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Measuring [Ca2+] in the endoplasmic reticulum with aequorin
1Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular, Universidad de Valladolid, Ramón y Cajal, 7, E-47005, Valladolid, Spain. jalvarez@ibgm.uva.es
Cell Calcium
|January 25, 2003
Summary
Aequorin is a valuable tool for measuring calcium levels in the endoplasmic reticulum (ER), offering precise targeting and a wide dynamic range. However, limitations include low light emission and potential cell damage during probe preparation.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Imaging
Background:
- The endoplasmic reticulum (ER) plays a crucial role in cellular calcium homeostasis.
- Accurate measurement of intracellular calcium ([Ca2+]) within the ER lumen is essential for understanding cellular function.
- Aequorin, a photoprotein, was the first probe developed for this purpose.
Purpose of the Study:
- To evaluate the utility and limitations of aequorin-based methods for measuring ER calcium levels ([Ca2+]ER).
- To compare the advantages and disadvantages of aequorin against other available techniques.
Main Methods:
- Utilizing aequorin, a calcium-sensitive photoprotein, targeted to the ER lumen.
- Measuring luminescence emitted by aequorin upon binding calcium.
- Calibrating luminescence signals to determine steady-state [Ca2+]ER.
Main Results:
- Aequorin provides accurate steady-state [Ca2+]ER values (around 500 microM) comparable to other methods.
- Advantages include precise probe targeting, wide dynamic range (10(-5) to 10(-3)M), insensitivity to pH/Mg2+, and straightforward calibration.
- Disadvantages involve low light emission for single-cell imaging, potential cell damage during probe reconstitution, rapid aequorin consumption, and requirement for cell transfection/cloning.
Conclusions:
- Aequorin is a robust tool for quantifying ER calcium, particularly in cell populations.
- The choice between aequorin and alternative methods depends on the specific experimental requirements and the balance of its advantages and disadvantages.