Abstract
Cyclic AMP (cAMP) is produced by activation of Gs protein-coupled receptors and regulates many physiological processes through activation of protein kinase A (PKA)1,2. However, a large body of evidence indicates that cAMP also regulates specific cellular functions through PKA-independent pathways3,4. Here, we show that a small GTPase of the Rho family, Rac, is regulated by cAMP in a PKA-independent manner. We also show that Rac activation results from activation of Rap1 through the cAMP guanine nucleotide-exchange factor (GEF) Epac1. Activation of the Gs-coupled serotonin 5-HT4 receptor initiates this signalling cascade in various cell types. Furthermore, we demonstrate that crosstalk between the Ras and Rho GTPase families is involved in cAMP-dependent processing of amyloid precursor protein (APP), a key protein in Alzheimer's disease. Indeed, Epac1 regulates secretion of the non-amyloidogenic soluble form of APP (sAPPα) through Rap1 and Rac. Our data identify an unsuspected connection between two families of small GTPases and imply that Rac can function downstream of cAMP/Epac1/Rap1 in a novel signal transduction secretory pathway.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
214,86 € per year
only 17,91 € per issue
Buy this article
- Purchase on SpringerLink
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Meinkoth, J.L. et al. Signal transduction through the cAMP-dependent protein kinase. Mol. Cell. Biochem. 127–128, 179–186 (1993).
Montminy, M. Transcriptional regulation by cyclic AMP. Annu. Rev. Biochem. 66, 807–822 (1997).
Brandon, E.P., Idzerda, R.L. & McKnight, G.S. PKA isoforms, neural pathways, and behaviour: making the connection. Curr. Opin. Neurobiol. 7, 397–403 (1997).
Robert, S.J., Zugaza, J.L., Fischmeister, R., Gardier, A.M. & Lezoualc'h, F. The human serotonin 5-HT4 receptor regulates secretion of non-amyloidogenic precursor protein. J. Biol. Chem. 276, 44881–44888 (2001).
Selkoe, D.J. Translating cell biology into therapeutic advances in Alzheimer's disease. Nature 399, A23–A31 (1999).
Mialet, J. et al. Isolation of the serotoninergic 5-HT4(e) receptor from human heart and comparative analysis of its pharmacological profile in C6-glial and CHO cell lines. Br. J. Pharmacol. 129, 771–781 (2000).
Briejer, M.R. et al. The in vitro pharmacological profile of prucalopride, a novel enterokinetic compound. Eur. J. Pharmacol. 423, 71–83 (2001).
Rothermel, J.D. & Parker Botelho, L.H. A mechanistic and kinetic analysis of the interactions of the diastereoisomers of adenosine 3′,5′-(cyclic)phosphorothioate with purified cyclic AMP-dependent protein kinase. Biochem. J. 251, 757–762 (1988).
Kroschewski, R., Hall, A. & Mellman, I. Cdc42 controls secretory and endocytic transport to the basolateral plasma membrane of MDCK cells. Nature Cell Biol. 1, 8–13 (1999).
Hong-Geller, E. & Cerione, R.A. Cdc42 and Rac stimulate exocytosis of secretory granules by activating the IP3/calcium pathway in RBL-2H3 mast cells. J. Cell Biol. 148, 481–494 (2000).
Lang, P. et al. Protein kinase A phosphorylation of RhoA mediates the morphological and functional effects of cyclic AMP in cytotoxic lymphocytes. EMBO J. 15, 510–519 (1996).
Feoktistov, I., Goldstein, A.E. & Biaggioni, I. Cyclic AMP and protein kinase A stimulate cdc42: role of A2 adenosine receptors in human mast cells. Mol. Pharmacol. 58, 903–910 (2000).
Gottesman, M.M., LeCam, A., Bukowski, M. & Pastan, I. Isolation of multiple classes of mutants of CHO cells resistant to cyclic AMP. Somatic Cell Genet. 6, 45–61 (1980).
Kjoller, L. & Hall, A. Signaling to Rho GTPases. Exp. Cell Res. 253, 166–179 (1999).
de Rooij, J. et al. Epac is a Rap1 guanine-nucleotide-exchange factor directly activated by cyclic AMP. Nature 396, 474–477 (1998).
