Carmichael’s Concise Review
experiments, they found that K&R was common for vesicles in
the “readily releasable pool,” whereas vesicles that had fused at
least once or vesicles from the “reserve pool” were less likely to
undergo K&R. Also, the rapidity of stimulation favored K&R.
SPEND LESS. GET MORE.
But apparently, although K&R is common, vesicles eventually
proceeded to FCF.
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How soon after K&R can a vesicle again undergo K&R or
proceed to FCF? Through a series of clever experiments, Zhang
et al. determined that a vesicle can go to another K&R in about
5 seconds, whereas it takes about 27 seconds to proceed to
NEW
FCF. Also, prompt pore closure and vesicle re-acidification are
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your microscopy
important during closely spaced K&R events to avoid “shooting
instruments, visit
blanks.” Studies showed that re-acidification appeared to be a
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rate-limiting step, but this was observed to be rapid, even at
different stimulation frequencies. Other results indicated that
fusion pore gating was under physiological control.
This novel technique developed by Zhang et al. allows
for study of secretory mechanisms in unprecedented detail.
Some vesicles from the readily releasable pool could fuse up
to four times, and the rate of vesicle reuse is much faster than
previously estimated. Future studies could employ Qdots of
different sizes, colors, and pH sensitivities to manipulate the
system in even more detail.
References
[1] The author gratefully acknowledges Drs. Richard Tsien and
Qi Zhang for reviewing this article. BUY & SELL MICROSCOPES AND LAB EQUIPMENT
[2] Q Zhang, Y Li, and RW Tsien, Science 323 (2009) 1448-1453.
LABX-2X2.indd 1 7/27/09 11:59:18 AM
8
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