The PKC1-MPK1 pathway in yeast functions in the maintenance of cell wall integrity and in the stress response. We have identified a family of genes that are putative regulators of this pathway. WSC1, WSC2, and WSC3 encode predicted integral membrane proteins with a conserved cysteine motif and a WSC1-green f luorescence protein fusion protein localizes to the plasma membrane. Deletion of WSC results in phenotypes similar to mutants in the PKC1-MPK1 pathway and an increase in the activity of MPK1 upon a mild heat treatment is impaired in a wsc⌬ mutant. Genetic analysis places the function of WSC upstream of PKC1, suggesting that they play a role in its activation. We also find a genetic interaction between WSC and the RAS-cAMP pathway. The RAS-cAMP pathway is required for cell cycle progression and for the heat shock response. Overexpression of WSC suppresses the heat shock sensitivity of a strain in which RAS is hyperactivated and the heat shock sensitivity of a wsc⌬ strain is rescued by deletion of RAS2. The functional characteristics and cellular localization of WSC suggest that they may mediate intracellular responses to environmental stress in yeast.

The design, synthesis, and characterization of novel water-soluble iodinated dendritic nanoparticles, G-4-(DMAA-IPA) 37 , is reported. They consist of a generation 4 Starburst PAMAM dendrimer core and 3-N-[(N′,N′-dimethylaminoacetyl)amino]-r-ethyl-2,4,6-triiodobenzenepropanoic acid (DMAA-IPA) molecules covalently attached to the surface. These nanoparticles have an average molecular weight of 37,000 g/mol, a hydrodynamic radius of 2.4 nm and high iodine content (33.06%), while retaining their overall charge and water solubility. Thus, G-4-(DMAA-IPA) 37 is the first representative of a novel class of dendritic nanoparticles for computed tomography (CT) imaging.

Wsc1p, Wsc2p, Wsc3p, and Wsc4p, members of a novel protein family in the yeast Saccharomyces cerevisiae, are putative sensors or receptors in the stress response. Genetic characterization suggests that the WSC family are upstream regulators of the stress-activated PKC1-MAP kinase cascade and are required for the heat shock response and for maintenance of cell wall integrity. The Wsc proteins share sequence characteristics: at their N terminus they have a cysteine motif and a serine/threonine-rich domain predicted to be extracellular, a hydrophobic domain suggested to be transmembranous, and a variable, highly charged C terminus that may be involved in intracellular signaling. Although a role for the WSC genes in maintenance of cell wall integrity has been firmly established, little is known about the properties of the proteins. As reported here, to study its properties in vivo, we epitope tagged the Wsc1 protein. Wsc1p was found to fractionate with the membrane pellet after high-speed centrifugation. Extraction experiments show that Wsc1p is an integral membrane protein present in two forms: one solubilized by detergent, the other Triton X-100 insoluble. Our results also show that Wsc1p is glycosylated and phosphorylated. To characterize the contribution of different domains to the function of Wsc1p, we generated various deletion constructs. Analysis of the properties and function of the mutant proteins shows that the predicted extracellular serine/threonine-rich domain is required for Wsc1p functionality, as well as its glycosylation. A mutant Wsc1 protein lacking the putative transmembrane domain is not functional and partitions to the soluble fraction. Overexpression of full-length Wsc1p inhibits cell growth, with the N terminus alone being sufficient for this inhibition. This suggests that Wsc1p may function in a complex with at least one other protein important for normal cell growth.