Rap1 is a member of the Ras-like small GTPases. Originally the protein was identified in a genome-wide screen for suppressors of Ras transformation, but the mechanism of this reversion remained elusive. We have investigated the signalling function of Rap1. We observed that Rap1 is activated by a large variety of stimuli, including growth factors, neurotransmitters and cytokines. Common second messengers like cAMP, diacylglycerol and calcium are mediators of this activation. These messengers activate guanine nucleotide exchange factors (GEFs), the most notable of which is Epac (exchange protein directly activated by cAMP). However, the downstream effectors of Rap1 are less clear. Although direct connections of Rap1 with the serine/threonine kinases Raf1 and B-raf have been reported, we were unable to find functional evidence for an interaction of endogenous Rap1 signalling with the Raf/extracellular-signal-regulated kinase (ERK) pathway. Instead we observe a clear connection of Rap1 with inside-out signalling to integrins. Indeed, introduction of a constitutively active Rap1 as well as Epac induces integrin-mediated cell adhesion, whereas inhibition of Rap1 signalling by the introduction of Rap1GAP (GTPase-activating protein) inhibits inside-out activation of integrins. More importantly, activation of a Gs-protein-coupled receptor results in integrin-mediated cell adhesion, by a pathway involving Epac and Rap1. From these results, we conclude that one of the functions of receptor-induced Rap1 activation is inside-out regulation of integrins.
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February 2003
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Conference Article|
February 01 2003
The role of Rap1 in integrin-mediated cell adhesion
J.L. Bos;
J.L. Bos
1
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
1To whom correspondence should be addressed (e-mail j.l.bos@med.uu.nl).
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K. de Bruyn;
K. de Bruyn
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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J. Enserink;
J. Enserink
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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B. Kuiperij;
B. Kuiperij
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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S. Rangarajan;
S. Rangarajan
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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H. Rehmann;
H. Rehmann
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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J. Riedl;
J. Riedl
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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J. de Rooij;
J. de Rooij
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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F. van Mansfeld;
F. van Mansfeld
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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F. Zwartkruis
F. Zwartkruis
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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Publisher: Portland Press Ltd
Online ISSN: 1470-8752
Print ISSN: 0300-5127
Copyright 2003 Biochemical Society
2003
Biochem Soc Trans (2003) 31 (1): 83–86.
Citation
J.L. Bos, K. de Bruyn, J. Enserink, B. Kuiperij, S. Rangarajan, H. Rehmann, J. Riedl, J. de Rooij, F. van Mansfeld, F. Zwartkruis; The role of Rap1 in integrin-mediated cell adhesion. Biochem Soc Trans 1 February 2003; 31 (1): 83–86. doi: https://doi.org/10.1042/bst0310083
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