JCB logo
R&D Systems: New Poster Available
  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents
This Article
Right arrow Full Text
Right arrow Full Text (PDF, 678K)
Right arrow PPT slides of all figures
Right arrow Alert me when this article is cited
Right arrow Citation Map
Services
Right arrow Email this article
Right arrow Similar articles in this journal
Right arrow Alert me to new content in the JCB
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Melikyan, G. B.
Right arrow Articles by Cohen, F. S.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Melikyan, G. B.
Right arrow Articles by Cohen, F. S.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Facebook   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

© The Rockefeller University Press, 0021-9525/1997//995 $5.00
The Journal of Cell Biology, Volume 136, Number 5, , 1997 995-1005

Article

Inner but Not Outer Membrane Leaflets Control the Transition from Glycosylphosphatidylinositol-anchored Influenza Hemagglutinin-induced Hemifusion to Full Fusion



Grigory B. Melikyan, Sofya A. Brener, Dong C. Ok, and Fredric S. Cohen

Department of Molecular Biophysics and Physiology, Rush Medical College, Chicago, Illinois 60612

Cells that express wild-type influenza hemagglutinin (HA) fully fuse to RBCs, while cells that express the HA-ectodomain anchored to membranes by glycosylphosphatidylinositol, rather than by a transmembrane domain, only hemifuse to RBCs. Amphipaths were inserted into inner and outer membrane leaflets to determine the contribution of each leaflet in the transition from hemifusion to fusion. When inserted into outer leaflets, amphipaths did not promote the transition, independent of whether the agent induces monolayers to bend outward (conferring positive spontaneous monolayer curvature) or inward (negative curvature). In contrast, when incorporated into inner leaflets, positive curvature agents led to full fusion. This suggests that fusion is completed when a lipidic fusion pore with net positive curvature is formed by the inner leaflets that compose a hemifusion diaphragm. Suboptimal fusion conditions were established for RBCs bound to cells expressing wild-type HA so that lipid but not aqueous dye spread was observed. While this is the same pattern of dye spread as in stable hemifusion, for this "stunted" fusion, lower concentrations of amphipaths in inner leaflets were required to promote transfer of aqueous dyes. Also, these amphipaths induced larger pores for stunted fusion than they generated within a stable hemifusion diaphragm. Therefore, spontaneous curvature of inner leaflets can affect formation and enlargement of fusion pores induced by HA. We propose that after the HA-ectodomain induces hemifusion, the transmembrane domain causes pore formation by conferring positive spontaneous curvature to leaflets of the hemifusion diaphragm.

Abbreviations used in this paper: CF, 6-carboxyfluorescein; CPZ, chlorpromazine; M-CPZ, metho-chlorpromazine; DB, dibucaine; DOPC, dioleoylphosphatidylcholine; DOPE, dioleoylphosphatidylethanolamine; GPI, glycosylphosphatidylinositol; HA, hemagglutinin; HD, hemifusion diaphragm; LPC, lysophosphatidylcholine; L-LPC, lyso-lauroylphosphatidylcholine; S-LPC, lyso-stearoylphosphatidylcholine; MPCA, membranepermeable, cationic amphipaths; NBD-t, NBD-taurine; PS, phosphatidylserine; RD, tetramethylrhodamine-dextran; R18, octadecylrhodamine B chloride; TFP, trifluoperazine; WT, wild type.

Address all correspondence to Fredric S. Cohen, Department of Molecular Biophysics and Physiology, Rush Medical College, 1653 W. Congress Parkway, Chicago, IL 60612. Tel.: (312) 942-6753. Fax: (312) 942-8711. e-mail: fcohen{at}rpslmc.edu

2. CPZ was more efficient in promoting aqueous dye redistribution between RBCs and GPI cells in these experiments than in the experiment of Fig. 3 A. For Fig. 3 A, NBD-t–loaded RBCs were treated with 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS; Sigma Chemical Co.) to prevent leakage of NBD-t (Sarkar et al., 1989). However, DIDS treatment inhibited R18 redistribution (not shown) and was omitted in this series of experiments to avoid possible interference with LPC or CPZ.


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Facebook Facebook   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?


This article has been cited by other articles:



  Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents