Selective delivery of membrane proteins to the cell surface in Saccharomyces cerevisiae

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 1997.Vita.Includes bibliographical references.by Kevin Roberg.Ph.D

Cytokine response patterns, exposure to viruses, and respiratory infections in the first year of life

Keywords: interferon-␥; respiratory syncytial virus; daycare; sibling Viral respiratory illnesses, many of which are contracted through contact with siblings or attendance at daycare, are the most common triggers for wheezing and asthma exacerbations among young children. In both the Tucson Children's Respiratory Study (1, 2) and the Italian Studies of Respiratory Disorders in Childhood and the Environment project (3), daycare attendance was shown to be a risk factor for viral infections and viral-associated wheezing in the first 2 years of life, but protective against viral infections and asthma later in life. Celedon and colleagues found that daycare attendance during the first year of life was associated with lower rates of asthma at 6 years of age, but only among children without a maternal history of asthma (4). Similarly, children with older siblings in the home are more likely to experience viral illnesses and wheezing in the first 2 years of life, but have decreased rates of wheezing, and decreased rates of atopic sensitization later in childhood (2, 3, 5, 6). Despite the convincing evidence linking exposure to other children with rates of respiratory illnesses and wheezing, the effects of increased exposure on specific viral infections have not been ascertained. While exposure is an important determinant of lower respiratory tract illnesses, it does not explain why some children entering daycare experience a dramatic increase in viral infections, while others are relatively healthy. In addition, recent genetic studies suggest that clinical outcomes of viral infections in infancy might also be influenced by polymorphisms in cytokine genes (7-9). These observations suggest the hypotheses that variations and/or subtle defects in the antiviral immune response also affect the clinical expression of viral respiratory infections. Furthermore, stressing the immune system with increased viral exposure may uncover relatively minor immune defects that are not apparent in children with less exposure to viruses. To test these hypotheses, we conducted a prospective birth cohort study to evaluate interactions between exposure to other children, the development patterns of cytokine responses in peripheral blood cells, and the etiology and severity of respiratory viral infections during the first year of life. Other study results pertinent to this cohort have been previously published as both original articles and abstracts (10-13)

Sit4p/PP6 regulates ER-to-Golgi traffic by controlling the dephosphorylation of COPII coat subunits

Traffic from the endoplasmic reticulum (ER) to the Golgi complex is initiated when the activated form of the GTPase Sar1p recruits the Sec23p-Sec24p complex to ER membranes. The Sec23p-Sec24p complex, which forms the inner shell of the COPII coat, sorts cargo into ER-derived vesicles. The coat inner shell recruits the Sec13p-Sec31p complex, leading to coat polymerization and vesicle budding. Recent studies revealed that the Sec23p subunit sequentially interacts with three different binding partners to direct a COPII vesicle to the Golgi. One of these binding partners is the serine/threonine kinase Hrr25p. Hrr25p phosphorylates the COPII coat, driving the membrane-bound pool into the cytosol. The phosphorylated coat cannot rebind to the ER to initiate a new round of vesicle budding unless it is dephosphorylated. Here we screen all known protein phosphatases in yeast to identify one whose loss of function alters the cellular distribution of COPII coat subunits. This screen identifies the PP2A-like phosphatase Sit4p as a regulator of COPII coat dephosphorylation. Hyperphosphorylated coat subunits accumulate in the sit4Δ mutant in vivo. In vitro, Sit4p dephosphorylates COPII coat subunits. Consistent with a role in coat recycling, Sit4p and its mammalian orthologue, PP6, regulate traffic from the ER to the Golgi complex