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Responses |
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Member |
Comments |
Rino
Rappuoli
Chiron Corporation,
Italy
Microbiology
 New
Finding
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This paper shows
that, in a model system, the soluble
N-ethylmaleimide-sensitive factor attachment
protein receptor (SNARE) proteins can be replaced
by a lipid-oligonucleotide complex and that
complementary oligonucleotides are able to drive
vesicle fusions. This simplified fusion model
driven by oligonucleotides provides a powerful
tool to ask many of the important questions about
vesicle fusions. For instance, they show that the
addition of non-complementary nucleotides up to
25bp long changes the efficiency of vesicle fusion
so that the distance from the membrane affects the
efficiency of the fusion process. In the
early 1990s working independently, Cesare
Montecucco, James Rothman, and Randy Schekman
generated complementary data that led to the
discovery that transmembrane proteins located in
vesicles (v-SNAREs) and in target cell membranes
(t-SNARES) mediate the specific fusion between
different biological membranes. The finding that
tetanus toxin blocks exocytosis of
neurotransmitter-containing synaptic vesicles by
cleaving VAMP/synaptobrevin, one of the SNARE
proteins, provided evidence that this was a key
molecule of the machinery that mediates
vesicle-target membrane recognition and fusion and
allowed to assign a function to the proteins
identified with biochemical and genetic
techniques. Since the initial discovery, we have
learned that the molecular basis of biological
membrane fusion is of fundamental importance to
any form of life and is also at the basis of any
other membrane fusion event, including viral entry
into host cells. In essence, the membrane fusion
is essential to organelle formation, to uptake and
secretion of hormones and neurotransmitters, and
to viral infection. In 2002, Rothman and Schekman
received the Lasker Award for this discovery. The
oligonucleotide-mediated fusion of vesicles
described in this paper provides additional
support to the present knowledge of this
fundamental process of life and an invaluable tool
to study the molecular mechanisms that govern it.
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Competing interests:
None declared
Evaluated
16 Mar 2009
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Axel Brunger
Stanford University
School of Medicine, United States of
America
Structural Biology
New Finding
Controversial
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This is an
important study on liposome fusion that utilizes
variable length synthetic lipid-oligonucleotide
conjugates to systematically alter the separation
between interacting liposomes. Both content-mixing
and lipid-mixing indicators are
employed. It is found that lipid mixing
generally proceeds at a much greater extent than
content mixing. Surprisingly, lipid mixing of both
inner and outer leaflets can occur without content
mixing. This is a landmark study that calls into
question liposome "fusion" assays that rely on
lipid-mixing indicators to assess fusion. This
study strongly suggests that future liposome
fusion experiments (of SNARE-induced fusion, for
example) have to employ content-mixing indicators
in addition to lipid-mixing indicators.
Competing interests:
None declared
Evaluated
6 May 2009
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Josep Rizo
University of Texas
Southwestern Medical Center at Dallas, United States of
America
Structural Biology
New Finding
 Tech Advance
Controversial
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This paper shows
the usefulness of complementary DNA
oligonucleotides as models to study membrane
fusion, and demonstrates that a lipid-mixing assay
widely used to study soluble
N-ethylmaleimide-sensitive factor attachment
protein receptor (SNARE) function is not a good
reporter of membrane fusion. Complementary
oligonucleotides anchored on separate vesicle
populations are shown to mediate lipid mixing
between the vesicles with very high efficiency (up
to 80%), and insertion of linker sequences of
different lengths between the membrane and the
complementary sequences leads to a graded decrease
in lipid mixing. Importantly, the oligonucleotides
yielding most efficient lipid mixing lead to only
1.5% content mixing. This result emphatically
shows that assays reporting only lipid mixing
cannot be used to demonstrate membrane fusion.
Although this notion is not new, a vast amount of
the SNARE literature still uses the term ‘membrane
fusion’ when only ‘lipid mixing’ has been
demonstrated. Hopefully, this beautiful work by
Boxer and colleagues will help to eliminate this
confusion in the field.
Competing interests:
None declared
Evaluated
29 Jun 2009
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| Faculty Comments & Author
Responses |
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How to cite the Faculty of 1000 Biology
evaluation(s) for this paper
1) To cite all the
evaluations for this article:
Faculty of 1000 Biology: evaluations for
Chan YH et al Proc Natl Acad Sci U S A 2009 Jan 27 106
(4) :979-84
http://f1000biology.com/article/id/1157241/evaluation
2) To cite an
evaluation by a specific Faculty member:
Rino Rappuoli: Faculty of 1000 Biology,
16 Mar 2009
http://f1000biology.com/article/id/1157241/evaluation
Axel
Brunger: Faculty of 1000 Biology, 6 May 2009
http://f1000biology.com/article/id/1157241/evaluation
Josep
Rizo: Faculty of 1000 Biology, 29 Jun 2009
http://f1000biology.com/article/id/1157241/evaluation
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