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Walker SA, Kupzig S, Bouyoucef D, Davies LC, Tsuboi T, Bivona TG, Cozier GE, Lockyer PJ, Buckler A, Rutter GA, Allen MJ, Philips MR, Cullen PJ. Identification of a Ras GTPase-activating protein regulated by receptor-mediated Ca2+ oscillations. EMBO J 2004; 23:1749-60. [PMID: 15057271 PMCID: PMC394250 DOI: 10.1038/sj.emboj.7600197] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Accepted: 03/05/2004] [Indexed: 02/02/2023] Open
Abstract
Receptor-mediated increases in the concentration of intracellular free calcium ([Ca2+]i) are responsible for controlling a plethora of physiological processes including gene expression, secretion, contraction, proliferation, neural signalling, and learning. Increases in [Ca2+]i often occur as repetitive Ca2+ spikes or oscillations. Induced by electrical or receptor stimuli, these repetitive Ca2+ spikes increase their frequency with the amplitude of the receptor stimuli, a phenomenon that appears critical for the induction of selective cellular functions. Here we report the characterisation of RASAL, a Ras GTPase-activating protein that senses the frequency of repetitive Ca2+ spikes by undergoing synchronous oscillatory associations with the plasma membrane. Importantly, we show that only during periods of plasma membrane association does RASAL inactivate Ras signalling. Thus, RASAL senses the frequency of complex Ca2+ signals, decoding them through a regulation of the activation state of Ras. Our data provide a hitherto unrecognised link between complex Ca2+ signals and the regulation of Ras.
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Affiliation(s)
- Simon A Walker
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Sabine Kupzig
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Dalila Bouyoucef
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Louise C Davies
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Takashi Tsuboi
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Trever G Bivona
- Department of Medicine, Cell Biology and Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Gyles E Cozier
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | - Peter J Lockyer
- Signalling Programme, The Babraham Institute, Babraham, Cambridge, UK
| | - Alan Buckler
- Ardais Corporation, One Ledgemont Center, Lexington, MA, USA
| | - Guy A Rutter
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
| | | | - Mark R Philips
- Department of Medicine, Cell Biology and Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Peter J Cullen
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
- Inositide Group, Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK. Tel.: +44 117 954 6426; Fax: +44 117 928 8274; E-mail:
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Walker SA, Kupzig S, Lockyer PJ, Bilu S, Zharhary D, Cullen PJ. Analyzing the role of the putative inositol 1,3,4,5-tetrakisphosphate receptor GAP1IP4BP in intracellular Ca2+ homeostasis. J Biol Chem 2002; 277:48779-85. [PMID: 12356770 DOI: 10.1074/jbc.m204839200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inositol 1,3,4,5-tetrakisphosphate (IP(4)) has been linked to a potential role in the regulation of intracellular free Ca(2+) concentration ([Ca(2+)](i)) following cellular stimulation with agonists that activate phosphoinositide-specific phospholipase C. However, despite many studies, the function of IP(4) remains unclear and indeed there is still some debate over whether it has a function at all. Here we have used various molecular approaches to address whether manipulation of the potential IP(4) receptor, GAP1(IP4BP), affects [Ca(2+)](i) following cellular stimulation. Using single cell imaging, we show that the overexpression of a constitutively active and a potential dominant negative form of GAP1(IP4BP) appear to have no effect on Ca(2+) mobilization or Ca(2+) entry following stimulation of HeLa cells with histamine. In addition, through the use of small interfering RNA duplexes, we have examined the effect of suppressing endogenous GAP1(IP4BP) production on [Ca(2+)](i). In HeLa cells in which the endogenous level of GAP1(IP4BP) has been suppressed by approximately 95%, we failed to observe any effect on Ca(2+) mobilization or Ca(2+) entry following histamine stimulation. Thus, using various approaches to manipulate the function of endogenous GAP1(IP4BP) in intact HeLa cells, we have been unable to observe any detectable effect of GAP1(IP4BP) on [Ca(2+)](i).
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Affiliation(s)
- Simon A Walker
- Department of Biochemistry, Inositide Group, Integrated Signalling Laboratories, School of Medical Sciences, University of Bristol, United Kingdom
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