Multistep Regulation of Membrane Insertion of the Fusion Peptide of Semliki Forest Virus

Don L. Gibbons, Anna Ahn, Maofu Liao, Lena Hammar, R. Holland Cheng, Margaret Kielian

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

A prevailing model for virus membrane fusion proteins has been that the hydrophobic fusion peptide is hidden in the prefusion conformation, becomes exposed once the fusion reaction is triggered, and then either inserts into target membranes or is rapidly inactivated. This model is in general agreement with the structure and mechanism of class I fusion proteins, such as the influenza virus hemagglutinin. We here describe studies of the class II fusion protein E1 from the alphavirus Semliki Forest virus (SFV). SFV fusion is triggered by low pH, which releases E1 from its heterodimeric interaction with the E2 protein and induces the formation of a stable E1 homotrimer. The exposure and target membrane interaction of the E1 fusion peptide (residues 83 to 100) were followed using a monoclonal antibody (MAb E1f) mapping to E1 residues 85 to 95. In agreement with the known structure of SFV and other alphaviruses, the fusion peptide was shielded in native SFV particles and exposed when E1-E2 dimer dissociation was triggered by acidic pH. In contrast, the fusion peptide on purified E1 ectodomains (E1*) was fully accessible at neutral pH. Functional assays showed that MAb E1f binding at neutral pH prevented subsequent low-pH-triggered E1* interaction with target membranes and trimerization. E1* was not inactivated by low pH when treated either in the absence of target membranes or in the presence of fusion-inactive cholesterol-deficient liposomes. Thus, the membrane insertion of the E1 fusion peptide is regulated by additional low-pH-dependent steps after exposure, perhaps involving an E1-cholesterol interaction.

Original languageEnglish (US)
Pages (from-to)3312-3318
Number of pages7
JournalJournal of Virology
Volume78
Issue number7
DOIs
StatePublished - Apr 2004

Fingerprint

Semliki Forest virus
Semliki forest virus
Membrane Fusion
peptides
Peptides
Membranes
Alphavirus
proteins
Membrane Fusion Proteins
Cholesterol
cholesterol
Viral Fusion Proteins
Virus Internalization
Proteins
Hemagglutinins
hemagglutinins
Orthomyxoviridae
virion
Liposomes
Virion

ASJC Scopus subject areas

  • Immunology

Cite this

Multistep Regulation of Membrane Insertion of the Fusion Peptide of Semliki Forest Virus. / Gibbons, Don L.; Ahn, Anna; Liao, Maofu; Hammar, Lena; Cheng, R. Holland; Kielian, Margaret.

In: Journal of Virology, Vol. 78, No. 7, 04.2004, p. 3312-3318.

Research output: Contribution to journalArticle

Gibbons, Don L. ; Ahn, Anna ; Liao, Maofu ; Hammar, Lena ; Cheng, R. Holland ; Kielian, Margaret. / Multistep Regulation of Membrane Insertion of the Fusion Peptide of Semliki Forest Virus. In: Journal of Virology. 2004 ; Vol. 78, No. 7. pp. 3312-3318.
@article{2908fe398dfb4f3d90ac8d77fe19a149,
title = "Multistep Regulation of Membrane Insertion of the Fusion Peptide of Semliki Forest Virus",
abstract = "A prevailing model for virus membrane fusion proteins has been that the hydrophobic fusion peptide is hidden in the prefusion conformation, becomes exposed once the fusion reaction is triggered, and then either inserts into target membranes or is rapidly inactivated. This model is in general agreement with the structure and mechanism of class I fusion proteins, such as the influenza virus hemagglutinin. We here describe studies of the class II fusion protein E1 from the alphavirus Semliki Forest virus (SFV). SFV fusion is triggered by low pH, which releases E1 from its heterodimeric interaction with the E2 protein and induces the formation of a stable E1 homotrimer. The exposure and target membrane interaction of the E1 fusion peptide (residues 83 to 100) were followed using a monoclonal antibody (MAb E1f) mapping to E1 residues 85 to 95. In agreement with the known structure of SFV and other alphaviruses, the fusion peptide was shielded in native SFV particles and exposed when E1-E2 dimer dissociation was triggered by acidic pH. In contrast, the fusion peptide on purified E1 ectodomains (E1*) was fully accessible at neutral pH. Functional assays showed that MAb E1f binding at neutral pH prevented subsequent low-pH-triggered E1* interaction with target membranes and trimerization. E1* was not inactivated by low pH when treated either in the absence of target membranes or in the presence of fusion-inactive cholesterol-deficient liposomes. Thus, the membrane insertion of the E1 fusion peptide is regulated by additional low-pH-dependent steps after exposure, perhaps involving an E1-cholesterol interaction.",
author = "Gibbons, {Don L.} and Anna Ahn and Maofu Liao and Lena Hammar and Cheng, {R. Holland} and Margaret Kielian",
year = "2004",
month = "4",
doi = "10.1128/JVI.78.7.3312-3318.2004",
language = "English (US)",
volume = "78",
pages = "3312--3318",
journal = "Journal of Virology",
issn = "0022-538X",
publisher = "American Society for Microbiology",
number = "7",

