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The mechanisms and carriers responsible for exocytic protein trafficking between the trans-Golgi network (TGN) and the plasma membrane remain unclear. To investigate the dynamics of TGN-to-plasma membrane traffic and role of the cytoskeleton in these processes we transfected cells with a GFP-fusion protein, vesicular stomatitis virus G protein tagged with(More)
The biogenesis and maintenance of asymmetry is crucial to many cellular functions including absorption and secretion, signalling, development and morphogenesis. Here we have directly visualized the segregation and trafficking of apical (glycosyl phosphatidyl inositol-anchored) and basolateral (vesicular stomatitis virus glycoprotein) cargo in living cells(More)
Under fusogenic conditions, fluorescent dye redistributed from the outer monolayer leaflet of red blood cells (RBCs) to cells expressing glycophosphatidylinositol-anchored influenza virus hemagglutinin (GPI-HA) without transfer of aqueous dye. This suggests that hemifusion, but not full fusion, occurred (Kemble, G. W., T. Danieli, and J. M. White. 1994.(More)
It has been proposed that membrane fusion events such as virus-cell fusion proceed through a hemifusion intermediate, a state where lipids but not contents of the fusing compartments mix. We engineered the influenza hemagglutinin (HA) such that it would be anchored in membranes via a glycosylphosphatidylinositol (GPI) tail. GPI-anchored HA forms a trimer(More)
ADAMs contain adhesive and metalloprotease domains. As major ectodomain sheddases, they release a variety of cell-surface proteins, including growth factors, cytokines, cell adhesion molecules and receptors. ADAMs can also cleave and remodel components of the extracellular matrix. Hence, ADAMs are emerging as key modulators of cell-cell and cell-matrix(More)
When BHK-21 cells with Semliki Forest virus (SFV) bound at the plasma membrane are briefly treated with low pH medium (pH 5-6), fusion between the viral membrane and the plasma membrane occurs, releasing the viral nucleocapsid into the cytoplasm. The fusion reaction resembles that described previously for Sendai virus but with one fundamental difference; it(More)
O-glycosylation of proteins is initiated by a family of UDP-N-acetylgalactosamine:polypeptide N-acetylgalactos-aminyltransferases (GalNAc-T). In this study, we have localized endogenous and epitope-tagged human GalNAc-T1, -T2 and -T3 to the Golgi apparatus in HeLa cells by subcellular fractionation, immunofluorescence and immunoelectron microscopy. We show(More)
Binding between sperm and egg plasma membranes is an essential step in fertilization. Whereas fertilin, a mammalian sperm surface protein, is involved in this crucial interaction, sperm receptors on the egg plasma membrane have not been identified. Because fertilin contains a predicted integrin ligand domain, we investigated the expression and function of(More)
In this study we tested the hypothesis that fusion mediated by the influenza virus hemagglutinin (HA) is a cooperative event. To so this we characterized 3T3 cell lines that express HA at nine different defined surface densities. HA densities ranged from 1.0 to 12.6 x 10(3) HA trimers/microns2 as determined by quantitative fluorescent antibody binding. The(More)
The hemagglutinin (HA) spike glycoprotein of influenza virus catalyzes a low pH-induced membrane fusion event which releases the viral genome into the host cell cytoplasm. To study the fusion mechanism in more detail, we have prepared the ectodomain of HA in water-soluble form by treating virus particles with bromelain. Under mildly acidic conditions (pH(More)