4. CONDITIONS
Donor Emission = Acceptor
Excitation
Close proximity of donor
and acceptor (1-10 nm)
Fluorescence Lifetime of the
donor should be sufficient
8. V A D I M D E G T Y A R e t a l , .
J NEUROSCI. 2013; 33(13): 5507–
5523.
Dance of the SNAREs: Assembly
and rearrangements detected with
FRET at neural synapses
10. MATERIALS AND METHODS
Scheme 1
Cerulean: N termini
VAMP
Citrine: SNAP-25
Changes in their
separation and orientation
Scheme 2
Cerulean: Syntaxin
Citrine: C termini VAMP
trans-cis conformational
change in SNAREs on
vesicle fusion
VAMP: Vesicle Associated Membrane Protein
SNAP: Synaptosomal associated protein of 25kD
11. ULTIMATE AIM
1. Detection of resting SNARE
complexes
2. Conformational rearrangement
during exocytosis
3. Disassembly prior to endocytosis of
vesicular protein
4.SNARE assembly at newly docked
vesicles
12. OUTCOME
Reoreintation
of the SNARE
motif upon
exocytosis
SNARE
disassembly in
the active zone
periphery
SNARE
assembly in the
newly docked
vesicles
Trans-cis
conformational
changes in
SNAREs on
vesicle fusion
13. SPECIFIC AIM 1
Labeling with fluorophores
Expression and correct targeting of VAMP and
SNAP-25-FM4-64 staining
Schematic of assembled SNARE complex comprising VAMP
labeled with cerulean, SNAP-25 labeled with citrine, and syntaxin
14. Continued…
No complete block of
neurosecretion by
Botulinum E and tetanus
toxin
Normal release by co-
transfected cells
Transfection procedure-
not fluorophores reduces
the release probability
15. SPECIFIC AIM 2
Resting FRET of pre-assembled SNAREs
Donor dequench on
acceptor photobleach
FRET-FLIM:
FRET ratio of donor:
2.7%(4.9% uncertainty)
With acceptor: 4.6% (5.9%
uncertainty)
Control:
FRET ration: 2.4%
Average: 2.4 -4.6 = 3%
FRET not from protein
crowding or un-complexed
donor or acceptor
16. SPECIFIC AIM 3
Dynamic FRET technique
Sensitized emission
“3 cube method”
Image splitter:Emission
of both fluorophores
measured
simultaneously
Polychroic mirror-
reflects both emission
bands
Quadruple- separate
donor, acceptor, bright-
field and FM4-64 images
18. Continued…
1
• Signals from non-transmitting boutons did not fit this pattern
2
• No consistent signals with donor or acceptor alone
3
• No signals, when exocytosis was blocked by omitting calcium-
signals dependency of the calcium
4
• Signals dependent on intact SNAREs- Botulinum toxin
5
• Signals also dependent on disassembly and reassembly of
SNAREs- Nethylmaleimide (NEM)
19. SPECIFIC AIM 5
Dispersion of SNARE complex
VAMP is deposited on the plasma
membrane on exocytosis and recovered
by endocytosis
Simultaneous lateral dispersion of both
SNAP-25 and syntaxin.
26. References
S. R. Swift and L. Trinkle-Mulcahy. Basic
principles of FRAP, FLIM and FRET.
S. A. Hussain et. al. An Introduction to
Fluorescence Resonance Energy Transfer
(FRET)
Janos Szollosi et al. Application of Fluorescence
Resonance Energy Transfer in the Clinical
Laboratory: Routine and Research.