Kinetics of endosome acidification detected by mutant and wild-type Semliki Forest virus.

Margaret Kielian, M. Marsh, A. Helenius

Research output: Contribution to journalArticle

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Abstract

The fusogenic properties of Semliki Forest virus (SFV) and its mutants were used to follow the kinetics of acidification during the endocytic uptake of virus by BHK-21 cells. It has previously been shown that the low pH of endocytic vacuoles triggers a conformational change in the SFV spike glycoprotein, activating membrane fusion and initiating virus infection. This conformational alteration was here shown to occur in endosomes and to follow the same time course as the intracellular fusion reaction, demonstrating that fusion occurs rapidly after virus exposure to endosome acidity. The kinetics of endosome acidification were monitored using wild type (wt) SFV and fus-1, an SFV mutant with a lower fusion pH threshold. The results presented here demonstrated that wt and mutant virus were internalized with a t1/2 of 10 min, and that endosomes were acidified to the wt threshold of pH 6.2 with a t1/2 of 15 min. In contrast, endosome pH reached the fus-1 threshold of 5.3 with a much longer t1/2 of 45 min. The subsequent degradation of SFV in lysosomes had a t1/2 of 90 min. It was found that after the initial uptake of virus from the plasma membrane, its transit through the endocytic pathway, exposure to endosome acidity and eventual delivery to lysosomes were markedly asynchronous.

Original languageEnglish (US)
Pages (from-to)3103-3109
Number of pages7
JournalEMBO Journal
Volume5
Issue number12
StatePublished - Dec 1 1986
Externally publishedYes

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Semliki forest virus
Acidification
Endosomes
Viruses
Kinetics
Lysosomes
Fusion reactions
Membrane Fusion
Acidity
Virus Diseases
Vacuoles
Glycoproteins
Cell Membrane
Cell membranes

ASJC Scopus subject areas

  • Cell Biology
  • Genetics

Cite this

Kinetics of endosome acidification detected by mutant and wild-type Semliki Forest virus. / Kielian, Margaret; Marsh, M.; Helenius, A.

In: EMBO Journal, Vol. 5, No. 12, 01.12.1986, p. 3103-3109.

Research output: Contribution to journalArticle

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abstract = "The fusogenic properties of Semliki Forest virus (SFV) and its mutants were used to follow the kinetics of acidification during the endocytic uptake of virus by BHK-21 cells. It has previously been shown that the low pH of endocytic vacuoles triggers a conformational change in the SFV spike glycoprotein, activating membrane fusion and initiating virus infection. This conformational alteration was here shown to occur in endosomes and to follow the same time course as the intracellular fusion reaction, demonstrating that fusion occurs rapidly after virus exposure to endosome acidity. The kinetics of endosome acidification were monitored using wild type (wt) SFV and fus-1, an SFV mutant with a lower fusion pH threshold. The results presented here demonstrated that wt and mutant virus were internalized with a t1/2 of 10 min, and that endosomes were acidified to the wt threshold of pH 6.2 with a t1/2 of 15 min. In contrast, endosome pH reached the fus-1 threshold of 5.3 with a much longer t1/2 of 45 min. The subsequent degradation of SFV in lysosomes had a t1/2 of 90 min. It was found that after the initial uptake of virus from the plasma membrane, its transit through the endocytic pathway, exposure to endosome acidity and eventual delivery to lysosomes were markedly asynchronous.",
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