It is proposed to investigate at both the cellular and the subcellular molecular level several aspects of glycoprotein metabolism in the lung. Glycoproteins have been demonstrated to accumulate in the alveoli of lungs from individuals with alveolar proteinosis, and have also been implicated as a component of surfactant. The cellular sources of such glycoproteins, the biosynthetic, secretory, and regulatory processes involved, and any possible funcitons of these glycoproteins are poorly understood. Specifically, the involvement of the colichol cycle in synthesis of glycoprotins having the N-asparaginyl linkage type will be investigated. The microsomal enzyme dolichol phosphate: UDP-G1cNAc G1cNAc 1-phosphate transferase that catalyzes the first glycosylation step in the cycle will be studied with respect to its requirement for phospholipids (phosphoglycerides) in the in vitro reaction. Structural features of the phospholipids that are required for reactivation of the delipidated inactive enzyme will be determined, and properties of the enzyme in reconstituted enzyme-phospholipid vesicles will be explored in efforts to understand the native environment and functioning of this enzyme in protein glycosylation. Specific metabolic functions of lung Type II alveolar cells will be studied in primary cell cultures. The functioning of the dolichol cycle in these cells will be ascertained by metabolic lableing experiments. Glycoproteins synthesized and secreted will be compared to previously reported lung lavage and surfactant glycoproteins in an effort to define their origin as the Type II cell. The possible involvement of the lamellar bodies in secretion of glycoproteins will also be explored. As glucocorticoids are known to enhance surfactant phospholipid synthesis in Type II cells, the effects of these hormones on dolichol cycle intermediates and on glycoprotein synthesis and secretion will be studied. These experiments should further our understanding of the use and effects of glucocorticoids in respiratory distress syndrome.
| Chandra, N C; Doody, M B; Bretthauer, R K (1991) Specific lipids enhance the activity of UDP-GlcNAc: dolichol phosphate GlcNAc-1-phosphate transferase in rat liver endoplasmic reticulum membrane vesicles. Arch Biochem Biophys 290:345-54 |
| Davidson, D J; Bretthauer, R K; Castellino, F J (1991) alpha-Mannosidase-catalyzed trimming of high-mannose glycans in noninfected and baculovirus-infected Spodoptera frugiperda cells (IPLB-SF-21AE). A possible contributing regulatory mechanism for assembly of complex-type oligosaccharides in infected cells. Biochemistry 30:9811-5 |
