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Role of a transbilayer pH gradient in the membrane fusion activity of the influenza virus hemagglutinin: Use of the R18 assay to monitor membrane merging

Abstract

It had been suggested that influenza virus-mediated membrane fusion might be dependent on a pH gradient across a target membrane. We have designed experiments in which this issue could be addressed. Two populations of liposomes were prepared, both simulating the plasma membrane of target cells, but with the pH of the internal aqueous medium buffered either at pH 7.4 (physiological cytosol pH) or at pH 5.0 (endosomal pH at which influenza virus displays maximal fusion activity). By monitoring fusion using the R18 assay, we found that the internal pH of the target liposomes did not influence membrane merging as mediated by the influenza virus hemagglutinin, thus demonstrating that a transmembrane pH gradient is not required in this fusion process.

Abbreviations

HA:

influenza virus hemagglutinin

FCCP:

carbonylcyanide-p-trifluoromethoxyphenyl hydrazone

LUV:

large unilamellar vesicles

PC:

phosphatidylcholine

PE:

phosphatidylethanolamine

R18:

octadecylrhodamine B chloride

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Correspondence to João Ramalho-Santos or Maria C. Pedroso de Lima.

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Ramalho-Santos, J., de Lima, M.C.P. Role of a transbilayer pH gradient in the membrane fusion activity of the influenza virus hemagglutinin: Use of the R18 assay to monitor membrane merging. Biol Proced Online 1, 107–113 (1999). https://doi.org/10.1251/bpo13

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Keywords

  • Influenza Virus
  • Membrane Fusion
  • Target Membrane
  • Semliki Forest Virus
  • Erythrocyte Ghost