature-sensitive growth phenotype upon cells that cosegregates with their endocytosis defect. Lucifer yellow, a marker for fluid-phase endocytosis, shows accumulation characteristics in the mutants that are similar to the uptake characteristics of 35S-alpha-factor. The endocytic defect in end4 cells appears immediately upon shift to restrictive temperature and is reversible at permissive temperature if new protein synthesis is allowed. Furthermore, the end4 mutation only affects alpha-factor internalization and not the later delivery of alpha-factor to the vacuole. Other vesicle-mediated processes seem to be normal in end3 and end4 mutants. END3 and END4 are the first genes shown to be necessary for the internalization step of receptor-borne and fluid-phase markers in yeast.

An IgG monoclonal antibody to group B meningococci cross-reacts with developmentally regulated polysialic acid units of glycoproteins in neural and extraneural tissues.

Abstract: The structurally similar polysialic acid capsules of group B meningococci and Escherichia coli K1 are poor immunogens, and attempts are currently being made to improve their immunogenicity by chemical modifications. An IgG monoclonal antibody to these polysialic acid capsules was used for the study of the presence of structurally similar components in tissue glycoproteins to investigate the reasons for the poor immunogenicity and to evaluate potential dangers in active or passive immunization. By immunoblotting polysialic acid was detected outside the brain in newborn rat kidney, heart, and muscle. It appeared in immunoblots as one component and with similar mobility to the neural cell adhesion molecule N-CAM. Specificity studies of the antibody and endosialidase treatment showed that the polysialic acid glycans detected were composed of chains as long as eight sialic acid residues or more. The polysialic acid was not detected in the corresponding tissues of the adult animal. These results indicate that polysialic acid units are developmentally regulated components of both neural and extraneural tissues, and are bound to components with properties similar to a known cell-adhesion molecule. This together with the presence of low amounts of polysialic acid even in the adult brain, suggests potential hazards in vaccination trials and suggested immunotherapy of meningitis caused by group B meningococci or E. coli K1, which should be carefully assessed.

The TOR-controlled transcription activators GLN3, RTG1, and RTG3 are regulated in response to intracellular levels of glutamine

Abstract: The essential, rapamycin-sensitive TOR kinases regulate a diverse set of cell growth-related readouts in response to nutrients. Thus, the yeast TOR proteins function as nutrient sensors, in particular as sensors of nitrogen and possibly carbon. However, the nutrient metabolite(s) that acts upstream of TOR is unknown. We investigated the role of glutamine, a preferred nitrogen source and a key intermediate in yeast nitrogen metabolism, as a possible regulator of TOR. We show that the glutamine synthetase inhibitor L-methionine sulfoximine (MSX) specifically provokes glutamine depletion in yeast cells. MSX-induced glutamine starvation caused nuclear localization and activation of the TOR-inhibited transcription factors GLN3, RTG1, and RTG3, all of which mediate glutamine synthesis. The MSX-induced nuclear localization of GLN3 required the TOR-controlled, type 2A-related phosphatase SIT4. Other TOR-controlled transcription factors, GAT1/NIL1, MSN2, MSN4, and an unknown factor involved in the expression of ribosomal protein genes, were not affected by glutamine starvation. These findings suggest that the TOR pathway senses glutamine. Furthermore, as glutamine starvation affects only a subset of TOR-controlled transcription factors, TOR appears to discriminate between different nutrient conditions to elicit a response appropriate to a given condition.