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Overexpression of calreticulin increases intracellular Ca2+ storage and decreases store-operated Ca2+ influx

Mesaeli, N.
Opas, M.
Published in The Journal of biological chemistry. 1996, vol. 271, no. 16, p. 9332-9339
Abstract The widely distributed and highly conserved Ca(2+)-binding protein calreticulin has been suggested to play a role as a Ca2+ storage protein of intracellular Ca+ stores. To test this hypothesis, we have generated a mouse L fibroblast cell line stably transfected with a calreticulin expression vector. The calreticulin content of the overexpressers was increased by 1.6 +/- 0.2-fold compared with mock-transfected cells. The total cellular Ca2+ content of calreticulin-overexpressing and control cells, as assessed by equilibrium 45Ca+2 uptake, was 141 +/- 8 and 67 +/- 6 pmol of Ca2+/10(6) cells, respectively (i.e. a 2.1 +/- 0.2-fold increase in the Ca2+ content of calreticulin-overexpressing cells). Over 80% of the increased Ca2+ content was found within thapsigargin-sensitive Ca2+ stores. The pattern of calreticulin distribution, revealed by immunofluorescence microscopy, showed an endoplasmic reticulum-like pattern and was identical in overexpressers and control cells. In overexpressers, cytosolic free [Ca2+] elevations due to Ca2+ release were enhanced when either ATP or a combination of ionomycin and thapsigargin was used as a stimulus. In contrast, thapsigargin-induced Ca2+ and Mn2+ influxes from the extracellular space were markedly diminished in calreticulin-overexpressing cells, suggesting an active involvement of calreticulin in the regulation of store-operated Ca2+ influx.
Keywords Adenosine Triphosphate/pharmacologyAnimalsCalcium/ metabolismCalcium-Binding Proteins/analysis/biosynthesis/ metabolismCalcium-Transporting ATPases/antagonists & inhibitorsCalreticulinDimethyl Sulfoxide/pharmacologyEnzyme Inhibitors/pharmacologyFluorescent Antibody TechniqueHomeostasisIonomycin/pharmacologyKineticsL Cells (Cell Line)Manganese/metabolismMiceMolecular Sequence DataMonensin/pharmacologyRecombinant Proteins/analysis/biosynthesis/metabolismRestriction MappingRibonucleoproteins/analysis/biosynthesis/ metabolismTerpenes/pharmacologyThapsigarginTransfection
PMID: 8621597
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Other version: http://www.jbc.org/content/271/16/9332.full.pdf
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MERY, Laurence et al. Overexpression of calreticulin increases intracellular Ca2+ storage and decreases store-operated Ca2+ influx. In: Journal of Biological Chemistry, 1996, vol. 271, n° 16, p. 9332-9339. https://archive-ouverte.unige.ch/unige:7430

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Deposited on : 2010-06-21

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