Kawasaki, H. et al. A family of cAMP-binding proteins that directly activate Rap1. Science 282, 2275–2279 (1998).
de Rooij, J. et al. Mechanism of regulation of the Epac family of cAMP-dependent RapGEFs. J. Biol. Chem. 275, 20829–20836 (2000).
Enserink, J.M. et al. A novel Epac-specific cAMP analogue demonstrates independent regulation of Rap1 and ERK. Nature Cell Biol. 4, 901–906 (2002).
Mei, F.C. et al. Differential signaling of cyclic AMP: opposing effects of exchange protein directly activated by cyclic AMP and cAMP-dependent protein kinase on protein kinase B activation. J. Biol. Chem. 277, 11497–11504 (2002).
Busca, R. et al. Ras mediates the cAMP-dependent activation of extracellular signal- regulated kinases (ERKs) in melanocytes. EMBO J. 19, 2900–2910 (2000).
Laroche-Joubert, N., Marsy, S., Michelet, S., Imbert-Teboul, M. & Doucet, A. Protein kinase A-independent activation of ERK and H,K-ATPase by cAMP in native kidney cells: role of Epac I. J. Biol. Chem. 277, 18598–18604 (2002).
Rehmann, H. et al. Structure and regulation of the cAMP-binding domains of Epac2. Nature Struct. Biol. 10, 26–32 (2003).
Hung, S.H. et al. A new nonhydrolyzable reactive cAMP analog, (Sp)-adenosine-3′,5′-cyclic-S-(4-bromo-2,3-dioxobutyl) monophosphorothioate irreversibly inactivates human platelet cGMP-inhibited cAMP phosphodiesterase. Bioorg. Chem. 30, 16–31 (2002).
Murthy, K.S., Zhou, H. & Makhlouf, G.M. PKA-dependent activation of PDE3A and PDE4 and inhibition of adenylyl cyclase V/VI in smooth muscle. Am. J. Physiol. 282, C508–517 (2002).
Liu, H.G. & Maurice, D.H. Phosphorylation-mediated activation and translocation of the cyclic AMP-specific phosphodiesterase PDE4D3 by cyclic AMP-dependent protein kinase and mitogen-activated protein kinases - A potential mechanism allowing for the coordinated regulation of PDE4D activity and targeting. J. Biol. Chem. 274, 10557–10565 (1999).
Pruyne, D. & Bretscher, A. Polarization of cell growth in yeast. J. Cell Sci. 113, 571–585 (2000).
Gulli, M.P. & Peter, M. Temporal and spatial regulation of Rho-type guanine-nucleotide exchange factors: the yeast perspective. Genes Dev. 15, 365–379 (2001).
Del Pozo, M.A. et al. Integrins regulate GTP-Rac localized effector interactions through dissociation of Rho-GDI. Nature Cell Biol. 4, 232–239 (2002).
Sebzda, E. et al. Rap1A positively regulates T cells via integrin activation rather than inhibiting lymphocyte signaling. Nature Immunol. 3, 251–258 (2002).
Koh, J.Y. & Choi, D.W. Quantitative determination of glutamate mediated cortical neuronal injury in cell culture by lactate dehydrogenase efflux assay. J. Neurosci. Meth. 20, 83–90 (1987).
Acknowledgements
We wish to thank M. Gottesman, J. Bos, X. Cheng, and J. de Gunsburg for providing CHO 10001/10260, Epac1 and Rap plasmid constructs. The cDNA encoding human APP695 was kindly provided by C. Haass. We thank P. Bochet for help with database searching, and J. Bréard, G. Gaudriault, J. de Gunsburg and S. Kerdine for helpful advice and critical reading of the manuscript. J.L.Z. is investigator from the Ramón y Cajal Program (Spanish Ministry of Science and Technology) associated to the University of Salamanca.
Author information
Authors and Affiliations
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Supplementary Information, Fig. S1
Supplementary Information, Fig. S2 (PDF 393 kb)
Supplementary Information, Fig. S3
Supplementary Information, Fig. S4
Rights and permissions
About this article
Cite this article
Maillet, M., Robert, S., Cacquevel, M. et al. Crosstalk between Rap1 and Rac regulates secretion of sAPPα. Nat Cell Biol 5, 633–639 (2003). https://doi.org/10.1038/ncb1007
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/ncb1007
