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Updated: Jul 26, 2026
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In vivo Neuronal Calcium Imaging in C. elegans
Published on: April 10, 2013
Dynamic and quantitative Ca2+ measurements using improved cameleons
A Miyawaki1, O Griesbeck, R Heim
1Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0647, USA.
Summary
New cameleon biosensors offer improved calcium (Ca2+) measurements by reducing pH interference. These genetically encoded indicators are valuable tools for cellular research despite potential calcium buffering effects.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Imaging
Background:
- Cameleons are genetically encoded fluorescent indicators for Ca2+ using green fluorescent protein variants and calmodulin (CaM).
- Original cameleons exhibited significant pH interference and uncharacterized Ca2+-buffering and cross-reactivity.
- Previous limitations hindered Ca2+ monitoring in various biological contexts.
Purpose of the Study:
- To reduce the pH sensitivity of cameleon biosensors.
- To improve the accuracy of Ca2+ measurements in biological systems.
- To characterize the Ca2+-buffering and signaling interactions of cameleons.
Main Methods:
- Introduced V68L and Q69K mutations into the acceptor yellow green fluorescent protein of cameleons.
- Developed genetically encoded fluorescent indicators for Ca2+.
- Utilized one- and two-photon excitation microscopy for imaging.
Main Results:
- Significantly reduced pH sensitivity in the modified cameleons.
- Enabled accurate Ca2+ measurements even during cytosolic acidification.
- Observed that elevated Ca2+ promotes intramolecular interaction within cameleons, reducing interaction with endogenous CaM.
Conclusions:
- Modified cameleons provide more reliable Ca2+ measurements by minimizing pH interference.
- Overexpression of cameleons primarily increases Ca2+ buffering rather than perturbing CaM-dependent signaling pathways.
- Cameleons are promising tools for monitoring Ca2+ in diverse biological environments.
