Cell
Volume 76, Issue 2, 28 January 1994, Pages 383-391
Journal home page for Cell

Article
Lipid-anchored influenza hemagglutinin promotes hemifusion, not complete fusion

https://doi.org/10.1016/0092-8674(94)90344-1Get rights and content

Abstract

It has been proposed that membrane fusion events such as virus-cell fusion proceed through a hemifusion intermediate, a state where lipids but not contents of the fusing compartments mix. We engineered the influenza hemagglutinin (HA) such that it would be anchored in membranes via a glycosylphosphatidylinositol (GPI) tail. GPI-anchored HA forms a trimer that can bind red blood cells (RBCs) and change conformation under fusion-inducing conditions. Using RBCs labeled with fluorescent lipid or fluorescent soluble content probes, we found that GPI-anchored HA mediated lipid mixing with similar time course and efficiency as wt-HA, yet did not mediate transfer of soluble contents. Hence, GPI-anchored HA appears to initiate, but not complete, a fusion reaction. We interpret our results as evidence for uncoupling a physiological fusion reaction, for trapping a hemifusion intermediate, and for assigning a role to a transmembrane domain in a fusion event.

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    Present address: Aviron, 1450 Rollins Road, Burlingame, California 94010.

    Present address: University of Virginia Medical Center, Department of Anatomy and Cell Biology, Charlottesville, Virginia 22908.

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