Sarcoplasmic reticulum interacts with the Ca(2+) indicator precursor fura-2-AM

doi:10.1016/S0006-291X(86)80403-X

Biochemical and Biophysical Research Communications

Volume 138, Issue 3, 14 August 1986, Pages 1153-1162

https://doi.org/10.1016/S0006-291X(86)80403-X Get rights and content

Summary

Fura-2-am, the pentaester precursor of the fluorescent Ca(2+) indicator fura-2, is modified when it is exposed to isolated skeletal muscle sarcoplasmic reticulum vesicles. The modified fura-2-am has enhanced fluorescence, is not sensitive to Ca(2+), and is partially bound to the SR membrane. The isolated product is further converted into fura-2 by esterase. It is suggested that the SR-induced modification is a selective enzymatic hydrolysis of only some of the five ester moieties on fura-2-am. A structure is proposed to account for the results. The potential for this effect of SR on fura-2-am to cause complications in measurements of in vivo intracellular free [Ca(2+)] is noted.

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Citation Excerpt :
We have not resolved whether mixtures of only the two forms of indicator, namely the very-low affinity (KDCa =93 mM), partially de-esterified form and Mag-Fluo-4 itself (KDCa ∼20 μM), are sufficient to explain our results. Analyses of other esterified Ca2+ indicators, namely 5F-BAPTA [36] and Fura-2 [37,38], concluded that partially de-esterified forms do not bind Ca2+, but the highest [Ca2+]m used in these studies were too low (∼300 nM [36], 100 μM [37] and ∼1 mM [38]) to identify very low-affinity Ca2+-binding sites. The Ca2+-binding site of indicators like Fura-2, 5F-BAPTA and Fluo-4 is based on BAPTA (1,2-bis(O-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid), wherein four carboxylate groups coordinate Ca2+ [39].
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Biochemical and Biophysical Research Communications

Summary

References (11)

J. Biol. Chem.

FEBS Letters

Biochim. Biophys. Acta

Biochim. Biophys. Acta

FEBS Letters

Cited by (59)

Reliable measurement of free Ca<sup>2+</sup> concentrations in the ER lumen using Mag-Fluo-4

Mag-indo1 affinity for Ca<sup>2+</sup>, compartmentalization and binding to proteins: The challenge of measuring Mg<sup>2+</sup> concentrations in living cells

Two dye two wavelength excitation calcium imaging: Results from bovine adrenal chromaffin cells

Methods for the isolation, culture and characterisation of equine pulmonary artery endothelial cells

Regulation of motility of cells from marine sponges by calcium ions

Intracellular concentrations of Fura-2 and Fura-2/AM in vascular smooth muscle cells following perfusion loading of Fura-2/AM in arterial segments