Monitoring of free calcium in the neuronal endoplasmic reticulum: an overview of modern approaches.
The concentration of free calcium within the lumen of the endoplasmic reticulum ([Ca2+]L) fluctuates between 100 and 1000 microM. High [Ca2+]L provides an electro-driving force for Ca2+ release and supports high Ca2+ diffusion rate within the endoplasmic reticulum lumen. Fluctuations in [Ca2+]L also regulate numerous chaperones, responsible for postranslational protein processing. Thus, [Ca2+]L integrates various signalling events and establishes a link between fast signalling, associated with the endoplasmic reticulum Ca2+release/uptake, and long-lasting adaptive responses relying primarily on the regulation of protein synthesis. This paper overviews modern approaches for the direct monitoring of [Ca2+]L which rely on three classes of low-affinity Ca2+ probes: ER-targeted aequorin, synthetic fluorescent Ca2+ dyes and GFP-based ER-targeted Ca2+ probes. These techniques, especially as applied to neurones, may substantially widen our appreciation of the endoplasmic reticulum as a universal signalling organelle.
Solovyova
Natasha
N
School of Biological Sciences, The University of Manchester, 1.124 Stopford Building, Oxford Road, M13 9PT, Manchester, UK.
Verkhratsky
Alexei
A
D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000032:analysis* / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D008163:Luminescent Measurements; D008164:Luminescent Proteins; D009474:Neurons / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods*
D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D000331:Aequorin; D002118:Calcium