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Fedor Ciampor

Publications and source records attributed to Fedor Ciampor.

4 recordsLinked to original sources
PubMed2005

Influence of residue 44 on the activity of the M2 proton channel of influenza A virus.

The influenza A virus M2 proton channel plays a role in two stages of virus replication. The proteins of two closely related strains of the avian H7 subtype of influenza A virus, Rostock and Weybridge, were found to differ in their pH-modulating activities and activation characteristics. Of three amino acid differences at residues 27, 38 and 44 within the membrane-spanning domain, substitution at residue 44 was necessary and sufficient to account for differences in trans-Golgi pH-modulating activity, whereas changes in all three were required to switch the activation characteristics of the Weybridge M2 to those of the Rostock M2. These results not only separate the two phenomena genetically, but also indicate that the 'unique' activation characteristics of the Rostock M2 channel were selected specifically. In addition, they point to the importance of functional complementarity between the activation characteristics of the M2 channel and the pH of membrane fusion by haemagglutinin during virus entry.

Amino Acid Sequence↗
PubMed2003

Carbonic anhydrase IX reduces E-cadherin-mediated adhesion of MDCK cells via interaction with beta-catenin.

Carbonic anhydrase IX (CA IX) is a cancer-associated transmembrane isoform of zinc metalloenzymes that catalyse interconversion between carbon dioxide and bicarbonate. CA IX is strongly induced by tumor hypoxia and has been proposed to participate in acidification of tumor microenvironment and in cell adhesion. To elucidate the cell adhesion-related role of CA IX, we investigated its subcellular localization and relationship to E-cadherin, a key adhesion molecule whose loss or destabilization is linked to tumor invasion. For this purpose, we generated MDCK cells with constitutive expression of human CA IX protein. During the monolayer formation, CA IX was localized to cell-cell contacts and its distribution in lateral membranes overlapped with E-cadherin. Calcium switch-triggered disruption and reconstitution of cell contacts resulted in relocalization of both CA IX and E-cadherin to cytoplasm and back to plasma membrane. A similar phenomenon was observed in hypoxia-treated and reoxygenated cells. Moreover, CA IX-expressing MDCK cells exhibited reduced cell adhesion capacity and lower levels of Triton-insoluble E-cadherin. Finally, CA IX was found to coprecipitate with beta-catenin. We conclude that CA IX has a capacity to modulate E-cadherin-mediated cell adhesion via interaction with beta-catenin, which could be of potential significance in hypoxia-induced tumor progression.

Animals↗
PubMed2003

Time course of Gag protein assembly in HIV-1-infected cells: a study by immunoelectron microscopy.

Recent biochemical studies have identified high molecular complexes of the HIV Gag precursor in the cytosol of infected cells. Using immunoelectron microscopy we studied the time course of the synthesis and assembly of a HIV Gag precursor protein (pr55gag) in Sf9 cells infected with recombinant baculovirus expressing the HIV gag gene. We also immunolabeled for pr55gag human T4 cells acutely or chronically infected with HIV-1. In Sf9 cells, the time course study showed that the first Gag protein appeared in the cytoplasm at 28-30 h p.i. and that budding started 6-8 h later. Colloidal gold particles, used to visualize the Gag protein, were first scattered randomly throughout the cytoplasm, but soon clusters representing 100 to 1000 copies of pr55gag were also observed. By contrast, in cells with budding or released virus-like particles the cytoplasm was virtually free of gold particles while the released virus-like particles were heavily labeled. Statistical analysis showed that between 80 and 90% of the gold particles in the cytoplasm were seen as singles, as doublets, or in small groups of up to five particles probably representing small oligomers. Clusters of gold particles were also observed in acutely infected lymphocytes as well as in multinuclear cells of chronically infected cultures of T4 cells. In a few cases small aggregates of gold particles were found in the nuclei of T4 lymphocytes. These observations suggest that the Gag polyprotein forms small oligomers in the cytoplasm of expressing cells but that assembly into multimeric complexes takes place predominantly at the plasma membrane. Large accumulations of Gag protein in the cytoplasm may represent misfolded molecules destined for degradation.

Animals↗