}

TY - JOUR

T1 - Multistep Regulation of Membrane Insertion of the Fusion Peptide of Semliki Forest Virus

AU - Gibbons, Don L.

AU - Ahn, Anna

AU - Liao, Maofu

AU - Hammar, Lena

AU - Cheng, R. Holland

AU - Kielian, Margaret

PY - 2004/4

Y1 - 2004/4

N2 - A prevailing model for virus membrane fusion proteins has been that the hydrophobic fusion peptide is hidden in the prefusion conformation, becomes exposed once the fusion reaction is triggered, and then either inserts into target membranes or is rapidly inactivated. This model is in general agreement with the structure and mechanism of class I fusion proteins, such as the influenza virus hemagglutinin. We here describe studies of the class II fusion protein E1 from the alphavirus Semliki Forest virus (SFV). SFV fusion is triggered by low pH, which releases E1 from its heterodimeric interaction with the E2 protein and induces the formation of a stable E1 homotrimer. The exposure and target membrane interaction of the E1 fusion peptide (residues 83 to 100) were followed using a monoclonal antibody (MAb E1f) mapping to E1 residues 85 to 95. In agreement with the known structure of SFV and other alphaviruses, the fusion peptide was shielded in native SFV particles and exposed when E1-E2 dimer dissociation was triggered by acidic pH. In contrast, the fusion peptide on purified E1 ectodomains (E1*) was fully accessible at neutral pH. Functional assays showed that MAb E1f binding at neutral pH prevented subsequent low-pH-triggered E1* interaction with target membranes and trimerization. E1* was not inactivated by low pH when treated either in the absence of target membranes or in the presence of fusion-inactive cholesterol-deficient liposomes. Thus, the membrane insertion of the E1 fusion peptide is regulated by additional low-pH-dependent steps after exposure, perhaps involving an E1-cholesterol interaction.

AB - A prevailing model for virus membrane fusion proteins has been that the hydrophobic fusion peptide is hidden in the prefusion conformation, becomes exposed once the fusion reaction is triggered, and then either inserts into target membranes or is rapidly inactivated. This model is in general agreement with the structure and mechanism of class I fusion proteins, such as the influenza virus hemagglutinin. We here describe studies of the class II fusion protein E1 from the alphavirus Semliki Forest virus (SFV). SFV fusion is triggered by low pH, which releases E1 from its heterodimeric interaction with the E2 protein and induces the formation of a stable E1 homotrimer. The exposure and target membrane interaction of the E1 fusion peptide (residues 83 to 100) were followed using a monoclonal antibody (MAb E1f) mapping to E1 residues 85 to 95. In agreement with the known structure of SFV and other alphaviruses, the fusion peptide was shielded in native SFV particles and exposed when E1-E2 dimer dissociation was triggered by acidic pH. In contrast, the fusion peptide on purified E1 ectodomains (E1*) was fully accessible at neutral pH. Functional assays showed that MAb E1f binding at neutral pH prevented subsequent low-pH-triggered E1* interaction with target membranes and trimerization. E1* was not inactivated by low pH when treated either in the absence of target membranes or in the presence of fusion-inactive cholesterol-deficient liposomes. Thus, the membrane insertion of the E1 fusion peptide is regulated by additional low-pH-dependent steps after exposure, perhaps involving an E1-cholesterol interaction.

UR - http://www.scopus.com/inward/record.url?scp=1842457801&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=1842457801&partnerID=8YFLogxK

U2 - 10.1128/JVI.78.7.3312-3318.2004

DO - 10.1128/JVI.78.7.3312-3318.2004

M3 - Article

C2 - 15016852

AN - SCOPUS:1842457801

VL - 78

SP - 3312

EP - 3318

JO - Journal of Virology

JF - Journal of Virology

SN - 0022-538X

IS - 7

ER -