Inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] 3-kinase catalyses the phosphorylation of InsP3 to inositol 1,3,4,5-tetrakisphosphate. cDNAs encoding three human isoenzymes of InsP3 3-kinase (A, B and C) have been reported previously [Choi, Kim, Lee, Moon, Sim, Kim, Chung and Rhee (1990) Science 248, 64–66; Dewaste, Pouillon, Moreau, Shears, Takazawa and Erneux (2000) Biochem. J. 352, 343–351; Dewaste, Roymans, Moreau and Erneux (2002) Biochem. Biophys. Res. Commun. 291, 400–405; Takazawa, Perret, Dumont and Erneux (1991) Biochem. Biophys. Res. Commun. 174, 529–535]. The localization of InsP3 3-kinase isoenzymes fused at their N-terminus to the green fluorescent protein has been studied by confocal microscopy. The A isoform appeared to associate with the cytoskeleton, whereas the C isoform was totally cytoplasmic. The B isoform had a more complex localization: it appeared in the plasma membrane, cytoskeleton and in the endoplasmic reticulum. The three human isoenzymes of InsP3 3-kinase can thus be distinguished by their N-terminal sequence, sensitivity to Ca2+/calmodulin and localization on transfection in COS-7 cells. We have compared the cytosolic Ca2+ responses induced by ATP in COS-7 cells transfected with the three isoenzymes. Cells expressing high levels of any of the three isoforms no longer respond to ATP, whereas cells expressing low levels of each enzyme showed a reduced response consisting of one to three Ca2+ spikes in response to 100 μM ATP. These effects were seen only in wild-type InsP3 3-kinase-transfected cells. 3-Kinase-dead mutant cells behaved as vector-transfected cells. The results highlight the potential role of the three isoforms of InsP3 3-kinase as direct InsP3 metabolizing enzymes and direct regulators of Ca2+ responses to extracellular signals.
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August 2003
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Research Article|
August 15 2003
The three isoenzymes of human inositol-1,4,5-trisphosphate 3-kinase show specific intracellular localization but comparable Ca2+ responses on transfection in COS-7 cells
Valérie DEWASTE;
Valérie DEWASTE
∗Institute of Interdisciplinary Research, Université Libre de Bruxelles, Campus Erasme, Bldg. C, 808 route de Lennik, B-1070 Brussels, Belgium
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Colette MOREAU;
Colette MOREAU
∗Institute of Interdisciplinary Research, Université Libre de Bruxelles, Campus Erasme, Bldg. C, 808 route de Lennik, B-1070 Brussels, Belgium
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Florence De SMEDT;
Florence De SMEDT
∗Institute of Interdisciplinary Research, Université Libre de Bruxelles, Campus Erasme, Bldg. C, 808 route de Lennik, B-1070 Brussels, Belgium
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Françoise BEX;
Françoise BEX
†Laboratoire de Microbiologie, Institut CERIA, Université Libre de Bruxelles, Brussels, Belgium
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Humbert De SMEDT;
Humbert De SMEDT
‡Laboratory of Physiology, K.U. Leuven, Campus Gasthuisberg O/N, Herestraat 49, B-3000 Leuven, Belgium
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Frank WUYTACK;
Frank WUYTACK
‡Laboratory of Physiology, K.U. Leuven, Campus Gasthuisberg O/N, Herestraat 49, B-3000 Leuven, Belgium
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Ludwig MISSIAEN;
Ludwig MISSIAEN
‡Laboratory of Physiology, K.U. Leuven, Campus Gasthuisberg O/N, Herestraat 49, B-3000 Leuven, Belgium
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Christophe ERNEUX
Christophe ERNEUX
1
∗Institute of Interdisciplinary Research, Université Libre de Bruxelles, Campus Erasme, Bldg. C, 808 route de Lennik, B-1070 Brussels, Belgium
1To whom correspondence should be addressed (e-mail cerneux@ulb.ac.be).
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Publisher: Portland Press Ltd
Received:
December 18 2002
Revision Received:
April 24 2003
Accepted:
May 15 2003
Accepted Manuscript online:
May 15 2003
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2003
2003
Biochem J (2003) 374 (1): 41–49.
Article history
Received:
December 18 2002
Revision Received:
April 24 2003
Accepted:
May 15 2003
Accepted Manuscript online:
May 15 2003
Citation
Valérie DEWASTE, Colette MOREAU, Florence De SMEDT, Françoise BEX, Humbert De SMEDT, Frank WUYTACK, Ludwig MISSIAEN, Christophe ERNEUX; The three isoenzymes of human inositol-1,4,5-trisphosphate 3-kinase show specific intracellular localization but comparable Ca2+ responses on transfection in COS-7 cells. Biochem J 15 August 2003; 374 (1): 41–49. doi: https://doi.org/10.1042/bj20021963
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