Virally mediated membrane changes: inverse effects on transport and diffusion.
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ABSTRACT:
SUBMITTER: Pasternak CA
PROVIDER: S-EPMC1168538 | biostudies-other | 1974 Dec
REPOSITORIES: biostudies-other
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Project description:1. Virally mediated permeability changes are not brought about by neuraminidase or other enzyme. They are not mimicked by local anaesthetics such as benzyl alcohol or dibucaine. 2. Virus induces an increase in the exchange rate of membrane-bound Ca2+. The temperature-dependence, and sensitivity to concanavalin A, of the permeability change and of Ca2+ exchange are similar. 3. It is concluded that an increase in the exchangeability of membrane-bound Ca2+ constitutes an early and specific event after the attachment of Sendai virus to cultured cells.
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Project description:1. Intact F glycoprotein is required to induce permeability changes in Lettrée cells or in erythrocytes. Some HN glycoproteins may also be required. Permeability changes thus offer a simple, accurate and rapid means of assaying the integrity of F glycoprotein in certain viral preparations. 2. The '1-day' virus (which contains intact F glycoprotein but which differs morphologically from '3 day' virus) does not cause permeability changes; it can be rendered active by various physical treatments. It is concluded that the environment in which F glycoprotein is embedded is a determining factor for permeability changes. 3. The entry of fluorescently labelled peptides into cells made permeable by virus has been measured. Peptides having a molecular weight in excess of 1000 enter poorly, suggesting a 'pore' size of approx. 1 nm in diameter. 4. Two novel assay methods concerned with virus--cell fusion are described. The first measures the fluorescence enhancement that occurs when anthroylstearate is transferred from anthroylstearate-labelled virus to cells. The second measures the giant-cell formation that occurs when partially fused erythrocytes are exposed to hypo-osmotic treatment. The '1-day' virus is active in these assays. In contrast with permeability changes, virus--cell fusion is insensitive to changes in external Ca2+-concentration. 5. The results are compatible with a model [Knutton & Pasternak (1979) Trends Biochem. Sci. 4, 220--223; Impraim, Foster, Micklem & Pasternak (1980) Biochem. J. 186, 847--860] in which virus--cell fusion is a prerequisite for permeability changes, and in which permeability changes are the cause of haemolysis and giant-cell (polykaryon) formation.
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Project description:1. The changes in membrane permeability to small molecules caused by Sendai virus [Pasternak & Micklem (1973) J. Membr. Biol. 14, 293-303] have been further characterized. The uptake of substances that are concentrated within cells is inhibited. Choline and 2-deoxyglucose, which become phosphorylated, and aminoisobutyrate and glycine, which are driven by a Na+-linked mechanism, are examples. The uptake of each compound under conditons where its diffusion across the plasma membrane is rate-limiting is stimulated by virus. Choline, 2-deoxyglucose and amino acids at high concentration, amino acids in Na+-free medium, and most substances at low temperature, are examples. It is concluded that virally mediated decrease of uptake is due to one of two causes. Substances that are accumulated by phosphorylation are not retained because of leakage of the phosphorylated metabolites out of cells. Substances that are accumulated by linkage to a Na+ gradient are no longer accumulated because of collapse of the gradient resulting from an increased permeability to Nat 2. Increased permeability to K+ and Na+ results in (a) membrane depolarization and (b) cell swelling. The latter event leads to haemolysis (for erythrocytes) and can lead to giant-cell (polykaryon) formation (for several cell types). 3. Recovery of cells can be temporarily achieved by the addition of Ca2+; permanent recovery requires incubation for some hours at 37 degrees C. 4. The possible significance of virally mediated permeability changes, with regard to clinical situations and to cell biology, is discussed.
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Project description:1. Sendai virus causes permeability changes when added to freshly isolated brain cells (cerebellum or ependymal cells) or to a culture of forebrain cells. 2. Sendai virus causes permeability changes when added to organ cultures of ferret lung or nasal turbinate. Influenza virus causes no permeability changes under these conditions. 3. Rabies virus and vesicular-stomatitis virus, in contrast with Sendai virus, do not cause permeability changes in BHK cells or Lettrée cells. 4. Serum from patients suffering from viral hepatitis does not cause permeability changes in human leucocytes; addition to Sendai virus causes permeability changes. 5. It is concluded that permeability changes accompanying viral entry occur only with certain types of paramyxovirus, but that there is little restriction on cell type. 6. MDBK cells infected with Sendai virus show permeability changes during viral release, similar to those that occur during viral entry. Because these changes do not appear to be restricted to paramyxoviruses, they may have considerable clinical significance.
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