Wang Y, Telmer CA, Schmidt BF, Franke JD, Ort S, Arndt-Jovin DJ, Bruchez MP. Fluorogen activating protein-affibody probes: modular, no-wash measurement of epidermal growth factor receptors.
Bioconjug Chem 2014;
26:137-44. [PMID:
25490520 PMCID:
PMC4306507 DOI:
10.1021/bc500525b]
[Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
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Fluorescence
is essential for dynamic live cell imaging, and affinity
reagents are required for quantification of endogenous proteins. Various
fluorescent dyes can report on different aspects of biological trafficking,
but must be independently conjugated to affinity reagents and characterized
for specific biological readouts. Here we present the characterization
of a new modular platform for small anti-EGFR affinity probes for
studying rapid changes in receptor pools. A protein domain (FAP dL5**) that binds to malachite-green (MG) derivatives for fluorescence
activation was expressed as a recombinant fusion to one or two copies
of the compact EGFR binding affibody ZEGFR:1907. This is
a recombinant and fluorogenic labeling reagent for native EGFR molecules.
In vitro fluorescence assays demonstrated that the binding of these
dyes to the FAP–affibody fusions produced thousand-fold fluorescence
enhancements, with high binding affinity and fast association rates.
Flow cytometry assays and fluorescence microscopy demonstrated that
these probes label endogenous EGFR on A431 cells without disruption
of EGFR function, and low nanomolar surface Kd values were observed with the double-ZEGFR:1907 constructs. The application of light-harvesting fluorogens (dyedrons)
significantly improved the detected fluorescence signal. Altering
the order of addition of the ligand, probe, and dyes allowed differentiation
between surface and endocytotic pools of receptors to reveal the rapid
dynamics of endocytic trafficking. Therefore, FAP/affibody coupling
provides a new approach to construct compact and modular affinity
probes that label endogenous proteins on living cells and can be used
for studying rapid changes in receptor pools involved in trafficking.
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