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research article

Quantitative fluorescence loss in photobleaching for analysis of protein transport and aggregation

Wuestner, Daniel
•
Solanko, Lukasz M.
•
Lund, Frederik W.
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2012
Bmc Bioinformatics

Background: Fluorescence loss in photobleaching (FLIP) is a widely used imaging technique, which provides information about protein dynamics in various cellular regions. In FLIP, a small cellular region is repeatedly illuminated by an intense laser pulse, while images are taken with reduced laser power with a time lag between the bleaches. Despite its popularity, tools are lacking for quantitative analysis of FLIP experiments. Typically, the user defines regions of interest (ROIs) for further analysis which is subjective and does not allow for comparing different cells and experimental settings. Results: We present two complementary methods to detect and quantify protein transport and aggregation in living cells from FLIP image series. In the first approach, a stretched exponential (StrExp) function is fitted to fluorescence loss (FL) inside and outside the bleached region. We show by reaction-diffusion simulations, that the StrExp function can describe both, binding/barrier-limited and diffusion-limited FL kinetics. By pixel-wise regression of that function to FL kinetics of enhanced green fluorescent protein (eGFP), we determined in a user-unbiased manner from which cellular regions eGFP can be replenished in the bleached area. Spatial variation in the parameters calculated from the StrExp function allow for detecting diffusion barriers for eGFP in the nucleus and cytoplasm of living cells. Polyglutamine (polyQ) disease proteins like mutant huntingtin (mtHtt) can form large aggregates called inclusion bodies (IB's). The second method combines single particle tracking with multi-compartment modelling of FL kinetics in moving IB's to determine exchange rates of eGFP-tagged mtHtt protein (eGFP-mtHtt) between aggregates and the cytoplasm. This method is self-calibrating since it relates the FL inside and outside the bleached regions. It makes it therefore possible to compare release kinetics of eGFP-mtHtt between different cells and experiments. Conclusions: We present two complementary methods for quantitative analysis of FLIP experiments in living cells. They provide spatial maps of exchange dynamics and absolute binding parameters of fluorescent molecules to moving intracellular entities, respectively. Our methods should be of great value for quantitative studies of intracellular transport.

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Type
research article
DOI
10.1186/1471-2105-13-296
Web of Science ID

WOS:000314181800001

Author(s)
Wuestner, Daniel
Solanko, Lukasz M.
Lund, Frederik W.
Sage, Daniel  
Schroll, Hans J.
Lomholt, Michael A.
Date Issued

2012

Publisher

Biomed Central Ltd

Published in
Bmc Bioinformatics
Volume

13

Start page

296

Subjects

Mathematical model

•

Crowding

•

Protein aggregation

•

Fractal kinetics

•

Rate coefficient

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Multi-compartment

•

Neurodegeneration

URL

URL

http://bigwww.epfl.ch/publications/wuestner1202.html

URL

http://bigwww.epfl.ch/publications/wuestner1202.pdf

URL

http://bigwww.epfl.ch/publications/wuestner1202.ps
Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LIB  
Available on Infoscience
March 28, 2013
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/91201
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